A NEW HORIZON IN HIGH SPEED CUTTING FOR MOLD AND MEDICAL
What once seemed to be a far-off machining goal for mold and die work and medical parts is now a reality based on the advancement of new technologies.
The challenge has always been threefold for mold and die work and medical parts machining, especially those medical parts in the highly competitive and material cost-intensive orthopedic markets: all of the programming, setup and machining time must be costed against a very short or even one-off run.
Worse, if the material is very expensive that means additional care is critical to minimize or eliminate scrap. The strategy for milling medical implants and even routine mold cavity inserts would often involve building an inventory of near-net shapes. Again, in the case of high-cost materials, this strategy is simply impractical.
Machine builders – and especially software providers – have long struggled with this scenario. Their potential solutions took two tracks.
For a decade or so, the rush to higher spindle speeds was all the fashion, similar to the ipm “contest” seen among the EDM builders of the past, as spindle technology was and remains a very popular technique for manufacturing mold cavity inserts and medical implants. Likewise, the translation software for CAD to CAM to post-processor to CNC ran in various directions for some time.
Now high speed cutting (HSC) has evolved into a highly sophisticated combination of spindle speed coupled with resolution inside linear motor, drive and encoder packages, while another trend has emerged on the software side.
Whether you work with high-precision mold cavity inserts, hip joints or dental implants, it is now possible to dramatically reduce the work steps involved to get the CAD drawing or even the data from a CAT/CT scan file into the CNC machine tool and produce a single part from a standard block of material.
New translation software on the CAM/PP/NC level is now on the market from several sources to permit the fast and accurate generation of a cutting path on the CNC, whether the cutting is done on a conventional HSC machine tool or even via some of the alternative machining methods, such as the ultrasonic technique that is gaining traction in the composites market.
For machining complex, non-linear surfaces, from the straight geometric designs of mold cavities to the totally non-uniform geometry of the human body, the translation software can be greatly assisted by the newer simulation software found on the market.
Ideally – and this is also a reality now – when the complete execution of the machining cycle can be accomplished offline in real time, the estimating is easier and far more precise, which results in closer approximations to true costs and more profitable work for your shop.
The CNC platforms needed to make the above scenario actually happen in your shop are now available. When seeking out the right solution it is most critical to find technology where the simultaneous measuring and calibration of all machine multi-axis kinematics for jerk limitation, feed forward control, look-ahead, pilot control and tool tip orientation are performed in process.
Adjustments can be made during the cycle to accommodate even slight variances in the material. Remember that these are not “someday” wishes for shops doing this type of work . . . they are realities that are now on the market.
Just as the jump from three-axis to five-axis machining seemed intimidating a few years ago, another notion might appear beyond your reach: that of going from a CT scan to a manufactured part in a seamless fashion with predictable CNC control on an HSC machine attaining a surface finish to Ra 0.2 mm.
As you seek this type of work for your shop, the new CNC technology on the market makes it more affordable and even more attractive than ever to enter these market sectors and make money. Now there’s a refreshing idea!
About the Author: Randy Pearson is the sales support manager for U.S. dealers and OEMs of Siemens Industry, Inc., Drives Technologies, Motion Control — Machine Tool Business, 390 Kent Avenue, Elk Grove Village, IL 60007, www.siemenscnc.com. A veteran of the machine tool industry, his interest is the training aspect on CNC machine tools, which he conducts through seminars and classes at votech schools and shops, and at Siemens training facilities. For questions or comments on this column, contact Randy at 847-640-1595 or email@example.com.