Vacuum Drying Sucks Wasted Time From Process Set-Up

The contrast before and after R&D Plastics installed a vacuum-drying system alongside its largest press was stark. Instead of two desiccant units with a large footprint and multiple hours of drying time, there was one vacuum dryer covering just over 5ft² with only a 30-min wait for process-ready material. “The difference was night and day,” states Don Altorfer, maintenance manager.

“We were putting materials in to dry way ahead of time, and on bigger jobs we needed two drying systems to do that: One dryer to predry material and then, of course, a production dryer to keep it dry and running.”

R&D Plastics is an ISO 9001:2008 certified custom molder based in Hillsboro, Ore. It serves markets as diverse as agriculture, medical, recreation, and defense. Supplying such disparate customers results in an eclectic mix of applications and a diverse array of materials.

R&D runs “everything from ABS to Xenoy” on its largest machine, a 720-ton Toshiba, according to Altorfer. When it used desiccant drying alongside that press, workers would start drying material “at least three, four, five hours before we’re going to start that job,” Altorfer said. But with the new VBD-150 vacuum dryer from Maguire Products Inc., Aston, Pa., the set-up team has a little more time on its hands.

“The result from buying the VBD-150, is that basically we’re going to let the material from the  revious job run out,” Altorfer said. “Then the set-up can start for the new job, and the material handlers can start. The material handlers will have the new material all dried and ready to go long before the set-up is finished on a machine that size.”

By eliminating predrying, R&D was able to re-evaluate how it sets up and runs jobs. “We had a little bit of relearning to do there,” Altorfer said. “In this case, you didn’t really have to prepare anything ahead of time. So the set-up team needed to learn not to predry—it’s just something that they didn’t have to do anymore. Now they can just let the hopper run out; clean it; put the new material in to dry; and it’s going to be ready before the mold has been changed.”

Faster drying means less energy is used. In comparison with desiccant dryers, Maguire says the VBD vacuum dryer consumes 60% less energy, drying resin in one-sixth the time, which substantially reduces the material’s heat history. In the dryer, once material reaches the desired setpoint, it’s discharged from the heating hopper into the vacuum vessel. Vacuum is brought to 700 mm of mercury (mm Hg) and held to a 20-mm Hg differential for the set cycle time. Maguire says the vacuum cycle typically lasts about 15-20 min, resulting in ready-to-process material in 30-40 min.

“It’s an easy system to use,” Altorfer said, “and it’s so fast. The setup time takes longer than the drying time now.”