⑶ cavity surface roughness: General vacuum forming mold are not the top of the device, molded by the compressed air stripping. When the surface roughness of the vacuum forming mold is too low, it is very unfavorable to the mold releasing after the vacuum forming, and the plastic is easy to be adhered to the mold forming surface and is not easy to be demolded. After the ejecting apparatus can be ejected, it is still easy to release the mold Deformation. Therefore, vacuum forming mold surface roughness is high. The surface processing, the best sandblasting.
⑷ edge seal: In the vacuum forming, in order to make the cavity outside the air does not enter the vacuum chamber, the plastic sheet to be in contact with the mold edge seal means. On the flat surface, the plastic sheet and the mold contact surface to seal more easily, but for the curved surface or the parting surface, the seal has a certain degree of difficulty.
⑸ heating and cooling device: Vacuum forming plastic sheet used for heating, usually using resistance wire or infrared. Resistance wire temperature up to 350 ℃ ~ 450 ℃, different plastic sheet for the different molding temperature, usually by adjusting the distance between the heater and the plate to achieve. The commonly used distance is 80 ~ 120mm.
Mold temperature on the quality of plastic parts and productivity have an impact. If the mold temperature is too low, the plastic plate and the cavity contact will produce cold spots or stress resulting in cracks; and mold temperature is too high, the plastic sheet may adhere to the cavity, the plastic mold will be deformed, and Extend the production cycle.
Therefore, the mold temperature should be controlled within a certain range, generally about 50 ℃. Mold temperature control generally depends on the plastic and the mold after contact with the natural cooling, additional air-cooled device to accelerate cooling and water cooling and other methods to open the mold in the cooling water is to control the mold temperature is the most effective and most commonly used method, the cooling water should be from the 8mm above the surface to avoid cold spots. There are different ways to set up the cooling water channel. You can cast brass or steel pipe into the mold. You can also punch holes or mills in the mold. You must use sealing elements and cover plates in the groove milling method.