Bar Feeder System Raises Throughput For Medical Machining

MedSource Technologies (Minneapolis, Minnesota), a provider of manufacturing services and supply chain management solutions to the medical device industry, has a long history of producing small, intricately machined components.

The company offers prototype to full production capabilities and can machine components from microminiature to a 1-inch diameter in a wide range of materials, including stainless steel, titanium, platinum and MP35N. The company has Swiss-type machines on which it currently manufactures a number of critical components for pacemakers, defibrillators and dental implants. Most of these parts begin as 1/8-inch diameter stock and have finished diameters of 0.030 inch to 0.090 inch.

MedSource Technologies used to use a gravity feed system to supply stock to each machine. Once the system reached a certain rpm, however, the bar began to whip, inhibiting the ability to hold tight tolerances and finishes. To solve this problem, the company decided to add 30 MiniRhinobar singletube hydrodynamic bar feeders, from Lexair (Lexington, Kentucky), to its Swisstype machines. One way the company has reached the high level of precision it has is the addition of these bar feed systems, which reduced stock vibration during machining on its CNC Swisstype turning machines.

The MiniRhinobar system is engineered especially for Swisstype turning machines and small, fixed head CNC lathes. They can be equipped with as many as 16 feed tubes in 1/8-inch increments to handle bars with diameters from 1/8 inch to 1 5/8 inch and 6-foot to 12-foot bar lengths. At MedSource Technologies, stock sizes run from 1/8 inch to ¼ inch with some ½-inch titanium stock.

The bar feeders improved bar stability, so MedSource Technologies could increase machine rpm and heighten productivity on CNC machines equipped with rotary guide bushings. For certain jobs, operators raised the rpm on the Swisstype machines by 50 percent, with 30 percent being the average. The resulting overall productivity improvement is about 20 percent.

The MiniRhinobar is designed to improve bar stock stability and reduce shop noise levels. Oil fills the gap between the bar stock and the feed tube, acting as a noise dampening support. As the bar begins to turn, hydrodynamic forces move it toward the center of the feed tube.

Centering forces increase as bar speed increases, reducing vibration. Oil flow and pressure are controlled with a single bar feeder for easy maintainability. The front swingout mechanism includes a large barrel clamp to help reduce bar vibration, ergonomically placed controls and a safety interlock switch to facilitate system operation.

This bar feeder system can be operated using a remote pendant. An end of bar signal and auto pusher retraction permit the MiniRhinobar system to operate untended. The compact size of this system makes it suitable for use by large or small shops. The model used by MedSource Technologies has an overall length of about 17 feet.