When processing hygroscopic resins (resins that absorb moisture in their natural state), it is imperative to make sure they are dry before processing. Here are 5 tips to help ensure you are processing dry resin:
- 1.) Determine how much drying residence time is in your hopper. This is determined by the volume in said hopper compared with the cycle time of the injection molding machine and part weight. Follow the manufacturer’s instructions on drying time and temperatures of each resin. (Caution: Do not over dry the resins as this can change the physical properties of the material).
- 2.) Make sure your dryer is functioning properly and the desiccant is fresh in the beds. Please note that this does not apply to Maguire’s vacuum dryers.
- 3.) Ensure dry resin is conveyed to the injection molding machine via a Just-in-Time loader or have a drying hopper directly on the feed throat.
- 4.) If using a Just-in-Time loader, make sure the transfer line is not too long that allows the material to sit in the line for long periods of time absorbing moisture.
- 5.) If using a dry hopper directly on the machine, make sure the lid is on tight and material is conveyed to the hopper automatically.
Of course, the best and most accurate way to determine if your hygroscopic resins are dry is to test a sample in a moisture analysis machine if one is available. Most dryers today have this option built into the machine.
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