Horizontal Boring Mill, Special Tooling Cut Teeth

March 31, 2011
MAG machine shop develops novel process to produce a giant gear
Specifications for the 19-meter gear:
- 20° full-depth, involute teeth, cut in accordance with AGMA 201.02
- Pitch diameter: 19,016.2 mm (748.6693 in.)
- Circular pitch: 101.6 mm (4.0 in)
- Teeth per segment: 49
- Fillet radius: 9.702 mm (0.382 in.)
- Addendum: 32.3 mm (1.273 in.)
- Min. dedendum: 40.4 mm (1.591 in.)
- Backlash: 2.286 mm (0.090 in) on pinion, 2.286 mm (0.090 in.) on rack, 4.572 (0.180 in.) total
- AGMA gear quality number: 6
- AGMA gear accuracy standard: AGMA 2000-A88
- Face Width: 230 mm
- ASTM A290 GR.3 CL.E
- SUP. REQ. S1, S2, S3 and S6
The gear teeth were manufactured with the involute built into the cutter, which was accomplished with a specially developed tool developed by grinding the tooth form into the cutter first.

Engineers at the MAG production center in Fond du Lac, Wis., proved recently they know well how to use machine tools — just as well as they build them — by developing a process for using a horizontal boring mill (HBM) and specially designed tools to cut 588 teeth, to produce a 19-meter (62.5-ft) diameter gear assembly. The alloy-steel workpiece weighed 60 tons (54,836 kg.)

MAG is a global designer and manufacturer of machine tools and systems for metal cutting and composites applications. Its numerous brands of equipment and technologies cover turning, milling, hobbing, grinding, and honing processes, as well as systems integration, composites processing, maintenance, automation and software, tooling and fluids, and core components.

The two-piece, gear assembly consists of a 24-section track that serves as its base, and a 12-section upper gear rack.

MAG engineers and technicians designed dedicated fixtures for each operation and special tooling for cutting and finishing the gear teeth on an HBM. "We cut the gear teeth on an unconventional machine," explained project manager Mark Huhn. "In most cases the tooth involute would be generated by the machine itself, but we used a tool with the involute built into the cutter, which was accomplished by grinding the tooth form into the cutter first."

The gear teeth were manufactured to American Gear Manufacturers Association (AGMA) Gear Quality No. 6, and the gear was assembled to a pitch diameter concentricity of 0.8 mm (0.031 in).

The gear track, which is comprised of A148M Grade 620-415 castings, called for a special cutter to produce a 2.127 ° surface angle. "The angle was circular interpolated onto the track surface and we designed a special cutter to cut the angle on one of our gantry-type machining centers," Huhn reported.

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