A Positive Change: Medical Manufacturing

Poor tool life and problems with chip control and surface finishes are not desired by any parts manufacturer but can be particularly consequential for medical manufacturers because of the high demand for aesthetically pleasing parts while they closely watch the bottom line. An Illinois manufacturer was experiencing these issues when machining an orthopedic surgical instrument made of 304L stainless steel on a Swiss-style machine, said Tyler Lipsky, specialist, on-site metalworking for Melville, New York-headquartered MSC Industrial Supply Co. Inc. For example, chips wrapped around the part when the subspindle transferred the part to the main spindle.

The manufacturer was using a standard single-sided DCGT with a negative cutting action and achieved 9,000 parts per each of its two cutting edges, Lipsky added. “It’s a very thin-walled tube, so putting too much force into the part is a big concern.”

Andy Wasilewski, manufacturers’ representative at Chief Engineering Group in Indianapolis, explained that a negative insert does not have a relief angle and therefore exerts more cutting force than a positive one.

Lipsky added that he has considerable experience with cutting tools from Tungaloy-NTK America Inc. in Arlington, Heights, Illinois, and suggested the MiniForce-Turn double- sided positive insert, specifically the AH8015-grade DXGU 070302 L-SS insert, to overcome the issues. “I said, ‘Hey, I think this product is great, offers better productivity, can run faster and last longer.”

The grade has a thin PVD coating, which is effective for turning high-temperature superalloys and exotic materials such as stainless steel, Wasilewski noted, and receives a premium surface treatment to minimize built-up edge. “It’s got a great balance of wear resistance and fracture resistance.”

Prior to switching inserts, the end user performed a capability study and then a test run to establish tool life, Lipsky said. “Once everything is agreed upon, once all the engineering documentation is in place, it’s fully implemented.”

The MiniForce-Turn AH8000 series insert features the JS chipbreaker, which has a large inclination angle on the cutting edge to ensure free cutting. Tungaloy-NTK America

Positive tools are used in about 90% of the applications for Swiss-style machines, according to Lipsky, but it is rare to have a double-sided positive insert. Having four cutting edges per insert reduces the cost per edge compared to an insert with two. “This being a tool that offers the productivity of a double-sided insert with the positive cutting action, it’s just a win in all regards.”

To ensure stability and a high level of cutting performance, Wasilewski pointed out that the MiniForce-Turn insert has a built-in dovetail so that the insert sits in the tool body pocket securely and doesn’t move while cutting. “It gives extra stability basically.”