Tru-Edge Grinding Inc. specialised in designing and grinding cutting tools for metal working applications
Recently, however, the St Henry, Ohio company has been applying its grinding expertise to surgical cutting tools. What it knows about tool grinding translates well into the medical field, delivering excellent results for its customers in shorter than typical delivery times.
The growing company is now ISO:9001 and ISO:13485 certified to perform medical grinding work, grinding the cutting tools for surgical instruments and supporting tier 2 and 3 medical suppliers. Applying its grinding expertise to medical instruments gives the company an edge.
Having ground over 100 different surgical tools, the company now has about 10% of its work in medical. Earning the ISO certification will serve to strengthen its reputation in the industry and earn additional work.
Tim Knapke, Owner/General Manager, with an ANCA MX7 machine
Tim Knapke, Owner/General Manager: “We do many different drills and reamers and we have developed a lot of special fixturing for our ANCAs that allow us to do a variety of medical work. Our grinding experience helped us to come up with efficient, time-saving ways of shaping the surgical tools.”
Until a couple of years ago surgical tools were produced by milling, turning and handwork because the geometries were so complex. But increasingly, medical device manufacturers are looking to grinding to impart the geometry and finish required to the cutting tools – qualities that turning, milling, and handwork cannot match consistently.
“At Tru-Edge, we can put the material in the grinder and machine the tool complete in one set-up, no deburring required. Cycle times may be an hour per part due to the complexity of a part such as a bone rasp and the number of teeth in the part. But previously such a part would have required hours of cycle time across six processes from milling to turning, deburring, and polishing. We’ve taken hours out of the time required to produce a finished bone rasp,” Tim said.
An example of the type of intricate medical instrument that can be made
ANCA software – the right fit
In order to do some of the more complex medical grinding work, ANCA software has been key. One of the parts Tru-Edge has been successful with is a bone rasp – the kind of medical part that, if you can do it successfully, you can do just about anything else, Tim says.
“I have to say, the ANCA iGrind Medical software within the ANCA ToolRoom suite is wonderful. We were a little sceptical at first – it seemed like it would be a stretch for the machine to make the demo bone rasp, but it came out perfect on the first attempt,” Tim said. “It is a very complex part to produce on a grinding machine, as are other medical tools and implants.”
“At times, the solid models of new medical parts we get from the customers are not always perfect and complete,” said Frank Seger, Engineering Product and Development Manager. “Nevertheless, ANCA went off those models to create a test grinding program for the rasp that worked very well. With that demonstration, we decided to invest in an ANCA to do other similar types of parts,” he said.
Machines for medical production
Of its 14 ANCA machines, Tru-Edge concentrates its medical production on the MX7 and TX7+. There are 4 machines dedicated to medical production with room on the floor for more as production increases.
The MX7 is optimised to grind tools up to 25 mm (1”) diameter. “With a wheel pack changer storing six HSK wheel packs, we have the flexibility to handle the different batches of stainless steel material and to produce a number of different complex tools in a single set-up, saving a good deal of cycle time,” Frank said.
The TX7+ is a production-oriented machine with a 37 kW (49 HP) spindle for precision grinding tough material. All machines in the Tru-Edge shop operate with the same software and any can run the medical part programs. The TX7+ can also hold a Big Plus milling toolholder, so Tru-Edge could add that capability.
The medical tools are usually of 17-4 stainless, and “we have learned a lot about stainless steel in the last few years,” Frank said. “It was a steep learning curve. Depending on the stainless material we are working with, vitrified CBN or standard CBN may be the best wheel. So it’s a bit of a process to get the right wheels for a particular batch of stainless steel.”
ANCA options make a difference
Certain options for the ANCA machines make them ideal for medical applications, assuring highly consistent grinding results. First, ANCA’s in-process wheel dressing.
“We will never buy another machine without in-process dressing,” Tim said, “due to the accuracy it affords our process. Part programs are based on a data point in the work area. In-process dressing allows the machine to know where the wheel surfaces are in relation to the data point and thus to the part at all times. The wheel imparts the form to the tool, and automatic dressing cycles maintain its form consistently.”
Grinding cycle times are also improved. By automating the stick dressing, downtime during production is reduced, permitting unattended production runs as wheel condition is maintained during the batch. Dressed wheels also permit high consistent feed rates.
And importantly for stainless steel grinding, regular dressing of grinding wheels reduces tool burn and material damage, as well as ensuring open cutting wheels that reduce grinding forces and minimise spindle load.
ANCA’s software, known for its flexibility and user-friendliness, fully supports the white stick dressing process, ensuring the least amount of wheel material is removed.
Another option for medical tools, which can be very long and narrow, is the Travelling Steady on the ANCA P-axis.
The Travelling Steady (P-axis) shown in use on an ANCA TX7+ machine
“With ANCA’s P-axis working with the grinding wheel and Travelling Steady rest, which holds the part straight, we are able to grind these long reamer-type parts successfully,” Tim said. “We will not buy a machine without it. It was out of the box perfect. Many of the medical cutting tools are complex and therefore difficult to hold in some cases, but the P-axis eliminates that concern.”
The ANCA Travelling Steady provides the machine with an additional axis (P-axis) which, under CNC control, keeps the tool support directly underneath the point of grinding at all times. Keeping support under the wheel means complex operations on long slender tools is reliable and consistent.
“A conventional stationary support steady provides adequate support on a short tool, but when you are manufacturing tools such as drills up to lengths of 600 mm long, a stationary support will not provide the continual support along the entire length of the tool,” Frank said.
The predictable, high quality of the medical grinding process at Tru-Edge is its overall key advantage. Tim Knapke: “One of the first comments we got from our first medical tool customer when they saw the first part was ‘This thing dimensionally is flawless.’ That’s where the ANCAs have simply shined.”
Visit the Tru-Edge website
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