Hobbing

Is hobbing as a section of milling a production process for Verzahnungsvor and finishing of gears.

History

The hobbing was invented in 1856 by Christian Schiele, however, was not at that time in a position to implement the process in appropriate equipment. In 1887 the first hobbing machines were built according to a patent of Grant and until the year 1897, the process continued through after Hermann PFauter from Chemnitz filed a patent for a universal gear hobbing machine.

Method

Gear hobbing is one of the continuous spline method and is very flexible and highly productive. The cutter rotation generates the actual cutting motion. With a hob keeps all tooth numbers, generate all addendum and any skew angle by varying the machine positions. A limitation is generally only through the work area of the machine tool.

The hob is geometrically a single or multi-start screw with flutes and forms with the interlocking workpiece to a worm gear. In addition to the rotation drive of the hobbing cutter in the axis of the workpiece at the workpiece along in order to produce the tooth gaps.

The teeth of the hob wear by machining. Therefore, the hob moved continuously or at certain time intervals tangent to the workpiece ( shifting ) in order to bring new teeth into engagement. All teeth are worn over the entire length of the hobbing machine, the tool is replaced and sharpened to a Wälzfräserschleifmaschine.

By hobbing teeth following types can be prepared:

  • External spur gears
  • Foreign helical gears
  • Internal helical gears ( with large inner diameters )
  • Bevel gears with straight teeth or spiral teeth ( spiral gear )
  • Crown wheels
  • Hypoid gears (axes do not intersect itself )
  • Palloid teeth
  • Ringing mountain and Gleason gears
  • Helical gears ( helical worm and helical gears )

Small internal gears can not be manufactured by hobbing; in these ( process: Shaping ) the teeth " pushed ".

Advantages of the hobbing process over other teeth

  • Versatility (any tooth shapes, splines, Kettenradverzahnungen, ratchet wheels, etc.)
  • Arbitrary skew angle possible
  • Any tooth widths available
  • Continuous cutting without return strokes
  • The cutting is done by a lot of cutting
  • Budget by continuous cutting force ratios and high accuracy
  • Simple production of tools
  • Easy tool setting on the machine

For high-precision gears, the tooth flanks are produced by milling and grinding after hardening, scraped or honed ( method: honing ).

Worm drive
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