Skeptical Canadian molders miss out on benefits of central raw materials handling
The vast majority of Canadian plastics processors could stand to significantly improve their raw materials handling systems, or upgrade to central raw materials handling systems, according to industry...
The vast majority of Canadian plastics processors could stand to significantly improve their raw materials handling systems, or upgrade to central raw materials handling systems, according to industry experts.
The majority of Canadian processors’, materials handling processes are adequate at best, said Keith Harris, Canadian sales representative at Mould-Tek Industries Inc. in Scarborough, Ont.
Rob Miller, president of Nucon Wittmann Inc., agreed. Some processors simply don’t believe raw materials handling systems will bring benefits. Others say they have invested too much money in their current systems and/or can’t find a way to justify the cost of upgrading or implementing a central materials handling system to their managers, he noted.
Many companies believe that unless they’re buying and storing material in bulk, then a central system isn’t worth considering, Harris noted.
“Unlike a high volume extrusion operation, many injection molding shops run many different materials combined with frequent mold changes and don’t have the need for bulk material storage,” he explained.
But processors can still benefit from central systems even if they aren’t buying resin by the silo. Any processor running a few machines or more, conveying different materials from any location and using several hundred pounds per hour, would benefit from some materials handling automation, Harris noted.
Jackson Products, in Belmont, Mich., recently moved to a central raw materials handling system with the assistance of Wittmann Inc., Nucon Wittmann’s American counterpart, and started buying in silos — automatically saving US$0.03 to US$0.05 per pound — and switched to central drying.
“Centralizing the materials handling and drying allowed us to reduce overall material inventory, eliminate materials storage at the machines and 27 warehouse locations for a gain of about 1,350 square feet (sq. ft.) in floor space,” said Todd Hoogewind, plant manager at Jackson Products. “This allowed us to add molding capacity for new products that we would not otherwise have been able to accommodate with the machines and space we had.”
Plus, Jackson Products was able to move away from storing molds in a central location to placing them right by the machines for faster mold changes, he said.
Now 10 months after the system was implemented, Jackson Products is well on its way to achieve return on investment (ROI) — initially projected at 14 months — of the US$250,000 it spent on the project.
TAKING A LOAD OFF
Both Mould-Tek’s Harris and Nucon Wittmann’s Miller said there is a misconception that switching to a central system requires a complete rip and replace, but in fact, central systems can be built incrementally, over months or years as needed.
Many Canadian plastics processors use integral loaders for all conveying requirements rather than a central system, not realizing that a central system expands easily to load blenders and dryers as well as the machines, Mould-Tek’s Harris explained.
“The problem is, once a company gets to a size where a central system should be considered, it has usually already invested in many integral loaders and is reluctant to discard them,” he added.
“Although some integral loaders can be converted to vacuum receivers to reduce the cost of a new central system, it is not always the best solution.”
However, processors can slowly work towards converting their integral loader-designed materials handling system to a central system by designing it to enable conversion to a central vacuum receiver at a later date.
“The trick is to introduce a central system but maybe only start with one vacuum receiver and add them as required as older motors (on integral units) fail, for example,” Harris said. “The only drawback is the initial expense, I guess, but even that pays for itself very quickly. If you have to replace 10 to 12 loaders a year that would pay for a central pump.”
PAST MISTAKES HINDER PROGRESS
But processors need to avoid satisfying their short-term needs rather than their long-term requirements, said Steve Buckley, sales and marketing manager at Process Control Corp. in Atlanta, Ga.
“Our past experience with a central materials handling system that had been abandoned made us realize the system must be designed to meet our specific needs or it would be a wasted investment,” Jackson Products’ Hoogewind explained.
The simple matter of conveying material from storage silos or gaylords can be thrown into chaos by adding a new injection molding machine, Buckley said.
Overestimating the importance of a vacuum pump’s horsepower is a mistake Steven Hamilton, general manager of Mississauga, Ont.-based Hamilton Avtec Inc. said he has often seen.
Horsepower depends on throughput, the number of bends and the diameter of the tubing of the vacuuming conveying system.
“It doesn’t do any good to install an extruder sized for 2,000 lb./hr when your pellet conveying system can deliver only 1,300 lb./hr,” Buckley said. “You might be tempted to simply hitch more powerful pumps to your vacuum-conveying tubes. But it’s not that simple. Pumps have to match the diameter of the conveying tube or else the material will move too fast or not fast enough.”
CENTRAL DRYING DEBATE
Opinions vary amongst the auxiliary equipment community about the most cost-effective drying methods.
Dan Saigh, Motan’s national sales manager, said central drying is definitely not a new concept, but is not widely used in North America. He said central drying would benefit most processors because it would help reduce the amount of lost resin, save floor space and improve quality control by minimizing the opportunities to contaminate materials.
But processors doing a lot of blending might find a central drying system more of an inconvenience than a benefit.
“If you choose to blend prior to drying the material and you have to convey it a long distance, you risk materials separation. That’s why many processors like to blend and dry at the machine,” Mould-Tek’s Harris explained.
“Once you go to central drying, it’s hard to change, and it can be costly if it’s not designed and used properly,” Harris said. “For the average injection molder, portable dryers at each machine offer maximum portability and versatility. Because you’re drying at the machine, it’s easy to blend first, dry, then process with less chance of contamination.”
Plus, conveying moisture-sensitive materials a long distance from the central dryer requires costly dry air conveying.
Also, if the central drying system goes down — usually due to improper maintenance — then production at all lines needing dried materials will halt. This is one reason Hamilton said he is seeing Canadian companies move away from central drying back to beside-the-press drying.
A CASE FOR CENTRAL DRYING
Some molders, however, swear by their central drying systems.
“The central system eliminated the cost and maintenance of beside-the- press dryers and downtime for spare parts issues wile providing added floor space around the machines and reduced materials costs,” Jackson Products’ Hoogewind said. “The central system also offered better inventory control by eliminating several boxes for the exact same resin at multiple machines, not to mention the potential loss of unused materials in the drying hoppers and part boxes.”
Central drying involves one dryer mounted with multiple hoppers that can be run at different temperatures, which allows processors running multiple jobs on the same machine to pre-dry material, minimizing machine downtime, Motan’s Saigh said. A single central dryer uses less energy than multiple standalone dryers, he added.
“Regenerating a desiccant bed in a dryer takes a lot of energy, so if you have a lot of dryers, you’re burning up a lot of energy,” Saigh explained.
Processors that are taking on new jobs or have resin changes for a
current job can also avoid purchasing new dryers; they can simply add a new hopper to the central dryer.
If implementing central drying in one step isn’t economically feasible, molders can build towards central drying over a period of time, Saigh said. To start, users could set up a dedicated drying area and convey the dried material to the molding machines. This would start by freeing up floor space. Later on, they could slowly replace their existing dryers with a central dryer and multiple hoppers.
Kevin Drummond, president and owner of Butler Plastics in Marine City, Mich., moved to central drying, using Conair’s ResinWorks system, from beside-the-press drying two years ago, but integrated two of its portable dryers. When those dryers fail, Butler will add two more hoppers to the central system.
Central drying helped Butler reduce the amount of downtime from mold changes, Drummond said. The company specializes in short-run and custom products, and conducts about three to five material changes a day. Prior to central drying, each injection molding machine had a dedicated dryer, but each time a new job was started, they had to wait about an hour for the new material to dry to conduct the mold change.
Starting up a new job takes now only five minutes.
“In our shop, we’re saving three to five hours of runtime a day at US$40 to US$60 an hour,” Drummond said.
That cost saving has enabled Butler to run a leaner, more efficient operation, and has helped solidify relationships with its existing customers.
“I can’t tell you our ResinWorks system got us a new job or a new account, but is certainly has, as far as our customer base is concerned, shown them we were willing to make that kind of investment,” Drummond said.
Jackson Products also used the implementation of its central materials handling system to clean up the mezzanine, paint the walls and rails, and add other improvements like epoxy coating of the floor to make its facility a showplace for the company. And having a clean, efficient, facility goes a long way to impressing new and potential customers.