In injection moulding machines, the screw is in constant contact with the molten resin.
One of the moulding defects, ‘black spots and foreign objects’, is caused by the resin remaining in the cylinder being degraded by heat and oxygen.
Resin remaining in the cylinder is degraded by heat and oxygen, and burns and turns into carbides. This occurs when these carbides peel off and flow into the moulded product as ‘black spots and foreign objects’.
The cylinders are cylindrical and relatively easy to clean, but the screws are uneven and time-consuming to clean as they mix the resin.
In addition, there were areas that could only be cleaned with a cutter knife, and the safety of the operators was being questioned.
So, as a result of searching for a safe and inexpensive way to clean the screws
A commercially available blasting machine was modified and used as a dedicated screw cleaning machine.
The media used for blasting was chosen to be resinous to avoid scratching the screws.
The operation of this specialised machine has reduced the screw cleaning time by a third.
Note that depending on how the blasting is applied, the screw may be subject to uneven wear, resulting in poor resin mixing. The operation should be managed by consulting the screw manufacturer and measuring the screw diameter.
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