In the field of medical component machining, it is essential to optimize tool performance. ARCH Cutting Tools are the industry leader in providing superior solutions for machining high-quality medical components through innovative design and advanced grinding technology.
Take, for example, the processing of polyethylene tibial liners. As Jim Gray, Director of Northeast Operations at ARCH Cutting Tools, explains, this machining almost always uses a single flat insert mounted on a tool holder to maximize the shear angle. However, Gray says this design often creates lines on the surface, or an "orange peel" effect due to burning, because it doesn't cut the polyethylene as cleanly as expected. The straight groove design also creates a large impact on the workpiece with each rotation.
Gray's team used their knowledge and ANCA's programming software to create a unique 11/2" (38.1mm) diameter 3-flute carbide helix cutter with high shear and multiple radii along the profile. They grind it on an ANCA MX7 machine with more than a dozen grinding wheels for a mirror finish and a "sharper-than-blade" cutting edge, as Gray describes it. You need a very sharp edge to cut plastic perfectly and cleanly. Even if the diamond particles pass through the cutting edge, leaving behind tiny chips, they will show up on the insert. These tools are examined under a microscope to confirm that the cutting edge is clear and clean. Gray added that their spiral design also distributes the cutting forces compared to straight grooves. In summary, ARCH cutting tool solutions deliver excellent part finishes, higher throughput, and longer tool life.
Replicate perfectly
Gray also points out that in addition to the tool design assistance provided by the ANCA programming software, which includes full 3D simulation, the ToolDraft feature provides detailed documentation for process control. Gray explains, "ToolDraft allows us to list every aspect of the tool and the grinding wheels we need, rather than relying on 2D drawings on the shop floor. One of the pages includes groove shapes, roughing wheels, finishing wheels, and any information related to the groove. The next page deals with profiling, which again contains all the wheel shapes and data, as well as the required clearance angle, bottom width, and other tool geometries. And so on to the end face. We also add annotations to each drawing to provide details related to the tool...... The details that make it really work. ”
"We love what ToolDraft has done for us. Because if all you have on the shop floor is a 2D drawing with the outside diameter or shape of the tool, the operator can say, 'A tool is good.' In reality, the body is very thin, and the rear angle is not right. If we can't provide the operator with complete information, then everyone will have a different opinion about what is the right copy. We promise our customers that no matter who uses what machine to grind a tool, they get the same tool every time. And the only way we can deliver on that promise is through ToolDraft to create documentation.
Gray adds, "While these tools can be ground using a ball screw-driven machine, it's much easier to produce them using ANCA's latest linear motor technology. Linear motors have undoubtedly changed our world when it comes to finishing and transitioning of forming tools," he explains: "Linear motors make contour grinding easier, especially for tools like condylar cutters, because there are multiple radii up and down through the cutting edge. If grinding in only one direction, the ball screw machine is fine. But if you need to grind multiple arcs at the front and rear ends, the small backlash or wear of the ball screw will force you to keep adjusting during the grinding process until it's all ground. With linear motor machines, this can be done right from the start. ”
Not all ball nose end mills are created equal
When it comes to hip bars, Gray says, "Machining these parts requires a ball nose end mill whose radius and transition to the outside diameter have to be perfect. The end face pores must also fit perfectly into the center. Any mismatch in the center of the ball head will create a line on the hip shaft, which is not allowed. Any deviation in the radius will cause the geometric distortion of the part profile," he adds, "We scan the entire radius to make sure it's correct." ”
Gray explains that hip stems are typically made of titanium and cobalt-chromium. The materials are challenging enough, but Gray says new 3D-printed titanium alloys from major medical suppliers are more difficult to machine. They are porous and facilitate integration with the patient's bone, which essentially guarantees the discontinuity of the cut. This material is also very abrasive. Therefore, to minimize the number of tool changes and increase production speed to achieve an acceptable level of efficiency, an engineering solution from a cutting tool company like ARCH is required.
Quick turnaround for custom tools and regrinding
In another example where ARCH Cutting Tools helped, a customer was suddenly missing an imported keyholder milling cutter with replaceable cutters during production. ARCH cutting tools delivered the customized solid carbide tool within 48 hours and were coated. In another case, ARCH cutting tools have created a multi-process countersinking tool for machining titanium and superalloys, integrating 6 different operations in a single tool. These two examples show once again that combining experienced grinding professionals with ANCA's software and machines can produce high-quality medical devices that improve people's lives.
Regrinding is another such field. Not only does ARCH Cutting Tools reliably restore used tools to new condition, but in many cases, Gray says, they actually improve the original tool. "One of our large medical customers purchased a faceted drill bit from one of the world's leaders in cutting tools," Gray recalls. "The drill is for titanium, and we added a roll point to it and made some other changes to the geometry to make the reground drill run better than the new tool."
In this case, Gray praised ANCA's integrated laser, which automatically checks and corrects tool run-out errors, as well as ANCA's detection capabilities. In addition to probing coolant holes to ensure the tool is in the correct direction when regrinding, Gray says ANCA can easily probe the entire point profile for K-land grinding, which is a notoriously daunting task. Gray explains, "You can adjust how many points you need along that edge. If you're making a tool, you can probe the profile once and store the data. From then on, you don't have to re-probe to get a good K-land until wheel wear becomes a factor.
"Wheel wear can cause the K value to change, but he again points out that re-probing the profile is easy to adjust, and they also have wheel probes on their ANCA machines." "The wheel probe is definitely a good thing because it eliminates human error and it's very accurate," Gray said. The old-fashioned method used a measuring rod, and Gray recalls that operators often forgot which direction they should use, resulting in ruined expensive grinding wheels.
Productivity Science
As Gray explains, for ARCH Cutting Tools to stay ahead of the competition, it has to be faster, and that requires a scientific process. For example, matching different wheel sizes to the various tool materials they need to grind, placing coolant correctly, and providing adaptable tool support. In the latter case, Gary praised the ANCA P-axis movement stabiliser and said that for some challenging applications they used Arobotech, a device that clamps the tool at 3 points and adjusts to the diameter change as the P-axis moves underneath the wheel, providing support. Gray concludes, "These are the strengths of our ability to manufacture these instruments. They virtually eliminate runout, allowing us to run faster."
But Gray retains the highest praise for ANCA's simulation software, calling it "the best tool ever...... We used to go on the machine blindly, and we ended up scrapping the blanks and finding these complex tools directly on the machine. With ANCA's software, you can create complex tools before you get on the machine, and by the time you run the first part, you're close to perfection."
From creative tool design, to efficient machine set-up and operation, to stringent quality control, ARCH Cutting Tools is a model for meeting the challenges of medical component machining.