Sandvik Coromant CoroCut XS with extensions.

Challenge: To increase quality and productivity in the manufacture of medical components.

Solution: Provide continual innovation with machining solutions and new grades.

Of all the precision machining challenges, making medical components represents the pinnacle of the art. Today Sandvik Coromant offers impressive tooling solutions that are essential to medical component manufacturing.

The company’s thread whirling solution is one of them, offering a complete solution for bone screws. One benefit of this solution is that it is a single-pass milling operation, thus offering significant productivity improvements while enhancing overall quality.

A thread whirling tool is basically a ring with inserts mounted on the inner diameter. A machine-mounted attachment carries the tool and rotates it at a high speed relative to the slower rotating workpiece. The ring is positioned slightly off center from the part so that a single insert engages the work per rotation. The thread angle of inclination is set by the angle of the cutter ring to the workpiece. The thread profile is determined by the design of the insert.

Thread whirling with inserts attached.

The thread whirling process enables bone screws to be produced in a huge variety of lengths and diameters. This is advantageous to bone screw manufacturers, which typically must develop custom threads to accommodate human bone requirements.

Human bone has a hard outer shell and a softer, sponge-like core. Bone screws need to be hard enough and sharp enough to penetrate the outer shell, but their thread form must be able to resist pulling out the bone’s softer core.

Thread whirling is an efficient, productive technique that produces high-quality threads. Common materials used are 316 LVN stainless steel and titanium. None of these are straightforward to cut because of the bone screws’ profile, which requires sharp angles, long thread lengths and large differences between the root and head diameters. The thread whirling capability offered by Sandvik Coromant is complemented by insert grade enhancements.

This latest development is backed by a deep knowledge of biomaterial manufacturing and its machining requirements through working with Sandvik Bioline and related specialists in the medical components industry. Consequently Sandvik Coromant has a specific program of development for this sector that encompasses all of its small-part manufacturing requirements.

Learn more about Tooling Solutions from Sandvik Coromant.

Learn more about Threading Solutions from Sandvik Coromant.

Originally published in Metalworking World 1.2010, a business magazine published by Sandvik Coromant.