Shutdown & Startup

Cleaner Stops. Cleaner Starts. Better Production.

In plastics manufacturing, shutdown and startup are critical for both productivity and equipment health. Whether you run injection molding machines, extruders, or complex hot runner systems, the way you clean during these transitions determines how quickly you can return to full production—and how many rejected parts you’ll avoid along the way.

That’s where using Purgex for shutdown and startup makes all the difference.

Why Purging Matters at Shutdown and Startup

During the injection molding process or extrusion, molten resin flows through the barrel and screw at precise operating temperatures. If you stop production without purging, residual production resin remains inside the machine. As the machine cools, resin often degrades—carbonizing, discoloring, and bonding to metal surfaces.

When you start up again, this degraded material can appear during production. That means:

• Black specks or color contamination/streaks on parts
• Scrap is produced during startup as contamination works its way out
• Higher scrap rates and wasted labor

A proper purge before shutdown and again at startup eliminates these issues, giving you a clean, consistent production run from the first part.

Common Problems Without Proper Purging

Skipping a purge—or relying solely on production resin to flush the machine—can cause:

• Carbon buildup in the barrel, screw flights, and hot runner system
• Contaminated parts for hours after startup
• Extended color-change times
• Reduced production efficiency

For manufacturers, every rejected part and minute of downtime costs money. Integrating the right purging procedure into your startup and shutdown routine for injection molding and extrusion molding pays off in both short- and long-term productivity.

How Purgex Compounds Protect Your Machines

All Purgex grades are engineered for effective cleaning during both shutdown and startup. They combine mechanical cleaning with a foaming action to reach every area in your system—including injection molding screw flights, hot runner manifold, drops, valve gates, tips, and extrusion melt pumps, screw flights, die blocks, and die edges.

During shutdown, Purgex removes residual resin and colorant, and one ingredient in most Purgex acts as a lubrication/release agent to prevent buildup of contaminants on metal surfaces. At startup, that same lubrication effect makes it easier to clear any cooled residual resin from the machine to begin production more quickly.

This means fewer rejected parts, shorter purge cycles, and less manual teardown.

Benefits of Using Purgex for Shutdown and Startup

Manufacturers across the injection molding, extrusion, and blow molding industries trust Purgex because it delivers measurable results:

• Faster changeovers with minimal scrap
• Consistent color and material quality from the first cycle
• Reduced downtime between production runs
• Lower maintenance costs from less wear and buildup
• Compatibility with a wide range of production resins and operating temperatures

Compatible with a Wide Range of Equipment Types

Whether you’re working with:

• Injection molding machines with complex mold design features
• High-output extruders
• Hot runner systems with valve gates
• Hybrid or electric molding machines

Purgex has a shutdown and startup purging procedure that fits your process. All grades are safe for your equipment and designed to work across multiple resin types, including commodity and engineering-grade plastics.

Best Practices for Shutdown Purging

A successful injection molding shut off or extrusion stop includes more than just the purge itself. For optimal results:

• Purge immediately after the final production shot while the resin is still at processing temperature.
• Use the correct Purgex grade for your resin and temperature range.
• Remove all material from the hopper and clean the feed throat, dryer, and grinder.
• Keep operating temperature stable during the purge to maximize cleaning efficiency.
• Follow the recommended purging procedures for your machine type and process.

By adopting these steps, you’ll prevent degradation during downtime and simplify your next startup.

Best Practices for Startup Purging

When it’s time for plastic injection molding startup after a shutdown or idle period:

• Heat your machine to the correct operating temperature before introducing Purgex.
• Run the purging compound through the barrel and screw until all residual material is cleared.
• Inspect purged material for signs of carbon or color contamination. Continue purging if needed.
• Transition to production resins only once the material output is clean.

These steps ensure your initial parts meet quality standards, reducing scrap and increasing production efficiency.

Why Sealing Machines During Shutdown Doesn’t Work

Some competitors recommend “sealing” the barrel during shutdown to block air and prevent oxidation. In reality, this isn’t possible—when the machine cools, the material inside shrinks, allowing air to enter anyway.

Worse, starting up with a barrel full of cold material will lengthen heat-up times and risk equipment damage. Purgex’s approach—purging before shutdown, only leaving residual Purgex in the machine, shutting down, and purging again at startup—avoids these pitfalls entirely.

Adding Purging to Your Preventive Maintenance Program

A clean machine is a productive machine. Incorporating purging compounds into your preventive maintenance plan will:

• Reduce unplanned downtime from carbon contamination
• Extend the life of injection molding machines and extrusion equipment
• Maintain consistent part quality over long production runs

Regular purging—whether weekly, biweekly, or monthly—should be tailored to your process, resin type, and operating temperature. Purgex can help you create a procedure and schedule that works for your facility.

Full-System Cleaning for Complete Results

A purge can only do its job if the rest of the system is clean. That’s why we recommend cleaning hoppers, feed throats, material lines, and grinders when changing colors or materials. This holistic approach ensures your purge delivers maximum results.

Purgex vs. Resin-Only Purging

Using virgin resin or regrind for shutdown or startup purging is a common practice—but it’s also ineffective. Resin-only purging:

• Flows over contamination instead of removing it
• Fails to reach low-flow areas in hot runners or dies
• Consumes costly production resin without delivering a clean machine

Purgex’s engineered purging compounds foam, and lift contamination from every surface, making it the superior choice.

The Purgex Advantage

When it comes to shutdown and startup purging compounds, Purgex offers:

• Universal compatibility across injection molding process and extrusion applications
• Effective cleaning at a wide range of operating temperatures
• Fast results that minimize downtime and scrap rates
• Expert support for solving purging issues and optimizing purging procedures

Whether you’re running high-volume production or short custom runs, Purgex gives you the clean start you need every time.

Purge Smarter. Start Cleaner. Run Longer.

Don’t let contamination or poor shutdown practices slow your operation. Using Purgex for shutdown and startup will protect your equipment, reduce waste, and maximize uptime.

Contact us today to find the right Purgex grade for your situation—and see how clean shutdowns and startups can transform your production process.