What Types of Granulators Are There? Industrial Size Reduction Equipment Guide

Introduction

The term "granulator" covers a much wider range of machines than most people expect. A shredder for scrap tires, a blade granulator for plastic trim, a hammer mill for wood chips, a grinder for spices — all of these can be called granulators, but use the wrong one on the wrong material and the result ranges from terrible efficiency to a completely jammed machine.

This article has one purpose: before you look at equipment quotes and talk specs with a supplier, help you figure out which category of machine you actually need.

Know Your Material Before Choosing Equipment

Many buyers approach granulator selection in the wrong order — they look at equipment specs first, then decide whether they will work. The correct sequence is: analyze your material's properties and your required output first, then map those to a machine type.

Four questions are the most critical for determining machine type:

How hard is the material?

Hard materials (minerals, glass-fiber or carbon-fiber reinforced plastics) require stronger impact force or harder blade materials. Soft materials can be handled by standard blade machines.

Is the material elastic?

Elastic materials like rubber, soft PVC, and TPU are nearly impossible to process with impact-type machines — the hammer just bounces off. These materials must be processed by shearing or tearing.

Does the material contain oil or moisture?

Oily materials tend to clog the screen; wet materials can cause powder to clump and block output, or cause rust in the chamber leading to material contamination. Both factors affect machine material selection, cleaning frequency, and screen choice.

What happens to the output?

Coarse granules for re-feeding a process and fine powder for further processing require completely different machines. The former uses a standard granulator; the latter may need a grinding mill.

Blade Granulators

Blade granulators are the most common granulating machines in factories. The core structure is a combination of rotating blades and fixed blades. Material fed into the chamber is sheared repeatedly between them until it can pass through the screen at the bottom.

Suitable materials

• Injection-molded plastic parts or trim, blown film waste, blow-molded products
• General engineering plastics: PP, PE, ABS, PS
• Rubber blocks (requires high-torque motor configuration)
• Soft industrial waste materials

Unsuitable materials

• Engineering plastics with high glass-fiber content (blade wear is extreme)
• Very hard materials such as minerals (use a hammer mill instead)
• Composite materials with strong adhesives (prone to jamming)

Vertical vs. horizontal configuration

Vertical granulators have the feed opening on top, suited to larger, irregularly shaped products such as whole hollow containers or large panels — easy to load. Horizontal designs are better for inline production: they can be installed directly beside a molding machine for simultaneous production and granulation, and provide more consistent output.

Blade material

SKD11 tool steel is the most commonly used blade material — high hardness, re-grindable, excellent cost-efficiency ratio. For materials containing glass fiber, carbon fiber, or mineral filler, carbide-tipped blades are recommended. The higher initial cost is offset by dramatically reduced wear rates.

Hammer Mills

Hammer mills are impact-type machines. Multiple hammers are fixed to a high-speed rotor. Material fed in is repeatedly struck by the hammers, then thrown against the serrated interior of the casing — the double impact rapidly breaks brittle materials apart.

Suitable materials

• Wood offcuts, scrap lumber, wood chips
• Agricultural waste: straw, rice husks, corn cobs
• Biomass fuel feedstock
• Some brittle minerals

Why they cannot process rubber or soft plastics

Impact-based reduction relies on breaking brittle materials. Against elastic materials it is almost completely ineffective — the hammer strikes the rubber, the rubber compresses and springs back, and nothing happens. Using a hammer mill on rubber or soft plastic not only produces no useful output; the sustained dry impact also generates abnormal heat and accelerated wear on the equipment.

Non-uniform output

Hammer mills produce a wider particle size distribution than blade granulators. Even with the same screen specification, the size spread is broader. If downstream processes require tight particle size uniformity, a screening step needs to be added after the hammer mill.

Shredders

Shredders are the type most often overlooked, yet for processing large-format waste they are frequently the only viable option.

Unlike the high-speed rotation of blade granulators, shredders turn very slowly — typically only a few dozen RPM — but generate enormous torque. The blade teeth are designed like claws, gripping material before rotating in opposite directions to force it to tear apart from the inside.

Suitable materials

• Whole scrap tires (will jam a blade granulator immediately)
• Large plastic drums, industrial waste bags, stretch wrap
• Whole electronic waste units (computer cases, appliance housings)
• Large timber or pallets

Position in the processing sequence

Shredders are typically the first stage in a size-reduction sequence, tearing large waste down to 20–50 cm chunks before feeding into a blade granulator for fine granulation. Feeding a whole tire directly into a blade granulator will either jam the machine or shatter the blades immediately.

Key difference from blade granulators

A shredder's purpose is volume reduction, not precise granulation. Irregular output shape and non-uniform particle size are expected and normal. The precision work is left to the blade granulator downstream.

Grinding Mills

Grinding mills operate on a fundamentally different principle from the other three types. They do not cut or smash material — instead, sustained micro-tooth friction between the material and grinding discs, wheels, or media gradually wears the material down to a powder.

Suitable applications

• Food processing: spices, grain, herbal medicine grinding
• Chemical raw materials: powder feedstock requiring a specific fineness
• Plastic powder manufacturing: powder coatings, powder molding feedstock

Heat-sensitive materials

Grinding generates heat. For heat-sensitive materials (some spices, medicinal herbs, low-melting-point plastics), overheating causes active ingredient loss or material softening and clumping. These materials require equipment fitted with cooling systems, or the material may need to be cryogenically frozen before grinding.

Food-grade design requirements

For food applications, every surface that contacts food must be food-grade stainless steel, and the machine must be easy to disassemble and clean. The welded-shut chamber construction common on industrial granulators is completely impractical in food processing.

Quick Comparison of All Four Types

Conclusion

There is no "best" granulator — only the one that best suits your material. Start from your material's properties, match them to the categories described above, and you can establish the right general direction.

Once the direction is established, you can have a productive conversation with suppliers about motor power, blade specifications, and throughput figures — without being led astray by numbers on a spec sheet.

To understand the internal operating principles and physics of these machines, see: How Does a Granulator Work? For real-world application examples by industry, see: What Is a Granulator? Principles, Types, and Industrial Applications.