When the new machine is used for half a year, due to the wear and tear, we must check the clearance between the screw and the barrel every three months, and make appropriate adjustments. This should be done to avoid an excessive clearance which could cause a decline in production output, and could even be the result of the large angle of the screw swing leading to a broken screw.
The clearance between the screw and the Bimetallic Screw Barrel is directly related to the quality of the product. If the clearance is too large, it will result in a low shear rate and bad plasticizing effect. Serious back-flow phenomenon of material will not only decrease the output, and will also make residence time of the material in the barrel longer and the material will be easy to burn. If the clearance is too small and the shear rate is too large, the material will also be burned easily, the screws will even scraping against barrel. Therefore, the clearance between the screw and the barrel can be neither too large nor too small.
Before measuring the clearance between the screw and the barrel, it is necessary to clear the material left in the barrel, and the screw shaft should be tightly close to the distribution box. As shown in the following image, measure the clearance by a feeler gage at the point of A and B. Reasonable clearance (marked by T) should be between 0.20~0.30mm. Follwing steps is about how to adjust clearance of conical twin screw barrel.
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