Steel is one of the most popular engineering materials used in industries. However, cutting steel directly with a diamond cutter causes severe tool wear. Various approaches have been investigated to improve the tool life and surface finish of the work piece. This includes cryogenic cooling, application of carbon-rich gas and ultrasonic vibration assisted machining.
We had successfully overcome this difficulty by development of a vibration assisted single-point diamond cutting module. It increased the cutting efficiency and surface finish of bare steel-alloy substrate, enabling its application for generating optical profile of mirror finish on hardened steel when attached on an ultra precision machine.
Hardened stainless steel work piece sizes from less than 1 mm to greater than 40mm in diameter have been machined using this method and a finish of better than 5 nm Ra can be obtained. A profile accuracy of 0.15μm had been achieved for 10mm diameter samples. It has bee used to produce numerous pieces of optical inserts for plastic lens molding applications
The advantages of diamond direct cut steel inserts over nickel plated ones:
- Shorter fabrication turn-around time (one week versus 4 weeks)
- Better quality surface (high scratch resistance, less peeling, no chipping/cracking on sharp edges, less prone to tarnishing, etc)
- Longer mold life (at least 3 times over nickel plated ones) & no DE-laminating of plating
- Higher molding temperature (over 300°C)