Adhesive Wear Causes

1. Improper Screw Design

If the design of the screw is not adequate to generate the necessary melting capacity, considering the resin type and processing parameters, the unmelted resin can result in an uneven plugging of the flow in the screw channels causing the screw to deflect against the barrel wall. This condition will occur more readily with new rather than old components that have considerable wear. The same condition can occur with a properly designed screw running in a barrel with an improper heat profile.

2. Wrong Component Materials

To avoid galling of metals which can rub against each other, the chemical analysis and/or hardness of the materials must be different. This “compatibility” of materials must be considered when selecting screw and barrel materials. Reiloy Westland Corporation can assist you in choosing the best combination of materials for your application.

3. Incorrect Heat Profile

In an effort to process resins at their lowest melt temperatures, low heater band settings in the transition and feed zones can cause the material to melt almost solely from shear heat generated by the screw. If the shear heat is not uniform, the same restrictive condition described in item (1) will occur, causing screw deflection and consequent adhesive wear and/or galling.

4. Poor Manufacturing Workmanship

Inferior plating, flight hard-surfacing or nitriding of screws, improper heat treatment of barrel lining or lack of straightness in the barrel (or screw) can cause adhesive wear and/or galling.

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