The Ultimate Guide to Cleaning Injection and Extrusion Machines: Screw, Hotrunner and Injection Molding Unit

11.03.2025

2 minutes

Do you often feel overwhelmed by the constant maintenance challenges of your injection molding and extrusion machines? You’re not alone. Poor cleaning and material buildup can lead to downtime, defective products, and unnecessary costs. But what if you had a proven method to eliminate these issues effortlessly? In this guide, you’ll discover how to keep your machines in top condition.

1. Why regular cleaning is essential

A well-maintained injection molding or extrusion machine is the key to consistent product quality and maximum productivity. But why is regular cleaning so crucial?

Impact on product quality
Buildup of residual material, contaminants, and degraded plastic can lead to defective products with inclusions, color variations, and impurities. A clean machine ensures a stable process and higher output quality.

Preventing downtime and defects
Machine contamination can result in stuck valves, blockages, and increased wear on components. This not only leads to production downtime but also costly repairs and lost productivity. By regularly cleaning your machine, you prevent unplanned shutdowns and minimize scrap.

Extending machine lifespan
Keeping critical components such as the screw, barrel, and hotrunner clean prevents premature wear and damage. This means fewer investments in replacement parts and a longer lifespan for your equipment.

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2. How to efficiently clean the injection molding unit

Proper cleaning of the injection unit is essential to keep the production process running smoothly. Below is a detailed step-by-step guide.

Step-by-Step Guide

Preparation: Ensure the machine is at a safe temperature and wear protective gear.
Empty the Barrel: Purge the existing material from the machine using an appropriate cleaning compound such as Dynapurge.
Add the Purging Compound: Use a purging compound that is compatible with your type of plastic.
Cycle Cleaning: Introduce the purging compound in small amounts while running the screw at low speed.
Inspection: Check for remaining contamination by running a transparent or light-colored material through the machine.
Final Check: Remove any residue and reset the machine for the next production run.

Best cleaning methods and materials

Mechanical Cleaning: Use brushes and cloths to remove loose residue.
Chemical Cleaning: Use purging compounds such as Dynapurge for deeper cleaning without causing wear.
Heat Treatment: For extreme contamination, controlled heating can help loosen stubborn buildup.

Common mistakes and how to avoid them

Waiting too long before cleaning: The longer contamination builds up, the harder it is to remove.
Using the wrong purging compound: Not all purging compounds are suitable for every type of plastic.
Insufficient cycling during purging: Running the screw multiple times back and forth increases cleaning effectiveness.

3. Cleaning the hotrunner: Tips and Tricks

The hotrunner is one of the most sensitive components in an injection molding machine. Contamination in this system can lead to poor flow properties and defective products.

Key considerations

Regularly inspect for burnt plastic buildup.
Prevent blockages by consistently using a purging compound.
Monitor temperature settings to avoid material degradation.
Using Purging Compounds.
Choose a purging compound specifically designed for hotrunner systems.
Run the purging cycle at a slightly elevated temperature to remove stubborn contamination.

When replacement is necessary

Persistent discoloration in products that doesn’t disappear after cleaning.
Slower material flow through the hotrunner.
Frequent blockages despite purging procedures.

4. Cleaning the Screw: Injection vs. Extrusion Machines

The screw is the heart of your machine and requires specific cleaning methods depending on the process (injection molding or extrusion).

When and how often to clean

After each material change.
When detecting discoloration or inclusions in the final product.
When there is a noticeable decrease in production efficiency.

Inspection and maintenance checklist

Inspect the screw after every material change.
Check for wear and buildup of degraded material.
Use the right purging compound based on your material type.

5. Maintenance Tips for Extending Machine Lifespan

A proper maintenance program prevents unexpected downtime and ensures your machine continues to perform at its best.

Preventive maintenance and periodic inspections

Set up a maintenance schedule with fixed cleaning intervals.
Conduct visual inspections on wear-sensitive components.
Document each cleaning procedure for future reference.

Critical components that require attention

Screw and Barrel: Remove residual material and check for wear.
Hotrunner: Ensure regular cleaning to prevent blockages.
Cooling System: Prevent scale buildup and rust by performing periodic flushes.

Signs that a deeper cleaning is needed

Increased number of defective products due to contamination.
Difficulty processing plastic due to reduced flow.
Buildup of resin or burnt polymers in the screw or hotrunner.

Why Dynapurge is the best choice for cleaning your machine

Proven performance – Dynapurge is the go-to choice for professionals who demand efficiency and reliability.
Fast and effective – Enables quick and thorough cleaning, minimizing costly downtime.
Safe for equipment – Leaves no harmful residues and helps prevent wear and tear.
Versatile and practical – Suitable for injection molding, extrusion, and hot runner systems.
Reduces waste and lowers costs – Helps prevent material loss, reduces rejects, and improves operational efficiency.
Supports sustainability – Minimizes scrap, energy waste, and unnecessary consumption of valuable resins and compounds.
Optimized for high-demand environments – Keeps production running smoothly, helping you stay competitive in a fast-paced market.