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Mold-temperature controllers & chillers.

You're paying for consistent process temperatures, so make sure the unit can deliver them reliably with minimal maintenance. And ask yourself how much control sophistication you really need.

Not all processors are especially choosy when it comes to chillers and mold-temperature controllers--except about price. But some recognize that process-cooling equipment, however simple in basic function, is much too vital to take for granted.

"I think it's one of the most important pieces of equipment we have," says Tom Opielowski, director of manufacturing for Precise Plastic Products Inc., a custom injection molder in East McKeesport, Pa. "If the unit is not accurate or precise and you get a wide variety of temperatures or you don't get good flow of coolant, it's going to have a direct effect on the quality of your parts."

WANTED: ROCK-STEADY CONTROL

Since as little as 5-10|degrees~ F fluctuation in mold temperature can have a detrimental effect on part quality, the assurance of consistency is one of the equipment's biggest selling points. The biggest factor in providing that consistency, users and manufacturers say, is a reliable coolant valve that does not stick. "One of the biggest reasons for downtime I've seen in these units is a valve problem," Opielowski notes.

Solenoids have been the most popular type of valves in chillers and mold-temperature controllers. But processors and suppliers quickly point out that solenoids have their problems. Ideally, the solenoid opens to let in a blast of cool water and at the same time releases a corresponding amount of overheated water, keeping the mold temperature constant. But if the valves sticks open or closed for just a few seconds, too much or too little cool water enters the unit, causing the mold to be overcooled or overheated.

In just the past few years, some mold-temperature controller suppliers have moved away from their reliance on solenoids, going to a motor-driven ball valve that provides continuous metering of water in and out of the system. Some processors who have tried them say they prefer the new valves because they ensure the most accurate and consistent temperature control. And those opting to stay with solenoid valves say they want suppliers to guarantee their reliability.

GET REAL-WORLD EXPERIENCE

The need for consistency harkens back to the factors most often cited by processors for buying any piece of auxiliary equipment--reliability, ease of maintenance, and quality of construction.

"What I really need to know is what will be my uptime," says Dick DuPlain, director of manufacturing for Sage Products, Crystal Lake, Ill., a molder of healthcare products with a 24-hr, seven-day operation. Because Sage runs mostly polypropylene, its need for reliable cooling is extremely important since the crystalline resin requires a great deal of heat removal in the mold.

Before buying temperature-control equipment, DuPlain recommends visiting a few plants using heat-transfer machinery from different suppliers to see how the units perform under normal processing conditions rather than in a demonstration at a supplier's lab.

"I want to see what happens when the rubber hits the road," DuPlain says. "And to do that I don't need a salesman hanging over my shoulder." Other processors' comments closely mirrored DuPlain's views.

In the maintenance area, potential buyers say they look for units where the side panels can quickly be removed for access to the machine's innards. Top concerns related to quality of construction are that tanks be insulated to ensure consistent water temperature, and be made of materials such as stainless steel or plastic to prevent corrosion.

CONTROLS: PLAIN OR FANCY?

The trend among new equipment offerings has been toward more sophisticated microprocessor controls and control panels that present a wider range of process information. But processors interviewed for this story said they mainly need simple controllers with basic readouts and alarms for monitoring coolant temperature. "We'll probably never use all the features in the controls we bought," reports one medical and electronics molder. "But it probably doesn't hurt to have them," he adds, as long as the extra control features don't increase the cost of the unit.

These comments may not reflect typical buying behavior. Equipment suppliers frequently offer a choice of level of control sophistication, with the more basic version typically costing around $300 less than the next step up. Although the processors interviewed said price was a major factor in their equipment selection, one major supplier of process-cooling equipment estimates that only 20% of the cooling units sold carry the more basic, lower-cost controls package.

One newer feature of electronic controls is very important to some processors: the ability to communicate with molding machines and provide SPC data. "We chose these temperature controllers because they allowed us to tie their controls in with our molding machines," says Rex Roe, maintenance manager for Nypro Iowa, Mt. Pleasant, Iowa. "All of our other auxiliaries have controls that allow us to set them up from the molding machine, and these units fit in nicely with that."

Beyond the initial purchase price, processors say they are concerned about the cost of maintaining sophisticated controls. "The electronics in the controllers can be too expensive to replace or even service," says Precise Plastic's Opielowski. He says one supplier told him it would cost $500 to repair or $1000 to replace the controller on one of his mold-temperature units. "That was just too much," he adds, "so we switched suppliers."

Suppliers respond that they guarantee the electronics in their controllers, usually for at least three years. At least one major supplier offers a lifetime warranty on the electronics, replacing any burned-out board for a $100 charge. This supplier agrees that "when the cost of the whole unit is only $2000, it's hard to justify $1000 to replace a circuit board."
COPYRIGHT 1992 Gardner Publications, Inc.
No portion of this article can be reproduced without the express written permission from the copyright holder.
Copyright 1992, Gale Group. All rights reserved. Gale Group is a Thomson Corporation Company.

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Title Annotation:Straight Talk on Buying
Author:Monks, Richard
Publication:Plastics Technology
Date:Oct 1, 1992
Words:950
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