Plastic Processing Tips
Purgex has been an industry leader for nearly 30 years and has extensive knowledge of purging, molding, and other industry services. Our plastic processing tips will provide purging compound guidelines that are not meant to be all-inclusive but can be used as a basic guideline for troubleshooting. For specific information on purging materials, machines, or molds, contact us today!
Plastic Processing Tip #1
Reasons for Screw Slippage and How to Solve It.
One problem for injection molders or extrusion molders is screw slippage. Screw slippage occurs when the screw has difficulty picking up material from the feed throat which causes increased cycle time and other molding issues. One situation that causes screw slippage is changing from a high-temperature material, such as nylon and ABS, to a lower temperature material like TPO or PP. If you start lowering your temperatures too soon, the previous material won’t be removed completely and buildup will occur. Buildup continues to accumulate after each material change until slippage occurs.
There are a variety of techniques used by individuals to remove this buildup, such as dropping pallet wood, walnut shells, or hand soap into the feed throat. Aside from potentially being very damaging to your machine, these methods are time-consuming since removing the nozzle or die head is still required. They also do nothing to clean internal components, such as the check ring, and can give off a very strong odor.
Solution: You can stop your machine and take it apart to manually remove the buildup. The major downside is that this will take considerable time away from production.
Another answer would be to use a Purgex™ purging compound as a maintenance purge. Purgex works to remove buildup in the feed zone, thus protecting against screw slippage. With consistent use of Purgex™ between material changes, a buildup of materials on your barrel, screw, and hot runner systems will be greatly reduced or eliminated.
Purging Tip #1
Avoiding the Odor of Acetals
Many individuals in the molding industry have first-hand knowledge of the smoke and smell emitted from Acetal when purging. One trick is to submerge the purge pile into a bucket of water immediately after purging. This creates a barrier around the purge pile, trapping the gas and odor inside.
Note: Purgex is recommended for use on Acetal materials; the active ingredients in Purgex neutralize Acetal, resulting in a significant reduction of odor and gas when purging.
Purging Tip #2
Using Purgex™ in Hot Runner Systems
Purgex is safe and effective for hot runner systems with gates as small as 0.030-inch (0.75 mm). Purgex contains a lubricant for fluidity and ease of removal. Depending on resin type and gate size, it may be necessary to raise the hot runner temperatures 50˚F to enhance the flow. Call or email us and we will work with you to determine the best method to use.