Injection mold exhaust problem

Exhaust can be one of the most important parts of an injection molded product. Many engineering materials, such as PBT (polybutylene terephthalate), have a tendency to deflate. My best practices so far are:

Add 10 mm wide ventilation holes around each parting line with a spacing of 30 mm.

Always follow the material company's recommendations for ventilation depth.

If the product has a 50mm core or larger, the injection mold must be ventilated through the ejector plate, which means you have to drill through the core side (don't hit any water line, etc.), I usually use a 5mm or 1/4 inch drill bit

It's always emitting into the atmosphere.

Polish vents and ventilation ducts. This allows the exhaust port to clean itself. It also allows gas to escape better.

A very old technique for determining whether an injection mold has an inherent exhaust problem, and this technique depends to some extent on the construction of the injection mold, so it must be evaluated on a case-by-case basis (there is more on this at the end) is to use a shipping tape or masking tape, depending on the desired gap, across the main parting line of the injection mold. To artificially "expand" the mold and create a ventilation gap. Evaluate the filling amount of belt V-shaped non-belt shot peening without changing the injection molding process Settings.

The reason this must be evaluated on a case by case basis is that, given the potential actions built into the injection mold, such as lifting, sliding, or core-pulling, creating this type of human parting line may cause bonding, or failure to properly "lock" the moving features, resulting in potential damage to the injection mold. In addition, pressing the tonnage of the die fixture to a position where it is not intended to carry all the clamping force may cause the hardened steel to crack or break. Therefore, use this troubleshooting method with caution and be sure to consult the injection mold design engineer first.

In addition, some injection mold designs/manufacturing have a preload built into the cavity and pellet, which means that the actual contact area of the parting line is greatly reduced to ensure that the parting line is sealed. In this case, attaching the parting line of the die stand will have a clear effect, unless you attach tape directly between these parting modules, which may actually seal any vents built into the parting line.