Achieving operational harmony
To reach a state of operation that maximizes efficiencies and throughput, you must consider the tools you use and how you implement them. In terms of extrusion processing and screw wear, this refers to the proper extruder components and proper application of basic extrusion principles.
First let’s address the component aspect of operational harmony. In most cases of galling wear and catastrophic failures, it is determined that the process was utilizing third-party or after-market screw/barrel components. Often these are no more than the original equipment manufacturer’s (OEM) parts “rebuilt” by a third party. The decision to use these third-party components is usually justified as a cost reduction measure.
Shown here is a screw that was rebuilt by an after-market part provider. It
should be noted this was a used OEM
part rebuilt using multi-pass welding
techniques to build up worn screw
flights. The end result: Welding materials
cracked away from the original screw
material and heat generated from the
welding process changed the hardness
of the screw unit, causing cracks
throughout the unit.
A rebuilt used OEM part often leads to galling wear and catastrophic machine failures.
Considered a way to reduce costs, rebuilding a screw can end up causing major damage to it and the barrel liner.
These two pictures illustrate the amount of damage resulting from other screws also rebuilt by an after-market part provider. In this case the mating surfaces between the screw sets were not machined flush or parallel after the rebuilding process, causing misalignment that resulted in major damage to not only the screw but also the barrel liner.
The same problems occur when purchasing copied dies, knives and similar components. Many after-market providers are just that—copiers— who duplicate close-to-original material sizing without taking into account metallurgy, pitches, angels, land lengths and other factors. These providers typically have no engineering or technical experience, specifically in extrusion. To the customer it looks the same, but it definitely doesn’t perform the same and often causes more production loss, even increasing the client’s chances of catastrophic equipment failure. ■
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