Five Signs Your Screw Barrel Is Finished (and When Repair Still Makes Sense)

Maintenance8 Oct 2026·5 min read

Wear is gradual enough that most operators adjust the process for months before they accept that the hardware is gone. These are the five signals that tell you where you actually stand.

1. Output drops at the same screw speed

As clearance between flight land and bore opens up, material leaks backwards instead of moving forward. You compensate by raising screw speed, which adds shear - and the cycle feeds itself.

2. Melt temperature creeps up

Higher shear from that same leakage means more heat. Watch for discoloration, black specks, or a cycle time that has quietly lengthened because cooling now takes longer.

3. Pressure and power draw climb

Restricted feed or degraded material pushes head pressure and motor load up together. Compare current readings with the figures from when the machine was new.

4. Visible scoring or pitting

During the next screw pull, look at the metering section and the compression zone. Polished-bright lands and visible pitting mean the hardened layer is gone, not merely scratched.

5. Product quality drifts between shots

Shot weight variation on injection, gauge variation on film and sheet: inconsistent plasticating is often hardware, not parameters.

Repair or replace?

• Screw with even wear, barrel bore still in tolerance → rebuild the screw, keep the barrel
• Localised heavy wear in a section → consider a segment replacement on a twin extruder
• Bore ovalised, nitrided layer gone, no dimensional record → replace the set
• Barrel body sound, bore worn → bimetallic relining is often worthwhile - we will tell you honestly when freight makes it pointless

← Back to all news