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Molding Conditions / Countermeasures for Mold Deposit
4. Molding Conditions
4.9 Countermeasures for Mold Deposit
When DURACON® POM is injection molded over a long period of time, certain precipitates deposit on the mold surface. The precipitates sometimes cause dimensional deviations exceeding tolerance or disturbance against mold release. The precipitates are called mold deposit. To control and prevent the precipitation of mold deposit, the following methods are recommended:
- Remove the moisture and formaldehyde in pellets by raising the predrying temperature (Raise to 100-120°C, from the usual 60-80°C). Conductive grades and specialty grades excluded.
- Reduce gas generation by setting the material temperature lower keeping within the general range of 190°C to 210°C.
- Appropriately balance the capacity of the molding machine and the material weight per shot so that the retention time in the cylinder is not too long.
- Set the mold temperature higher (higher than 60°C) since deposits are bound to stick to the mold at lower temperature.
- Providing gas vents for the mold is a very effective measure. Also, provide gas vents for runners.