What is the principle of plastic mold injection molding?

Plastic molds mainly consist of three parts: pouring system, forming parts, and structural parts. The pouring system and molding parts are the parts that come into direct contact with plastic and change with plastic and products. They are the most complex and variable parts in plastic molds, requiring the highest processing smoothness and accuracy.

The plastic mold pouring system refers to the part of the flow channel before the plastic enters the mold cavity from the nozzle, including the main channel, cold material cavity, diversion channel, and gate. Formed parts refer to various parts that form the shape of a product, including moving molds, fixed molds, cavities, cores, forming rods, and exhaust ports.

1、 Mainstream channel

It is a channel in the mold that connects the injection machine nozzle to the diversion channel or cavity. The top of the main channel is concave in shape to connect with the nozzle.

The diameter of the main channel inlet should be slightly larger than the nozzle diameter (0.8mm) to avoid overflow and prevent blockage caused by inaccurate connection between the two.

The import diameter depends on the size of the product, usually 4-8mm. The diameter of the main channel should be expanded inward at an angle of 3 ° to 5 ° to facilitate demolding of the channel debris.

2、 Cold material cavity

It is a cavity located at the end of the main flow channel to capture the cold material generated between two injections at the nozzle end, thereby preventing blockage of the diversion channel or gate. If the cold material is mixed into the mold cavity, it is easy to generate internal stress in the produced product.

The diameter of the cold material hole is about 8-10mm, and the depth is 6mm. To facilitate demolding, the bottom is often supported by the demolding rod. The top of the demolding rod should be designed in a zigzag hook shape or with a sinking groove to facilitate the smooth removal of debris from the main channel during demolding.

3、 Diversion channel

It is a channel connecting the main flow channel and various cavities in a multi slot mold. To ensure that the molten material fills the various cavities at an equal speed, the arrangement of the splitter channels on the mold should be symmetrical and equidistant. The shape and size of the splitter section have an impact on the flow of plastic melt, the difficulty of product demolding, and mold manufacturing.

If the flow rate is equal to the amount of material, the resistance of the flow channel with a circular cross-section is the smallest. However, due to the small surface area of the cylindrical flow channel, it is not conducive to the cooling of the debris in the flow channel, and this type of flow channel must be opened on the two halves of the mold, which is both labor-intensive and easy to align.