Resin Lot and Dryer Log Worksheet
Moisture in hygroscopic resin causes splay, brittleness and unpredictable viscosity. This log records lot, dryer settings and drying hours against the required time, so you can prove a lot was dried properly or find the one that was not.
| Date | Resin lot | Resin and grade | Dryer | Dry temp (C) | Dew point (C) | Hours dried (h) | Hours required (h) | Margin | Regrind share (%) | Quantity loaded (kg) | |
|---|---|---|---|---|---|---|---|---|---|---|---|
1 hrs | |||||||||||
-1 hrs | |||||||||||
1 hrs | |||||||||||
1 hrs | |||||||||||
0 hrs |
Take required hours, temperature and dew point from the resin supplier datasheet for your grade. Values in the sample rows are illustrative only. Include regrind in the drying plan, since it is often wetter than virgin pellets.
Trace resin lots through your ERP
Optional: discuss lot traceability from receiving through molding in your system.
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How to use the log
Enter one row per lot loaded to a dryer. Take the drying temperature, dew point and minimum time from the resin supplier datasheet for the exact grade. Record the actual time dried before the material went to the press. The margin column compares actual hours with required hours, and a negative margin signals under drying. Keep the sheet with the production records so lot traceability is complete.
- Use the datasheet for your exact grade
- Log the dew point at the dryer outlet or hopper
- Record regrind share with the lot
- Treat a negative margin as a hold item
Why drying matters
Nylon, polycarbonate, PET and many engineered grades absorb moisture from air. At melt temperature the water reacts with the polymer or turns to steam, giving splay, silver streaks, bubbles and lower impact strength. Desiccant dryers with a low dew point remove moisture far more reliably than hot air alone. Over drying and long residence time can also degrade some resins, so more is not always better.
Reading the results
A positive margin means the material met the minimum time. A small negative margin may be tolerable in some cases, but that call belongs to your process engineer. The lowest margin figure in the summary tells you whether any lot in the period was at risk. If a defect occurs, you can match the date and lot to the dryer entry and check the settings.
- Negative margin: investigate before molding
- Dew point warmer than spec: check desiccant and filters
- High regrind share: confirm it was dried too
Common mistakes
Refilling a hopper with undried material on top of dry material defeats the dryer. Using a dryer that is too small for the throughput gives less residence time than the datasheet requires, even when the setpoint looks right. Forgetting to include regrind and ignoring a dryer filter that needs cleaning are other frequent issues.
Frequently Asked Questions
How long should resin be dried?
Follow the supplier datasheet. Typical times are several hours at a temperature that depends on the polymer, and they are tied to a dew point. Do not use generic values for critical parts.
Do I need to dry polypropylene?
Usually not, because it absorbs very little moisture. Always check the datasheet, since fillers and colorants can change behavior.
What dew point should I target?
Many drying specs call for about minus 30 to minus 40 degrees Celsius at the dryer, but your resin supplier gives the right figure for your grade.
Why track regrind share?
Regrind has already been through a heat history and may have picked up moisture. Knowing the percent helps explain a change in part quality and viscosity.
If lot numbers and material usage already sit in your ERP, we can help connect them so drying records follow the lot automatically.
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