What Is a Molding Plastic Shredder?

A molding plastic shredder processes waste plastic products — from small rejected parts to large solid blocks — into reusable chips or flakes. It uses high-speed rotating blades to impact, shear, and tear material to a controlled particle size. Standard components include a feed inlet, cutting chamber, discharge outlet, drive system, and blade assembly. Electrical controls and overload protection ensure safe, stable operation.

Where Molding Waste Comes From

Molding processes — injection, blow, compression, and extrusion — generate significant plastic waste:

Sprues and runners — Channels that feed molten plastic into the mold cavity

Purgings — Solid blocks of plastic expelled during color or material changes

Reject parts — Defective products that fail quality inspection

Excess parison — Leftover material in blow molding
This waste is often as clean as virgin material. Recycling it back into production — rather than discarding — cuts raw material costs and reduces environmental impact.

Recycling Process

Molding scrap is typically solid and dense, so size reduction is the first step:

Large purgings — Single shaft shredders cut solid blocks into flakes using a high-speed rotor and hydraulic pusher

Small scraps — Mini granulators handle sprues, runners, and reject parts directly

The output — called regrind — is blended with virgin resin at a set ratio (typically 10–30%) and fed back into molding machines. This closed-loop approach lowers material costs, improves utilization rates, and reduces demand for new plastic production.

Wanrooe offers molding plastic shredders and granulators in multiple sizes and configurations. Contact us to match the right equipment to your scrap type, throughput, and regrind specifications.

FAQ: Molding Plastic Recycling

What is the difference between a shredder and a granulator for molding scrap?

Shredders handle large, solid purgings that would jam a granulator. Granulators process smaller, more uniform scraps like sprues and runners. Many facilities use both: shredder for purgings, granulator for daily production scrap.

How much regrind can I mix with virgin material?

It depends on the application and material type. Most processors run 10–30% regrind for cosmetic parts, up to 50% for non-visible components. Excessive regrind can affect melt flow, color consistency, and mechanical properties. Test and validate your specific ratio.

Does regrind quality degrade with each recycling cycle?

Minimal degradation occurs if the material is clean and not overheated during processing. However, each heat history slightly reduces molecular weight. Track regrind generations and limit regrind percentage for critical applications.