[Science] Basic classification of plastic injection mold structure

Plastic injection mold is a tool for producing plastic products with certain shape and size requirements. A complete mold usually has two parts, one is the molding part, which is the part related to the shape and size of the plastic product. The second is the mold base part, also known as the mold base, which is used to install and fix the molding part.

The plastic injection mold consists of 6 major systems:

1. Pouring system. The pouring system consists of 4 parts: main runner, branch runner, gate and cold material cavity.

2. Forming mechanism. The molding mechanism is the part that is in direct contact with the plastic product, including the front and rear mold cores, inserts, sliders, and lifter mechanisms.

3. Ejection mechanism. The ejector mechanism includes ejector pin, ejector block, cylinder, ejector pin fixing plate, ejector pin backing plate, reset rod and other mechanisms.

4. Guiding mechanism. The guide mechanism includes a guide post, a guide sleeve, a top plate reset rod, a top plate guide post, a top plate guide sleeve and other mechanisms.

5. Cooling system. The cooling system is mainly a circulating water circuit, including oil cooling, water cooling, air cooling, etc.

6. Exhaust system. The exhaust system mainly includes exhaust grooves, exhaust needles, exhaust inserts, and other parts. 

There are two types of plastic injection molds:

1: Two-plate mold. The biggest difference in appearance between the two-plate mold and the three-plate mold is that there is a stripper plate between the upper fixed plate and the front mold base of the three-plate mold. Two-plate molds are not suitable for molds with front mold sliders and point-gated molds. Except for these two structures, all other structures and feeding methods can be used.

2: Three-plate mold. The three-plate mold is also known as the fine nozzle mold. According to the type of mold base, it can be divided into three forms: fine nozzle, simplified nozzle and false three-plate, as shown in the figure below.

The shroud and the simplified shroud are a type of mold base structure specially designed for the mold of the dispensing port, and it is also suitable for the mold with the front mold slider. The difference between the narrow nozzle mold base and the simplified narrow nozzle mold base is:

①The runner die set has 4 guide posts fixed in the "B" plate on the back die side, while the simplified runner die set has no guide posts.

②There are limit washers on the 4 tie rods of the narrow nozzle die set, while the simplified narrow nozzle die set has no limit washers.

③The narrow nozzle mold base can realize the push plate mold structure, while the simplified narrow nozzle mold base cannot be designed with the push plate push plate structure.

The fake three-plate mold base is specially designed for the mold of the front mold slider mechanism. It has no discharge plate and is not suitable for the dispensing port mold. This structure is very similar to the two-plate type, but there is one more parting of the upper fixed plate and the front mold base than the two-plate type.