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Processing these materials efficiently requires more than simply selecting a granulator. Material type, wall thickness, part geometry, throughput requirements, and desired regrind size all influence equipment selection and overall performance.

For demanding applications involving thick purgings, bulky parts, engineering plastics, and heavy-wall components, processors often utilize granulators with larger cutting chambers, heavier rotors, higher horsepower drives, and more robust knife configurations. In the most demanding applications, shredders or granulator systems may be used to help process large, dense, or difficult-to-cut materials more efficiently.

Why Thick-Wall Plastic Scrap Requires a Different Approach

Not all plastic scrap behaves the same during size reduction.

Lightweight runners, flash, and thin-wall molded parts generally require less cutting force and are often processed using standard granulation equipment. Thick-wall plastic parts, dense purgings, and large molded components place significantly greater demands on the machine.

As material thickness and density increase, so do cutting forces. Larger components can also create feeding challenges, increase rotor loading, and generate greater stress on knives and drive systems. Selecting equipment that is properly matched to the application helps maintain throughput, improve regrind consistency, and reduce wear on critical components.

In many applications, processors must evaluate not only part size but also wall thickness, density, material characteristics, and production requirements before selecting the appropriate solution. 

Common Types of Heavy Plastic Scrap

Manufacturers across the plastics industry routinely process materials such as:

• Injection molding purgings
• Thick-wall molded components
• Heavy wall pipe fittings
• Structural foam parts
• Rotationally molded products
• Large blow molded containers
• Engineering plastics
• Thick sheet and thermoformed scrap
• Plastic rods and blocks
• Large rejected production parts

These materials vary considerably in shape, density, and size, but they often require equipment capable of handling more demanding cutting loads than traditional production scrap.

Can a Granulator Grind Plastic Purgings?

Yes. Granulators are commonly used to process plastic purgings and reclaim valuable material that would otherwise be discarded.

The ideal solution depends on several factors, including:

• Purge dimensions
• Material density
• Resin type
• Throughput requirements

Thinner purgings can often be fed directly into a granulator. Larger or denser purgings may require heavier-duty equipment designed to manage higher cutting loads while maintaining consistent throughput and particle size.

Because purgings can vary significantly from one operation to another, evaluating the material characteristics is essential when selecting size reduction equipment.

When Should You Use a Shredder Instead of a Granulator?

Granulators and shredders are designed for different purposes.

Granulators utilize high-speed cutting action to produce a consistent, uniform regrind suitable for reprocessing. Shredders use lower-speed, higher-torque operation to reduce large and bulky materials into smaller pieces during the initial stage of size reduction. 

A shredder may be the better choice when processing:

• Extremely large molded parts
• Oversized startup purgings
• Thick cast blocks
• Bulky scrap that is difficult to feed directly into a granulator
• Large-volume reclaim streams

The best solution depends on the material and desired end result. 

When Does a Shredder-Granulator System Make Sense?

Some applications benefit from using both technologies together.

In a shredder-granulator system, the shredder performs primary size reduction before feeding material into a granulator for final sizing. This approach can improve throughput, create a more consistent feedstock, and reduce stress on downstream equipment.

Processors often evaluate this type of system when dealing with:

• Very large plastic components
• Heavy purgings
• Thick blocks and rods
• High-volume recycling operations
• Bulky production scrap

For many demanding applications, a two-stage process can provide the most efficient path to consistent, reusable regrind. 

How Cumberland Supports Demanding Size Reduction Applications

Cumberland offers a broad range of plastics size reduction solutions, including beside-the-press granulators, central granulators, heavy-duty granulators, thermoforming granulators, and shredders. These systems are designed to address a wide range of plastic reclaim applications. 

Heavy-duty granulators are frequently used to process challenging materials such as:

• Thick purgings
• Heavy wall fittings
• Blocks and rods
• Engineering plastics
• Thick sheet
• Large molded parts
• High-impact plastic scrap

By matching equipment capabilities to the material being processed, manufacturers can improve material recovery, maintain reliable throughput, and support long-term operational efficiency.

Finding the Right Size Reduction Solution

No two size reduction applications are exactly alike. Material type, density, geometry, throughput goals, and downstream processing requirements all influence equipment selection.

Whether you’re processing thick-wall molded parts, startup purgings, heavy wall fittings, engineering plastics, cast blocks, or oversized components, understanding the material characteristics is the first step toward selecting the right solution.

With the proper combination of granulation and shredding technologies, processors can improve reclaim efficiency, reduce waste, and recover more value from production scrap.