Laser assisted turning and grinding of ceramic materials

At room temperature, PCD or PVD tools can only be used to cut ceramics on a lathe. Due to the impact vibration caused by pores and defects during processing, the tool is prone to edge collapse or abnormal wear, and the tool life is extremely low. Therefore, almost no one uses this method to process ceramics.

Therefore, in order to fundamentally change the current status of ceramic processing, there must be new breakthroughs in processing methods. The key is to change the hard brittle characteristics of ceramic materials during processing, that is, to change brittle cutting to plastic cutting. The general heating method is limited by the properties of ceramic materials, such as the insulation of ceramics, which makes it irrelevant to electric heating. The flame heating temperature is low and the energy density is insufficient. Japan's Takashi Ueda once used far-infrared technology to heat the hot-pressed silicon nitride workpiece as a whole to over 2500 ℃, and then used ordinary turning tools to process internal threads, which can be described as "effortless". But this heating method will inevitably lead to phase transformation of the material, unless it is in situations where there are very low requirements for the use of parts.

Plasma heating poses certain difficulties for ceramic materials. Due to the non-conductivity of ceramic workpieces, they cannot directly serve as cathodes, and other methods can only be used for arc ignition. If non transfer arc heating is used, the heat flux density is insufficient. Tian Xinli once attempted to use the auxiliary electrode method to draw out a plasma arc with a maximum current of 100A, and then used the inertial flame socket at the outlet to measure Al ² O ³ The ceramic coating is heated, and the temperature at the center of the flame nest is measured by an infrared thermometer to be 2500 ℃. Due to the rapid movement of the heat source with the tool holder, the time history for the workpiece is only 0 For 4 seconds, the radius of the softening zone can reach 0.5mm, which is the only way to meet the normal cutting requirements for turning. Processing ceramic coatings is barely achievable, but for structural ceramics, it is still necessary to significantly increase the power density of the plasma source.

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Laser heating has the following advantages:

(1) Power density up to l0 to the 8th to the 10th power of W.CM - ²， The heating speed is extremely fast, enough to achieve plastic processing under high-speed cutting conditions for any ceramic material;

(2) The laser spot can be focused to the micrometer level, with a small heat affected zone;

(3) The output power is adjustable, and the heating temperature and spot diameter can be adjusted according to different workpiece materials.

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