Overcome the difficulty of hard material processing
Its better to produce cutting tool with ceramic knife and cubic boron nitride (CBN). Cutting tool has been rapidly developed in the short time. Some cutting tools manufacturers claim: if you use the tools wlth right ways ,the time can be shorten by 300%, also the right use way can improve the cutting precision.
The supplier recommended ceramic knife, which has negative rake Angle and larger T - chamfering(could increase pressure on the workpiece), On the contrary, According to the processing of CBN workpiece, both sides are OK.For example, when use CBN intermitted cutting ,it needs T to stand large vibration.
Ceramic cutting tool is becoming more common than the CBN, because of lower cost and more cutting edge. However, they are highly vulnerable crack due to heat.
In addition, if the blade is not grinding well, it should not be used by interrupted cutting. Although CBN is more expensive than ceramic, it has other special advantage of better cutting performance, high precision processing and longer service life .
The key choice of two kinds cutting tool materials are how to make the workpiece material, geometry and cutting speed adapt to work. Some users do not compare details one by one , they just evaluate the processing costs, and benefit.These suppliers use cheap ceramic knife first do heat treatment, iron scale and so on, then, use better precision CBN tools. In general, if the depth of hardening is greater than the desire of material, its better choose CBN.
Choose right processing method
From practical point, hard material cutting is one process closely related to the workpiece feature.It is especially suitable for cutting complex workpiece geometry like intricate arc, Angle, and the radius. You can adopt the method of single point programming turning, to complete the processing rapidly and economically, rather than purchase the grinding wheel, According to experience,hard material cutting speed:91-150 m/min and feed cutting speed: 0.05- 0.13 mm/min .Fine turning cutting depth is 0.08- 0.5 mm.
Therefore, the key points of confirming the precision of the determinants are:how to control the purity of good material,turning before heat treatment, rough turning and forming process. For example,if the tolerance of workpiece hardness are only three hardness number, cutter cutting pressure will change and cant guarantee the accuracy of 5 (including m dimensional. Unstable hardness and depth of the turning will damage the processing.Therefore,Qualified materials should be used to maintain constant rate of metal cutting, and confirm batch heat treatment hardness within + / - 1 or + 2 HRC value.
Length of artifacts will affect the accuracy of tolerance.Typical fixed bed type can be produced accurately with diameter ratio for 5: l - 6:1 soft artifacts, Due to the hardness of workpiece, cutting tool of negative rake Angle and cutting hard materials necessary for T - chamfering,so the pressure is large, therefore, when workpiece is without one block, they must limit the length diameter ratio in 3:1-4:1.
Of course, this restriction is changed according to different processing, such as hardness and roughness of workpiece, precision requirement. We have tailed block turning diameter artifacts of 13 mm, length 64 mm,the precision is poor .The tailstock play key role, but it is not a panacea for all problems. For example, the top can't prevent the workpiece tremor of 25 mm diameter and 300 mm length. To this kind of artifacts, you can only use grinding method. To ensure the strict tolerance accuracy more than 0.005 mm, the grinding process is better.
Although hard material cutting cannot completely replace the grinding, but it can take part role of considerable part , especially artifacts when the length diameter is small and shape more complex.