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How to select the ring die compression ratio of biomass pellet machine
Nov 08, 2018

How do we calculate the compression ratio of sawdust machine?

The compression ratio of ring die is the ratio of effective working length and diameter of die hole. The compression ratio of the ring die can be chosen according to the raw material formulation and product requirements.

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Well, according to Jinwu's past practice, let's take some simple timber. The compression ratio of Eucalyptus is 1:3.7-1:4, mahogany is 1:4-1:4.5, hardwood is 1:4.5, pine is 1:5-1:6, poplar is 1:6-1:7, bamboo chips is 1:4, corn straw is 1:6-1:8, grass is 1:9-1:10. (Approximately, the specific local relationship with the customer's raw materials, the most important thing is to know the principle, after actual testing can be considered standard).

The compression ratio of different raw materials is different. The harder the material is, the smaller the compression ratio is, the more fluffy the raw material is. That is to say, the more fluffy the raw material is, the easier it is to be pressed. The more fluffy the raw material contains more fibers and the more fibers the material is easy to be formed. Let's talk about the compression ratio of poplar wood 1:6, 1 and 6 of the figures are respectively. What does it stand for? The diameter of each hole in the annular die granulator is 6 mm, 8 mm and 10 mm. This 1 represents the diameter of each hole. If the diameter of the annular die hole is 8 mm, then this 1 represents 8, and 6 represents the effective aperture. The effective aperture is equal to the diameter of the hole multiplied by the effective aperture length, that is 6*8=48. 8:48.8:48 is simplified to 1:6, 1:6 is the compression ratio of poplar wood. That's how it is converted. The discharging quality of sawdust granulator depends on the compression ratio of ring die. But if the forming rate of sawdust granules produced by customers is not very high, then you can reduce the compression ratio appropriately, which can not only increase the output, but also reduce the die. And the service life of the pressing wheel.

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So how to choose the right mold?

Firstly, on the premise of choosing high-quality ring die, the appropriate form of die hole, opening rate and shrinkage ratio (shrinkage ratio = useful length of die hole diameter) should be selected according to the specific gravity of the product. On the premise of ensuring the strength of the ring die, try to improve the opening rate of the ring die as much as possible. For some kinds of materials, under the condition of ensuring reasonable shrinkage ratio, the ring die is too thin, which results in the failure of the strength of the ring die and the phenomenon of explosion in production. At this time, the thickness and the length of the ring die should be increased on the premise of ensuring the useful length of the die hole. Add relief holes.

The ring die shrinkage ratio is the ratio of the useful length of the ring die hole to the minimum diameter of the ring die hole. It is an objective to reflect the kneading strength of sawdust particles. The larger the compression ratio, the stronger the extruded sawdust particles. 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. For the release step hole and the outer cone hole, the useful length of the die hole is the total thickness of the ring die minus the length of the release hole or the length of the outer cone hole, and the aperture of the small diameter section. That is to calculate the aperture of the shrinkage ratio; for the shrinkage step hole and the inner cone hole, this situation is special. Generally, the thickness of the whole ring die is regarded as the useful length of the die hole, and the minimum diameter is taken as the aperture of the small diameter section. Of course, the meaning of the shrinkage ratio of the ring die calculated in this way is different from the former two cases.

Roughness is also an important target for measuring the quality of ring mold. At the same shrinkage ratio, the greater the roughness value, the greater the extrusion resistance of wood chips particles, the more difficult the discharge is. Excessive roughness also affects the surface quality of the particles. The suitable roughness value should be between 0.8~1.6.




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