An increasing emphasis on minimally invasive surgical procedures is hastening the development of more intricate instruments that require specialists to produce them. As a consequence, the medical device industry, in general, and precision machining shops in particular, are in an upswing, particularly in California.
Shops that have invested in the right level of metalworking technology are benefiting from a region that is also rich with die and mold machining and prototype work, as well as productionpart manufacturing for industries other than medical.
Spec Engineering in Van Nuys is one California shop that has all the prescribed equipment in place and has a healthy bottom line thanks to its medical device customers.
The shop produces stainless steel, titanium and plastic surgical instruments that are delicate, intricate and can require precision-machined surface finishes of 32 Ra to 40 Ra. Materials the shop works with range from soft 303 stainless steel to hard 465 custom, which, like PH 13-8 stainless steel, is difficult to machine. Positional part tolerances typically run around +/- 0.002 in. for true position and +/- 0.0003 in. for hole sizes.
According to Gregory Viksman, Spec Engineering’s owner, two of the shop’s toughest parts are medical drill guides and guide drops. He explained that his shop machines holes in two different planes on these parts, and the features require extremely close-tolerance work – hole diameter tolerances are typically +/- 0.0002 in., and through-position projection tolerances may be +/- 0.003 in. over a 4.25-in. span.
To tackle such challenging parts, Viksman said that the “right level of metalworking technology” has included MAG Fadal vertical machining centers. The shop currently operates 10 Fadal VMC 4020 machines, and their 40-in. by 20-in. table sizes provide the space to fixture 10 to 20 parts in one setup. Some parts are set up in multiples in a vice.
“The Fadal 4020s have the rigidity and capability needed to machine titanium, while holding the dimensional tolerances and surface finish quality our customers need,” said Viksman. “We also use Fadal VH 165 fourth-axis rotary tables on some of the 4020s, and have a setup for 5-axis machining using a TR 165.”
Spec Engineering’s Fadals sport 10,000-rpm coolant-thru spindles for high-speed machining, with rigid-tapping options. Machine axes accurately position to +/- 0.0002 in., with repeatability of +/- 0.0001 in.
Cutting feedrates run to 600 ipm, and rapid traverse rates are 900 ipm in the X axis and Y axis. MAG Fadal also produces an FX series of machines that increases cutting feedrates of the 4020 to 800 ipm and rapid traverses to 1,000 ipm. The 4020s have 21-tool automatic tool changers.
Batch sizes at Spec Engineering range from 25 to 300 or more, with a typical production run being approximately 100 pieces. The shop develops part programs off-line and downloads them to the machine controls. Spec Engineering rounds out its medical machining capabilities with a Hardinge turning center and Star Swiss screw machines.