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In every injection molding machine, the barrel and screw assembly is a core component of the processing system. Plastic granules are melted, mixed, pressurized, and then injected into the mold cavity. While the mold and clamping system receive much attention, the actual lifespan of an injection molding machine often depends on the maintenance of the barrel and screw. Preventative maintenance is not just a technical requirement, but a long-term business strategy. Neglecting maintenance accelerates wear, exacerbates material degradation, and degrades performance. Careful maintenance, on the other hand, can keep the same injection molding machine performing consistently for years or even decades.
Why are the barrel and screw of an injection molding machine so important?
In any injection molding machine, the barrel and screw are responsible for transforming raw materials into a homogeneous molten polymer for precise injection. The screw rotates, conveys, compresses, melts, and homogenizes the material, while the barrel provides heat and structural guidance. Together, they influence every critical factor: melt quality, injection consistency, cycle stability, and energy consumption.
However, these components operate under extreme conditions. Barrel temperatures typically exceed 400°F (204°C), and internal pressures can exceed 20,000 PSI. Simultaneously, the screw constantly rubs against the material and barrel walls, resulting in natural wear over time. This wear is unavoidable, but its rate is entirely controllable. Symptoms of barrel and screw degradation in injection molding machines include: extended cycle times, unstable melt flow, black spots or contamination on parts, unstable back pressure readings, and increased energy consumption. If left uncontrolled, these problems can reduce part quality and increase scrap rates.
Material Selection for Injection Molding Machine: A Hidden Danger of Wear
One of the most easily overlooked factors affecting the lifespan of plastic injection molding machine barrels and screws is material selection. Specific polymers—especially glass- or mineral-fiber-reinforced or flame-retardant plastics—can abrade metal surfaces like sandpaper during processing. Over time, they erode metal surfaces from the inside.
For example: glass fiber-reinforced nylon, calcium carbonate-filled polypropylene, flame-retardant ABS, ceramic- or metal-filled engineering plastics—while providing excellent end-product performance, they significantly increase wear inside the injection molding machine. To reduce wear, Topstar recommends using bimetallic screws for abrasive materials, choosing nitrided or alloy steel barrels, applying wear-resistant coatings such as tungsten carbide, and carefully adjusting screw speed and back pressure. Another key factor is the material’s dryness. If the granules contain moisture, steam will be generated during heating. This microexplosion effect can damage the barrel surface and cause oxidation.
Temperature Management: Protecting Materials and Metals
Heat is crucial for every injection molding machine. Without proper temperature control, plastics cannot melt evenly. However, excessively high temperatures are one of the biggest enemies of the barrel and screw.
When temperatures are too high, polymers undergo chemical degradation, carbon deposits form on metal surfaces, friction increases, and barrel wall strength decreases. Many operators believe that increasing the temperature improves flowability. However, in reality, this increases thermal stress and accelerates wear.
Best practices for temperature management include maintaining each barrel zone’s temperature as recommended by the manufacturer, avoiding sudden temperature rises, using a closed-loop temperature control system, regularly calibrating thermocouples, and preventing uneven temperature distribution that can cause screw jamming or internal hot spots. This can cause stress cracking and uneven wear, thus shortening the lifespan of the injection molding machine. A balanced temperature profile ensures stable melt flow and significantly extends machine life.
Preventing Contamination and Erosion
One of the most vulnerable causes of damage to the barrel and screw systems of plastic injection molding machines is improper cleaning. Many operators often wait until problems arise before cleaning or flushing the system. By then, carbonized residues have already caused damage.
Contaminant residues in the barrel can: obstruct material flow, cause localized blockages, trigger corrosion reactions, and lead to uneven melting. Therefore, a well-maintained injection molding machine should follow these cleaning procedures: use commercial cleaning agents when changing materials, clean the barrel before long-term shutdowns, perform slow cleaning after handling high-temperature materials, and avoid using complex metal tools that can scratch surfaces. Scratching the barrel or screw increases friction, thus accelerating wear.
Operating Practices: Small Habits, Big Impact
Many technicians believe that only parts affect machine wear. In reality, the operator’s behavior is equally important. The following settings, including excessive screw speed, excessive back pressure, rapid decompression, and excessively long holding time, can increase internal stress. Adjusting these parameters to the lowest effective settings can reduce friction without sacrificing part quality. This simple change can significantly extend the lifespan of the injection molding machine. Shutdown procedures are also crucial. Stopping a hot barrel without cleaning it can lead to internal carbon buildup. Before each shutdown, the barrel temperature should be gradually reduced, residual material removed, and the barrel kept clean.
Injection Molding Machine Life Extension Strategies
At Topstar, our injection molding machine design philosophy centers on durability and intelligent maintenance. We employ advanced metallurgical technology, wear-resistant coatings, servo-driven precision processes, and intelligent control systems to protect internal components. A well-maintained injection molding machine not only produces parts but also instills confidence in production.
How to Design for Improved Reliability
At Topstar, our injection molding machines are designed with long-term hydraulic protection at the core. This includes: servo-driven pump systems to reduce pressure shocks, high-quality German and Japanese materials, intelligent pressure monitoring, built-in filter-clogging and temperature-rise alarms, energy-efficient operation, and reduced hydraulic stress. Maintenance is essential, but clever design fundamentally minimizes the need for it. Our systems reduce vibration, optimize pressure response, and extend oil life—thus preventing leaks and pressure instability at the source.
