ShopSolutions Case Histories of Manufacturing Problem Solving Machining Gears ‘Not-As-Gears’ Pays Off L
ook beyond the obvious and you may well find a better way to machine a part, and serve your customer better. That’s the lesson illustrated in a gear-machining ap- plication at Allied Specialty Precision Inc. (ASPI; Mishawaka, IN). To make a long story short, the company dramatically improved the material removal rate and yield while reducing fixture cost and delivery lead time on a family of gears by “not treating them as gears.” First, the tooth-forming operation was moved from a traditional gear shaper to a CNC multitasking center. Next, the tooth throat was treated as a short slot rather than the usual tooth throat, using a form-matched Chip-Surfer replaceable-tip carbide slotting tool from Ingersoll Cutting Tools (Rockford, IL).
Step one enabled “done- in-one” machining, which led to simpler in-process parts handling and shorter delivery
en operations in all—than just cutting the teeth. Now we grab the part once and complete all seven operations.” A typical workpiece is a sector gear, machined from solid 17-4PH bar stock, that looks like half a gear with a lever arm attached. Measuring about 3½" (89-mm) diameter with 46
Allied Specialty Precision’s CEO Pam Rubenstein and Todd Stoddard (right) discuss with Ingersoll’s Andy Thornburg “done-in-one” production of gears from 17 4PH cut-off bar stock using Ingersoll’s Chip-Surfer T-slotting tool.
lead times as well as reducing total machining cycle time by more than 2 to 1. Step two streamlined the tooth-cutting operation itself, the longest operation on the part, by about 3 to 1.
Running 24/6 with 60 employees in the shop, Allied Spe- cialty Precision has earned a reputation as the “go-to guys” for challenging manufacturing projects, said CEO Pam Ruben- stein. Because of its location and that reputation, ASPI has become a preferred supplier for aerospace manufacturers. “When you see a gear, you naturally think of a stroker- type gear shaper, equipped with the familiar single-point high speed steel form tool,” said Todd Stoddard, ASPI manufac- turing engineer. “But completing this particular part is more about machining the web, hub and stepped shaft bore—sev-
teeth over a 180° arc, the gear goes into helicopter flight controls. Annual volume for the earliest orders was just 100 pieces, all similar.
In 2008, ASPI initiated the “done-in-one” approach on a plant-wide basis. To that end, the company moved the job to a new Integrex CNC multitasking center from Mazak Corp. (Florence, KY) with all available auxiliary axes. “In effect it’s a 9-axis machine,” said Stoddard.
Originally on the new Integrex, teeth were formed with a 2" (51-mm) high speed steel (HSS) gear gasher, essentially a slitter with form-matched teeth. It completed the teeth in two roughing and one finishing pass. Total cycle time for tooth machining was 28 minutes, the same as before on the shaper. The big savings were in the other operations and in reduced part handling.
June 2013 |
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