Article From: 1/21/2013 Production Machining, Lori Beckman, Managing Editor
Marshall Manufacturing Company was chosen by Dr. Emil Verban to manufacture DrillStops, a device created by Dr. Verban that increase the safety and precision of dental implant procedures. In use, a tiny set screw locks the stop to the drill bit, and the stop rotates with the drill bit while avoiding tissue damage as the drill penetrates the bone.
Marshall was chosen to machine the stop because the company is a registered medical device component manufacturer with complete Swiss machining capabilities. This means it can suggest process changes that make the product easier to manufacture and improves product performance.
Marshall’s new multi-function Swiss machines were best suited for the job because DrillStops demand numerous turning and milling operations. Its machines could perform all of the needed operations on one machine in a single setup.
“We chose Marshall Manufacturing because of its up-to-date capabilities and willingness to help us with our early prototypes,” Dr. Verban says. “These included the efficient planning of the machining for all 22 components in a DrillStops kit. The company’s manufacturing experience resulted in improvements to the component finishes and the addition of laser marking for permanent product identification.”
DrillStop collars were designed in a range of diameters and lengths to accommodate different implant requirements and to fit the range of drill bit sizes customarily used by dentists. The collar diameters range from 6 to 13 mm and collar lengths from 10 to 14 mm. DrillStops do not include drill bits, which are purchased separately.
Marshall Manufacturing machines these collar components on their Citizen L20 Swiss machines equipped with CAV20-IS bar feeders. Designed for ultra-precision, high productivity work, these machines have a main spindle and secondary spindle that share machining operations. The main spindle offers maximum rotational speed of 10,000 rpm while the secondary spindle offers 8,000 rpm.
The Citizen CNC Swiss machine on which DrillStop components are machined are specifically designed for small diameters. The components are machined from 303 stainless steel in 12-foot barstock lengths in 3/16 and ¼ inch diameters. 303 stainless steel is an FDA-approved material used in the manufacture of dental instruments.
Marshall’s single-setup Swiss machining operation of the DrillStops include turning the OD to size by the machine’s primary spindle, followed by facing, drilling and boring to specified depth. A cross hole is drilled and tapped for the DrillStop set screw. A flat is milled on the part with the machine’s end mill. The machine’s secondary spindle then grips onto the part, at which point the part is cut from the barstock. The secondary spindle then faces off the back-side of the part, puts a radius on the part’s outer diameter and the part’s inner diameter through-hole.
Spindle speeds vary according to the operation and ramp up to the machine maximum where possible. The machining process takes less than 2 minutes per part. Accuracy on critical surfaces is 0.0005 inch. Certain components in the DrillStop kit are bead-blasted to a matte finish to minimize glare when in use, while others in the kit are laser marked for easy identification. As a final step, all collar components are passivated to remove surface impurities, avoiding corrosion.