Original Date: 09/20/2004
Revision Date: 01/18/2007
Best Practice : Shaping
Forest City Gear has made continuous investments in obtaining and maintaining modern, high-tech gear shaping equipment. This equipment gives the company a competitive advantage through high production rates with a minimum requirement for special fixturing and lengthy set-up. The unique features of the machines allow Forest City Gear to shaper-cut specialty gears.
The typical gear shaping equipment used by the U.S. Gear Industry is strictly mechanical and features a mechanical link between the cutter and the worktable. In addition to the many (possibly worn) mechanical components (each contributing to variations in shaped gears), the mechanical linkage places other limitations on the process. In order for these machines to shape helical gears, a special guide is required. The cost of this guide is $5,000 to $30,000, and it can only be used to cut gears with one helix angle or lead. Another critical limitation is that the location of the cutter relative to the worktable is fixed; thus, each gear must be fixtured to a specific location before cutting. In addition to the cost of the fixturing, only one gear can be cut on a part with each set-up.
Forest City Gear (FCG) reinvests 25% to 40% of its gross revenue into the company every year with state-of-the-art gear cutting equipment. FCG has obtained several, modern, Computer Numerical Control (CNC) gear shaping machines and owns more CNC gear shapers than other gear shops. The CNC shaping machines give FCG a number of unique gear shaping capabilities. Several of the machines feature CNC guideless technologies, which allow the machines to shape helical gears without the expensive guide required by the older technology. The relative locations of the cutter and worktable can vary over a wider range than was previously possible, minimizing the need for expensive fixturing. This also allows FCG to shape multiple gears on a part in a single set-up, provided the same shaper cutter can be used (e.g., same pitch, pressure angle, and helix angle) (Figure 2-4). FCG’s re-cut gears have an approximate hardness equivalent to 50 Rockwell C.
The CNC machines can cut with different feeds and speeds for roughing and finishing cuts. The need to rotate the cutter relative to the work piece is not necessary; thus, form-shaped cutters can be used which allows shaper cutting of very small, internal gears. Since no gear train exists linking the cutter and the work piece, CNC machines can be readily programmed to shape gears with prime numbers of teeth. The column supporting the shaper cutter can be tilted with CNC control, permitting further variation in the gears cut, and labor set-up for a given part can be accomplished in approximately four hours less time.
With the addition of a 90° adapter, the machines can also cut face gears. This is a fast growing segment of the gear market, and this modern, CNC gear shaping equipment gives FCG a further competitive advantage.
Figure 2-4. Shaping a Face Gear
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