Study on fabrication and cutting performance of high quality diamond coated PCB milling tools with complicated geometries

The diamond film was deposited on a complex shaped WC-Co printed circuit board (PCB) milling tool in a revised hot filament chemical vapour deposition apparatus, in which the vertical spiral hot filament arrangement was adopted. The SEM investigation on the surface of the fabricated diamond coated PCB milling tool exhibited a continuous layer of fine grained diamond films, with grain size of about 2-3 mm, was uniformly deposited. To evaluate the cutting performance of the fabricated diamond coated tool, comparative milling tests were conducted for both diamond coated and uncoated WC-Co PCB milling tools, with glass fibre reinforced composite materials as the workpiece. The milling test results showed that the flank wear on circle and end cutting edge of the fabricated diamond coated PCB milling tool were only 0.08 and 0.18 mm respectively after 40 min milling, about one-fifth and a quarter of that for uncoated WC-Co PCB milling tool, which could attribute to both the good wear resistance of the deposited diamond coating and the strong adhesion between them and the tool surface. Additionally, the thrust forces acted on the milling tools during the milling process were measured using a Kistler dynamometer measuring system. The results presented that all measured axial, radial and tangential thrust forces were smaller for diamond coated PCB milling tool, which was due to the low friction coefficient of the diamond film that could facilitate the chip evacuation.