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How to choose the right ring die
Apr 02, 2018

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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.
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