Abstract
It is difficult to cut hard and brittle quartz glass chips. Hence, a method involving micro-crack-induced severing along a non-crack microgroove-apex by controlling the loading rate is proposed. The objective is to realize the rapid and precision severing of the hardest quartz glass in chip materials. Firstly, micro-grinding was employed to machine smooth microgrooves of 398–565 μm in depth; then the severing force was modelled by the microgroove shape and size; finally, the severing performance of a 4-mm thick substrate was investigated experimentally. It is shown that the crack propagation occurred at the same time from the microgroove-apex and the loading point during 0.5 ms in micro-crack-induced severing. The severing efficiency is dominated by the severing time rather than the crack propagation time. When the loading rate is less than 20–60 mm/min, the dynamic severing is transferred to static severing. With increasing microgroove-apex radius, the severing force decreases to the critical severing force of about 160–180 N in the static severing, but it increases to the critical severing force in the dynamic severing. The static severing force and time are about two times and about nine times larger than the dynamic ones, respectively, but the static severing form error of 16.3 μm/mm and surface roughness of 19.7 nm are less. It is confirmed that the ideal static severing forces are identical to the experimental results. As a result, the static severing is controllable for the accurate and smooth separation of quartz glass chips in 4 s and less.
Highlights
Rolling scribing with a tungsten carbide or polycrystalline diamond (PCD) wheel is widely used to separate silicate glass substrates without any coolant and material removal
In the case of loading rate v = 60–300 mm/min, the severing force rapidly increased with increasing loading time T, but it slowly increased in the case of v = 5–20 mm/min
Compared to a mechanical rolling scribe, the micro-crack-induced severing by a non-cracked microgroove-apex produces smooth severing edges without any breakages, median cracks, radial cracks and lateral cracks
Summary
Rolling scribing with a tungsten carbide or polycrystalline diamond (PCD) wheel is widely used to separate silicate glass substrates without any coolant and material removal. In the case of low and high loading rates, it was found that the loading rate produced little influence on the maximum load for the V-notch on fracture [16] These workpieces only concerned easy-to-cut polymeric and metallic materials. The micro-grinding with a sharpened diamond wheel micro-tip may be employed to fabricate accurate and smooth microgrooves on difficult-to-cut silicon, carbide alloy and glass surfaces [20], but it has not yet been applied to the crack propagation for precision and smooth severing of difficult-to-cut materials. The trued diamond wheel micro-tip was employed to grind the accurate and non-crack microgroove on workpiece surface; the severing force was modelled in micro-crack induced severing by microgroove parameters and loading rate; severing force, severing time, cracking propagation time, severing form errors and severing surface roughness were experimentally investigated
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