Abstract
To realize high efficiency, low/no damage and high precision machining of tungsten carbide used for lens mold, a high frequency ultrasonic vibration cutting system was developed at first. Then, tungsten carbide was precisely machined with a polycrystalline diamond (PCD) tool assisted by the self-developed high frequency ultrasonic vibration cutting system. Tool wear mechanism was investigated in ductile regime machining of tungsten carbide. The cutter back-off phenomenon in the process was analyzed. The subsequent experimental results of ultra-precision machining with a single crystal diamond tool showed that: under the condition of high frequency ultrasonic vibration cutting, nano-scale surface roughness can be obtained by the diamond tool with smaller tip radius and no defects like those of ground surface were found on the machined surface. Tool wear mechanisms of the single crystal diamond tool are mainly abrasive wear and micro-chipping. To solve the problem, a method of inclined ultrasonic vibration cutting with negative rake angle was put forward according to force analysis, which can further reduce tool wear and roughness of the machined surface. The investigation was important to high efficiency and quality ultra-precision machining of tungsten carbide.
Highlights
Today, there is an increasing demand for aspheric lenses with the rapid development of the optical industry
Wear mechanisms of the single crystal diamond tool were mainly abrasive wear and micro-chipping according to Figure 11 as well as surface topography of the Figure 10 showed that surface roughness of 4.72 nm was obtained near the edge of the workpiece workpiece; (a) Surface roughness (Ra 4.72 nm) near the edge of workpiece; (b) Surface roughness when the diamond tool cut into the workpiece
1 mm by a diamond tool with tip radius of 0.5 mm; (a) Ra 2.55 nm when diamond tool cutting in a very a very short distance; (b) Ra 8.85 nm when diamond tool cutting in a distance of 1 mm
Summary
There is an increasing demand for aspheric lenses with the rapid development of the optical industry. The ultrasonic assisted ultra-precision diamond turning has already proved its potential for machining hard-to-cut materials such as steel [12], Co-Cr-Mo alloy [13], single-crystal silicon [14] and glass [15,16]. These publications demonstrate that ductile mode processing of tungsten carbide is possible [17,18,19]. Some phenomena and problems in the process will be analyzed, and corresponding solutions will significance for ultra-precision machining tungsten carbide andextensive optical molding industry.
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