Basic Principles of Injection Mold Gating System Design

1. Consideration of cavity layout

1) Balances Layout shall be adopted as far as possible;

2) The mold cavity layout and gate opening shall be symmetrical as far as possible, so as to prevent the uneven force of the mold from generating eccentric load, which may lead to the problem of mold overflow;

3) The mold cavity layout shall be as compact as possible to reduce the mold size.

2. Consideration of flow guidance

1) The utility model can smoothly guide the molten plastic to fill the mold cavity, without generating eddy currents, and can smoothly exhaust;

2) Try to avoid the impact of plastic melt adhesive on the core and metal insert with smaller diameter to prevent core shift or deformation.

3. Consideration of heat loss and pressure drop

1) The smaller the heat loss and pressure drop, the better;

2) The process should be short;

3) The sectional area of the runner shall be large enough;

4) Try to avoid channel bending and sudden change of flow direction (change direction with arc angle);

5) The surface roughness of runner shall be low (not too smooth);

6) Multi point pouring can reduce the pressure drop and the required injection pressure, but there will be suture problems.

4. Consideration of flow balance

1) When filling the first mock examination with multiple cavities, the flow channel should be balanced to make the plastic fill each mold cavity at the same time as far as possible, so as to ensure the quality consistency of products formed in each mold cavity;

2) The natural balanced layout shall be adopted for the diversion channel as far as possible;

3) If natural balance is not available, balance the runner by manual balance method.

5. Waste consideration

On the premise of smooth filling without affecting the flow and pressure loss, reduce the flow channel volume (length or sectional area) to reduce the waste generation and recovery costs of the flow channel.

6. Consideration of cold materials

Proper cold slug well and overflow chute shall be designed on the runner system to supplement and fill the cold plastic wavefront at the initial stage, so as to prevent cold materials from directly entering the mold cavity and affecting the filling quality.

7. Exhaust considerations

The plastic shall be guided to fill the mold cavity smoothly, and the air in the mold cavity shall escape smoothly to avoid the problem of encapsulation burning.

8. Quality consideration of formed products

1) Avoid short shot, burr, encapsulation, suture, flow mark, jet, residual stress, warping deformation, die core offset and other problems;

2) When the flow of the runner system is long or multiple gating, warpage and deformation of finished products caused by unbalanced flow, insufficient pressure holding or uneven shrinkage shall be prevented;

3) The appearance of the product is good, and it is convenient to remove and trim the gate. The gate mark is nondestructive to the appearance and application of the plastic parts.

9. Consideration of production efficiency

The required post-processing shall be reduced as far as possible to shorten the forming cycle and improve the production efficiency.

10. Consideration of ejection point

Proper ejection position shall be considered to avoid demoulding deformation of formed products.

11. Consideration of using plastics

For plastics with high viscosity or short L/t, avoid using too long or too small runner.