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Specialized Centerless Grinder Speeds Production of Critical Tolerance Parts for Orthopedic Surgeons

A new arthroscopic shaver application, developed by Glebar Company for its advanced GT-610 CNC centerless grinder, is now delivering the most precise inner and outer tubes for use by orthopedic surgeons.

Arthroscopic shavers allow surgeons to insert a small and hollow cylindrical metal tube into a small incision in a patient. They allow surgeons to remove bone and tissue while at the same time flushing fluids and debris through the tube and out of the patient.

"Part size and tolerance is critically important, especially on the tip of these devices, and have been difficult to manufacture in volume since their design requires as minimal a gap as possible -- as small as 0.0005 inches between parts so that the inner sleeve moves freely inside the outer tube without the risk of binding due to debris caught between the surfaces," said John Bannayan, president, Glebar Company.

Using the Glebar GT-610 CNC to infeed grind the shape of the inner tube, Glebar is able to maintain a ± 0.0002 inch tolerance on the elliptical tip dimensions. The team developing the application also ground three diameter features to within .0002 inches maintaining a TIR of 0.0001 inch and producing a smooth 9 Ra surface finish on 304V stainless steel with a ± 0.001 inch wall thickness. They removed 0.012 inch in stock for the majority of the part and 0.004 inch off the tip geometry.

"The entire automated process was complete in under 20 seconds adjusting for part length variation, heat expansion and a near zero tip geometry requirement," said Mr. Bannayan. "Our process eliminates an extra step in previous manufacturing methodologies which also left unacceptable tool marks on the surface and vastly reduced the scrap rate due to geometry imperfections."

Outer sleeve manufacturing occurs on a Glebar GT-610 thrufeed grinder which grinds the OD of the blank tubes maintaining a surface finish between 3-6 RMS and maintains a comfortable 2-3 Cpk on the outside diameter of the part. Material removal of 0.005 inches, with a tolerance requirement of ± 0.0005 inches, is met easily in a turnkey, fully automated process.

The first two systems equipped with the innovative application have been sold to a major manufacturer of arthroscopic shavers. The system will be on display for the first time at the 11th Annual Orthopaedic Manufacturing and Technology Expo and Conference (OMTEC 2015) being held at the Donald E. Stephens Convention Center in Chicago, today and tomorrow (June 17 and 18).

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