Signs of Parts Wear
One of the most asked questions by customers when they encounter problems with their extruders is with a part’s life. Simple inspection of both the inlet chamber and the inlet feed screws of your extruder can determine the need to replace parts. It is recommended to completely dismantle the extruder once a month and inspect for wear.
The inlet chamber of the extruder is often neglected because there is less heat and pressure generated there. The product being extruded is more abrasive at this point, it can often be where the most wear is found. Unstable amperage and surging of the extruder usually indicate worn parts in the inlet. Rotation of the screws in the inlet can dramatically increase the service life of these parts.
The following advises what to look for and how to solve the issues:
1) Inlet and middle compression chambers: If the rifling in the chambers is worn smooth, the chamber can be rebuilt by welding with a mild steel rod to bring the height of the rifling to its original dimension (these dimensions can be found in the operator’s manual). It is only recommended to rebuild chambers once or twice. If pitting in the original casting is evident, make sure to replace.
2) Screws: Screws with severely rounded or sharp flighting should be replaced. Never rebuild a screw. A crack in the screw is also an indicator it is time to change.
3) Wear sleeves: Wear sleeves will get a visible groove with time. This will indicate wear to half of the sleeve surface, with the worn surface visibly thinner than the unworn surface. Wear sleeves can be turned once before replacing by loosening the set screw in the compression chamber and using a long punch to drive the wear sleeve out. It is flipped end for end and replaced in the chamber.
4) Steam locks: Steam locks’ wear is noticed when the outside edges become round instead of flat, and the grooves on the face of the steam lock become smooth. The loss of 1/8 inch of the outside diameter, in addition, can signal time for a change. Cracks indicate need for replacement.
5) Bullets: Bullets that have a pointed tapered end or rounded, outside edge needs to be replaced.
6) Nose Cones: Nose cones should be replaced if the inside face has a rounded tapering or severe grooving. Monthly inspection can avert costly down time, and also save on parts’ cost. If parts are let go past their normal service life, they can cause other parts to wear out prematurely.
