Plastics Size Reduction : Plastics Technology

The overall goal of most plastic recycling programs is to turn scrap and non-conforming parts back into a similar size and form to the virgin material being processed. This “regrind” will often have the proper material characteristics, such as strength or optical qualities, to be blended with the original resin. This can then be reused to make more parts. It’s both cost efficient and environmentally friendly.

Plastics processors use size reduction equipment for a variety of reason, but generally alongside injection molding, blow molding, extrusion, and thermoforming processes. It’s also used for general recycling purposes. There are three common types of resizing equipment:

Granulators are very effective at reprocessing sprues, runners, and small to medium size parts. They typically generate particles from 1/8” to 3/4” in size, though most granulate runs between ¼” and 3/8”. Granulators are most commonly found near injection molding machines but are also used with other processes such extrusion, blow molding and thermoforming. The three common types of granulators are: beside-the press, central and special units designed primarily for thermoforming. But there are many more granulator technology options which customize a unit to fit any broad or specific application.

Shredders are for large or very dense parts. They can rip up large items into smaller pieces about 2” to 4” in size and are effective on a wide range of materials. Shredders reduce the time and effort required to cut up large parts in preparation for granulating. Previously this had been done by hand. Like granulators, shredders also have several technology options that will suit them best for any given application.

Pulverizers take 5/16” particles and grind them into powder. The powder is commonly used for compounding, blending, PVC recycling, or rotational molding. A wide range of materials can be ground by pulverizers.

For this Size Reduction Knowledge Center, we will focus on granulators and shredders which are most commonly used by plastics processors.