Plastic extrusion machine malfunction solutions of screw and barrel

Quality of work the screw and barrel combination of these two parts of the plasticized material, product quality and production efficiency, and have a significant impact. Their work quality and accuracy of the two parts of the manufacturing, assembly space related. When twenty badly worn extruder production drops, they should arrange for the screw, barrel repairs.

First, the damage causes the screw and barrel

A screw in the barrel rotates, the material and the friction between the two, so that the work surface is gradually screw and barrel wear: screw diameter is gradually reduced, the inner diameter of the barrel is gradually increased. Thus, the gap with the diameter of the screw and barrel, with the gradual wear and tear and a little bit of both increased. However, due to the resistance in front of the cylinder head and manifold does not change, which increases the material to be extruded move forward leakage flow, i.e., material from the diameter of the feed gap at the direction of the flow amount. Resulting in decreased production of extruder. This phenomenon has also caused material increases the residence time in the barrel, causing the material to decompose. If polyethylene, hydrogen chloride gas generated by the decomposition of enhanced corrosion of the screw and barrel.

2, the material in any calcium carbonate filler and glass fiber, etc., can speed up the screw and barrel wear.

3, due to the plasticizing material is not uniform, or a metallic contaminant compound, so that a sudden increase in screw rotation torque, the torque exceeds the ultimate strength of the screw, the screw is broken. This is an unconventional accident damage.

Two screw fixes

1, broken screw according to the actual internal diameter of the barrel to consider, according to the normal clearance barrel outside diameter of the screw gives new manufacturing deviations.

2, reduced diameter threaded screw wear surface after treatment, thermal spraying wear-resistant alloy, and then by grinding to size. This method is generally a professional spray processing plant repair, the cost is still relatively low.

3, the threaded portion of the screw in wear resistant alloys. According to the degree of wear surfacing screw 1 ~ 2mm thick, then screw grinding to size. This wear-resistant alloy of C, Cr, Vi, Co, W and B, such as material composition, increasing the screw anti-wear and corrosion resistance capabilities. The high cost of professional welding plant for such processing, in addition to the special requirements of the screw, seldom used.

4, can also be used to repair the screw method of hard chrome plated, chrome is also wear-and corrosion-resistant metal, but hard chromium layer is relatively easy to fall off.

Third, the restoration of the barrel

Inner surface of the barrel higher than the hardness of the screw, it is more damaging than the screw late. Scrapped diameter is the diameter of the barrel due to increased wear and tear of time. Its restoration follows:

1, due to increased wear of the cylinder diameter, if there is a certain time of the nitrided layer can be directly put the barrel hole boring, grinding to a new diameter size, and then click the preparation of a new screw diameter.

2, the inner diameter of the barrel again after finishing machining cast alloy thickness between 1 ~ 2mm, then finished to size.

3, under normal circumstances barrel wear faster homogenization segment can be paragraph (take 5 ~ 7D long) was boring dressing, adding a nitriding steel bushings, screw diameter bore diameter of the light, stay in normal with the gap, preparation for processing.

Emphasize here, screw and barrel of these two important parts, one is elongated threaded rod, a relatively small diameter and long holes, their machining and heat treatment processes are more complex, are more difficult to ensure accuracy . Therefore, these two parts are worn to repair or replace with new parts, some comprehensive analysis from an economic perspective. If the repair cost is lower than the cost of some new ones screw, it was decided to repair, which is not necessarily the right choice, compare the cost of repairs and updating costs, is only one aspect. Also depends on the cost of repairs and the repair time and update costs and screw the screw using a ratio of time updating. A scheme using the ratio of small economies, is the right choice.

4, screw and barrel manufacturing materials

Screw and barrel manufacturing, currently used materials 45,40 Cr and 38CrMoAlA.

Extrusion pump machine manufacturing materials imported screw and barrel, common alloy has 34CrAINi7 and CrMoV9. This material has a yield strength of about 900MPa. After nitriding, hardness 1000HV above, both wear and good corrosion resistance.

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