(Excerpted from Medical Product Outsourcing on February 14, 2014)
Machining and laser processing providers must stay ahead of OEMs’ needs while making their own technology strides.
By Mark Crawford
Medical devices continue to get smaller and more complex. That means, of course, that machining and laser processing technology must follow suit. It’s tough (and sometimes impossible) for standard machining and laser methods to produce the complicated geometries and contours that medical device OEMs are asking for, and still deliver super-tight tolerances and process repeatability. Tolerance of plus or minus 0.005 inches once was considered acceptable. Today, that value is closer to plus or minus 0.001-0.0005 inches. Medical devices also are being made from specialized materials such as 400-series stainless steels, carbides, ceramics and nitinol, all of which create their own unique processing challenges.
Meeting lower-cost expectations for complex parts and products sometimes can be achieved by coming up with a process that eliminates assembly steps or secondary operations, such as deburring. Burrs are costly to remove and conventional deburring methods are time-consuming and also can damage tolerances, especially on very small parts. This is why a process called electrochemical grinding (ECG) has become popular for small parts such as slotted needles, stylets and trocars.
“ECG has a niche as the only truly burr-free process,” indicated Tom Travia, director of business development for Tridex Technology Ltd., a Philadelphia, Pa.-based provider of electrochemical grinding and cutoff machinery and ECG grinding services. “Even though EDM, laser, water jet and conventional grinding may not leave a big burr, ECG cutting can be set up to leave a very rounded edge or a very sharp, but burr-free, edge, by varying the cutting parameters. There is also no recast layer or heat affect zone that results from the high temperatures created by EDM or laser. ECG is also preferred for plain tube cutoff because production time is so much faster—up to 10 times faster than EDM.”
Another process that OEM engineers aren’t as familiar with is ECG, especially as an alternative to conventional machining, laser or EDM.
“Every technology has its sweet spot and tube cutoff and grinding is especially suited to the ECG process,” said Travia. “Although tubing can be cut using other methods, the productivity and true burr-free quality of the ECG process is unmatched. The move into point grinding and other sharpening with the ECG process is also a new concept to many OEMs. The advantages of fast stock removal and low wheel wear make this a worthwhile option for specialty needle and surgical tool applications.”