There is little denying that plastic injection-molding presses are far from being energy efficient pieces of equipment. Processing at temperatures in excess of 600°F (316°C), molding presses generate a good deal of residual heat - heat that, left to its own, simply would be released into the environment and ultimately wasted.

Mold Precision Engineering Inc. (MPE), Simi Valley, CA, a $2 million per year custom injection-molding company, operates eight machines that range in size from 28 to 250 tons. The company also operates two additional units - one for transfer molding and another for compression molding. Proactive in his approach to management, company president Peter Minaskanian recognized that rising energy costs in California could negatively impact his bottom line. He looked to his presses and realized that much of the heat generated was lost.

"If we could reduce the amount of heat being lost through the barrel of the mold press, we could reduce operating expenses," Minaskanian said. "We run our presses at temperatures from 350 to 700°F [177 to 371°C], so the dollars wasted in heat loss can be substantial."

Reducing heat losses from the presses also would increase worker comfort. 'In one area of our facility, we operate a pair of 165-ton presses parallel to each other, with the operator situated between the two," Minaskanian explained. "In the past, that area would regularly get about 20°F warmer than the ambient temperature."

Following research, Minaskanian realized that a thermal blanket-type insulation system such as the one manufactured by UniTherm Insulation Systems, Lewisville, TX, could satisfy both the energy cost and worker comfort concerns. Working with GRT Inc., Sun Valley, CA, the authorized dealer of UniTherm products to the southern California area, Minaskanian sized and ordered the company's UniVest insulation system for each of the two 165-ton presses.

When delivered, press operators at MPE found that the blankets installed easily onto the barrels of the presses. "The fit is excellent in that it simply wraps around the barrel and is secured using Velcro straps," Minaskanian said. During the sizing process, additional care was taken to ensure that all openings for electrical connections were correct and did not compromise the insulating values.

NET INCREASE EQUALS ZERO

With the blankets in place, the improvement was immediate

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and measurable. "From the operator's point of view, it's as if there are not even any machines there," Minaskanian said. "The ambient temperatures do not rise at all, with the presses in operation."

Heat losses from the barrels are minimized, reducing energy consumption by a measurable factor. 'Though it was purely coincidental, at the same time we installed the blankets, we added another press," Minaskanian explained. "With the savings realized from using the blankets, we barely noticed any increase in our electric bill as a result of adding the new machine. So, it could be said that adding the two blankets allowed us to add one machine."

Additional cost savings resulted from a reduction in the time needed to bring the presses up to operating temperature for the morning's first runs. "At the end of the day, the machines are, of course, shut down. In the past, that would have meant they'd cool to a temperature equal to ambient temperature. Now, with the blankets in place, the machines retain heat so well that they are still warm when we start up in the morning. Granted, they are not at the temperature we need, but they are still a good deal above ambient temperature. As a result, we use far less energy getting those units up to processing temperature."

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In addition to cost savings, the thermal blankets provide an extra safety benefit, Minaskanian noted. Because temperatures on an exposed barrel can reach 700°F (371°C), the risk of worker injury resulting from brushing against the barrel is always present. Covering the barrel with the blankets essentially eliminated that risk. And, while MPE's application involved the injection-molding process, the same benefits can be realized in blow molding or extrusion.

For Minaskanian, the performance of the UniVest system can on occasion be too good. "For example, if we are running high temperature materials, at the end of the run we have to open the blankets to allow the machine to cool down. But with the Velcro straps, opening up the blankets and then refastening them when the barrel has sufficiently cooled is not a problem."

MPE has been so pleased with the performance of the insulation systems thus far that it is currently having two additional machines sized. The California state legislature is considering raising electric rates as much as 30% to bring the state's power crisis under control. Should those rate increases become a reality, Minaskanian is convinced this approach will help MPE continue to flourish. PH

Dealing With a Power Crisis

So, how bad can the energy crisis in California possibly be? It is easy to dismiss the plight of Californians as nothing more than a corporate-level PR campaign geared toward gouging utility customers, or a minor inconvenience blown out of proportion by the media. The fact is, however, there is a finite amount of electricity available to many customers. Exceeding their energy quota can mean one of two things for manufacturers: paying exorbitant rates or temporarily shutting down. A surprising number have chosen the latter. Many, however, have taken steps to reduce consumption of this suddenly exhaustible power supply.

lnterbath is an injection molder of bath accessories, shower heads, hand-held showers and other bath fixtures. At its City of Industry plant alone, the firm employs approximately 500 people and uses 40 molding presses ranging in size from 28 to 250 tons. The current power situation prompted Ron Zamora, lnterbath's process engineer, to set up an appointment with UniTherm Insulation Systems to do an energy study.

"Most of our heaters and molds are open and exposed to the atmosphere, forcing us to waste a lot of heat. Our company is committed to a savings plan with Southern California Edison that places a ceiling on our power consumption. Up to that ceiling, we pay a rate of $0.06 per kW/hr. However, should we exceed that ceiling, the rate rises to $9 per kW/hr," Zamora said.

Rates like that have put everyone at lnterbath on alert. "The situation has become so critical that we had a warning light installed in the center of our plant. The light flashes to notify us when we are exceeding our consumption," Zamora continued. "When that happens, we shut down until the light goes off, indicating that our usage is back within the specified limits. Obviously, we are looking at all means to avoid having that happen too frequently."

UniTherm's Dan Sherrill conducted a study on one representative press at lnterbath, both with and without any form of insulation. The findings showed that with a thermal blanket-type insulation system in place, power consumption was reduced by 36% over a 30-min period.

"I was surprised at the level to which we could reduce wasted heat," Zamora said. "At this point, we are looking into blanketing all the machines in this facility. It's one of the few solid recourses we have to help deal with this tough situation."