How to choose the right ring die?
First of all, under the premise of selecting high-quality ring die, the appropriate mold hole shape, hole opening ratio and shrinkage ratio should be selected according to the specific gravity of the product material (condensation ratio = useful length of mold hole diameter of the mold hole). Under the premise of ensuring the strength of the ring die, the open hole rate of the ring die should be improved as far as possible. For certain types of materials, under the condition of ensuring a reasonable tightening ratio, the ring die of sawdust pellet mill is too thin , resulting in insufficient strength and bursting in production. In the mold phenomenon, the thickness should be increased and the pressure relief hole should be opened to increase the useful length of the ring die hole.
The ring die shrinkage ratio refers to the ratio of the useful length of the ring die hole to the minimum diameter of the ring die hole, which is a target reflecting the kneading strength of the wood chip particles. The larger the shrinkage ratio, the more robust the extruded wood chips. With regard to the ring die shrinkage ratio of the straight hole, the useful length of the ring die hole is the total thickness of the ring die, and the minimum diameter is the diameter of the die hole itself; regarding the released stepped hole and the outer tapered hole, the die The useful length of the hole is the total thickness of the ring mold minus the length of the release hole or the length of the outer tapered hole. The diameter of the small diameter segment is the hole diameter of the calculation of the compression ratio; regarding the compact step hole and the inner tapered hole, This situation is rather special. Generally, the entire ring die thickness is used as the useful length of the die hole, and the minimum diameter is taken as the diameter of the small diameter segment. Of course, the calculated ring die shrink ratio is different from the first two cases.
Roughness is also an important measure of the quality of the ring die. Under the same tightening ratio, the greater the roughness value, the greater the resistance of wood chips to extrusion, the more difficult it is to discharge, and the excessive roughness also affects the appearance of the particles. The appropriate roughness value should be between 0.8 and 1.6.