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moldmakingtechnology.com 17 ACKNOWLEDGEMENTS: Thank you to Eric Beauregard for helping to run the resin test and Patrick Clemensen at Victrex PLC for supplying the resin for the resin test. CONTRIBUTOR Mohammad Rafi, BASc, is an applications engineer at Husky Injection Molding Systems. FOR MORE INFORMATION Husky Injection Molding Systems / 802-859-8000 mrafi@husky.ca / husky.co These ripples appeared on the part's surface at low injection speeds due to solidification occurring too quickly. Increasing injection speed eliminated the ripples. FIGURE 6 resistance to resin flow produces uneven frontal flow, and solidified resin will not fully contact the cavity wall. Even longer holding pressure was unable to smooth out the ripples (see Figure 6). By increasing the injection speeds, the ripples and record grooves were eliminated. Although high-temperature polymers with processing tem- peratures in the range of 350-400ºC present certain molding challenges, hot runners are still the optimal choice for small- to medium-size part applications when direct gating is used. Moldmakers and molders can justify the increased upfront costs for direct-gating these types of plastic parts with the substantial cost savings over the product lifecycle. It is cru- cial to select a suitable hot runner design to ensure that the entire melt channel, from the sprue bushing to the gate, are maintained to within ±5ºC of the set temperatures to avoid any hot/cold spots for crystalline polymers. Microtron 1A is BACK The Mold Maker's Answer for all Welding Repairs from Micro to Macro The Microtron 1A System • Take it anywhere - plugs into 100v or 220v • Weighs just 19 lbs. • Dimensions 5 x 10 7/8 x 12 1/2 • Advanced technology - stable arc down to 1 amp • Starting mode to protect CNC equipment • Laser - micro - standard size welding wire for ALL mold steels Dytron Corp. - Micro Welding Products Division Tel: 800.521.3060 www.microweldingproducts.com