How to Fix Plastic Pelletizing Machine Overheating & Screw Friction: A Practical Guide for Ghana Recycling Plants

If you run a plastic recycling business in Accra, Kumasi, or anywhere in Ghana, you’ve probably met this one before: the middle zone of your pelletizing machine suddenly climbs well past the set temperature, and even after the panel cuts power to the heater bands, the heat keeps rising.

Around the local yards, operators call it “the machine catching fire,” or plain overheating. With electricity tariffs where they are now, and voltage drops — or the odd Dumsor — never far away, this is not something you can shrug off.

When a pelletizing machine overheats, the plastic inside burns, turns black, and that whole batch of recycled pellets is ruined. Worse, the extra friction loads up the main motor and can burn it out, which can put the line down for days.

Why does it keep overheating?

A lot of plant managers first suspect a blown heater band or a bad thermocouple. But if the temperature keeps climbing after the heaters are cut, the heat isn’t coming from the electrics. It’s coming from mechanical shear — physical friction inside the barrel.

In Ghana, much of the feedstock is locally collected: HDPE jerry cans, crushed hard plastics, dirty PP woven bags. When these go in and the gap between the screw and barrel is too tight, or cold lumps of hard plastic weren’t cleared before a restart, the material throws off a lot of frictional heat. You can’t switch that off. So no amount of toggling the electrical panel fixes it.

Based on what actually happens in Ghana’s workshops, here are three low-cost, practical steps — no big spare-part spending needed.

Step 1: Drop the motor RPM and adjust the pre-heat temperature

Start by slowing the main motor to cut shear heat at the source. Too many operators run at max rpm to chase the day’s tonnage, and the screw ends up tearing and squeezing the plastic far too hard. Ease the rpm down on the VFD inverter panel; it slows the melt travel, and the friction drops with it.

If you’re running LDPE water sachets or thin film, you can also nudge the previous zone up by 5–10°C so the plastic is fully molten before it reaches the problem zone — a soft melt makes a lot less friction. Keep an eye on it, though: pushing too far just burns the material.

Step 2: Clean the barrel cooling blowers, and check for hard-water scale

Next, get the built-in cooling system working properly. Ghana’s yards are dusty, and plastic dust flies around, so the mesh covers on the barrel cooling blowers clog up fast. Often the panel tells the blower to run, but the fan is jammed or the air duct is blocked. Have operators blow the blades out regularly with an air-compressor gun.

If you run a water-cooling loop, watch for hard-water scale. Our local water builds up scale that blocks the small pipes, so check the cooling lines now and then to keep the water flowing and carrying the friction heat away.

Step 3: Check screw alignment and look for warp damage after Dumsor

If the temperature still stays high after you’ve slowed the speed and cleaned the fans — and you hear a metallic grinding when the machine runs empty — the screw has shifted out of line.

A sudden power cut (Dumsor) while the barrel is full of molten plastic can warp a long screw shaft as the plastic hardens inside. Have your mechanic pull the screw during weekend downtime.

Check the outer flights by eye for shiny spots or black scratch marks. If there’s real rubbing, the honest answer is that this wants a careful hand: polish that local area lightly with a grinder and check the gap, or realign the gearbox and barrel so the screw isn’t fighting the inner wall. If in doubt, call the machine supplier before grinding — it’s easy to take off too much and open up the clearance, which causes more trouble than it fixes.

Summary

Get these three steps into your routine and the temperature settles down, you turn out clean pellets without black spots, and you spare your motors — and your electricity bill.