Seven parameters that must be taken into account when setting the injection molding process

Seven parameters that must be taken into account when setting the injection molding process

1. Injection speed:

The injection speed is slower, the plastics are carried in the cavity, there will be more heat loss, the flow viscosity will increase, and the pressure loss will increase;

Higher firing speeds tend to result in higher precision, less deformation of the molded product, only through the flesh thickness, small changes, intense changes, corners and other areas, prone to appearance defects, and prone to exhaust defects, Feng Feng, and maintaining pressure Problems such as incorrect switching.

2. Switching pressure:

Too early to switch, the finished product size is easy to lack, or even short shots, and the surface is sunken, otherwise it forms excessive compression, small size is too large, flash, white, deformation, and the use of mold is damaged;

In order to switch pressure, there are usually control methods such as injection stroke (position) and time.

3. Packing size setting:

If the holding pressure is too high, excessive filling will occur, which will cause the plastic that has entered the cavity to flow backwards.

Correct and appropriate pressure setting should be based on the principle that the screw can continue to advance to the lower pressure of the target point after passing through the pressure maintaining switching point;

In the holding stage, the pressure inside the mold cavity gradually decreases due to the cooling of the plastic, so the packing pressure should be properly followed down, otherwise high stress residuals will be easily formed.

4. Set the dwell time:

The pressure holding time should be maintained until the gate condenses. It is meaningless for too long. However, if the time is too short, it is easy to reverse flow, making the position near the gate easily recessed and insufficient in size.

Maintaining the appropriateness of time is usually judged by the stability of weight;

The gate is small, the mold temperature is low, and the holding time should be set short. If the situation is reversed, it is set to a longer time.

5. Set the cooling time:

Plastic cooling in the mold cavity, most of which began with the end of pressure switching mode, the theoretical cooling time = pressure holding time + post-cooling time;

The theoretical time required should be based on the principle that the product can be smoothly ejected (not deformed), and its length varies depending on the thickness of the molded product, the material, and the cooling rate of the mold;

Gate thickness and mold temperature will affect the holding time (set the cooling time of the machine, that is, the post-cooling time). Large gate and high mold temperature will be appropriate to increase the pressure holding time, otherwise the packing pressure should be reduced appropriately.

6. Mold temperature setting:

If the mold temperature is set too low, the melt flows in the mold cavity, and the temperature drops faster, so that the material flow resistance increases, so the pressure loss increases, the internal stress increases, and the internal pressure of the mold cavity increases.

7. High mold temperature setting:

Increase the degree of crystallinity and more uniform structure of molded products, reduce internal stress residual, deformation and increase strength, reduce material flow resistance during filling, reduce pressure loss, make product appearance luster is good, but prone to flash, increase near-gate location Reducing the sag at the far runner site reduces the bond line and increases the cooling time.