Extrusion problems generally involve temperature control, mechanical wear, and process conditions. The symptoms and corrective measures differ between rubber and plastic extruders, so troubleshooting should begin by identifying the material, the affected component, and the conditions under which the defect occurs.
1. Common problems with rubber extruders
Excessive temperature and scorching
Excessive temperature occurs when the extruded rubber semi-finished product leaves the machine above the process limit of 120°C. The surface may become uneven, and the compound may show signs of scorching.
Two possible causes are excessive clearance between the screw and barrel, which allows rubber to flow backward and remain in the machine longer, and an unsuitable pin arrangement with too many long pins.
Measure the screw clearance against the equipment specifications and replace the screw if it exceeds the permitted limit. Inspect the pin arrangement and adjust the proportion of long pins where necessary. The reference process recommends keeping long pins at no more than 85% of the total pin count and arranging them at intervals that gradually decrease along the direction of material flow.
Scorched particles, dead rubber, delamination, and blisters
These defects can be associated with temperature fluctuations, changes in compound viscosity, pin configuration, or the condition of the screw and temperature control system.
For recurring problems, check the temperature settings alongside the screw clearance, pin wear, cooling performance, and material properties. Seasonal changes in ambient temperature may also require adjustments to the established process parameters.
2. Process problems with plastic extruders
Unstable output
Fluctuating output may result from uneven barrel heating or excessive clearance caused by screw wear. Both conditions can affect melt flow and extrusion consistency.
Check the temperature control system and calibrate its control modules where necessary. Inspect the screw for wear and establish a regular maintenance schedule to monitor temperature accuracy and screw condition.
Material buildup at the die head
Material sticking or accumulating at the die head may be associated with insufficient lubrication, unsuitable temperature settings, screw wear, or excessive environmental humidity.
If the temperature is too high, the plastic may degrade. If it is too low, the material may not melt sufficiently. Review the formulation and lubricant proportions, verify the temperature settings in each zone, and inspect the screw and die head for wear or residue. Environmental conditions should also be controlled according to the material requirements.
3. Mechanical and electrical faults
Unstable main motor current
Fluctuations in main motor current may be caused by inconsistent feeding, damaged motor bearings, faulty heating elements, or misaligned screw adjustment shims.
Inspect the feeding mechanism first, then check the motor bearings and lubrication, heating elements, and mechanical alignment. Correcting the underlying fault is preferable to compensating for it by changing operating settings alone.
Main motor fails to start
A main motor may fail to start because of an incorrect startup sequence, an electrical fault, an activated safety interlock, or residual charge in the variable frequency drive.
Check the prescribed startup procedure and inspect the electrical circuit and safety interlocks. If the drive has a discharge waiting period, follow the manufacturer's instructions and confirm that the equipment is safe to service before opening electrical enclosures or handling components.
Do not bypass safety interlocks to force the machine to start.
4. Preventive measures for extrusion equipment
A preventive maintenance program helps identify faults before they interrupt production. The inspection schedule should reflect the extruder type and operating conditions.
For rubber extruders, check screw clearance, pin arrangement, pin wear, and temperature control performance. Pay particular attention to cooling and the effect of seasonal temperature changes on compound processing.
For plastic extruders, calibrate the temperature control system, monitor screw wear, and verify that the selected temperature profile matches the resin and formulation.
For both types of equipment, keep startup and shutdown procedures consistent and record recurring defects, temperature variations, and mechanical faults. These records can help distinguish a process problem from component wear or control system failure.
5. Custom machining for extrusion equipment components
When an extrusion problem results from a worn or damaged mechanical component, replacement may require a part made to specific dimensions and fitting requirements. Hansheng Automation can assess custom machining based on customer drawings, material specifications, and dimensional tolerances.
Our precision machining services also cover non standard components for rubber processing, packaging, filling, and tobacco machinery. We can assess parts for yacht equipment and RC racing cars according to the supplied drawings and machining requirements.
