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Similar to all other dynamic machine components, screws and barrels have not unlimited life and are subject to wear. There is no generally applicable description for screw wear. Wear occurs in many different forms and is subject to many causes.
The most important form of wear is that occurring at the outer screw diameter due to the friction between the screw flank and the barrel. This causes the inner diameter of the barrel to be extended and the outer diameter of the screw to be reduced, which leads to a gap between screw and barrel. The wear models of screw and barrel are coherent and therefore, both components always should be checked for wear.

Wear can be described in a qualitative manner. A worn screw and barrel will lead to less output as well as degradation of the quality of the melted mass.
The gap created between the screw and the barrel due to wear will generate a retrograde leakage flow of melted mass in the machine. The output decreases and the retention time of the plastics in the machine is extended. Due to the extended exposure to the high temperatures, the plastic is susceptible to burn and to degrade, thus affecting the finished product.

Wear can also be quantified. Using appropriate measuring equipment, the wear of the screw and the barrel can be accurately measured up to one tenth or one hundredth of a millimetre.

Euro-Stel is specialised in wear measurements.
Certain production problems are due to wear, but can have other causes as well. In such cases, our wear measurements will definitely reveal the cause of the problem.
Many companies ask us to perform the preventive wear measurement of their screws and barrels.

Depending on the situation, we can measure the wear on site at the customer’s or ask the customer to send us the components. In both cases, the screw and the barrel must be clean and the screw must be removed from the barrel. If the measurement is carried out at the customer’s, the machine must be cold as well, in order to protect our collaborators and our measuring equipment on the one hand and to avoid measuring deviations on the other hand.

We establish a detailed report for each wear measurement, listing the measured wear in the different zones of the screw and the barrel. Our experienced collaborators check the diameters as well as the core diameter, the flank radius, the degree of flash and the overall condition of the screw. Their findings are also included in the report. Finally, we indicate if the screw and barrel need overhauling and the technical feasibility of this process.

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