Canadian Plastics

Granulators: Take a systems approach to scrap

GRANUTEC'S TRANSFORMER 1624 granulator addresses challenging grinding applications using an innovative Duo Pak cutting chamber design. This granulator is designed to handle both thin parts and purging...

November 1, 2003   Canadian Plastics



GRANUTEC’S TRANSFORMER 1624 granulator addresses challenging grinding applications using an innovative Duo Pak cutting chamber design. This granulator is designed to handle both thin parts and purgings. By changing the replaceable cutting chamber insert, it will process bulky parts. Also, the replaceable insert design ultimately extends the life of the granulator, since the inserts can be replaced when worn down by abrasive, glass-filled or high-impact plastic applications.

The tangential feed cutting chamber insert accepts a wide range of rigid parts such as: long, bulky blow molded parts, hot collapsed parisons and trim.

The top drop cutting chamber insert features a special angle downstroke to provide quick and efficient feeding of thick-wall cross sections. The rotor’s nibbling cutting action minimizes energy consumption and maximizes granulator throughput.

Hamilton Avtec 905-568-1133

REPLACEABLE BACK PLATES provide a high level of versatility to Conair’s CW Series central granulators. The cutting chamber can be modified in the field using back plates to create three feed configurations, from open tangential to restricted. The bed knives, down-stroke cut and feed opening can be fine tuned to the scrap being processed, so one basic granulator design can perform equally well in blow molding, extrusion or injection molding applications.

As well, CW granulators have “open door” access to all internal components for cleaning and maintenance. Instead of the conventional clamshell style, Conair’s CW units have a large swing-away front panel door. The screen cradle and granulate catch bin are mounted on the door so they swing out of the way. A power-assisted hopper tilts back to give access to all areas of the cutting chamber.

Stephen Sales Group 905-940-5577

Auxiplast Inc 450-922-0282

TWO OPTIONS which address downtime are now available on Rotogran’s larger granulators. To address excessive wear in the cutting chamber caused by abrasive material such as glass-filled resins or dirty post consumer waste, Rotogran offers easily removed wear plates. These can be replaced in minutes with tungsten carbide or any other material the customer may require (see photo).

Regarding downtime for blade changes and cleanout, Rotogran offers adjustable rotor knives on its three-, five- and seven-blade rotors. These can be pre-set outside the machine for a faster turnover time. To speed cleanout, the adjusting bolts are protected from exposure with 3/4 in. thick cover plates.

Rotogran International Inc. 905-738-0101

A CUSTOM-DESIGNED granulation system from Neue Herbold is being used in China to reduce PE and PP pipes up to 6 m in length, 70 cm in diameter with wall thickness of 10 cm. The automated system consists of a heavy-duty Type SR 1200/800 granulator with a special rotor and extra heavy-duty cutting chamber, plus a feed hopper suitable for lengths up to 7 m. A specially-designed device which feeds material into the cutting chamber is combined with a pre-loading trough that can be loaded during the grinding process.

Neue Herbold offers the SR granulators in various sizes and capacities suitable for grinding PE, PP and PVC pipes and profiles.

Accuplast Solutions 514-630-0808

A BREAKTHROUGH in metallurgy has made it possible to manufacture long-life knives for granulators, says Tony Eccles of Uni-Shred. These knives, based on semi- carbide compositions, are said to provide an exceptional combination of wear resistance and impact strength, far in excess of that provided by conventional knife steels such as A2 or D2.

These long-life knives can extend the re-sharpening interval by a factor of three compared with conventional steel. They do, however, carry a price premium of about 60%.

Uni-Shred, through its Black Cat Knives division, offers three grades to span most applications. BC15 knives are suitable for applications where the current re-sharpening interval is determined, to a degree, by excessive chipping of the cutting edge. This grade offers extreme toughness with a small sacrifice in wear resistance.

BC30 knives are optimized for long life in recycling operations, and perform well when grinding abrasive material such as LLDPE, metallocene films and heavily-filled resins.

BC20 is a general purpose grade with wear and toughness between BC15 and BC30.

Uni-Shred 905-844-9954

HARD, BRITTLE PLASTICS such as styrenes, acrylics or engineering grades filled with glass-fibre, minerals or talc are effectively granulated by Nucon Wittmann’s SJ Series of low-speed, high-torque screenless granulators.

The cutting knives on these beside-the-press units are trapezoidal and helically aligned on the rotor for higher quality regrind and reduced power consumption. The rotor knives operate at 27 rpm. Screenless technology ensures that no longs are present in the regrind.

The hopper and cutting chamber can be opened separately for fast, convenient access for knife roller changes and easy cleaning.

Nucon Wittmann Inc. 888-GO-NUCON

CUMBERLAND’S 6500 Series beside-the-press granulators combine flexibility with a compact, space saving footprint. These units are suitable for small injection or blow molded parts, small extruded tubes and profiles, sprues, runners or edge trim. The reversible multi-feed hopper will accept hand, conveyor or robot feed applications.

Vacuum discharge integrates regrind into the material flow, while a view window permits discharge inspection. The granulator also has a double-walled, sound insulated hopper.

Roy Kirkness & Associates 905-453-3379

A systematic upgrade

Like all grand projects, it started with a vision. Steve Gilmer watched two co-workers reach into wire bins, pull out automotive bumpers and hand-feed them to two huge granulators, while wearing safety gear and working on a mezzanine. “I watched them one day, and my eyes were opened. I never realized just how difficult and physically demanding this task was,” says Gilmer, maintenance manager with automotive molder Plydex, a division of Decoma International.

“I thought: Wouldn’t it be nice if all a guy had to do was drive a lift truck over to the granulator and drop the bin of scrap?”

That vision prompted Gilmer to start a granulator upgrade project at Plydex’s Aurora, ON facility.

With an innovative two-phase automated regrind system Gilmer has reached his goal. Now, a single operator with a lift truck can place the scrap bin in the tipper, start up the system, and walk away.

The tipper dumps the scrap into a low-speed ReTech shredder, which expels its regrind onto a conveyor. The conveyor takes the regrind to the granulator infeed. From the granulator the material goes through a dust collector and metal detector, and into a gaylord. “We end up with a gaylord of pure, clean material, and no one had to touch a single part,” says Gilmer.

“Our throughput has gone sky-high,” he notes. The ergonomic and repetitive strain issues of manual feeding are eliminated, and the process is less dusty.

The new scrap management process starts at press-side. Gilmer designed bins that hold discarded bumpers neatly, with the wingtips pointing down. These are carried by lift truck to the shredder. An automated tipper built by National Bulk Equipment is able to dump the bumpers from these open-top, open-side “bins” into the shredder.

The shredder is a ReTech RG 62/125 from Vecoplan LLC. It has a low speed, high torque design, with hydraulic ram feed. Gilmer says he chose this unit because of its solid construction. Despite its solidity, certain parts of the granulator are designed to break away and be easily repaired or replaced when, inevitably, someone drops a piece of metal into the unit.

To convey the flake from shredder to the granulator housed in its own grinding room, an inclined conveyor is used. Again, Gilmer chose a rugged, well-built system from a local supplier, General Conveyor. The regrind system was initially constructed using a blower and piping to convey the regrind, but velocity and abrasion quickly defeated that design.

One of Gilmer
‘s key concerns was to make the system safe and foolproof. The shredder is surrounded by guarding, with safety interlocks on the doors. A basic, wireless video surveillance system is mounted near the operator panel to easily show an operator what’s in shredder infeed at all times. “It’s all wired so that all the components must be started up in sequence,” explains Gilmer. That way, there’s no chance of starting the shredder but forgetting the conveyor, etc. “The independent group that did our pre-start health and safety review was very impressed with the safety procedures designed and implemented by the maintenance department at Plydex.”

Anyone who has hand-fed a granulator would be impressed with the system too.

National Bulk Equipment Inc. 616-399-2220

Vecoplan, LLC 336-861-6070


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