June 1, 2007
As virgin plastics’ prices climb, and in some cases adequate amounts of resin are scarce, processors are becoming increasingly savvy in using post-production scrap. “Scrap shouldn’t be considered waste, but secondary raw material,” says Paul Niedl, division sales manager recycling, Starlinger & Co. (Vienna, Austria).
The right granulator, such as this one from Conair, can help processors get maximum value out of their post-production scrapTop: Vecoplan’s RG64K single-shaft rotary shredder helps reduce processors’ virgin resin costs by producing quality regrind, in-house.
The [processing] industry has changed its view of reclaiming plastics. I think injection molders see the benefits of press-side reclaiming,” says Don Maynard, president of Size Reduction Specialists (SRS, E. Lansing, MI), a producer of screenless granulator equipment. Yet many processors still won’t use regrind even if they can due to a misconception that it is harder to process, citing inclusion of fines, dust, and non-uniform material compared to virgin resin, says Robert Harrison, granulator product manager, Wittmann (Torrington, CT).
Dust and fines are often caused by dull knives, plugged screens, improperly gapped knives, excessive rotor speed, and screen holes that are too small, Harrison says. Many problems come from poorly maintained equipment or older granulators.
Some processors look at scrap reclaim “as an extra expense, and one that they would rather avoid,” says Mike Verner, regional product sales manager granulation, Conair (Pittsburgh, PA). “Rising resin prices have brought added focus to the inherent value of scrap.” But the customer needs to understand that universal production waste-recovery solutions don’t exist.
Verner points to a customer who molded thick-walled parts with machining threads used in it. “He had both scrap parts and thread cutting shavings from the process. Initially he told us only about the scrap parts, assuming that any granulator that could handle the thick-wall sections could easily gobble up the lightweight thread shavings,” he recalls. The thick-walled parts were nibbled away by a conventional cutting chamber and multiple rotating knives, but the lightweight thread shavings simply sat above the rotor and never were ground. The processor needed a tangential-style cutting chamber for this material.
“Having the wrong granulator is as bad as or worse than not having one at all. Such was the case of a medical products molder who just replaced 13 existing granulators with a like number of [our] units,” says Verner. To justify the purchase, the processor analyzed the cost of scrap and downtime and found it was costing the company with its old equipment $10,000/month. These produced polycarbonate fines, longs, and dust that clogged his materials handling system and the molding machines’ feed throats, forcing cleaning downtime and extra labor. “It got so bad that they simply couldn’t run regrind at all on some parts and had to landfill 500 lb/day because the company couldn’t take a chance on using it,” he says. The switch to the right granulator eliminated the problem.
Horses for courses: ensure the right granulator for the job
As a rule of thumb, equipment makers say each polymer waste calls for a different size reduction system. Luciano Anceschi, managing director of granulation equipment maker Tria (Cologno Monzese, Italy) says as much information as possible is needed from the customer about what he wants to grindâ€”density, color, throughput, and his expectations for required maintenanceâ€”to avoid equipment that doesn’t suit.
Most granulator equipment manufacturers like Rapid (Bredaryd, Sweden) provide customers with a way to make their own granulator investment cost calculations (www.rapidgranulator.se) online. H. Sattler Plastics (Chicago, IL), a plastics distributor and recycling operation for engineering thermoplastic scrap with operations in the U.S. and Malaysia, visits processors’ operations to analyze the maximum value of excess scrap that can be achieved through a material-management analysis program. President John Sattler emphasizes that what many processors term as post-production “scrap” is a misnomer and should be seen more positively as “surplus material” with a lot of value left.
Key issues today in size reduction, says Bengt Rimark, Rapid’s marketing manager, are regrind quality that blends well with virgin, lowering noise levels, eliminating as many labor costs as possible through automation, and energy consumption. If the regrind quality is up to standards, says Tria’s Anceschi, in 90% of all cases processors can use the material without having to re-pelletize it, an added expense which negatively adds to the material’s melt history.
Sattler says ideal processing operations would have beside-the-press recycling to eliminate problems of contamination that could occur with centralized shopfloor size reduction. But for many processors, it pays to send their production waste out to operations such as his, which specializes in grinding, sifting, and classification of materials which are often returned for reprocessing with virgin.
Wittmann’s Harrison says one driver to use regrind has come from processors’ OEM customers, such as in the automotive sector, who want a certain amount of regrind included in a job. “We have a customer molding trash containers for cities that require the container be made of a certain percentage of regrind. These requirements force up the price of recycled material on the market, close to virgin, and require the processor at the very least to reclaim his own scrap,” Harrison says.
Reducing costs significantly was the objective of processor Wheaton USA (Milville, NJ), where on some applications resin runner systems’ scrap composed up to 70% of the overall shot size, says Rob Krawiec, micromolding manager. The company is using SRS Bi-Cutter two-stage cutting granulators to recoup this scrap, which permits Wheaton to lower its quote price when bidding for jobs, he says. Using its conventional grinders, Krawiec says, the company had difficulties feeding because the polyethylene tended to cling and bridge.
Anthony Purdy, micromolding maintenance supervisor at the processor, says when starting one new job he figured how much polymer, additives, and colorants cost. Then he figured the amount of regrind that could be used from its conventional grinders (250 lb) compared to the SRS unit (1996 lb). He says the savings was $1159 but that Wheaton was also able to reduce its colorants needs by re-feeding colored regrind with virgin. Purdy says quality of the regrind was so good that it didn’t negatively affect end-product color. By switching granulators, he estimates that the company saved nearly $10,000 on regrind material in a single month, which translated into about $30,000 in 2006.
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