Elk Grove Village, Ill. — Conformal cooling — molds built with cooling channels that curve to follow the shape of the part — can make injection molded parts with better quality, less molded-in stress and no sink marks.
It's been around for years. There are thousands of conformal molds in use around the world, many in Europe. But in the United States, the technology is not well known. In fact, it's almost a secret, said consultant Robert Beard.
Why? “Non-disclosure is the bane of this technology,” Beard said to kick off the Conformal Cooling Conference. “Anytime anybody's built one, they signed an NDA (non-disclosure agreement).”
His firm, Robert A. Beard & Associates Inc., and Plastic Technologies Inc. of Holland, Ohio, organized the Conformal Cooling Conference, held Sept. 29 at Toshiba Machine Co. America's headquarters in Elk Grove Village. The conference drew 42 people.
Beard said conformal cooling “is almost the standard in Europe, but it's not the standard in this country.” He's trying to change that, by holding the first U.S. conference in the topic last year in Detroit. Elk Grove Village marked the second conference.
“The only thing we have in North America that gives us a global advantage is technology,” Beard said. “We don't have the lowest, cheapest labor.”
Beard, a plastics industry veteran, got interested in conformal cooling about 10 years ago when he was hired to help a European automotive molding operation start up a new mold — a tool with conformal cooling channels built by Germany-based Contura MTC GmbH. Like others, he signed an NDA, but a few years later, contacted Reiner Westhoff, Contura's managing director.
Westhoff shared details of some projects. That led Beard to write articles for U.S. trade magazines — and ultimately organize the conferences.
Reducing cooling time is an important way to cut cycle time, speakers said. Westhoff said cooling, including the packing stage, can amount to two-thirds of the total cycle time. What if you could cut that ratio to just one-third? You may not be able to change the part thickness or the design, but just a small change in mold cooling can make a big difference, he said.
Traditionally, mold makers cut cooling channels in a straight line, known as gun drilling. “But we need to get close to the cavity wall,” Westhoff said. Conformal molds also can install copper pins in key tight spots, to aid cooling, he added.
Contura, of Menden, Germany, makes conformal inserts for molds, using vacuum brazing and diffusion bonding. Westhoff said both processes cut slices of metal from a three-dimensional computer model, then fuse them together.
Mold temperature control is important, and Westhoff said conformal molds can have different water circuits for specific parts of the mold. “You need segmented water lines,” he said. One example is the gate area, which gets very hot because so much plastic is flowing there over the entire cycle.
“In Europe, we are equipping, each month, 40 tools with conformal cooling,” he said. Many of those molds go into the German auto industry, for parts like B-pillars, center consoles and engine covers. “This is not something new. It's been done thousands and thousands of times,” Westhoff said.
But Westhoff said interest by the U.S. auto sector has been slow. “Fifteen years ago, nobody in the U.S. was interested in cutting cycle times,” he said. “But now we have more interest because the cost pressure is coming more and more.”
Beard said one basic problem is that big companies have a mold buyer and another person coordinating the part. The result is buying the cheapest mold, often a gun-drilled tool, he said. Conformal molds cost more but give longer payback, which could win out “if we would ever get them together,” he added.
3-D printing is another way to make conformal mold inserts. Linear Mold & Engineering Inc. of Livonia, Mich., uses the direct metal laser sintering process to make conformal inserts. The company also makes traditional molds.
Jason Warr, senior account manager, said the “best fits” for conformal molds include structural components with thick walls made from engineering resins, parts that have high scrap rates, parts that require a long cooling time and high-volume, long-running parts.
Conformal Cooling Conference attendees also heard about rapid mold heating and cooling, which makes parts with smooth, glossy surfaces with no sink marks. Swiss company Regoplas AG, uses pressured water in a closed loop for its heating and cooling.
Pressured water “has very good thermal conductivity,” said Kip Petrykowski, national sales director for Regoplas Corp. in St. Joseph, Mich. He said pressurized water is more effective than oil for rapid heating and cooling.
Rapid heating and cooling is especially good for filling thicker-walled parts, he said.