Get Better Mixing From Your Injection Molding Screw
In the injection molding process when using standard general-purpose, single-stage screws, operators will typically increase the back pressure whenever better mixing is needed.
In injection molding, operators running a machine using a standard, general-purpose, single-stage screw will typically increase the back pressure whenever they need better mixing. Their thinking is, by increasing the backpressure on the screw, the screw will work harder to pump the material forward, which in turn will result in a high mixing action in the metering section of the screw. But there are two big flaws to this approach: the resulting high melt temperature and longer recovery time. Since the screw has to work harder to convey the resin forward, this additional work results in higher melt temperature. Higher melt temperature results in extended part-cooling time after molding. And since the screw has to work harder to pump the resin, it takes long for it to recover.
Not only will the achieve better mixing with the new screw design, but they also will have fast recovery times, and lower melt temperature which will translate into faster overall cycles and in turn more savings to the customers bottom line.
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Tim Womer is a recognized authority in plastics processing and machinery with a career spanning more than 35 years. He has designed thousands of screws for all types of single-screw plasticating. He now runs his own consulting company, TWWomer & Associates LLC. Contact: (724) 355-3311; tim@twwomer.com; twwomer.com
