How to replace the screw barrel of the waste plastic granulator?

Plastic granulator screw

The operation of replacing the screw barrel of the waste plastic granulator should be carried out in accordance with safety regulations and equipment structural requirements to ensure stable operation, good plasticizing effect, and extended service life of the equipment after replacement. The following is a detailed step-by-step guide that combines the structure of a universal extruder with the characteristics of a recycled plastic granulator:

1、 Preparation before replacement

Shutdown cooling and material cleaning

Stop feeding and continue running the main engine until the material is basically emptied.

If processing high viscosity plastics (such as PC, ABS), it is recommended to add PP or PE cleaning materials before shutdown to help remove residual materials.

Turn off the power supply of the head heater, but keep the temperature of each section of the body at the set value for easy cleaning while it is hot.

Power outage and safety protection

Cut off the main power supply and hang a "Do Not Start" warning sign in the control cabinet to prevent accidental operation.

Wear thick asbestos gloves, goggles and other protective equipment before dismantling to avoid high temperature burns.

Preparation of tools and spare parts

Prepare specialized disassembly tools: screw pulling tool, copper shovel, wire brush, wooden hammer, copper rod, adjustable wrench, hex wrench, etc.

Confirm that the new screw barrel model matches the original equipment (such as diameter, aspect ratio, thread form).

Prepare high-temperature resistant lubricating grease (above 350 ℃), paraffin, rust proof oil and other auxiliary materials.

2、 Dismantle the old screw and material cylinder

(Suitable for single screw and twin-screw equipment)

Dismantle external components

Remove the temperature and pressure measuring components, as well as the cast aluminum heater, from the machine head.

Remove the flange connecting the machine head, remove the machine head components, and clean the internal debris while it is still hot.

Disassemble the screw tail connector

Loosen the fastening screws or caps on the shaft end of the coupling, and pay attention to recording the corresponding markings of the splines and sleeves at the ends of the two screws (the twin-screw should maintain synchronous configuration).

For left-hand threaded fasteners, use a special tool to disassemble counterclockwise.

Pull out the screw

Install specialized screw bolts and slowly synchronize the external pulling of the screw.

Clean the residual material on the surface of the screw with a copper shovel and wire brush while it is hot, and avoid scratching the surface with iron tools.

Place the screw flat on the wooden board or sleeper to prevent bending and deformation.

Dismantling screw components (suitable for modular design)

Remove the threaded sleeve, mixing head and other components while they are hot, and it is strictly prohibited to strike them with hard objects.

If stuck, the cylinder can be reheated and the material in the gap can be softened before dismantling.

Disassemble the material cylinder

Loosen the locking nut at the tail of the material cylinder, remove the heating ring and temperature sensing wire, and perform insulation treatment.

Use steel pipes to push out the material barrel from the rear end, or use a crane to lift it out.

Clean the rack and installation position, and check if the seals are aging.

3、 Install a new screw barrel

Cleaning and Inspection

Thoroughly clean the inner hole of the machine barrel, and use a wooden stick wrapped in cloth dipped in paraffin to wipe it.

Check whether there are scratches or deformations on the surface of the new screw, and confirm that the clearance between it and the material barrel meets the standard.

Assemble screws (if segmented)

Apply high-temperature resistant grease evenly to the core shaft and the inner holes of each component.

Assemble the screw components in the original configuration order to ensure a smooth fit and connection of the end faces.

Tighten the head screw (pay attention to the left-hand thread direction).

Install the screw and barrel

Reset and fix the material cylinder, and reconnect the heating system circuit.

Slowly push the screw into the barrel to ensure that it does not scratch the inner wall.

Connect the tail of the screw to the drive shaft, align with the spline mark, and tighten the coupling.

Restore external components

Reinstall the machine head, heater, and temperature and pressure measuring components.

Check if the water, gas, and oil pipelines are unobstructed and eliminate leaks.

4、 Testing and Debugging

Heating and preheating

Start the heating system, raise the temperature of each section to the process set value, and hold for more than 30 minutes.

Manual turning inspection

Manually rotate the screw in the power-off state to ensure no jamming or scratching.

No load trial operation

Start at low speed for a short period of time and observe whether the current and sound are normal.

Gradually increase the speed to the working range and confirm that there are no abnormal vibrations.

Load trial production

Add a small amount of raw materials for trial extrusion, observe whether the discharge is uniform and whether the pressure is stable.

Adjust temperature control parameters and screw speed based on actual output.

5、 Maintenance suggestions and precautions

Regular replacement cycle: The lubricating oil should be replaced after the first 500 hours of operation of the new machine, and comprehensive maintenance should be carried out once a year thereafter.

Wear monitoring: When there is a decrease in production, poor plasticization, or pressure fluctuations, the wear of the screw barrel should be checked in a timely manner.

Refurbishment and repair options: If the wear is not severe, tungsten carbide spray refurbishment can be considered, with a cost of only 30% -50% of replacing new parts, and durability close to that of new products.

Prohibited behavior:

Do not repair or clean moving parts while the equipment is in operation.

It is strictly prohibited to clean the barrel or screw by grilling with fire.

Do not use sharp metal tools to directly scratch the surface of the screw.