Ten Elements Of Seamless Injection Mold Making

In the process of injection molding, defects such as weld marks, air marks,  and deformation are easy to appear; The high-gloss traceless mold can solve the above defects. The following are the ten factors that affect the design of high-gloss seamless injection mold.

First, understand the principle of high-gloss traceless injection molding.

1. The temperature is high

Mold forming requires high temperature (generally about 80℃-130℃), and cooling water is used after injection molding is changed to pressure maintaining so that the mold temperature is reduced to 60-70℃. Pressure-holding molding at higher mold temperatures is beneficial to eliminate defects such as weld lines, flow marks, and internal stress of products. Therefore, the mold needs to be heated when working. In order to prevent heat loss, an insulation board is usually added to the fixed mold side.

2. The surface of the cavity is extremely bright (generally mirror level 2 or higher)

3. There are more hot nozzles in the hot runner system.

4. Heating mode

There are usually two ways to heat molds: steam (hot water) heating and electric heating rod (tube) heating. They are the same in principle, that is, the heat sources are different. Electric heating is secondary energy and water heating is tertiary energy. In principle, electric heating has less energy consumption, high utilization rate, and good energy-saving benefits.

Second, the mold material

1. Mould materials with general requirements for product surface can be used: NK80 (Datong, Japan), etc.

2. Materials required for high gloss: S136H (Sweden), CEANA1 (Japan), etc.

3.NK80 need not be quenched; S136H should be quenched to 52 degrees after rough machining; CEANA1 itself has 42 degrees and does not need quenching treatment (it is recommended to use this steel because it will not affect the subsequent processing or modification);

4. There is also a good choice among German brands: CPM40/GEST80.

Third, the mold waterway design

1. Pay attention to the design of the waterway aperture size.

2. Pay attention to product surface design

3. Design of water channel joint of mold

4. Design of water inlet and outlet nozzle of mold

5. Mold construction holes

Fourth, the mold insulation system

1. Mold core design

2. Mould frame design

The detailed structure of the formwork and core insert, and the cooling water of the formwork are very important. In order to prevent the heat energy in the die core from being transmitted to the formwork, a circle of water transport should be arranged up and down near the guide post.

3. Guide sleeve design

As far as possible, the moving parts of the guide sleeve should be made of graphite material or the front end of the guide pillar should be avoided, and it is enough to ensure the length of 25mm at the matching place;

Five, mold gate design

Mold gate design should reduce weld marks as much as possible, which is beneficial to exhaust and reduce shear. For the mold with water heating and temperature control machine, the gate size should be larger and the large gate should be used as far as possible. The gate should be shortened in length, depth,  and width without affecting the product function and molding efficiency.

1. If the gate is too small, it is easy to cause appearance defects such as insufficient filling (a short shot), shrinkage depression, and weld line, and the molding shrinkage will increase.

2. If the gate is too large, there will be too much residual stress around the gate, which will lead to the deformation or rupture of the gate, and it is difficult to remove the gate.

6. The exhaust of the mold should be as long as 10mm apart around the product, and the exhaust slots should be evenly distributed with a depth of 0.15mm; The middle veneer of the product also needs exhaust design.

VII. Matching of parting surface of the mold

Eight, heating rod (tube) high-gloss mold design

Nine, high-gloss mold requirements for products

High-gloss mold has strict requirements on product structure. The brighter the product, the more sensitive it is to the refraction effect of light, and the slight surface defects will be found soon. Therefore, how to solve the shrinkage problem is the primary problem of high-gloss products.

X. Selection of plastic materials for high gloss mold

At present, the commonly used high-gloss plastic materials are ABS+PMMA and ABS+PC, PMMA, ASA, and so on.

As a common shell material, ABS+PC products are better than HIPS in impact resistance, surface gloss, and hardness, so when producing high-gloss products, high-gloss ABS materials are usually selected. If weather resistance is needed, ASA may be selected, and PMMA alloy material may be selected in terms of hardness.