Canadian Plastics

Granulators: Bigger and Better

Throughput and quality of granulate are the key differentiating points among the various types of size reduction equipment available for large, bulky or dense plastic pieces. Traditional granulators h...

October 1, 2001   By Cindy Macdonald, associate editor



Throughput and quality of granulate are the key differentiating points among the various types of size reduction equipment available for large, bulky or dense plastic pieces. Traditional granulators have the benefit of high throughput, while shredders or shredder/granulator combinations tend to operate more quietly on less energy but don’t have high throughput levels.

When dealing with post-consumer scrap, throughput is a critical factor in profitability, explains Mike Cyr, vice-president, sales at Rotogran International Inc. “The key to a high throughput is to have a large screen area,” says Cyr, “and a large diameter cutting circle.”

Rotogran recently sold a giant granulator that will be used by a recycler in the Toronto area to process post-consumer scrap from Toronto’s curbside collection program. Rotogran has guaranteed this WO 4465-36-HD granulator will process 8000 lb./hr. of post-consumer scrap, and reduce it to granulate that passes a 3/8 in. screen. The machine has an infeed opening of 44 in. x 65 in. with a 36 in. cutting circle. It weighs about 20 tons, says Cyr.

Cumberland’s 3200 Series of granulators are suitable for post-consumer products, heavy extruder purgings, sheet, pipe and blow molded parts for automotive, appliance and furniture applications. The 3200 Series is available in three sizes. All have a 36 in. cutting circle, hydraulic hopper/cradle, 200 to 400 hp motors and throughput rates up to 12,000 lb./hr.

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MEET THE MULTI-TASKING GRANULATOR

To take full advantage of the size and power of a large granulator, Granutec’s Multi-Task Granulation System Model TFG3648 has a convertible hopper and rear feed chute for simultaneous feeding of parts to achieve maximum throughput.

The convertible hopper design uses a transition insert to accommodate changes in part size and eliminate the possibility of overfeeding.

Through the rear feed chute, the operator can feed sheet, foam plank or parts such as fascia from floor level.

Similarly, IMS has introduced a dual feed option on its granulators. The new hoppers have an opening in the front for manual feeding and a chute on top to accept feeds from a robot. The top feed chute is removable and can be replaced with a lid. The dual feed option is available on all four sizes of IMS granulators, ranging from 10 in. x 8.5 in. to 24 in. x 12 in.

FOCUS ON FUNDMENTALS

CMB Wittmann’s granulators were highest rated among seven granulators tested recently by Plastic Product Review. They scored particularly well for quality of cut. The company’s MC Series ranges from throughput of 330 lb./hr. to 3300 lb./hr. Infeed hopper configurations are available for sheet, pipe and profile, continuous granulation of film or edge trimmings, and belt conveyor feeding.

An angled rotor design coupled with a pre-cutter makes Getecha’s ARG granulators virtually unjammable, the company reports. The scissors-type cutting action also produces clean, dust-free regrind of uniform size. The ARG machines are designed for regrinding plastic sprues and small parts. The ARG 77 has a 7 in. cutting diameter and the ARG 1012 a 12 in. cutting diameter.

Design advances in the Maguire’s Shuttle Granulator have made it more efficient than the original version, and have resulted in more consistent granulate, according to the company. Among the changes are a pneumatic drive system that prevents jams by sensing an over-feeding condition, and a pneumatically-driven follower plate inside the containment chamber that prevents material fly-back.

The Shuttle granulator is a new type of plastics size-reduction equipment. The two-stage unit literally planes reject parts into small pieces (in a manner similar to a carpenter’s plane), then granulates the pieces into highly uniform regrind using a Maguire Radial granulator.

In the Radial design, the rotor moves in a circular path around a nearly vertical axis at 1750 rpm. Maguire reports that this design produces less dusting and less heat build up in the granulate than conventional granulators.

MEGA GRINDERS

The ReTech RG98K from Vecoplan also makes light work of big jobs. Its 98 in. x 120 in. hopper opening and 15 cubic feet hopper volume allow the machine to process large extruder purgings, reject parts, trim scraps, baled or loose film, synthetic fiber and carpet without prior size reduction. The RG98K’s 250 hp drive motor powers a 25 in. diameter rotor with 30 cutters, delivering throughputs up to 45,000 lb./hr.

The machine is equipped with ReTech’s hydraulic Bridge Breaker vertical feed ram and airspring counterknife shock absorption system for contaminated applications.

Rotogran also produces a rotary grinder. The machine uses a drum-type rotor and a ram that pushes the material horizontally into the rotor. It is particularly suited to dense parts and purgings.

Holzmag single-shaft, shredder-granulators use a patented cutter design engineered for plastics applications. The rotor shaft construction minimizes cutting friction and heat build-up. The machines are also available in dual shaft configuration.

Wayne Winkler, from Expon-Holzmag in Vancouver, explains that the Holzmag line includes machines large enough to handle 300 lb. purgings and large thermoformed parts (8 ft. x 8 ft.), reducing these to 3/8 in. particles in a single pass.

SMALL BUT POWERFUL

From Moditec’s Goliath range of low-speed, high-torque granulators, the Twin design is most suitable for larger parts. With twin rotors, these units can have from 5 to 9 pre-cutters. The cutting chamber can be up to 29.5 in. x 33.5 in.

The Goliath Twin units operate at 25 rpm with up to two 4 hp motors.

An optional Masher system pulls parts into the cutting chamber. The Masher is located inside the hopper, on top of the cutting chamber. The blades rotate to grab parts and push them into the cutters of the cutting chamber.


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