Great Lakes Feedscrews Inc. has spent about $1.5 million to build a new testing laboratory and buy a machine from Leistritz AG that makes screws by both the whirling and milling processes. Speed is the reason.
Manufacturers of screws for extrusion, injection molding and blow molding are facing the same time pressures as mold makers, according to Jeffrey Kuhman, president of Great Lakes Feedscrews.
``If we don't shave our hours and time to create a screw, then we're not going to be there to compete,'' he said.
A screw is made by selectively removing metal from a shaft. Because whirling removes much more material than milling does, it is about four times faster than traditional milling. Whirling uses a doughnut-shaped cutting tool that cuts screw flights by spinning rapidly, usually about 1,000 revolutions per minute, around the top part of the shaft. The screw also turns slowly to expose fresh steel to the tool. The computer-controlled mill head pivots to cut angles in the screw.
With milling, employees at Great Lakes Feedscrews had to transfer the screw to at least three different machines. Now, on a single, computer numerically controlled Leistritz PWM 280 machine, a whirling tool first cuts the screw, then a milling tool finishes the work.
According to Great Lakes Feedscrews, it typically takes about six to 12 weeks to make a screw once an order is received. The German-made machine, sold by Leistritz Corp. of Allendale, N.J., began turning out screws at Great Lakes Feedscrews in March. The machine has enabled the company to run on the low end of that range, usually six to eight weeks. Some priority rush jobs have been completed in two or three weeks. Kuhman thinks the combination of the whirling machine and a new, 3,200-square-foot lab in Tecumseh could cut development time more dramatically-down to 24 hours.
The lab contains a Shinwa Seiki injection press with 220 tons of clamping force and an extruder built in-house by Great Lakes Feedscrews. The company and its customers can test screws on-site. Also making design quicker is the company's access to the melt simulator at Rensselaer Polytechnic Institute of Troy, N.Y.
Kuhman said the whirling machine has helped the company enter new markets.
``We have, up until this point in time, concentrated on single screws,'' he said. ``With the capacity of that machine, it takes us into twin screws, tapered screws and a lot of things that, from the milling standpoint, we haven't been able to do before.''
Whirling's higher output and consistency also helped Great Lakes Feedscrews win contracts to make injection molding screws for the new Ube Machinery Inc. assembly plant in Ann Arbor, Mich., for Methods Plastics Machinery, the Sudbury, Mass., representative of Shinwa Seiki machines, and for Sandretto Plastics Machinery Inc. of Middleburg Heights, Ohio. The Ube deal is an exclusive contract to supply screws to the Ann Arbor plant, Kuhman said.
Whirling is hardly new.
``The process has been around a long time. But automating that process with CNC is what is new,'' Kuhman said.
Great Lakes Feedscrews is the first North American company to buy the new CNC Leistritz whirler, equipped with CASEM software.
Two German companies also have bought the Leistritz whirling machines, according to Ralph Wehmann, national sales manager for Leistritz Corp. in Allendale, N.J. In Germany, Leistritz began making the machines to produce rotors for its screw pumps.
Leistritz also uses its own whirling machines to make screws for its extruders.
``What Leistritz has been able to do is bring CNC technology and better tool systems'' to whirling, Wehmann said. ``We now have a very reliable, automated machine.''
Leistritz will demonstrate CASEM software for whirling at the International Manufacturing Technology show Sept. 4-11 at McCormick Place in Chicago.