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 MiniForce-Turn AH8000 series insert features the JS chipbreaker, which has a large inclination angle on the cutting edge to ensure free cutting. Photo courtesy Tungaloy-NTK America.
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.”
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.”
He noted that the way the insert is oriented in the pocket along with the design of the chipbreaker, the insert is a negative-style shell but with a positive cutting action.
The insert features Tungaloy’s light cutting JS chipbreaker, which reportedly provides excellent chip control in a range of applications and has a large inclination angle on the cutting edge to ensure free cutting.
Once the medical manufacturer implemented the MiniForce-Turn insert, Lipsky said tool life increased from 9,000 parts per edge to 35,000 parts, or 140,000 parts for the total insert.
Wasilewski added that the MiniForce-Turn line includes both ground inserts and molded inserts.
To leverage the tool life gain into more throughput by decreasing the cycle time, Lipsky said the end user is increasing cutting parameters in a still ongoing process.
He added that the medical manufacturer switched another insert to the MiniForce-Turn and experienced a similar increase in tool life and is looking for additional opportunities. However, because of the critical nature of medical components, the parts manufacturer is proceeding with caution. “Medical improvement can be a slow process.”
For more information about Tungaloy-NTK America Inc., call 888-554-8394 or visit www.tungaloy.com/us.
Contact Details
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Related Glossary Terms
- built-up edge ( BUE)
built-up edge ( BUE)
1. Permanently damaging a metal by heating to cause either incipient melting or intergranular oxidation. 2. In grinding, getting the workpiece hot enough to cause discoloration or to change the microstructure by tempering or hardening.
- chipbreaker
chipbreaker
Groove or other tool geometry that breaks chips into small fragments as they come off the workpiece. Designed to prevent chips from becoming so long that they are difficult to control, catch in turning parts and cause safety problems.
- cutting force
cutting force
Engagement of a tool’s cutting edge with a workpiece generates a cutting force. Such a cutting force combines tangential, feed and radial forces, which can be measured by a dynamometer. Of the three cutting force components, tangential force is the greatest. Tangential force generates torque and accounts for more than 95 percent of the machining power. See dynamometer.
- inclination angle
inclination angle
Angle that the cutter edge makes with a plane that is perpendicular to the direction of tool travel. Determines the direction the chip curls.
- metalworking
metalworking
Any manufacturing process in which metal is processed or machined such that the workpiece is given a new shape. Broadly defined, the term includes processes such as design and layout, heat-treating, material handling and inspection.
- physical vapor deposition ( PVD)
physical vapor deposition ( PVD)
Tool-coating process performed at low temperature (500° C), compared to chemical vapor deposition (1,000° C). Employs electric field to generate necessary heat for depositing coating on a tool’s surface. See CVD, chemical vapor deposition.
- relief
relief
Space provided behind the cutting edges to prevent rubbing. Sometimes called primary relief. Secondary relief provides additional space behind primary relief. Relief on end teeth is axial relief; relief on side teeth is peripheral relief.
- superalloys
superalloys
Tough, difficult-to-machine alloys; includes Hastelloy, Inconel and Monel. Many are nickel-base metals.
- turning
turning
Workpiece is held in a chuck, mounted on a face plate or secured between centers and rotated while a cutting tool, normally a single-point tool, is fed into it along its periphery or across its end or face. Takes the form of straight turning (cutting along the periphery of the workpiece); taper turning (creating a taper); step turning (turning different-size diameters on the same work); chamfering (beveling an edge or shoulder); facing (cutting on an end); turning threads (usually external but can be internal); roughing (high-volume metal removal); and finishing (final light cuts). Performed on lathes, turning centers, chucking machines, automatic screw machines and similar machines.
- wear resistance
wear resistance
Ability of the tool to withstand stresses that cause it to wear during cutting; an attribute linked to alloy composition, base material, thermal conditions, type of tooling and operation and other variables.
Author
Alan holds a bachelor’s degree in journalism from Southern Illinois University Carbondale. Including his 20 years at CTE, Alan has more than 30 years of trade journalism experience.
