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Newsletter 2005 issue 1 |
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Site Visit—Port Placement
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| Kyle Bartholomew, MnTAP FRP specialist, reviewed Precision’s part dimensions to analyze resin flow through the mold. |
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Because regulations are pushing fiberglass reinforced plastic (FRP) shops to control hazardous air pollutant (HAP) emissions, Precision Fiberglass Products, in Grove City, was testing Light RTM—a reduced air emission technology. But, defects were at 50 to 60 percent.
The company builds lots of big FRP parts for agricultural vehicles, boats and other applications. It typically uses open molding, with operators spraying glass and resin onto a mold. The spraying releases styrene emissions which can negatively impact health and the environment.
Closed molding uses a two-part mold, with an injection port that pumps resin in and a vacuum port, near the opposite end, that draws the resin through a glass mat to coat the entire mold. Because the mold is closed, air emissions are essentially eliminated.
Problem
“We were testing RTM-lite and having a high reject rate,” said Bob Meyer, pattern and mold maker at Precision. “Some parts worked fine. Other times, the resin wouldn’t completely fill the mold.”
The resin was not able to completely circle the mold before being pulled into the vacuum port, leaving a bubble of air at the end of the mold—resulting in a defective part.
Kyle Bartholomew, MnTAP’s FRP specialist, helped the company work through some of its start-up issues with Light RTM. “I spent a day at Precision thinking real hard about that bubble,” said Bartholomew.
Solution
Bartholomew worked with Precision to determine how the resin flowed through the mold; he also discussed the problem with a few FRP experts. He determined where to move the vacuum port so resin would flow properly. “When they changed the port, the effect was immediate—they got good parts right away,” noted Bartholomew.
An industry rule of thumb is to set the vacuum port away from the injection port by 65 percent of the length of the mold. “It’s common practice to move the ports, but I don‘t think port placement needs to be so much trial and error. Why not get it right the first time?” Bartholomew questioned.
“Kyle asked lots of questions and tried to find out what we could do to improve our situation,” said Meyer. ”He asked the technical questions that I didn’t have the know-how to ask.”
By improving resin flow, defects were reduced, cutting polyester resin and fiberglass waste by 300 pounds and saving $1,000.
After testing this technology, Precision has a better understanding of Light RTM. “We’ll use RTM-lite again in the future if the opportunity arises, when we have the right customers,” said Meyer.
Contact Kyle Bartholomew, MnTAP, at 612/624-4633, for help with closed mold, low HAP gel coating, nonatomized spraying and robotics to reduce FRP emissions. See MnTAP’s FRP Web resources.
FRP Demo Day: Closed-Mold Technology
MnTAP is sponsoring Seeing is Believing, a Fiberglass Reinforced Plastics Closed Mold Demo Day, to showcase closed-mold technology on Wednesday, June 22, 2005, at Century College in White Bear Lake.
The event will feature demonstrations of Light RTM, vacuum infusion and low VOC gel coats. Larry Craige, American Composites Manufacturing Associations (ACMA) is the keynote speaker, addressing what continued regulatory emphasis on worker safety and improving the environment means for fabricators. |
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Site Visit—Port Placement
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