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Screw And Barrel For Injection Molding Machine The Occurrence Of Wear
- Jul 03, 2017 -

Screw and Barrel for Injection Molding Machine The occurrence of wear

Excessive wear will cause serious damage to the processor. The excess gap between the screw thread and the barrel surface can affect the machine's performance, efficiency and energy consumption. In extrusion, the occurrence of wear may cause the extrusion of the extruder screw barrel to be lower, thus requiring a higher screw speed and energy usage. At the same time, this is usually accompanied by higher melting temperatures and more quality problems.

With a good PM plan, careful testing of key screw / barrel clearance ensures maximum throughput, and no unplanned downtime. When producing high-quality components, the PM plan becomes more important, such as the production of medical catheters and components for medical devices.

The inspection process is to pull the screw out and thoroughly rinse while checking the outside diameter (OD) of the thread and the inner diameter (ID) of the barrel. The plastic material on the surface of the screw and barrel can be removed with a wire brush and a copper wire mesh. Precision wear measurement instruments for accurate measurement and easy to use, and a variety of specifications and functions to choose from.

First, remove the plastic from the barrel and insert an electronic aperture meter into the barrel to read the ID data at each measurement location. The thread diameter and depth of the screw can be measured by means of a screw micrometer, and the digital model tester provides a liquid crystal reading and records the data to a computer.

In order to be able to predict when the screw or barrel will need to be replaced or repaired, and the downtime in a favorable time, the need for regular measurements. For a pair of new screw and barrel sizes up to 5.08 cm, the recommended clearance range is 0.01016 to 0.01524 cm.

There is a rule of thumb is that the screw and the barrel of the reasonable gap is generally the size of 1/1000. When the maximum clearance is exceeded, the screw should be reassembled. Compared to the complete replacement, the repair service can re-use the worn parts at a lower cost. In addition, the injection molding machine screw barrel in the wear part, you can re-replace the bushing, and the extruder barrel is usually the entire bushing replaced, so the maintenance costs are more expensive, and thus not cost-effective.

Once the screw is worn at a certain point, the melt will return to the thread, causing the screw and barrel wear to further accelerate. Severe wear can cause a large amount of resin to be wasted and to reduce productivity. However, through regular PM testing, it is possible to prevent the occurrence of severe wear. The best maintenance strategy is to keep the screw / barrel clearance within a reasonable range.

Corrosive, abrasive and high temperature resistant resins may unknowingly damage the screw and barrel. For example, some engineering materials, thermoplastic elastomers and biopolymer materials sometimes form a corrosive environment. In addition, reinforcing materials (such as glass fiber, glass ball, etc.), some fillers and additives, are abrasive.