Abrasive generation of non-metallic gear

Details Abrasive generation of non-metallic gear Abrasive generation of non-metallic gear

2000-12-27

2003-07-01

Wellington, A. L. (Department: 3722)

Cutters, for shaping

Gear cutting tool

Hob

C407S027000, C451S070000

Reexamination Certificate

active

06585457

ABSTRACT:

TECHNICAL FIELD
This disclosure relates to gear hobbing, and, more particularly, to a hob cutter that generates and abrasively finishes a face gear.
BACKGROUND
Gears used in applications in which components are rotated at extremely high speeds (e.g., automotive and aircraft drive train applications) generally require that the gears be manufactured with significant precision. Such precision usually requires an elaborate multi-step manufacturing process in which the gear is first cut to produce teeth that are close to the final shape desired within a small tolerance limit, then removed from the cutting machine and placed in a finish-cutting or grinding machine to form the teeth into the precise shape having the proper dimensions.
Prior art plastic gears used in such applications are typically cut with special hob cutters on standard hobbing equipment. Some of the difficulties encountered with using special equipment in conjunction with standard hobbing equipment to generate plastic gears include spacing problems associated with the positioning of the hobs on a multiple start cutter, deflection of the plastic material of the workpiece during the cutting process, burrs of plastic left on the workpiece after the cutting process, and variations from standard hob cutting tooling that limits the ability to minimize the variation within the total gear geometry. Furthermore, a multi-step manufacturing process in which a cut gear is removed from one machine to be placed in another machine for final processing increases the amount of handling of the gear, and, therefore, increases the cost of labor associated with the final product.
A method of hob cutting gears in which the above-mentioned drawbacks are alleviated is needed.
SUMMARY
A hob cutter is used to generate and abrasively finish face gears fabricated from non-metallic materials. In a typical application, the synchronous capabilities of a CNC hobbing machine are used to maintain the relationship of the cutter to a workpiece as the cutter and workpiece are manipulated to produce a finished face gear with a minimum of operator intervention. The hob cutter includes a cutting portion and an abrading portion positioned adjacent to and in mechanical communication with the cutting portion. The cutting portion includes a plurality of hob teeth adjacently positioned to each other and helically arranged and at least one gash extending therethrough to define a cutting face on a front of each of the teeth and a trailing face on a back of each of the teeth. An upper edge is formed between the cutting face and the trailing face, and a juncture of the upper edge and the cutting face forms a cutting point. Each of the teeth is cammed to enable the cutter to create a “chip” in the workpiece. The abrading portion of the cutter includes a plurality of abrading teeth positioned adjacent to each other continuously formed and helically arranged. An abrasive surface is deposited onto the cutting portion of the cutter to facilitate the cutting of the workpiece.
In another embodiment, the hob cutter comprises a plurality of abrading teeth positioned adjacent each other and arranged helically without the cutting portion. Each of the abrading teeth have disposed thereon abrasive surfaces, which may be of varying degrees of roughness, in order to “cut” the teeth of the face gear. The abrasive surfaces may be arranged such that abrading teeth having decreasing degrees of roughness successively engage the workpiece. Abrasive surfaces having varying degrees of roughness may be disposed on the flank surfaces of a single abrading tooth.
A method of generating a face gear involves using a hob cutter to cut teeth into a workpiece and abrading the teeth cut into the workpiece in a sequential manner using an abrasive portion in mechanical communication with the hob cutter. The use of the hob cutter to cut the teeth involves engaging a cutting portion of the hob cutter with the workpiece. The cutting and abrading of the workpiece may be articulated through the use of a CNC hobbing machine.
The disclosed hob cutter in accordance with its proper method of use enables the teeth of a manufactured face gear to be more accurately shaped and dimensioned in a single processing step. Accuracy in the dimensioning of the face gears minimizes material and production costs associated with the manufacturing process by limiting raw material waste and minimizing the amount of labor required to manufacture the gear. This allows for the production of a higher quality gear while ensuring a better total functionality of the system into which the gears are installed.


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