For Press-Seal Gasket Corp., a Fort Wayne, Ind.-based injection molder of specialized fasteners and high-precision sealing products for underground collection systems, close part tolerances are crucial. The company previously outsourced the custom molding of its parts but decided to move production in-house several years ago for better control. With its in-house tool design and fabrication, as well as its ISO 9000-2000 registered quality management system, Press-Seal was well aware of the steps that would be required to ensure that parts met all tolerances. Precise mold cooling was critical to prevent parts from warping. An added challenge was that the plant ran “lights-out,” without any operators on site, five days per week. Because of the high volume of parts and the plant’s just-in-time manufacturing (the plant has little inventory), the company could not afford to have any problems with the production of its parts.
Press-Seal contacted Wittmann Inc., Torrington, Conn., a manufacturer of temperature control units (TCUs). Wittmann reviewed the process to best determine the specific heating and cooling requirements for the molds. Through various calculations, engineers concluded that only one TCU was required per mold, instead of the two less-efficient TCUs that Press-Seal was already using on each system.
Based on its knowledge of Wittmann products, combined with the available features, Press-Seal decided to purchase Tempro Basic temperature control units.
“Unlike other units, the Wittmann TCUs have several standard cost-saving features, like leak stop and mold purge,” said Rick Morrison, operations manager for the Press-Seal Fastener Division. “Although we don’t use the mold purge feature, the leak stop feature has been a lifesaver for us as it is part of the standard unit. Previously we needed to bring a separate unit over to the machine and hook it up. Now we just push a button, and the unit runs in negative-pressure mode. We have been saved about a dozen times already with this feature and have run the units for as long as two to three days in the negative-pressure mode to complete the production run.”
Increased Temperature and Process ControlMorrison noted that the plant has not had any issues with cooling capacity using only one TCU per mold because of the higher pressure provided by the more-efficient TCUs.
“These units have really been gems. We have had one for four years and the other for five years, and they have had virtually no downtime or required any maintenance. The TCUs hold the temperature at 140°F [60°C] with no more than ±1°F [0.6°C] variation, thereby preventing any part tolerance issues,” he said.
The units are equipped, as a standard, with a dry-contact alarm. Because the plant runs a lights-out operation, Press-Seal decided to tie the dry-contact alarm into the machine. If something goes wrong in the cooling circuit, the machine automatically shuts down. For example, if a cooling hose were to leak or break, the TCU automatically would sense a drop in fluid level and trigger the alarm, which, in turn, would signal the injection molding machine to shut down.
“We have probably seen this happen four or five times since installing the TCUs,” said Morrison. “Although it doesn’t happen often, the TCUs offer a substantial benefit in terms of preventing scrap parts and minimizing fluid leaks from a bad hose.”
“If we really wanted to maximize the benefit of the TCU in an alarm situation we could have it page us, but we have yet to find any added advantage to doing so,” he added. “The most important thing is that we are not molding parts without cooling for the whole night. Once the tank empties, the unit shuts down, preventing any further mess as a result of a broken line, etc.”
The automatic shutdown feature of the TCUs has provided Press-Seal with direct cost benefits. “Molding bad parts costs us $2,000 to 2,500/hr in lost productivity based on the selling price. We don’t stock parts and only mold to order, so there is no inventory reserve to make up any shortages. Every hour of production is very important,” Morrison said.
The savings generated after a single cooling line failure essentially allowed Press-Seal to achieve a 100 percent return on its TCU investment.
Flexible CapacityPress-Seal soon will be adding a new four-cavity mold, which will run in a larger machine than its other molds.
“With the latest project, we wanted to be sure we did not overextend the capacity of our chillers when adding the additional TCUs. Wittmann met with us to perform the calculations and determined we were running only at about 60 percent of full load,” Morrison pointed out.
When Press-Seal purchased its original units, they had a lot of capacity. “The Wittmann TCUs are very deceiving, being so compact in size yet with so much capacity. We learned quickly how important it is to perform the calculations for each molding application and not just go with the size of the unit that what was used previously,” Morrison added.