The secrets of micro milling
A bar machining center, tiny tools, and applications ofmicro milling
By Frederick Mason Editor
Secret of Micro Milling - 2002 - 16496 M
icro milling and drilling on the chip-making side are expanding in suchindustry sectors as medical parts,fiber optics connectors, and microhydraulics. With a lot of ordinary machiningapplications and jobs moving from Europeand America to the Far East, says AlainGuerdat, President of Willemin-Macodel Inc(Elmsford, NY), "one way to make a living inmachining has been in micro machining.Many shops can no longer seem to make a liv-ing doing ordinary machining.""Micro machining developed earlier inEurope than the USA but it is now coming upin the USA. Switzerland has its tradition ofthe watch industry and fully half of Willemin'sannual production of about 130 machiningcenters per year stays in Switzerland. Butmicro machining has its learning curve. Forexample, you need people who can thinkabout how to make a tiny part yet not make ittoo weak during the machining process. Soyou need smart programmers and smartmachinists. Management has to be willing topay top people for their skills. Then you needa good machine with high spindle speeds, soyou can get enough surface speed on the tinytools to get close to the right cutting parame-ters. Many of the jobs we know run at the topspindle speed of 30,000 rpm on some of ourmachines.""Then, because you are often cutting withvery small diameter cutting tools, you need a
quick way to check if one is broken and thenyou bring in a 'sister' tool from the tool mag-azine. The need for such backup tools is oneof the reasons a machining center with a toolmagazine is sometimes abetter way to go than, for example,a CNC Swiss turning machine withmilling capabilities. Such turningmachines may have up to 16 live tools, butthey generally will not have the backup toolcapacity. Some of our machining centers canrun jobs from barstock and, with the ability tocheck tools and backup or 'sister' tools in thetool magazine, jobs can run unattended untilthey run out of barstock or tools. The unat-tended machining time saves on labor cost.In addition, you do not get the same rpms ona Swiss lathe that you can get on a machiningcenter spindle. For these reasons someSwiss turning shops are interested in ourbar-fed machining centers. Programming isnot particularly difficult and many of our cus-tomers use Mastercam or Surfcam for pro-gramming our 5-axis machines." Five-axis bar-fed machining center Latest in Willemin's line of 5-axis machin-ing centers is the bar-fed W-408B 30,000 rpmmachining center for manufacturing smallcomponents that fit within bar stock up to0.900-in. diameter. The idea is to finish partswithout setup and without burrs. Sincemachining is from barstock, no setup or
w o r k-h o l d-ing isrequired and the manpower requirement isminimized. With a tool magazine holding 24
HSK 40 tools, numerous milling and drillingoperations may be performed and backup or"sister" tools may be available in case one ofthe tiny tools breaks. The finished part is cutoff with a rotary saw and backworking may bedone thereafter using the main spindle. The
Pedicle screwsScrew Dia. 0.216 in.Titanium screwturned on a swissscrew machineUsed 7 cutting tools Cervical hook0.550 x 0.550 x 0.315 in.TitaniumBar dia. 0.900 in.Used 15 cutting tools Dental implants0.215 in.TitaniumBar stock dia. 0.315 in.Used 12 cutting tools Medicalstainless steelBar stock dia. 0.630 in.Used 14 cutting tools Medicalstainless steelBar stock dia. 0.630 in.Used 14 cutting tools
(All data supplied by Willemin)
Reprinted by permission from the September 2002 issue of Machine Shop Guide
