Common problems and countermeasures of plastic granulation
Common problems in cutting
The following situations often occur in pelletizing. The most frequent occurrence is pelletizing debris, even continuous material.
How to solve this kind of problem, start with the mechanism of cutter wear
Granulation mechanism
The actual process of pelletizing is to form a pair of cutting blades between the cutter and the template discharge hole.
The cutting knife is actually a movable knife, and the cutting edge formed by the discharge port of the template granulation belt and the granulation belt is a fixed knife.
When the molten plastic is pelletized through the template with the discharge hole, the surface of the material is instantly solidified when it encounters the cooling water at 50-65°C, and the material is passively sheared into particles with a fixed knife.
The cutter is in contact with three substances during the work. The first is contact with the material to be cut, the second is in contact with the cooling water and the water vapor generated by its sudden vaporization when heated; the third is in contact with the surface of the template granulation belt when the knife is sharpened.
Therefore, the wear of the pelletizing knife is affected by these three factors, but in actual work, the template pelletizing belt is not in direct contact with the pelletizing knife.
The process of cutting the material is like this: when the material is extruded from the die hole The surface solidifies instantaneously, the blade and the discharge port produce extrusion stress on a certain section of the material, and the material begins to deform elastically and release heat, especially when the contact with the blade is violently squeezed, friction and heat are melted.
When the plastic deformation increases to exceed the yield limit, the tensile stress between the plastics disappears and the plastic is cut. At the same time, part of the melted plastic is pasted in the form of a thin film on the blade edge and the template discharge port to accumulate scabs.
When the scabs grow to a certain size, they are scraped off by water and subsequent materials. When the accumulated tumor falls off, the material at the cutting edge and template cutting edge is also stuck.
When countless pasting and falling off, the cutting edge of the tool and the template granulation belt are worn. The cutting edge is not sharp, the quality of the cut pellets is reduced, and the prominent manifestation is the increase of tailings.
If measures are not taken in time, continuous material cannot be produced normally.
Quote-[1] Qin Yujun. Application of metal composite ceramic template cutter in plastic pelletizing [J]. Industry, 2016,000 (007): P. 267-268
