The follow picture is the vertical cracking of our 28 mm (Diameter)*16mm (Height）PCD wire drawing die blanks, the analysis and measures are as follows:

Based on our experience, there have three main reasons for this vertical crack.

1) The size of the hole processing is slightly larger;

2) The pressure of the mounting is too high; the third is that

3) The cooling is too fast after the mounting is finished, and the released pressure of the shrinkage of the steel sleeve is focused on the core.

After the mounting, put the die in a 400-degree oven. After the heat is kept for two hours, turn off the power, close the oven door and the vent, and the temperature is naturally 

lowered to normal temperature to prevent the steel sleeve from shrinking too fast, and the stress is concentrated on the polycrystal.