1.Introduction of PCD

At present, the application scope of PCD, PCBN tool expands to automobile, aerospace, precision machinery, home appliances, wood, electronics and electrical industries, for the production of turning tools, boring tools, milling tools and drill, reamer, countersink, saw knife, carving knife, razor, etc.

Although the development of PCD, PCBN tool is so fast, but because of its high hardness caused by the tool grinding difficulties has been troubled by most users, the regrinding of the blade is mainly completed by the original tool manufacturers. Not only the tool price is high, the delivery time is long, and the occupation of enterprises and institutions working capital. Therefore, it is necessary to study the grinding characteristics of PCD and the grinding technology of PCD cutter.

2. Manufacturing process of PCD cutting tools

The production process of PCD cutting tools generally includes polishing, cutting, fixing, grinding, quality inspection, etc. The surface of the blank of PCD superhard material is generally rough (Ra2 ~ 10μm), so we can not be directly used to make the tool. It must be polished to achieve the mirror effect (Ra≤0.01μm). Then the blade is through laser cutting or EDM wire cutting processing into a particular geometric shape and required size. Further mechanical and chemical treatment of the edge and matrix to be cemented joint, the blade is fixedly connected to the matrix by hard brazing of silver base.  Finally, we grind it with a diamond grinding wheel.

PCD cutting tool manufacturing technology is one of the vital, cutting-edge grinding qualities; using a good grinding process will improve the quality of the tool product, reducing the use of the tool cost.

3. Grinding characteristics of PCD material

PCD is made of specially treated diamond and a small binder sintered at high temperature and ultra-high pressure. The disordered diamond grains make PCD have a uniform and extremely high hardness and wear resistance. Many factories made pcd into cutting tools, grinding wheel dressing, geological drilling, measuring instruments, wire drawing tools, sandblasting tools, etc. However, the high hardness and wear resistance of PCD also lead to significant difficulties in processing.

In order to obtain good PCD cutting edge quality, the most ideal machining method is still grinding or grinding with diamond wheel.

The grinding process of PCD is mainly the result of the mixed action of mechanical and thermochemical. The mechanical action is the micro-crushing, wear, shedding or cleavage of diamond formed by the continuous impact of diamond grinding wheel on PCD material. The thermochemical process is the oxidation or graphitization of diamond caused by the high temperature formed by grinding PCD with diamond wheel. As a result of their mixing, the PCD material was removed. Its grinding processing characteristics are:

(1)Great grinding force

The hardness (HV) of PCD is 80 ~ 120KN/mm2, second only to single crystal diamond, much higher than carbide. When using the diamond wheel to grind PCD, the initial cutting strength is very high, about ten times of hard alloy (0.4MPa); Specific grinding can reach 1.2×104 ~ 1.4 ×105J/mm3, So grinding force is much higher than grinding carbide.

(2) The grinding ratio is small

Due to the high hardness and wear resistance of PCD (the relative wear resistance is 16 ~ 199 times of hard alloy), the grinding ratio of PCD is only 0.005 ~ 0.033, about 1/1000 ~ 1/100000 of hard alloy. Grinding efficiency is only 0.4 ~ 4.8mm3/min. Therefore, the grinding time is very long to ensure the cutting edge quality and removal amount of cutting tools, and the processing efficiency is very low. In addition, when the hardness, content, and particle size of PCD are different, its grinding time is also other

(3) Particle size has a significant influence
As cutting tool pcd size is mainly divided into three types: rough size (20 ~ 50μm), medium size (10μm or so), and finish size (-5μm). Different grinding sizes process different workpieces as follows,

4 PCD cutting tool grinding requirements for tooling
Based on the above characteristics of PCD grinding, the diamond grinding wheel has much higher requirements on grinding equipment than standard tool grinding machines. There are mainly:

(1) The machine tool has good rigidity in the processing system

(2) The machine tool has a short-range swing mechanism with adjustable stroke and speed