Finishing of polycrystalline diamond tools by combining laser ablation with grinding

Abstract

In manufacturing polycrystalline diamond (PCD) tools, the finishing process in order to obtain the required surface and edge quality and to remove the damaged PCD layer induced by the prior manufacturing steps is mostly done by grinding. However, grinding is currently inefficient and costly due to low material removal rates and high wear of the grinding wheel. The project "Pro-PKD" aims to increase throughput and reduce tool wear by an additional laser ablation step prior to grinding. In first process investigations, the influence of different laser parameters on the ablation rate was analyzed and an optimum parameter set for maximum ablation efficiency was found. By measuring the overall material removal from the grinding wheel and the PCD tool, it could be shown that the G-ratio can be increased by at least a factor of two. Furthermore, the time required for grinding can be significantly shortened. As the time needed for laser ablation is only several seconds, in this way the whole time required for the finishing process can be reduced. In any case, the combined process presented here has the distinct advantage that it can be implemented into already existing grinding machines with comparatively low investment costs

Surface engineering of ultra-hard polycrystalline structures using a nanosecond Yb fibre laser: Effect of process parameters on microstructure, hardness and surface finish

“…The former technology is performed using diamond abrasives wheels; however, this introduces undesirable microcracks into the workpiece due to the diamond crystals bonded in cobalt, thus the abrasive tool can excise individual grains, leaving voids. At the same time Brecher et al (2013) reported that grinding is costly due to low material removal rates and high wear of the grinding wheel, thus it is relatively inefficient. Micro wire-EDM has emerged as a fast, economic and precise way to micro-machine electrically conductive PCD blanks.…”

“…Pacella et al (2015) also reported that, since cobalt is embedded in the diamond matrix, because of a difference in thermal conductivity between diamond grains and binder, important phenomena of expansion and compression between diamond and cobalt take place during the ablation process, which are also dependent on the energy density involved in laser processing. Brecher et al (2013) studied the effects of a two-step process technique (laser and grinding) in precision finishing of a 10 µm sized diamond grains PCD cutting tool. In this case a neodymium-doped yttrium orthovanadate (Nd: YVO4) laser was used after dicing and prior grinding to remove the surface layer of the cutting edge promoting improved surface finish, reduced time for manufacture and improving grinding wheel wear resistance.…”

Femtosecond laser micromachining of diamond: Current research status, applications and challenges

“…Additionally, both the nsand ps-laser processing has been successfully combined with precision grinding to improve the machining performance by several researchers, such as Brecher et al [15,81] employed a ns-laser combined with grinding for fabrication of PCD turning tools. In this process, the surface was micromachined using ns-laser irradiation to remove the bulk of the material, assisted by conventional grinding process to remove the residual.…”

Clarification of the Mechanism of Pulse Laser Grinding of Nanosecond Lasers Using High-Speed Camera Imaging

“…Everson et al used nanosecond laser processing to perform the two-dimensional fabrication of microtools in polycrystalline diamond (PCD), although the phase transformation towards amorphous carbon and graphite occurred on the processed surface. In other studies [8,9] of edge shaping using PCD or chemical vapor deposition (CVD) diamond tools, the thermal impact of the nanosecond laser was used to combine laser-induced diamond graphitization with precision grinding to improve the edge quality. However, these processing methods have the problems of complex operation, low efficiency, and high cost, and the resulting edge sharpness is insufficient for application in high-precision machining.…”