The exhaust of injection mold is a problem that can not be ignored in mold design. Poor exhaust will cause many problems, such as: air hole, cavity, scorch, bubble, surface craze, obvious melting line, etc.
The gas accumulated in the mould mainly comes from the following sources:
Air in the feed system and cavity
2. Water vapor generated by evaporation of water contained in plastic under high temperature
3. Gas produced by plastic decomposition
4. Gases generated by volatilization or chemical reaction of some additives in plastics
5. Air and moisture in the feed!
The basic design points can be summarized as follows:
The exhaust shall be fast and complete, and the exhaust speed shall be suitable for the filling speed;
2. The exhaust slot shall be set at the molding part with thick rubber parts as far as possible;
3. The exhaust slot shall be set on the parting surface as far as possible;
4. The exhaust tank shall be set at the end and junction of material flow as far as possible, such as the end of cold material well;
5. For the convenience of mold manufacturing and cleaning, the exhaust slot shall be set on the concave side as far as possible;
6. The direction of the exhaust slot shall not be toward the operation surface, so as to prevent personnel injury caused by material leakage during injection molding;
7. There should be no * angle in the exhaust slot to prevent the accumulation of cold materials;
8. The size and size of the exhaust slot must be appropriate (generally, the thickness is Zero point two - 0.3mm Select and process according to the specific material and product requirements to avoid flash as far as possible.
Common exhaust forms are:
Vent tank or hole
2. Exhaust of parting surface
3. Vent the gap of the insert
4. Exhaust between push rod or thimble
5. powder burning and gold block exhaust
6. Set the exhaust rod to force exhaust
7. Apply vacuum exhaust machine to achieve the effect of active exhaust and complete exhaust.
8. Die exhaust steel, exhaust bolt, etc
