Please tell me how to remove vacuum bubbles in polyformaldehyde products.
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This post was last edited by QXZ-1966 on 2009-7-25 09:12 How to remove vacuum bubbles in polyformaldehyde products? Are there any requirements on the grades of injection molding machines and polyformaldehyde raw materials?
For bubbles in POM products, there are generally the following improvement methods based on their causes:: 1) Due to the large wall thickness of the product, the outer surface cools faster than the central part. Therefore, as the cooling proceeds, the resin in the central part shrinks and expands toward the surface, causing insufficient filling of the central part. The main solutions to this situation include: a) According to the wall thickness, determine the reasonable gate and runner size. b) Until the gate is sealed, a certain amount of additional injection material remains. c) The injection time should be slightly longer than the gate sealing time. d) Reduce the injection speed and increase the injection pressure. e) Use grades with high melt viscosity grades. 2) Bubbles caused by the generation of volatile gases. The main solutions are: a) Carry out sufficient pre-drying. b) Reduce the temperature of the resin to avoid the generation of decomposition gas. The thermal decomposition temperature of POM is approximately 235~250°C. Please pay attention to this. 3) Bubbles caused by poor fluidity can be solved by increasing the temperature of the resin and mold and increasing the injection speed.
Upstairs, you said "c) the injection time should be slightly longer than the gate sealing time. ”It should be the holding time. In addition, analyzing the position of the bubble and adding a push rod at that position to assist in exhausting can also solve the problem.
Thank you all heroes. I don't know how to add a push rod at this position to assist with exhaust. And until the gate is sealed, there will be a certain amount of additional injection material left.
Because it is the first time to process it, I don’t know much about it. Is it toxic? Under what circumstances are there.
Poisonous! If the POM injection temperature is too high, the resin will decompose, and formaldehyde will be released. . .
To solve the problem of toxicity, will the resin not decompose due to low temperature?