What is the screw OD65 wear characteristic and counter measure?

Jul 08,2016

Base on the data information screw OD65, its L/D ratio reach 37.17, which is very rare seen. With this kind of L/D ratio, when the screw running, the screw flight outer diameter at the metering zone will create a heavy adhesive wear which is unavoidable. At the same time it will happen under abrasive and material fatigue wear as a priority. 

To select using such a longer L/D ratio screw, mainly it can have better plasticizing and homogenous mixing feature. High polymer material is required to add in additive filler such as Calcium Carbonate powder at high proportion, higher mixing function is needed. In fact it is more suitable to use a Co-rotating twin screw extruder but now unfortunately, only one single screw extruder to handle it, the longer L/D ratio screw is our only choice, it really is manage to do a difficult job beyond ita reach. 

This stone powder not only aggravate three kinds of mechanism wear mentioned above, but also creates a very high torsional force until the screw deflection and distorted, causes one side of the screw to be scratched, even the alloy layer the hardness of which is up to 60HRC, to be scraped off, to be chipped off in a metal pieces chip off. You can see the seriousness of the stone powder.

For this kind of mechanism wear characteristics of this screw, our counter measure are : 

1. It is not advisable to use the screw with the worn off and without hardness inner ID barrel condition. For the barrel recommended to use α101 bimetallic inner liner for compatibility; 

2. Screw material has to be changed to use High Tensile Strength normalizing steel with medium carbon 40CrNiMo to withstand the high torsional force; 

3. The thermal refining on screw body must reach around 300HB; 

4. When all the screw making process has finished, addition of Stress Relieving Process;

5. Screw metering section can use detachable section design, its material could be tool steel with High Speed Steel and thru a hardening process. 

For your reference only.

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