Because of the large volume ofmanufactured sets, hypoid gearsare usually hard finished after heat treatment using the lappingprocess. In the lapping process, a gear set is run at varyingoperating positions and under a light load in order to lap thetooth surface. An abrasive lapping compound is used as a metalremoval media.
Because of the rolling and slidingmotion inherent to hypoidgears, the lapping compound abrades and refines the tooth surfaceto achieve smoothness in rolling action and produce high qualitygear sets. The pinions and gears are lapped in pairs and musttherefore remain as coordinated pairs for the rest of theirlives.
However, heat treatment distortion can vary significantly frombatch to batch, and even within one batch if the temperature is notconsistent throughout the heat treatment furnace. Thus, developinga lapping sequence for manufacturing requires both time andexperienced technicians who can establish lapping operatingpositions and sequence times to produce quality gear sets both interms of performance and cost. This development is generally trialand error as past operator experiences factor heavily into theprocess.
In this paper, the lapping process is simulated using advancedmodelling tools such as gear vectorial simulation for the toothsurfaces and path of contact and reverse engineering to analyze thetooth contact pattern of existing gear sets under load (staticLTCA). Test gear sets are measured using a CMM prior to a speciallapping cycle where the position of the gear sets on the lapperdoes not change, and then re-measured after lapping in order toestablish how much, and where, material was removed. A wearconstant named “wear coefficient” specific to the lapping compoundcomposition is then calculated.
Based on the obtained wear coefficient value, an algorithm forsimulating the lapping process is presented. Gear sets lapped onthe production line at American Axle and Manufacturing are used forsimulation case studies. Results show that it is possible topredict how much and wherematerial will be removed on the toothsurface, thereby opening the door to better understanding of thelapping process.
- Edition:
- 05
- Published:
- 10/01/2005
- Number of Pages:
- 18
- File Size:
- 1 file , 250 KB
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