6. High-light mold exhaust system
In a sense, the injection mold is also a displacement device, that is, the plastic melt enters the mold cavity and simultaneously displaces the air in the mold cavity, and these gases must be discharged in time, otherwise, many hazards will be caused. In order to achieve high light effects, the exhaust system of the high-gloss mold must be reasonable and sufficient. Generally, the high-light mold exhaust system is set up in the following ways:
(1) Opening a venting slot
For molds for forming large and medium-sized plastic parts, the amount of gas to be removed is large, and a venting groove must be opened. The venting groove is usually opened on the pusher (the parting surface and the side of the core) and the biliary surface. The position of the venting groove is preferably at the end of the melt flow, and the size of the venting groove can be smoothly discharged by gas. The principle is not flashing, the width is 3-5mm, the length is 3-10mm, and thereafter it can be deepened to 0.8-1.5mm, and the spacing of the grooves is kept at about 50mm.
(2) Using the slot gap to exhaust
For the combined fixed mold or core, it can be exhausted by the split gap, and if necessary, the high pressure air gun can be used for backflushing to clean the blocked air passage.
(3) Using the ejector pin and the cylinder exhaust
In the absence of flash, the gap between the thimble, the cylinder and the core is intentionally increased to complete the venting.
(4) Exhaust at the end of the pouring system
The exhaust of the gating system is often the most easily overlooked, which is a very important part.