Study on lapping performance of agglomerated diamond abrasive

Abstract

A new lapping process is proposed for high efficiency and low surface roughness lapping of hard-brittle materials such as sapphire, which sinters single crystal diamond abrasive (average grain size 3 μm) with vitrified bond into agglomerated abrasives (average grain size 30 μm). The lapping performance of agglomerate abrasives was studied through machining sapphire substrate with comparison to those using 3 μm or 30 μm single crystal diamond abrasive. The results show that the agglomerated has higher material removal rate (MRR), which is 1.127 μm/min after 15 min machining under the same conditions. It is also found that the agglomerated abrasive performs stable during the machining, the MRR of which is 0.483 μm/min after 120 min lapping, decreasing 57.14% from that after 15 min lapping, while the MRR of 3 μm single crystal diamond decreases for 78.02%. The roughness of surfaces lapped by agglomerated abrasive or 3 μm single crystal diamond is similar, which is Ra 9.45 nm or Ra 8.75 nm, respectively. Both are far lower than the Ra 246 nm of 30 μm single crystal diamond abrasive. The mechanism that agglomerated abrasive can achieve low lapping surface roughness and high MRR can be summarized as follows: it has the characteristics of multiple cutting edges which effectively improve the contacts between abrasive and sapphire surface and enhance the MRR; at the same time, it has the ability of self-sharpening, which ensures that the blunt abrasive falls off during the lapping and that new abrasives are put into process, thus ensuring the stability of the process.

Keywords

• agglomerated diamond
• multi-edge cutting
• self-sharpening characteristics
• lapping mechanism