What once seemed a far-off goal for mold and die work, as well as medical parts, is now a reality, based on new technologies you can investigate today.
|The implant is produced with the highest CNC
precision on an HSC machine
The challenge had 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. Namely, all the programming, setup, and machining time needed to be costed against a very short, or even one-off run. Worse, if the material was very expensive, additional care was 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 was simply impractical.
Machine builders and especially software providers had long struggled with this scenario, with the potential solutions taking two tracks. For a decade or so, the rush towards higher spindle speeds was all the fashion, similar to the ipm “contest” seen among the EDM builders in the past, as that technology was and remains a very popular technique for manufacturing these products. Likewise, the translation software for CAD to CAM to post-processor to CNC was running in various directions for some time.
Today, high speed cutting (HSC) has evolved to a highly sophisticated combination of spindle speed coupled with resolution in linear motor, drive and encoder packages, while another trend has emerged on the software side. Whether you’re working with high-precision mold cavity inserts, hip joints, or dental implants, it’s 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 ultrasonic. The latter method is gaining traction in the composites market especially.
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 today, when the complete execution of the machining cycle can be accomplished offline in real time, the estimating is easier and far more precise, resulting in closer approximations to true costs and more profitable work for your shop.
|Finished knee joint ready for implanting.|
The CNC platforms needed to make the above scenario actually happen in your shop are also available today. Most critical when seeking out the right solution is 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, these are not “someday” wishes for shops doing this type of work, they are realities on the market now. Just as the jump from three- to five-axis machining seemed intimidating a few years ago, this notion that you can go from a CT scan to a manufactured part in a seamless fashion, with predictable CNC control on an HSC machine with surface finish to Ra 0.2 m, might appear beyond your reach.
Randy Pearson, a longtime veteran of the machine tool industry, is the Siemens sales support manager for U.S. dealers and OEMs. His special interest is the training aspect on CNC machine tools, through the various seminars and classes the company conducts at votech schools and on-site at shops, as well as the Siemens training facilities around the country.
For additional information on the products and technologies discussed in this article, see Eldon James Corporation.