Recently a customer asked us for help, he bought several ring die matrixes from other factory and used for a short time then cracked. He would like to know the reason. After checking, we found his pellet die's thickness is only 26mm.

Why are your pellet machine ring dies easy to crack and burst?Many factors cause the cracking of the ring die of  pellet machine, which are as follows:

●Ring die material and blank quality

At present, X46Cr13/4Cr13 and 20CrMnTi are mostly used, and the material quality is relatively stable. However, due to different material manufacturers, there will be a certain gap in the trace elements of the same material. In addition, there will be differences in the forging process and preparatory heat treatment of different manufacturers. Irregular process and unreasonable preparatory heat treatment can easily lead to cracks in the ring die blank.

●Ring die heat treatment

The key process in the heat treatment of ring die is quenching and tempering. If it is overheated during quenching and heating, it will not only cause greater brittleness of the workpiece, but also easily cause deformation and cracking during cooling, which will seriously affect the life of the mold. After the heat treatment of the ring die, there will be a large deformation. If it is not repaired, the ring die will also crack during use.

●Installation of the ring die and the problem of pellet machine

Improper installation of the ring die or when the pellet machine itself is defective, such as the shaking of main shaft of the pellet machine, is also one of the factors.

●High load operation

During the pelleting process, if the amount of material entering is operated at 100% load, such a long-term high-intensity operation will also lead to cracking of the ring die. It is generally recommended to control at 75-85% of the load to ensure the service life of the ring die. In addition, the gap between the ring die and the pressing roller is too tight, which is also prone to cracking.

●Ring die abrasion

When the ring die is worn to a certain thickness and the strength is reduced to a point where it cannot withstand the pressure of granulation, cracking will occur.

●Some impurities get into pellet machine

When there are hard objects such as iron blocks, stones etc. get into pellet mill,it is easy to cause cracking problems.

●The opening rate of ring die is too high

The diameter of pressed feeds die is small. If the opening rate of the ring die is too high, the strength and toughness of the ring die of the feed pellet machine itself will also decrease, resulting in cracks.

●Influence of ring die thickness

Too thin Ring die is easy to crack.Effective thickness of pellet dies influences the pellet mill's productivity and pellet quality.

Taking the feed pellet machine as an example, the thin ring die has a higher advantage in improving the production capacity, which can reduce the danger of the ring die being blocked, and also reduce the cost of energy consumption. But the disadvantage is that it increases the demand for steam and requires more effort and experience from the operator to ensure the quality of the pellets.

The thick ring die reduces the workload of workers and ensures the quality of the pellets, but the productivity is low, the ring die is often blocked, and the ring die roller wear and cracking probability will also increase. Therefore, the correct selection of the appropriate mold thickness is an important link to ensure the quality and output of the pellet machine.

The customer mentioned at the beginning of the article, the ring die was only used for a short time, and then it burst. The biggest reason is that spare part manufacturer deliberately reduced the thickness of the die in order to save material cost, making it too thin and the strength decreased, resulting in The phenomenon of ring die cracking occurs in production.