Breviary Technical Ceramics


      From Powder to Part

 Lapped surfaces

DIN 8589 defines lapping as a cutting process using loose grains distributed in a paste or liquid (the lapping mixture) that is applied to a lapping tool, most often one that provides shaping, where the cutting tracks of the individual grains are largely unordered.

Because of the low rate at which material is removed, lapping processes are used to improve forming accuracy and surface quality. The almost isotropic surface topography of the microgeometry, in which the scratches are unordered, a large number of very homogeneously distributed hollows and isolated inter-crystalline surface break-outs are characteristic of this process. These structures are often found to be beneficial when the tribological or optical functional demands are high
In lapping, the surface material is carried away by the rolling motion of the cutting body and by scratches made by cutting grains that have temporarily anchored themselves in the lapping wheel.

gure 70: Silicon carbide surfaces lapped using F180 and F800 lapping grains

Figure 71:
Model of material removal by lapping

The surface quality that can be achieved with lapping depends on the microstructure of the ceramic material being machined. The more fine-grained and the denser the material is, the higher the achievable surface quality. Depending on the grain size, process conditions and microstructure of the ceramic being lapped, dimensional precision of 1 µm/m, plane parallelism of up to 0.2 µm, and mean roughness figures Ra < 0.3 µm, can be achieved.


<< back   home   next >>