Adding a high-speed electric-spindle system to an existing CNC vertical machining center can improve the machine's productivity by providing quick, infinitely variable speed selection and higher rpm capabilities. Integrating the auxiliary spindle permanently onto the machine allows a company to meet the constantly changing demands of machining fine details and still retain the main spindle's capabilities for larger cutters.
In a typical application, one company recently purchased a five-axis Fadal VMC 4020 vertical machining center and modified it so it could also be used for machining fluidic circuit prototypes. Modifications include a Precise SC 102-O high speed electric spindle system (Precise Corp., Racine, Wisconsin), a special mounting plate that allows the spindle to remain in place while the main spindle is in use, some tool changer and programming adaptations, and cable carriers to keep all fluid and electrical lines neat and manageable.
The high rpm capability makes it possible to use carbide end mills from as small as 0.009" diameter up to about 1/4-inch. To make the high spindle rpm needed for small diameter cutters readily available, the auxiliary Precise spindle is mounted permanently on the side of the machine's column. Offset approximately ten inches, the spindle's fixed location enables it to be programmed into operations with little or no special accommodation. The machine's main spindle remains intact to provide the higher power and lower speed range needed to use larger diameter cutters.
With the auxiliary spindle, tools are set up in their own quickchange toolholders. This makes it possible to preset all of the tools and quickly change from tool to tool as needed, roughing with a larger diameter end mill for part of the program and finishing with smaller diameter end mills.
The machine can be programmed so switching from the main spindle to the high speed spindle can be done quickly, without interruption. When the operator specifies a speed above the main spindle's 10,000 rpm limit, the custom postprocessor recognizes the condition and applies the fixture offset, negates the main spindle, turns on the auxiliary spindle, turns it off when the cycle is through and returns to the main spindle.
The Precise spindle is equipped for automatic tool changing but the toolholder release can also be operated manually. A conveniently located pushbutton that releases the toolholder is tied to a zero-speed sensor so the tool will not be released until the operator is ready. Pre-set tooling allows the cutters to be changed quickly.
http://www.mmsonline.com/articles/0995bp3.html
Tuesday, December 18, 2007
Retrofit Increases Productivity And Reduces Capital Outlay
Monitor Aerospace Corporation of Amityville, New York, is a producer of aerospace structural components for companies such as The Boeing Company. The company invested heavily in the 1970s in large expensive machinery, but more than 20 years later these aging machines were no longer keeping up with productivity demands. The older controls on these machines had limited functionality, and operators had to continuously tweak the machines to compensate for wear. Moreover, maintenance costs were soaring and downtime was increasing.
Gary Kahrau, director of manufacturing engineering, and Chris Nagowski, facilities manager, had a dilemma. They needed to address the machines’ performance problems, but they did not have access to the enormous capital outlay necessary to replace them. Mechanically the machines were in fairly good condition, so they decided to explore retrofitting the machines with new controls as a solution to their problem. They knew that new controls would provide more flexible functionality, higher reliability and less downtime, but they also hoped that newer error compensation capabilities would help make up for some of the machines’ wear related tolerance problems.
current control technology
Adding current control technology has breathed new life into Monitor's older machine tools.
As Mr. Kahrau and Mr. Nagowski explored their retrofit options, their first task was to decide on a control. They wanted a control that would give them ease-of-use, high reliability, and sophisticated capabilities such as five-axis movements and advanced error compensation. Just as importantly, however, they wanted an open control that they could integrate into their existing plant system architecture and that would be poised for integration with undefined systems of the future.
Traditional controls offered the motion and compensation sophistication they were looking for but did not offer the flexibility and integration capabilities they wanted. On the other hand, purely PC-based controls, which offered the integration and operator flexibility they wanted, did not offer the motion sophistication they needed.
As their search went on, Mr. Kahrau and Mr. Nagowski spoke with CNC Engineering, Inc. (Enfield, Connecticut) and learned about CNC Engineering’s PC-based Open Vision HMI system for the GE Fanuc series of controls. This system provides a hybrid solution that ties together a flexible and powerful PC-based front-end with the motion and compensation capabilities of a GE Fanuc control. Based on GE Fanuc’s HSSB, and using an industrial PC for the operator interface, Open Vision HMI provides access to all of the control’s native functions through intuitive touch screen menus. And, since the operator interface is on a PC running Windows NT, custom screens and options are readily available, and advanced network and system connectivity is fully supported.
The first machine Monitor decided to retrofit was a three-axis Cincinnati Bridgemill. This was a sound machine, but the X-axis gearboxes were worn, and the machine was not holding tolerances well. Rebuilding the gearboxes would be an expensive undertaking, and Mr. Kahrau and Mr. Nagowski thought that this expense could be avoided by applying some of the advanced error compensation functions available in a newer control. Working with CNC Engineering, a specification was developed for the control. For this application, Monitor decided to use a GE Fanuc 15MB control with CNC Engineering’s standard Open Vision HMI Software. (The front-end software would run under Windows NT Workstation, and the PC initially would be connected to Monitor’s Local Area Network via a standard Ethernet topography.) Since the GE Fanuc control had many options that might help compensate for the worn gear boxes, it was decided to add compensation features one at a time and perform accuracy tests after each feature was implemented to quantify the results.
Monitor has tight production schedules, and it could not spare the machine for the protracted period of time associated with a full in-field retrofit. CNC Engineering’s CPR (Certified Pre-assembled Retrofit) package solved this problem. Under the CPR program, engineering and design specifications were worked out in advance during an initial site visit. During the site visit, detailed measurements were taken of the machine, and new component placement was finalized. The engineers at CNC Engineering spent considerable time working with Monitor to specify the optimum operators’ pendant for the application. In this case, the original operator console was removed, freeing up a large amount of floor space, and a new three joint operator pendant was designed for maximum operator convenience. With the information from the site visit the entire retrofit package was engineered, designed and assembled at CNC Engineering’s facility. During the engineering and assembly phase all necessary electrical schematics, cable lists, panel layouts, mechanical prints and ladder programs were developed. The exact equipment that was to be installed at Monitor was then assembled, wired and powered up. All parameters were loaded into the control, and the entire package was then tested exactly as it would be on the machine—right down to servomotors with their custom length servo cables. Once testing was finalized, the package was shipped to Monitor for field installation. For this machine the installation took 3 weeks.
When the new control was in place, it was time to test the impact of various error compensation capabilities. Laser measuring was performed along each axis. The results of the laser measurements were input into the Pitch Error Compensation Tables, and a circle-diamond-square test was performed. This test part was compared to a previous test part cut before the retrofit was done. The comparison showed a significant improvement in accuracy as well as finish. After analyzing the laser results for the X axis, a definite cyclic error, every 0.750 inch, could be seen—probably the result of worn gears in the gearboxes. The cyclic compensation function was added, the proper parameters were set, the machine was re-lasered, and a circle diamond square was cut. Again further improvement was made. The wear in the rack and pinions of the X axis was also contributing to bi-directional errors. By implementing bi-directional error compensation, further improvements were once again realized. With these three compensation options applied, Monitor was able to avoid the expense of dual gearbox rebuilds while improving part quality and increasing productivity.
http://www.mmsonline.com/articles/1000bp1.html
Gary Kahrau, director of manufacturing engineering, and Chris Nagowski, facilities manager, had a dilemma. They needed to address the machines’ performance problems, but they did not have access to the enormous capital outlay necessary to replace them. Mechanically the machines were in fairly good condition, so they decided to explore retrofitting the machines with new controls as a solution to their problem. They knew that new controls would provide more flexible functionality, higher reliability and less downtime, but they also hoped that newer error compensation capabilities would help make up for some of the machines’ wear related tolerance problems.
current control technology
Adding current control technology has breathed new life into Monitor's older machine tools.
As Mr. Kahrau and Mr. Nagowski explored their retrofit options, their first task was to decide on a control. They wanted a control that would give them ease-of-use, high reliability, and sophisticated capabilities such as five-axis movements and advanced error compensation. Just as importantly, however, they wanted an open control that they could integrate into their existing plant system architecture and that would be poised for integration with undefined systems of the future.
Traditional controls offered the motion and compensation sophistication they were looking for but did not offer the flexibility and integration capabilities they wanted. On the other hand, purely PC-based controls, which offered the integration and operator flexibility they wanted, did not offer the motion sophistication they needed.
As their search went on, Mr. Kahrau and Mr. Nagowski spoke with CNC Engineering, Inc. (Enfield, Connecticut) and learned about CNC Engineering’s PC-based Open Vision HMI system for the GE Fanuc series of controls. This system provides a hybrid solution that ties together a flexible and powerful PC-based front-end with the motion and compensation capabilities of a GE Fanuc control. Based on GE Fanuc’s HSSB, and using an industrial PC for the operator interface, Open Vision HMI provides access to all of the control’s native functions through intuitive touch screen menus. And, since the operator interface is on a PC running Windows NT, custom screens and options are readily available, and advanced network and system connectivity is fully supported.
The first machine Monitor decided to retrofit was a three-axis Cincinnati Bridgemill. This was a sound machine, but the X-axis gearboxes were worn, and the machine was not holding tolerances well. Rebuilding the gearboxes would be an expensive undertaking, and Mr. Kahrau and Mr. Nagowski thought that this expense could be avoided by applying some of the advanced error compensation functions available in a newer control. Working with CNC Engineering, a specification was developed for the control. For this application, Monitor decided to use a GE Fanuc 15MB control with CNC Engineering’s standard Open Vision HMI Software. (The front-end software would run under Windows NT Workstation, and the PC initially would be connected to Monitor’s Local Area Network via a standard Ethernet topography.) Since the GE Fanuc control had many options that might help compensate for the worn gear boxes, it was decided to add compensation features one at a time and perform accuracy tests after each feature was implemented to quantify the results.
Monitor has tight production schedules, and it could not spare the machine for the protracted period of time associated with a full in-field retrofit. CNC Engineering’s CPR (Certified Pre-assembled Retrofit) package solved this problem. Under the CPR program, engineering and design specifications were worked out in advance during an initial site visit. During the site visit, detailed measurements were taken of the machine, and new component placement was finalized. The engineers at CNC Engineering spent considerable time working with Monitor to specify the optimum operators’ pendant for the application. In this case, the original operator console was removed, freeing up a large amount of floor space, and a new three joint operator pendant was designed for maximum operator convenience. With the information from the site visit the entire retrofit package was engineered, designed and assembled at CNC Engineering’s facility. During the engineering and assembly phase all necessary electrical schematics, cable lists, panel layouts, mechanical prints and ladder programs were developed. The exact equipment that was to be installed at Monitor was then assembled, wired and powered up. All parameters were loaded into the control, and the entire package was then tested exactly as it would be on the machine—right down to servomotors with their custom length servo cables. Once testing was finalized, the package was shipped to Monitor for field installation. For this machine the installation took 3 weeks.
When the new control was in place, it was time to test the impact of various error compensation capabilities. Laser measuring was performed along each axis. The results of the laser measurements were input into the Pitch Error Compensation Tables, and a circle-diamond-square test was performed. This test part was compared to a previous test part cut before the retrofit was done. The comparison showed a significant improvement in accuracy as well as finish. After analyzing the laser results for the X axis, a definite cyclic error, every 0.750 inch, could be seen—probably the result of worn gears in the gearboxes. The cyclic compensation function was added, the proper parameters were set, the machine was re-lasered, and a circle diamond square was cut. Again further improvement was made. The wear in the rack and pinions of the X axis was also contributing to bi-directional errors. By implementing bi-directional error compensation, further improvements were once again realized. With these three compensation options applied, Monitor was able to avoid the expense of dual gearbox rebuilds while improving part quality and increasing productivity.
http://www.mmsonline.com/articles/1000bp1.html
The Economics Of Converting Manual Mills To CNC
It's no secret that CNC retrofits of older 1 to 5 hp manual machine tools increase productivity and profits for machine shops. By automating manual operations, a CNC retrofit typically turns out parts 75 to 300 percent faster than a manual machine. It also assures repeatable accuracy; makes complex parts more easily; and reduces scrap, rework and manufacturing costs.
In function and price, a CNC retrofit for a manual mill fills the gap between a $2,000 digital readout (DRO) retrofit package and a $50,000 to $60,000 two-axis CNC milling center, but increasing capabilities of newer CNC retrofits are narrowing the gap between them and new machines.
For instance, a CNC retrofit control package recently introduced by Mitutoyo/MTI Corporation (Aurora, Illinois) approaches the functionality of a low horsepower CNC milling machine at about one-fifth the cost. Called MILLSTAR, this CNC retrofit package includes a control with Windows 95 compatibility, choice of shop or G-Code program language, advanced geometry calculations, and glass linear scales. According to MTI, it enables a manual mill to turn out low to medium volume work at the same rates as a full CNC milling machine of equal spindle horsepower.
Connectivity to Windows 95 software makes programming user-friendly and intuitive for machine operators, freeing operators up for more complex jobs. This helps shops cope with the skills shortage, especially programmers, and the need for operators to program on their own. Shop and G-Code language, likewise, facilitate programming by operators. Part prints in G-Code can be downloaded directly to create the program, saving time and eliminating another error source.
The company reports that high-precision glass linear scales provide better positioning accuracy than rotary encoders: This is why they are offered as extras on many CNC retrofit packages and built-in controls. The difference becomes especially important on older mills where there may be more play in the table ways. Positioning repeatability of a retrofit CNC control with glass linear scales matches that of the controls on a full CNC milling machine.
This retrofit package includes servo-motors with adequate power to move the table at optimum feed rates for heavy cuts, even on large 5-hp manual mills. Because the CNC part programs will be calling for higher material removal rates than are customary for manual work, under-powered servomotors are likely to hold the operation back.
A DRO-equipped machine provides no such automatic table movement, but rather clear, more readable positional readings. The operator must dial in table feeds and stops, and start each cut as if on a manual mill; there is still a possibility for error.
Advanced geometry calculation saves both programming and running time for complex shapes including angles, radii, and irregular pockets. During programming, the operator inputs the known linear and curved measurements and designates the type of cut. No calculations are necessary on the part of the operator. The machine's geometry calculator computes the unknown measurements and the required tool path. During operation, moreover, complex cuts are made at the same removal rates as simpler cuts. The control "thinks" fast enough to keep the cutter running at full speed. If a shop's work involves a lot of circles, hole patterns, arcs and pockets, the additional programming efficiency of canned cycles may justify a retrofit.
Large memory for routines means that routines can be retrieved and used on another job. The larger the memory, the more routines available for the next job. The MILLSTAR's memory can store hundreds of routines, depending on their length. Similar parts do not have to be reprogrammed; only new dimensions need to be inputted. The system recognizes the part and updates the routine with the new data.
Manual override enables the operator to run a one/off or prototype job as usual. Where there's an applicable routine or subroutine, the operator can pick it up from memory. Where something unique to the part needs to be done, the operator switches to the manual mode, makes the cut, and returns to program mode.
The benefit of thee-axis readout in a two-axis CNC retrofit is precise control of height/depth at lower cost than full three-axis control. The company is launching a three-axis CNC control at IMTS 98. However, current two-axis units will be upgradable to three-axis control.
Owners of old manual milling machines confronted with today's capacity crunch have at least three choices for increasing throughput without buying a new CNC machining center. They can retrofit an existing mill with a CNC control package or a DRO, or they can buy a new manual mill with a CNC retrofit package in place from the outset. MTI reports that a substantial number of MILLSTARs are going onto brand new manual mills.
CNC retrofit packages vary widely in capability, standard features, extras, and cost. Each shop's choice should be dictated by specific requirements including workload and its complexity, volume and lot size, delivery requirements, and availability of capital and skilled labor. It is a good idea to spend no more than you can recover in a year out of increased throughput and labor savings in programming and chipmaking.
http://www.mmsonline.com/articles/0998scan3.html
In function and price, a CNC retrofit for a manual mill fills the gap between a $2,000 digital readout (DRO) retrofit package and a $50,000 to $60,000 two-axis CNC milling center, but increasing capabilities of newer CNC retrofits are narrowing the gap between them and new machines.
For instance, a CNC retrofit control package recently introduced by Mitutoyo/MTI Corporation (Aurora, Illinois) approaches the functionality of a low horsepower CNC milling machine at about one-fifth the cost. Called MILLSTAR, this CNC retrofit package includes a control with Windows 95 compatibility, choice of shop or G-Code program language, advanced geometry calculations, and glass linear scales. According to MTI, it enables a manual mill to turn out low to medium volume work at the same rates as a full CNC milling machine of equal spindle horsepower.
Connectivity to Windows 95 software makes programming user-friendly and intuitive for machine operators, freeing operators up for more complex jobs. This helps shops cope with the skills shortage, especially programmers, and the need for operators to program on their own. Shop and G-Code language, likewise, facilitate programming by operators. Part prints in G-Code can be downloaded directly to create the program, saving time and eliminating another error source.
The company reports that high-precision glass linear scales provide better positioning accuracy than rotary encoders: This is why they are offered as extras on many CNC retrofit packages and built-in controls. The difference becomes especially important on older mills where there may be more play in the table ways. Positioning repeatability of a retrofit CNC control with glass linear scales matches that of the controls on a full CNC milling machine.
This retrofit package includes servo-motors with adequate power to move the table at optimum feed rates for heavy cuts, even on large 5-hp manual mills. Because the CNC part programs will be calling for higher material removal rates than are customary for manual work, under-powered servomotors are likely to hold the operation back.
A DRO-equipped machine provides no such automatic table movement, but rather clear, more readable positional readings. The operator must dial in table feeds and stops, and start each cut as if on a manual mill; there is still a possibility for error.
Advanced geometry calculation saves both programming and running time for complex shapes including angles, radii, and irregular pockets. During programming, the operator inputs the known linear and curved measurements and designates the type of cut. No calculations are necessary on the part of the operator. The machine's geometry calculator computes the unknown measurements and the required tool path. During operation, moreover, complex cuts are made at the same removal rates as simpler cuts. The control "thinks" fast enough to keep the cutter running at full speed. If a shop's work involves a lot of circles, hole patterns, arcs and pockets, the additional programming efficiency of canned cycles may justify a retrofit.
Large memory for routines means that routines can be retrieved and used on another job. The larger the memory, the more routines available for the next job. The MILLSTAR's memory can store hundreds of routines, depending on their length. Similar parts do not have to be reprogrammed; only new dimensions need to be inputted. The system recognizes the part and updates the routine with the new data.
Manual override enables the operator to run a one/off or prototype job as usual. Where there's an applicable routine or subroutine, the operator can pick it up from memory. Where something unique to the part needs to be done, the operator switches to the manual mode, makes the cut, and returns to program mode.
The benefit of thee-axis readout in a two-axis CNC retrofit is precise control of height/depth at lower cost than full three-axis control. The company is launching a three-axis CNC control at IMTS 98. However, current two-axis units will be upgradable to three-axis control.
Owners of old manual milling machines confronted with today's capacity crunch have at least three choices for increasing throughput without buying a new CNC machining center. They can retrofit an existing mill with a CNC control package or a DRO, or they can buy a new manual mill with a CNC retrofit package in place from the outset. MTI reports that a substantial number of MILLSTARs are going onto brand new manual mills.
CNC retrofit packages vary widely in capability, standard features, extras, and cost. Each shop's choice should be dictated by specific requirements including workload and its complexity, volume and lot size, delivery requirements, and availability of capital and skilled labor. It is a good idea to spend no more than you can recover in a year out of increased throughput and labor savings in programming and chipmaking.
http://www.mmsonline.com/articles/0998scan3.html
Lathe retrofit package offers low-cost path to CNC - computer numerical control - Scanning the Horizon
For many shops, the first step into CNC can be difficult. It's not just the apparent complexity of a computer-controlled machine tool that concerns them, it's also the expense. If you've never been there before, putting down such a large sum of money can seem a very large risk. That's why more shops these days are taking their first step into CNC with low-cost retrofit packages. Moreover, as the retrofits continue to improve, veteran CNC shops are finding them to be a cost-effective way to reclaim manual machines that no longer provide the productivity they need.
A good example of this kind of package is the Slant-8 CNC turning attachment from Scan-O-Matic Inc. (Racine, Wisconsin). Equipped with a tool turret and a two-axis slide, the attachment is designed to convert manual lathes to full CNC capability at low capital outlay. The retrofit can be conducted in the field by the builder's own technicians who provide operational training as well.
The durable Meehanite slides are lined with Tetralon to improve slip-stick performance. Mounting bracketss for the control slide are provided for each individual make and model of machine to which it is to be adapted. The brackets are positioned off the rear way of the lathe and are further supported along the bed casting. An automatic lubrication system is also provided with the slide assembly to deliver lubricants to the ballscrews, slide ways, and bearings. The slides are driven by two Fanuc servomotors capable of delivering 52 inch-pounds of torque through two one-inch diameter ballscrews.
Mounted to the X-axis slide is a bidirectional, eight-position tool turret with an octagon tool disk. The turret is available in three different sizes which appropriately span lathes ranging from 12 to 24 inches of swing. The turrets provide coolant distribution for each station and accommodate shank sizes from 3/4 to 1 1/4 inches.
The retrofit package includes a Fanuc O-TC computer numerical control, designed for shop floor programming. The control is designed to help new users of CNC. Step-by-step prompting guides the operator through the procedures of setup, cycling, programming, editing, and complete machine functions and operations. Also, a manual pulse generator (MPG) is provided for high-efficiency manual positioning of the slide. By rotating the MPG handle, the operator can control each axis independently for tool positioning and setup.
Options for the package include a full enclosure and a coolant delivery system. The seven-gallon capacity system includes a 1/2-hp pump capable of generating 30 psi.
http://cnc-info.blogspot.com/search/label/cnc%20retrofit
A good example of this kind of package is the Slant-8 CNC turning attachment from Scan-O-Matic Inc. (Racine, Wisconsin). Equipped with a tool turret and a two-axis slide, the attachment is designed to convert manual lathes to full CNC capability at low capital outlay. The retrofit can be conducted in the field by the builder's own technicians who provide operational training as well.
The durable Meehanite slides are lined with Tetralon to improve slip-stick performance. Mounting bracketss for the control slide are provided for each individual make and model of machine to which it is to be adapted. The brackets are positioned off the rear way of the lathe and are further supported along the bed casting. An automatic lubrication system is also provided with the slide assembly to deliver lubricants to the ballscrews, slide ways, and bearings. The slides are driven by two Fanuc servomotors capable of delivering 52 inch-pounds of torque through two one-inch diameter ballscrews.
Mounted to the X-axis slide is a bidirectional, eight-position tool turret with an octagon tool disk. The turret is available in three different sizes which appropriately span lathes ranging from 12 to 24 inches of swing. The turrets provide coolant distribution for each station and accommodate shank sizes from 3/4 to 1 1/4 inches.
The retrofit package includes a Fanuc O-TC computer numerical control, designed for shop floor programming. The control is designed to help new users of CNC. Step-by-step prompting guides the operator through the procedures of setup, cycling, programming, editing, and complete machine functions and operations. Also, a manual pulse generator (MPG) is provided for high-efficiency manual positioning of the slide. By rotating the MPG handle, the operator can control each axis independently for tool positioning and setup.
Options for the package include a full enclosure and a coolant delivery system. The seven-gallon capacity system includes a 1/2-hp pump capable of generating 30 psi.
http://cnc-info.blogspot.com/search/label/cnc%20retrofit
CNC Retrofit for Knee Mills
The ProtoTrak(R) EDGE is a two-axis CNC retrofit for knee mills which has been designed to give you all the features you need to be productive without all the bells and whistles that make other CNCs complicated.
Sold as a complete kit, which includes: ballscrews, computer, motors and all the hardware. Easy to install, most people can be trained to use the EDGE in two hours or less, the company claims. Ideal CNC for tooling and fixtures, molds, dies, prototypes and many other applications.
http://cnc-info.blogspot.com/search/label/cnc%20retrofit
Sold as a complete kit, which includes: ballscrews, computer, motors and all the hardware. Easy to install, most people can be trained to use the EDGE in two hours or less, the company claims. Ideal CNC for tooling and fixtures, molds, dies, prototypes and many other applications.
http://cnc-info.blogspot.com/search/label/cnc%20retrofit
Retrofit Using Six-Axis DRO Offers Flexibility
Following a retrofit using Heidenhain's (Schaumburg, Illinois) Positip 880 six-axis readout on a partial machine rebuild of a vertical milling/boring machine, UKAEA Fusion Special Purposes Workshop in England is now benefiting from greater flexibility on existing machinery.
The BOKO WF1 vertical milling machine has been a machine shop favorite because of its integrated rotary table, swivelling head and Z-axis capacity from either the head or quill. This translates to four axes of linear movement and two rotary axes.
BOKO WF1
UKAEA Fusion Special Purposes Workshop's BOKO WF1 is more than 20 years old. Following the Positip 880 retrofit, the machine is said to be in “as good as new” condition.
Retrofitting an encoder to the rotary table allows the rotary movement of the table to be shown on the readout, which offers greater positional accuracy and ease of positioning. On the BOKO, however, this usually requires the removal and re-engineering of the underside of the table to accept the encoder. When the Special Purposes Workshop of UKAEA Fusion decided to get some rebuild work and have a new five-axis readout fitted to its 20-year-old machine, Eric Clarke from Promtech Services (Milton Keynes, United Kingdom), Heidenhain's regional retrofit distributor in the United Kingdom, suggested a new approach. This approach incorporates an encoder retrofitted to the end of the rotary table's worm gear, combined with some reworking of the existing worm gear to remove excessive backlash.
“We are now positioning the rotary table to within 5 arcseconds, with backlash of less than 10 arcseconds,” comments Dave Langridge, workshop supervisor at UKAEA. “A recent job involved 40 holes around a flange at a nine-degree pitch angle. Having the angular display on the readout made the job much quicker to produce.” Mr. Langridge described the ability to sum both the head and quill movements into one Z-axis display, which allows either the head or the quill to be used without losing the Z-axis display value, as “fantastic.”
Specializing in R&D work for the fusion research program worldwide, the Special Purposes Workshop provides the machining expertise for the UKAEA (Fusion) Special Techniques Group based at the Culham Science Center near Abingdon. Gordon Harrison is the manager of the Special Purposes Workshop.
“Promtech had previously undertaken two Bridgeport Interact CNC upgrades with Heidenhain controls—both with four-axis capability,” Mr. Harrison says. “This gave us the confidence in its ability to undertake the work on the BOKO that has now returned the machine to ‘as good as new' condition with the retrofit, adding more flexibility in the type of work undertaken on the machine. This helps us to be competitive in bidding for work in our specialist field.”
http://www.mmsonline.com/articles/0305bp3.html
The BOKO WF1 vertical milling machine has been a machine shop favorite because of its integrated rotary table, swivelling head and Z-axis capacity from either the head or quill. This translates to four axes of linear movement and two rotary axes.
BOKO WF1
UKAEA Fusion Special Purposes Workshop's BOKO WF1 is more than 20 years old. Following the Positip 880 retrofit, the machine is said to be in “as good as new” condition.
Retrofitting an encoder to the rotary table allows the rotary movement of the table to be shown on the readout, which offers greater positional accuracy and ease of positioning. On the BOKO, however, this usually requires the removal and re-engineering of the underside of the table to accept the encoder. When the Special Purposes Workshop of UKAEA Fusion decided to get some rebuild work and have a new five-axis readout fitted to its 20-year-old machine, Eric Clarke from Promtech Services (Milton Keynes, United Kingdom), Heidenhain's regional retrofit distributor in the United Kingdom, suggested a new approach. This approach incorporates an encoder retrofitted to the end of the rotary table's worm gear, combined with some reworking of the existing worm gear to remove excessive backlash.
“We are now positioning the rotary table to within 5 arcseconds, with backlash of less than 10 arcseconds,” comments Dave Langridge, workshop supervisor at UKAEA. “A recent job involved 40 holes around a flange at a nine-degree pitch angle. Having the angular display on the readout made the job much quicker to produce.” Mr. Langridge described the ability to sum both the head and quill movements into one Z-axis display, which allows either the head or the quill to be used without losing the Z-axis display value, as “fantastic.”
Specializing in R&D work for the fusion research program worldwide, the Special Purposes Workshop provides the machining expertise for the UKAEA (Fusion) Special Techniques Group based at the Culham Science Center near Abingdon. Gordon Harrison is the manager of the Special Purposes Workshop.
“Promtech had previously undertaken two Bridgeport Interact CNC upgrades with Heidenhain controls—both with four-axis capability,” Mr. Harrison says. “This gave us the confidence in its ability to undertake the work on the BOKO that has now returned the machine to ‘as good as new' condition with the retrofit, adding more flexibility in the type of work undertaken on the machine. This helps us to be competitive in bidding for work in our specialist field.”
http://www.mmsonline.com/articles/0305bp3.html
Faster Milling Of EDM Electrodes With Retrofit CNC Package
Dana Heckendorf of D. Heck Tool LLC (Thompson, Connecticut), a precision moldmaker working out of his garage, wanted to compete with bigger shops that had Computer Numerical Control (CNC) equipment. This led him to consider retrofitting his manual Kent milling machine with a CNC retrofit package. With a Mitutoyo MillStar CNC from Mitutoyo Corp. (Aurora, Illinois), the shop owner can program the shape of a complex EDM electrode in 45 minutes and mill the part in 30 minutes. According to Mr. Heckendorf, the single electrode does the work of a dozen simpler ones that would take most of a day to mill or grind manually.
"Basically, we've boosted electrode throughput more than seven to one and streamlined our EDM die sinking as well," Mr. Heckendorf says. With two-axis CNC, the moldmaker quickly mills the more intricate electrodes he needs to cut mold cavities faster and with a better finish than before. Faster electrode milling and subsequent cavity cutting trimmed delivery time on what was a six-week job by seven days. "With the MillStar, I'm doing very high quality EDM electrodes in far less time," says Mr. Heckendorf.
D. Heck Tool specializes in prototype and small production molds for plastic parts. Much of the tooling produces tiny medical and switch components. The stainless and tool steel mold frames are generally about 8 inches square by 10 inches high. While mold cavities are usually cut by a Hansvedt 201 CNC EDM, the graphite electrodes used to cut the pockets must be milled.
The smallest electrodes used by D. Heck Tool are just 0.010 inch wide. "I could mill them manually," says Mr. Heckendorf, "but electrodes are very time consuming parts to make manually."
When Mr. Heckendorf started his business three years ago, he thought CNC conversion was the smart way to go. "It's hard to sell mold-making services without talking CNC," he says. "The first question they ask you is, `what do you have for CNC equipment?'"
Sophisticated computer control was a new endeavor for the small shop owner. As a lead moldmaker, Mr. Heckendorf had long made molds with a manual finish grinder and knew nothing about CNC programming. However, the milling machine he'd bought had a bolt-on power feed and Mitutoyo digital readout, so he spoke to his MTI representative about a new CNC retrofit package.
About a year ago, he upgraded his milling machine with the Mitutoyo MillStar control package. The expandable two-axis control promised the right capability, given the type of work to be done and the background of the user. "I knew I wanted a two-axis CNC because I had no hands-on experience programming," says Mr. Heckendorf.
Mr. Heckendorf visited surrounding job shops and tried several CNC packages. "The Mitutoyo package was one of the very few to run through Windows 95, which is an easy operating system to learn," he says. "It's also got good graphics and can be programmed in G-code or plain shop language."
In addition, canned cycles automate routine operations such as hole patterns, lines and arcs. More complex jobs are set up through drop-down menus on the 10-inch color screen. Function keys let the user override the automatic control and change feed rates and other parameters on the fly. Mr. Heckendorf was able to use the control after only four hours of instruction.
Precision EDM electrodes for cutting molds are milled to the shape of the finished plastic part. Customers typically supply Mr. Heckendorf with hard copy drawings of their molded parts. Mr. Heckendorf extrapolates electrode dimensions from the drawings allowing for plastic shrinkage, overburn, and other factors.
Most electrode jobs at D. Heck Tools are programmed in conversational mode. Programs stored in the MillStar memory or on disk also give D. Heck Tool repeatability difficult to achieve with manual operation.
The EDM uses the precision electrodes to cut mold contours within 0.0002 inch. Using more complicated electrodes closer to the shape of the finished part burns away more of the mold cavity faster and leaves better quality finishes.
One complex mold for a speedometer/tachometer case previously required 28 different electrodes that were set up and machined manually. By comparison, a similar gage case mold required just 12 electrodes milled under CNC. As a result, the typical six-week job was shortened by seven working days. For D. Heck Tool, the switch to CNC is paying off in shorter mold delivery times and lower costs.
Time saved in setup also means more effective use of the milling machine. Mr. Heckendorf estimates his milling machine actually ran just four days a month in the days of manual setups. Setup occupied the rest of the time. With CNC operation and stored programs, the same machine now makes chips three weeks a month, a great increase.
For a one-man shop in a competitive market, a CNC retrofit package has proven itself a powerful business advantage. "The control allows me to quote five weeks on a job someone else is quoting nine weeks on. That's what my business is built on," he says.
http://www.mmsonline.com/articles/0599bp1.html
"Basically, we've boosted electrode throughput more than seven to one and streamlined our EDM die sinking as well," Mr. Heckendorf says. With two-axis CNC, the moldmaker quickly mills the more intricate electrodes he needs to cut mold cavities faster and with a better finish than before. Faster electrode milling and subsequent cavity cutting trimmed delivery time on what was a six-week job by seven days. "With the MillStar, I'm doing very high quality EDM electrodes in far less time," says Mr. Heckendorf.
D. Heck Tool specializes in prototype and small production molds for plastic parts. Much of the tooling produces tiny medical and switch components. The stainless and tool steel mold frames are generally about 8 inches square by 10 inches high. While mold cavities are usually cut by a Hansvedt 201 CNC EDM, the graphite electrodes used to cut the pockets must be milled.
The smallest electrodes used by D. Heck Tool are just 0.010 inch wide. "I could mill them manually," says Mr. Heckendorf, "but electrodes are very time consuming parts to make manually."
When Mr. Heckendorf started his business three years ago, he thought CNC conversion was the smart way to go. "It's hard to sell mold-making services without talking CNC," he says. "The first question they ask you is, `what do you have for CNC equipment?'"
Sophisticated computer control was a new endeavor for the small shop owner. As a lead moldmaker, Mr. Heckendorf had long made molds with a manual finish grinder and knew nothing about CNC programming. However, the milling machine he'd bought had a bolt-on power feed and Mitutoyo digital readout, so he spoke to his MTI representative about a new CNC retrofit package.
About a year ago, he upgraded his milling machine with the Mitutoyo MillStar control package. The expandable two-axis control promised the right capability, given the type of work to be done and the background of the user. "I knew I wanted a two-axis CNC because I had no hands-on experience programming," says Mr. Heckendorf.
Mr. Heckendorf visited surrounding job shops and tried several CNC packages. "The Mitutoyo package was one of the very few to run through Windows 95, which is an easy operating system to learn," he says. "It's also got good graphics and can be programmed in G-code or plain shop language."
In addition, canned cycles automate routine operations such as hole patterns, lines and arcs. More complex jobs are set up through drop-down menus on the 10-inch color screen. Function keys let the user override the automatic control and change feed rates and other parameters on the fly. Mr. Heckendorf was able to use the control after only four hours of instruction.
Precision EDM electrodes for cutting molds are milled to the shape of the finished plastic part. Customers typically supply Mr. Heckendorf with hard copy drawings of their molded parts. Mr. Heckendorf extrapolates electrode dimensions from the drawings allowing for plastic shrinkage, overburn, and other factors.
Most electrode jobs at D. Heck Tools are programmed in conversational mode. Programs stored in the MillStar memory or on disk also give D. Heck Tool repeatability difficult to achieve with manual operation.
The EDM uses the precision electrodes to cut mold contours within 0.0002 inch. Using more complicated electrodes closer to the shape of the finished part burns away more of the mold cavity faster and leaves better quality finishes.
One complex mold for a speedometer/tachometer case previously required 28 different electrodes that were set up and machined manually. By comparison, a similar gage case mold required just 12 electrodes milled under CNC. As a result, the typical six-week job was shortened by seven working days. For D. Heck Tool, the switch to CNC is paying off in shorter mold delivery times and lower costs.
Time saved in setup also means more effective use of the milling machine. Mr. Heckendorf estimates his milling machine actually ran just four days a month in the days of manual setups. Setup occupied the rest of the time. With CNC operation and stored programs, the same machine now makes chips three weeks a month, a great increase.
For a one-man shop in a competitive market, a CNC retrofit package has proven itself a powerful business advantage. "The control allows me to quote five weeks on a job someone else is quoting nine weeks on. That's what my business is built on," he says.
http://www.mmsonline.com/articles/0599bp1.html
Profile follower burner can be CNC retrofitted
For those fabricators looking to move away from employing sub-contract plate profiling services, a co-ordinate gas cutting machine is being offered at a low 'entry level' price
For those fabricators looking to move away from employing sub-contract plate profiling services, the Ultrarex UXB co-ordinate gas cutting machine is being offered at 'entry level prices - an economical way of bringing plate profiling in-house. Esab Automation, Andover, said the machine has low capital investment cost, low maintenance needs, high speed cutting and precise guiding accuracy.
It is offered with photo-electric tracing or can be fitted with CNC.
Capacity is for cutting metals from 3mm to 200mm in thickness, depending upon the model purchased.
The tracer control system copies outlines or silhouettes on a 1:1 basis.
The drawings are not needed for linear cutting or rectangular bevelling of plates.
Up to four oxy-fuel gas torches can be fitted.
http://www.manufacturingtalk.com/news/eab/eab101.html
For those fabricators looking to move away from employing sub-contract plate profiling services, the Ultrarex UXB co-ordinate gas cutting machine is being offered at 'entry level prices - an economical way of bringing plate profiling in-house. Esab Automation, Andover, said the machine has low capital investment cost, low maintenance needs, high speed cutting and precise guiding accuracy.
It is offered with photo-electric tracing or can be fitted with CNC.
Capacity is for cutting metals from 3mm to 200mm in thickness, depending upon the model purchased.
The tracer control system copies outlines or silhouettes on a 1:1 basis.
The drawings are not needed for linear cutting or rectangular bevelling of plates.
Up to four oxy-fuel gas torches can be fitted.
http://www.manufacturingtalk.com/news/eab/eab101.html
Thursday, December 13, 2007
CNC Retrofits Answer Scarcity Of Manual Machinists
By retrofitting CNCs to three manual Hardinge lathes, Mansfield Screw Machine Products Co. (Lexington, Ohio) increased the throughput on these machines by about 15 percent. That's the estimate of shop floor supervisor Keith Reed, who performed the retrofits, and now writes the machines' NC programs. But improving performance was not the main reason for the retrofits; the machines were always productive. Instead, retrofitting was a way to keep them productive, even without an experienced machinist in control. That became important when one of the company's best Hardinge operators retired. "We just can't find machinists with those skills anymore," Mr. Reed says. So the company purchased retrofit kits from OmniTurn (Farmingdale, New York), a supplier offering these kits for a variety of Hardinge lathes.
Now, the upgraded machines run more productively. The underlying lathes were all over ten years old. With the newer, more rigid axis drives, the machines cut accurately at higher speeds and feedrates than the previous drives would permit. At the same time, there is now far less time lost to manual toolchanges. The retrofit kit includes a gang tooling system allowing the machine to employ several tools in one cycle, like almost any CNC lathe. And because the machines are now NC, they deliver these performance gains regardless of the skill level of the operator.
The retrofitted machines also improve the efficiency of the shop's process overall. A part featuring a surface finish requirement of 15 microinches illustrates this. Using the manual machines, the shop couldn't hold this finish consistently, so bench work was needed. But since the retrofit, "those parts come off of the lathes smooth enough to ship," Mr. Reed says. Benching has been eliminated.
For other parts, savings come from eliminating expensive time on more costly machines. Like many automatic machining contractors, Mansfield Screw Machine uses CNC equipment for secondary operations. However, to provide customers with just-in-time delivery, this shop routinely runs blanks in large volumes on the automatic machines, then performs the CNC machining in small batches, to complete the parts only as the customer needs them. But now there is an alternative to higher-end CNC equipment for some of this work. The retrofitted lathes have the capability to perform many of the same complex machining routines as a full CNC lathe, including single-point threading.
The retrofit kits came largely pre-assembled. Working with an electrician, Mr. Reed performed each retrofit in about a day and a half. He writes the NC programs for these machines on a PC at his desk, using software which also came with the kit. Once the program is written and the correct tools are loaded, he says, the operator's only role is to load each workpiece, start the cycle, and check parts against the specification.
This simplicity, combined with the efficiency gains, has convinced Mr. Reed that CNC retrofitting was the right investment to make. At least one other manual Hardinge lathe operator in the shop is nearing retirement, he says. "And when he goes, I think we'll retrofit two more machines.
http://www.productionmachining.com/articles/mms014.html
Now, the upgraded machines run more productively. The underlying lathes were all over ten years old. With the newer, more rigid axis drives, the machines cut accurately at higher speeds and feedrates than the previous drives would permit. At the same time, there is now far less time lost to manual toolchanges. The retrofit kit includes a gang tooling system allowing the machine to employ several tools in one cycle, like almost any CNC lathe. And because the machines are now NC, they deliver these performance gains regardless of the skill level of the operator.
The retrofitted machines also improve the efficiency of the shop's process overall. A part featuring a surface finish requirement of 15 microinches illustrates this. Using the manual machines, the shop couldn't hold this finish consistently, so bench work was needed. But since the retrofit, "those parts come off of the lathes smooth enough to ship," Mr. Reed says. Benching has been eliminated.
For other parts, savings come from eliminating expensive time on more costly machines. Like many automatic machining contractors, Mansfield Screw Machine uses CNC equipment for secondary operations. However, to provide customers with just-in-time delivery, this shop routinely runs blanks in large volumes on the automatic machines, then performs the CNC machining in small batches, to complete the parts only as the customer needs them. But now there is an alternative to higher-end CNC equipment for some of this work. The retrofitted lathes have the capability to perform many of the same complex machining routines as a full CNC lathe, including single-point threading.
The retrofit kits came largely pre-assembled. Working with an electrician, Mr. Reed performed each retrofit in about a day and a half. He writes the NC programs for these machines on a PC at his desk, using software which also came with the kit. Once the program is written and the correct tools are loaded, he says, the operator's only role is to load each workpiece, start the cycle, and check parts against the specification.
This simplicity, combined with the efficiency gains, has convinced Mr. Reed that CNC retrofitting was the right investment to make. At least one other manual Hardinge lathe operator in the shop is nearing retirement, he says. "And when he goes, I think we'll retrofit two more machines.
http://www.productionmachining.com/articles/mms014.html
Choosing A Retrofit CNC
Intel co-founder Gordon Moore predicted the growth rate which now bears his name. Moore's Law suggests that the state of the art in computer processing power will double every 18 months.
This exponential pace of development affects computers everywhere. But on the floor of a machine shop, the impact is particularly striking. Here, rapidly evolving computer numerical controls (CNCs) meet machine tools whose basic structures have changed little since before these controls were introduced. The lopsided rate of change often means that the machine tool remains mechanically sound and serviceable long after its control has been eclipsed by newer models. There is no Moore's Law for the iron. As a result, some shops find themselves saddled with inoperative machines, idled only because the control is obsolete and replacement components can no longer be found. Still more shops use CNC machines whose mechanical structures could be employed much more effectively if only the controls had access to the power and features of more recently developed models. In each of these cases, one option is to scrap the old machine in favor of an entirely new one, with its own new control. However, another option is to retain the mechanical structure, and retrofit a replacement CNC.
Conserving the iron in this way is not always the more economical choice. CNCs are not simply plug-in devices. Any combination of CNC and machine tool is in fact a carefully engineered system, and the work of integrating this system is typically more expensive than the CNC itself. A new, mass-produced machine tool carries almost none of this engineering cost. The OEM spreads the one-time expense for system integration across the entire run of that machine. That option is not available for most retrofit jobs, where the "production run" typically amounts to just one unit.
Because of this integration expense and its effect on overall cost, many shops don't even consider CNC retrofitting. And perhaps rightly so; retrofitting instead of buying new is still cost-effective only for a minority of machine tools. However, retrofitting today may be worth a second look. The economics have changed significantly, even in just the last five years. There is an expanded range of choices among retrofit CNCs, and this has produced an expanded range of machine tools for which retrofitting now makes sense.
CNC
Today, two things can be said of the CNC retrofit market:
1. Machines that were once too old to justify a CNC retrofit now make excellent candidates.
2. Machines that were once too new to justify a CNC retrofit also make excellent candidates.
In the case of the older machines, today's controls are more forgiving of ballscrew error, backlash, way friction and other symptoms of mechanical wear. By compensating electronically for these errors, the right CNC alone may be enough to return a worn machine to like-new precision. Thus, the retrofit may not have to include costs for replacement bearings, ballscrews, or gearing, or for scraping the ways or other mechanical service.
In the case of the newer machines, recent improvements in control technology can make a more recent or more specialized CNC far more productive for the machine than its standard control unit, even when that older control is still functioning well. The retrofit CNC may offer important capabilities the standard one does not, including:
* High-feed rate, high-accuracy machining, particularly during contour milling. This can be the result of features including look-ahead, faster servo updates, and curve interpolation. It can also be the result of expanded program storage capacity or faster data transmission across a network.
* The ability to run third-party PC software directly on the control, for functions like shopfloor programming, or updating machining offsets based on trends in SPC data.
* Data exchange with networked PCs. Fast, two-way data transfer not only enables the CNC to obtain a part program quickly from a remote source, but can also let a remote PC monitor and react to the machine's status.
CNC Retrofit
Most of these benefits are products of increased computing power (a la Moore's Law), which has expanded the choices available to control buyers by allowing CNCs to deliver more sophisticated and specialized functions. However, there is another factor spurring CNC development. Some features, like memory and networking improvements, have grown from the low-cost platform now available thanks to the spread of non-proprietary, commodity PC hardware. And this PC hardware has also produced more choices, as different CNC vendors apply the hardware in different ways.
If you are shopping for a replacement control, should you choose one that is in some way PC-based or PC-interfaced? Today there is a good chance the answer is yes.
But does this mean you should favor the control that includes the most off-the-shelf PC hardware? Not necessarily.
No, the best way to choose a replacement CNC in today's market is to take advantage of the range of choice now available to find the right control for the application. This will mean selecting the one that best delivers the features—including price—which that application demands. However, it will also mean finding the most appropriate mix of proprietary and non-proprietary hardware.
Not "Either/Or"
There are varying degrees to which a control can employ widely available hardware. Thus "proprietary" and "non-proprietary" are not either/or conditions. They can better be imagined as opposite directions along a common axis.
At the extreme "proprietary" end of this axis would be the CNC which was essentially the only type available ten years ago. This control has hardware built or specified entirely by the manufacturer, and at best offers only a slow serial interface for (one-way) data exchange.
PC-based Control
PC-based Control
PC-based Control
PC-based Control
A PC front end can bring networking, memory, and third-party software benefits to a control system that still offers the advantages of single-source hardware. Illustration courtesy GE Fanuc.
Today, at or near the opposite end of this axis would be a control like the one offered by Manufacturing Data Systems, Inc. (MDSI; Ann Arbor, Michigan). Designed to permit a low-cost retrofit, or low-cost entry into CNC networking, MDSI's control consists of PC software running entirely on non-proprietary hardware. Its hardware requirements include a touch-screen monitor, and interface cards for encoders, servos, and I/O, all of which can be purchased from any of a variety of vendors. It has no motion control card. Instead, it closes the servo loop via algorithms in the software. For this reason, it requires just a digital-to-analog converter to interface with the servomotors.
Between these two extremes would be a CNC like the one offered by Creative Technology Corporation (Arlington Heights, Illinois). This is a control optimized to serve the needs of shops interested in milling intricate contoured forms at high feed rates. These include makers of molds, dies, and prototype parts. Accordingly, this PC-based control employs one particular vendor's motion control card, chosen for its fast servo cycle time, among other features. While this single-source card technically qualifies as proprietary hardware, the overall control is not as proprietary as the "extreme" proprietary control cited above. The customer does not have to return to the control vendor for replacement parts or upgrades. The maker of the motion control card has licensed the right to produce and market its hardware to a variety of competing manufacturers, and the rest of the control consists of generic PC hardware that is widely available.
This leads to another frequently used CNC term necessary to carry this discussion further. That term is open. (As in, "open architecture.") It is used together with "PC-based" so often that the two may appear identical in meaning. However, while the definitions may overlap, these two terms describe very different ideas.
In fact, different CNC vendors embrace any of at least two definitions for an open control. Some define this as a control using off-the-shelf hardware, which therefore (in theory) can be maintained and upgraded inexpensively, without the vendor's involvement.
Other vendors view an open control as one that can easily share information across a network. This information includes both input, like an NC program, and output, like machine status data.
These two definitions of open don't necessarily go together. A CNC can be open to hardware without being open to a network, and a CNC favoring proprietary hardware can be constructed to interface with a network freely. In the retrofit world, one example of this second case comes from Memex Electronics (Burlington, Ontario, Canada), which offers retrofit boards allowing older, "closed" Fanuc CNCs to connect directly to a PC network.
However, a more general example of a system delivering network openness to a proprietary CNC comes from yet another approach to a control employing PC hardware. This is an approach offered by GE Fanuc (Charlottesville, Virginia) and Siemens (Elk Grove Village, Illinois), among others. These companies place a PC front end on a control system in which all hardware comes from a single source—from pushbuttons through servomotors. This is the PC-enabled control system that most resembles the traditional, proprietary CNC. And for this reason, it may be the right approach for many applications.
Costs And Benefits
The determining factor, according to both GE Fanuc and Siemens, is the productive value of the machine tool.
For example, the purpose of a CNC retrofit may be to give new life to a machine that is non-critical and/or relatively inexpensive. The machine may be one that sits idle because needed hardware for its dated control can no longer be found, or because the control itself limits the machine's capabilities or makes it difficult to use. The machine may also be a low-cost vertical machining center that a different control might make faster or more accurate. In any of these cases, the shop will likely see the productivity gain from a retrofit as "gravy"—extra machining capacity acquired for significantly less than the cost of buying a new machine. If so, then the shop has to minimize the cost of the retrofit to make the upgrade cost-effective. This means finding the most inexpensive control that is feasible, and this may well mean choosing one that maximizes its use of widely available electronics.
But as the value of the machine tool increases, the outlook may change. There is no precise dollar value at which a machine can no longer be said to be "low cost." However, somewhere on an ascending scale of the machine's replacement cost—whether this is $200,000, $300,000, $500,000—there comes a point where the machine is valuable enough, and machine downtime is costly enough, that a compelling case can be made for proprietary hardware. With a single-source control system, the shop has the support of just one vendor behind all of the electronics that keep this costly machine productive.
Siemens marketing manager Peter Herweck adds another consideration when evaluating a largely non-proprietary control versus a largely proprietary one. A common selling point of the former option is its promise to let the buyer upgrade the control without the vendor's involvement, just as one would upgrade an office PC. The more proprietary controls do not promise this same freedom. However, Mr. Herweck cautions potential CNC buyers to weigh how valuable this promise really is. Questions he would have them ask include: "How often will I really want to upgrade this control? Can I truly perform this upgrade more economically in-house? And if so, am I willing to trade the support advantages of a single-source control to realize these savings?"
As for the other selling points of a non-proprietary control, he notes that a more proprietary control can also deliver these. He lists them: "Expanded part program storage; freedom to run third-party software; and data I/O, whether this is networking, zip or floppy drive, or a PCMCIA slot. A single-source control with a PC front end can provide all of these advantages," he says. And while the single-source system adds the support benefits to this, he notes that it also delivers these benefits not through general-purpose hardware, but via hardware that has been engineered around one function—reliably and repeatably controlling a machine tool.
The argument, in other words, is that you get what you pay for. However, today's market offers a corollary to this: If you don't want to pay for the advantages of a proprietary system, you no longer have to. Both of the less-proprietary systems mentioned in this article illustrate this, albeit in different ways. Using MDSI's control, shops have not only "resurrected" machines that were once too low-cost to justify retrofitting, but in some cases have realized performance benefits—including accuracy at higher feed rates—which the original control never permitted. And the specialized focus of the Creative Technology control has allowed die-mold shops to devote the price of a CNC retrofit to maximizing the control features most beneficial to the die-mold milling application. In fact, the control's benefits have proven profitable enough in this application that some die-mold shops have not waited for obsolescence, but instead have retrofitted the control to practically new vertical machining centers.
Upgrades like these illustrate how CNC technology has evolved rapidly in recent years. As to where this evolution might lead, the answer may lie no farther (from me) than my own fingertips.
Look To The Office
I am writing this article on a word processor. By this I mean a generic PC running word processing software. One generation ago, another person doing my job would have used a typewriter. A little later, that same editor might have used one of the early versions of the word processor. This first word processor was not an "open" system, but instead a dedicated machine. Its built-in logic could be upgraded only through a costly hardware replacement.
CNC vendors seem to agree: The development of technology for putting ideas on paper provides some insight into how CNCs will continue to develop. The two technologies could be said to have followed parallel courses already. The manual typewriter, for example, equates to a manual machine tool. In both cases, the operator pushed levers that directly corresponded to what he wanted the machine to do. Later, operators of both types of equipment acquired the ability to input commands all at once, and have the machine execute them in sequence later. The typist moved up to a word processor, and the manual machinist moved up to NC.
Today, the difference between these two technologies is that the word processor is now a software-only product that has made the jump completely away from proprietary hardware. The word processor today can run on any number of generic PCs, can have its documents printed on any commonly used printer, and can even interact with a variety of printers and other peripherals sharing a common network. Can we assume from this that someday we will see software-only CNCs, which run on any computer, and control any of a variety of machine tools without the need for costly system integration?
In short, will everything needed to install a CNC one day come in a shrink-wrapped box?
Probably yes. At least, that's what a variety of successful CNC vendors believe. However, one can only guess how soon that day will come. And it may not come for some time.
There is another piece of office equipment that offers a loose parallel to machine tool technology. This is the CAD plotter—the one used to make hard-copy prints of CAD drawings. This device looks a lot like a machining center. It has a tool (the pen) and a toolchanger (to switch to other pens). It interpolates in linear axes to draw complex lines. And it even has material handling, for loading the next sheet of paper.
With a machine tool, there is a difference of degree; the machining center requires more complex control functions than the plotter. However, the machine tool in service today is also different in a fundamental way: It was never designed with the intention that a plug-in PC would be running it.
That may change. The day may come when machine tool builders see their iron as PC peripherals similar to printers or plotters. However, because that day is not here yet, any shop looking at CNCs right now must give consideration to the different ways generic PC hardware is applied right now.
This is the nature of CNC shopping today. Exactly which strengths the control should deliver, and just how much non-proprietary hardware is right for the application, are choices which today's CNC market makes freely available to the consumer.
The vendors mentioned in this article can all provide more information on the CNC technology they offer.
http://www.mmsonline.com/articles/059803.html
This exponential pace of development affects computers everywhere. But on the floor of a machine shop, the impact is particularly striking. Here, rapidly evolving computer numerical controls (CNCs) meet machine tools whose basic structures have changed little since before these controls were introduced. The lopsided rate of change often means that the machine tool remains mechanically sound and serviceable long after its control has been eclipsed by newer models. There is no Moore's Law for the iron. As a result, some shops find themselves saddled with inoperative machines, idled only because the control is obsolete and replacement components can no longer be found. Still more shops use CNC machines whose mechanical structures could be employed much more effectively if only the controls had access to the power and features of more recently developed models. In each of these cases, one option is to scrap the old machine in favor of an entirely new one, with its own new control. However, another option is to retain the mechanical structure, and retrofit a replacement CNC.
Conserving the iron in this way is not always the more economical choice. CNCs are not simply plug-in devices. Any combination of CNC and machine tool is in fact a carefully engineered system, and the work of integrating this system is typically more expensive than the CNC itself. A new, mass-produced machine tool carries almost none of this engineering cost. The OEM spreads the one-time expense for system integration across the entire run of that machine. That option is not available for most retrofit jobs, where the "production run" typically amounts to just one unit.
Because of this integration expense and its effect on overall cost, many shops don't even consider CNC retrofitting. And perhaps rightly so; retrofitting instead of buying new is still cost-effective only for a minority of machine tools. However, retrofitting today may be worth a second look. The economics have changed significantly, even in just the last five years. There is an expanded range of choices among retrofit CNCs, and this has produced an expanded range of machine tools for which retrofitting now makes sense.
CNC
Today, two things can be said of the CNC retrofit market:
1. Machines that were once too old to justify a CNC retrofit now make excellent candidates.
2. Machines that were once too new to justify a CNC retrofit also make excellent candidates.
In the case of the older machines, today's controls are more forgiving of ballscrew error, backlash, way friction and other symptoms of mechanical wear. By compensating electronically for these errors, the right CNC alone may be enough to return a worn machine to like-new precision. Thus, the retrofit may not have to include costs for replacement bearings, ballscrews, or gearing, or for scraping the ways or other mechanical service.
In the case of the newer machines, recent improvements in control technology can make a more recent or more specialized CNC far more productive for the machine than its standard control unit, even when that older control is still functioning well. The retrofit CNC may offer important capabilities the standard one does not, including:
* High-feed rate, high-accuracy machining, particularly during contour milling. This can be the result of features including look-ahead, faster servo updates, and curve interpolation. It can also be the result of expanded program storage capacity or faster data transmission across a network.
* The ability to run third-party PC software directly on the control, for functions like shopfloor programming, or updating machining offsets based on trends in SPC data.
* Data exchange with networked PCs. Fast, two-way data transfer not only enables the CNC to obtain a part program quickly from a remote source, but can also let a remote PC monitor and react to the machine's status.
CNC Retrofit
Most of these benefits are products of increased computing power (a la Moore's Law), which has expanded the choices available to control buyers by allowing CNCs to deliver more sophisticated and specialized functions. However, there is another factor spurring CNC development. Some features, like memory and networking improvements, have grown from the low-cost platform now available thanks to the spread of non-proprietary, commodity PC hardware. And this PC hardware has also produced more choices, as different CNC vendors apply the hardware in different ways.
If you are shopping for a replacement control, should you choose one that is in some way PC-based or PC-interfaced? Today there is a good chance the answer is yes.
But does this mean you should favor the control that includes the most off-the-shelf PC hardware? Not necessarily.
No, the best way to choose a replacement CNC in today's market is to take advantage of the range of choice now available to find the right control for the application. This will mean selecting the one that best delivers the features—including price—which that application demands. However, it will also mean finding the most appropriate mix of proprietary and non-proprietary hardware.
Not "Either/Or"
There are varying degrees to which a control can employ widely available hardware. Thus "proprietary" and "non-proprietary" are not either/or conditions. They can better be imagined as opposite directions along a common axis.
At the extreme "proprietary" end of this axis would be the CNC which was essentially the only type available ten years ago. This control has hardware built or specified entirely by the manufacturer, and at best offers only a slow serial interface for (one-way) data exchange.
PC-based Control
PC-based Control
PC-based Control
PC-based Control
A PC front end can bring networking, memory, and third-party software benefits to a control system that still offers the advantages of single-source hardware. Illustration courtesy GE Fanuc.
Today, at or near the opposite end of this axis would be a control like the one offered by Manufacturing Data Systems, Inc. (MDSI; Ann Arbor, Michigan). Designed to permit a low-cost retrofit, or low-cost entry into CNC networking, MDSI's control consists of PC software running entirely on non-proprietary hardware. Its hardware requirements include a touch-screen monitor, and interface cards for encoders, servos, and I/O, all of which can be purchased from any of a variety of vendors. It has no motion control card. Instead, it closes the servo loop via algorithms in the software. For this reason, it requires just a digital-to-analog converter to interface with the servomotors.
Between these two extremes would be a CNC like the one offered by Creative Technology Corporation (Arlington Heights, Illinois). This is a control optimized to serve the needs of shops interested in milling intricate contoured forms at high feed rates. These include makers of molds, dies, and prototype parts. Accordingly, this PC-based control employs one particular vendor's motion control card, chosen for its fast servo cycle time, among other features. While this single-source card technically qualifies as proprietary hardware, the overall control is not as proprietary as the "extreme" proprietary control cited above. The customer does not have to return to the control vendor for replacement parts or upgrades. The maker of the motion control card has licensed the right to produce and market its hardware to a variety of competing manufacturers, and the rest of the control consists of generic PC hardware that is widely available.
This leads to another frequently used CNC term necessary to carry this discussion further. That term is open. (As in, "open architecture.") It is used together with "PC-based" so often that the two may appear identical in meaning. However, while the definitions may overlap, these two terms describe very different ideas.
In fact, different CNC vendors embrace any of at least two definitions for an open control. Some define this as a control using off-the-shelf hardware, which therefore (in theory) can be maintained and upgraded inexpensively, without the vendor's involvement.
Other vendors view an open control as one that can easily share information across a network. This information includes both input, like an NC program, and output, like machine status data.
These two definitions of open don't necessarily go together. A CNC can be open to hardware without being open to a network, and a CNC favoring proprietary hardware can be constructed to interface with a network freely. In the retrofit world, one example of this second case comes from Memex Electronics (Burlington, Ontario, Canada), which offers retrofit boards allowing older, "closed" Fanuc CNCs to connect directly to a PC network.
However, a more general example of a system delivering network openness to a proprietary CNC comes from yet another approach to a control employing PC hardware. This is an approach offered by GE Fanuc (Charlottesville, Virginia) and Siemens (Elk Grove Village, Illinois), among others. These companies place a PC front end on a control system in which all hardware comes from a single source—from pushbuttons through servomotors. This is the PC-enabled control system that most resembles the traditional, proprietary CNC. And for this reason, it may be the right approach for many applications.
Costs And Benefits
The determining factor, according to both GE Fanuc and Siemens, is the productive value of the machine tool.
For example, the purpose of a CNC retrofit may be to give new life to a machine that is non-critical and/or relatively inexpensive. The machine may be one that sits idle because needed hardware for its dated control can no longer be found, or because the control itself limits the machine's capabilities or makes it difficult to use. The machine may also be a low-cost vertical machining center that a different control might make faster or more accurate. In any of these cases, the shop will likely see the productivity gain from a retrofit as "gravy"—extra machining capacity acquired for significantly less than the cost of buying a new machine. If so, then the shop has to minimize the cost of the retrofit to make the upgrade cost-effective. This means finding the most inexpensive control that is feasible, and this may well mean choosing one that maximizes its use of widely available electronics.
But as the value of the machine tool increases, the outlook may change. There is no precise dollar value at which a machine can no longer be said to be "low cost." However, somewhere on an ascending scale of the machine's replacement cost—whether this is $200,000, $300,000, $500,000—there comes a point where the machine is valuable enough, and machine downtime is costly enough, that a compelling case can be made for proprietary hardware. With a single-source control system, the shop has the support of just one vendor behind all of the electronics that keep this costly machine productive.
Siemens marketing manager Peter Herweck adds another consideration when evaluating a largely non-proprietary control versus a largely proprietary one. A common selling point of the former option is its promise to let the buyer upgrade the control without the vendor's involvement, just as one would upgrade an office PC. The more proprietary controls do not promise this same freedom. However, Mr. Herweck cautions potential CNC buyers to weigh how valuable this promise really is. Questions he would have them ask include: "How often will I really want to upgrade this control? Can I truly perform this upgrade more economically in-house? And if so, am I willing to trade the support advantages of a single-source control to realize these savings?"
As for the other selling points of a non-proprietary control, he notes that a more proprietary control can also deliver these. He lists them: "Expanded part program storage; freedom to run third-party software; and data I/O, whether this is networking, zip or floppy drive, or a PCMCIA slot. A single-source control with a PC front end can provide all of these advantages," he says. And while the single-source system adds the support benefits to this, he notes that it also delivers these benefits not through general-purpose hardware, but via hardware that has been engineered around one function—reliably and repeatably controlling a machine tool.
The argument, in other words, is that you get what you pay for. However, today's market offers a corollary to this: If you don't want to pay for the advantages of a proprietary system, you no longer have to. Both of the less-proprietary systems mentioned in this article illustrate this, albeit in different ways. Using MDSI's control, shops have not only "resurrected" machines that were once too low-cost to justify retrofitting, but in some cases have realized performance benefits—including accuracy at higher feed rates—which the original control never permitted. And the specialized focus of the Creative Technology control has allowed die-mold shops to devote the price of a CNC retrofit to maximizing the control features most beneficial to the die-mold milling application. In fact, the control's benefits have proven profitable enough in this application that some die-mold shops have not waited for obsolescence, but instead have retrofitted the control to practically new vertical machining centers.
Upgrades like these illustrate how CNC technology has evolved rapidly in recent years. As to where this evolution might lead, the answer may lie no farther (from me) than my own fingertips.
Look To The Office
I am writing this article on a word processor. By this I mean a generic PC running word processing software. One generation ago, another person doing my job would have used a typewriter. A little later, that same editor might have used one of the early versions of the word processor. This first word processor was not an "open" system, but instead a dedicated machine. Its built-in logic could be upgraded only through a costly hardware replacement.
CNC vendors seem to agree: The development of technology for putting ideas on paper provides some insight into how CNCs will continue to develop. The two technologies could be said to have followed parallel courses already. The manual typewriter, for example, equates to a manual machine tool. In both cases, the operator pushed levers that directly corresponded to what he wanted the machine to do. Later, operators of both types of equipment acquired the ability to input commands all at once, and have the machine execute them in sequence later. The typist moved up to a word processor, and the manual machinist moved up to NC.
Today, the difference between these two technologies is that the word processor is now a software-only product that has made the jump completely away from proprietary hardware. The word processor today can run on any number of generic PCs, can have its documents printed on any commonly used printer, and can even interact with a variety of printers and other peripherals sharing a common network. Can we assume from this that someday we will see software-only CNCs, which run on any computer, and control any of a variety of machine tools without the need for costly system integration?
In short, will everything needed to install a CNC one day come in a shrink-wrapped box?
Probably yes. At least, that's what a variety of successful CNC vendors believe. However, one can only guess how soon that day will come. And it may not come for some time.
There is another piece of office equipment that offers a loose parallel to machine tool technology. This is the CAD plotter—the one used to make hard-copy prints of CAD drawings. This device looks a lot like a machining center. It has a tool (the pen) and a toolchanger (to switch to other pens). It interpolates in linear axes to draw complex lines. And it even has material handling, for loading the next sheet of paper.
With a machine tool, there is a difference of degree; the machining center requires more complex control functions than the plotter. However, the machine tool in service today is also different in a fundamental way: It was never designed with the intention that a plug-in PC would be running it.
That may change. The day may come when machine tool builders see their iron as PC peripherals similar to printers or plotters. However, because that day is not here yet, any shop looking at CNCs right now must give consideration to the different ways generic PC hardware is applied right now.
This is the nature of CNC shopping today. Exactly which strengths the control should deliver, and just how much non-proprietary hardware is right for the application, are choices which today's CNC market makes freely available to the consumer.
The vendors mentioned in this article can all provide more information on the CNC technology they offer.
http://www.mmsonline.com/articles/059803.html
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