Injection Mold Builders

Conformal cooling takes new twist

The holy grail of molding is the rapid cooling of molds, and while several techniques have been tried (and some have failed) conformal cooling of molds is making some headway.

Mold cooling is at the heart of molding-cycle optimization and part quality, which means that mold manufacturers need to understand mold cooling, molding cycle optimization and be up on the latest cooling technologies. "Mold manufacturers need to be concerned about cycle time if they want to help their customers maintain a competitive edge, improve efficiencies, productivity and profits in order to compete on a global basis," said Bob Beard of Robert A. Beard Associates Inc .  His mantra was given in a webinar for the American Mold Builders Association , and it's something he preaches often to various groups.

As a "mold-cooling guru," Beard is familiar with the many technologies that have been developed over the past couple of decades to reduce cycle times and improve both quality and profitability. Beard noted that using high-thermal conductivity metals such as beryllium copper and aluminum has helped molders achieve cycle reductions of 20% or more. Of course, aluminum isn't suitable for every mold application.

While optimizing the choice of mold material may represent 50% of available cycle reduction, Beard said that the other 50% "is analyzing and optimizing how the cooling lines are connected to the plant cooling system." Beard's "enhanced cooling" analysis is the first step toward improving cooling in mold/molding systems. "By taking an engineering systems approach," Beard said, "cycle times can be reduced by 20% or more on existing molds. Measuring and optimizing water flow to ensure that turbulent flow is truly present in the mold-cooling system, and by changing the process, significant cycle reductions can be achieved."

Conformal cooling isn't new technology, however there are several new approaches to conformal cooling that have been introduced of late that promise to improve this technology. Beard commented that from a "theoretical dynamic heat transfer standpoint, conformal cooling would or should, always produce a faster cycle time than conventional mold-cooling techniques." However, he added, "no one has developed a working, cost-effective commercial process for injection molding that is being sold on the open market."

A few years ago, FloodCooling Technologies LLC, filed for a patent on "Brazed Aluminum Laminate Mold Tooling." From research, it appears that the patent was issued on March 4, 2008.  While FloodCooling Technologies still owns the intellectual property, a subsidiary company ThermaForm LLC , based in Troy, MI, developed the technology called ThermaBlocks, in blowmolds for rigid packaging applications. That seems to be the ideal niche for this technology, said Cole Clark, whose father, J. Thomas Clark, founded the company and serves as ThermaForm's CEO.

what is the Wear Challenge in injection mold « pfmold

Mold designers and builders try to use the typical methods of minimizing wear—such as using differential metals; using low-wear coatings; specifying high metal hardness thus equating high hardness with low wear; designing shutoffs with high angles thus avoiding locking shutoff angles; and, many more concepts that their experience leads them to believe works best in specific applications. However, one design principle that is not well understood by mold designers and mold builders is wear caused by mold components that are under some load or stress during the molding cycle. Mold designers and builders see the mold as it is built and especially during the mold assembly phase. Every attempt is made by them to assemble the mold components such that all inserts are fitted so the mold can be assembled by hand. In the better mold building shops, the use of hammers, pry bars and clamps is either strictly forbidden or the use is severely limited. Most molds then are assembled by hand with many of the mold components fitted with close tolerances but, by design, are not under a stress. On the bench then, the mold is in a Static condition. The molder then sees the mold in a Dynamic condition. Components may be moved out of position due to a variety of molding conditions—such as being clamped up under tonnage; cams moving back and forth with the opening and closing of the mold; thermodynamic changes in the mold due to differential heating and cooling; and, stresses caused by injection pressures trying to move mold components out of position. Therefore, to the perceptive molder, a mold is alive or a dynamic device, not a static device during the molding process. For years there has been a small group of molders and mold builders that recognize that molds are dynamic devices. They have recognized that this dynamic condition often has caused mold components to be forced out of a designed position. As forces are exerted on mold components, they move out of their desired position and may be forced against their mating components such that very high loads or stresses between these components occur. One of the more serious results of these stresses is high rates of mold wear. It is almost inevitable that increasing loads will increase the wear between these mold components. Molders who recognized that excessive wear was being caused by unanticipated stresses on the mold components began to use a variety of designs to address the problem. One of the most common was to utilize increasingly expensive mold alignment features—such as high cost straight line interlocks. The reasoning was that adding complex alignment features would not allow components to move regardless of the forces being exerted in the mold. Thus, instead of attacking the problem of movement, they continued to try to stop movement.

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