What are the main problems of common defective defects in injection molded products

1. Not enough to play (lack of rubber)

Process problems: plasticization temperature too low, nozzle temperature too low, injection time too short, injection speed too slow, mold temperature too low.

Mold problems: too small runner, too small gate, unreasonable gate position, poor exhaust, debris in the cavity.

Raw material problems: poor liquidity, mixed with debris.


2. Flying edge

Process problems: too high plasticization temperature, too long injection time, too much material addition, too high injection pressure, too high mold temperature, debris between templates.

Mold problems: mold deformation, core and cavity with the size of the error, the combination of the template is not parallel, the exhaust slot is too deep.

Equipment problems: non-parallel templates, poorly closed templates.

Raw material problem: too high liquidity.

3. Deformation

Process conditions: too high material temperature, too high mold temperature, too short holding time, too short cooling time for forced demoulding.

Mold: improper gate position, insufficient number of gates, improper ejector position to make uneven force.

4. Flow marks

Process conditions: material temperature is too low and not fully plasticized, injection speed is too low, injection pressure is too small, holding pressure is not enough, mold temperature is too low, injection volume is not enough.

Mold: too small gate, too few gates, rough runner gate, poor surface finish.

Equipment: temperature control system failure, oil pump pressure drop.

Raw material: too many volatiles, poor fluidity, mixed with miscellaneous materials.

5. Bubble

Process conditions: low injection pressure, insufficient holding pressure, insufficient holding time, too high material temperature.

Mold: bad exhaust, unreasonable gate position, too small gate size.

Raw material: not dry or not enough drying time, shrinkage rate is too large.

6. Shrinkage pit

Process conditions: insufficient amount of material, too short injection time, too short holding time, too high material temperature, too high mold temperature, too short cooling time.

Mold: too small runners, too small gates, poor exhaust.

Equipment: insufficient injection pressure, nozzle plugged with foreign objects.

Raw material: shrinkage rate is too large.

7. Dimensional instability

Process conditions: too low injection pressure, too high barrel temperature, change in holding time, unstable injection cycle, too high mold temperature.

Mold: uneven gate size, inaccurate cavity size, loose core, too high mold temperature or not set waterway.

Raw material: change in grade, uneven particle size, volatile substances.

8. Demoulding difficulties

Process conditions: injection pressure is too high, holding time is too long, injection volume is too much, mold temperature is too high.

Equipment: insufficient ejecting force, insufficient ejecting range.

Mould: no release slope, insufficient finish, improper ejecting method, improper matching precision, bad exhaust, deformation of template.

9. Silver pattern

Process conditions: too high material temperature, too fast injection speed, too much injection pressure, uneven plasticization, too much mold release agent.

Mold: too small gate, poor mold finish, poor exhaust.

Equipment: too low back pressure, nozzle with flowing material.

Raw material: moisture not dried, excessive lubricant

10. Burnt

Process conditions: too high material temperature, too high injection pressure, too fast speed, too long downtime, unclean mold release agent.

Mold: too small gate, poor exhaust, complex cavity, poor cavity finish.

Raw material: there are debris mixed in the material, there is powder material in the granule material.

11. Discoloration

Process conditions: too high material temperature, too high injection pressure, long molding cycle, uncooled mold, high nozzle temperature.

As for the mold: the gate is too small.

Equipment: obstruction in the barrel or nozzle, high screw speed. Different center of core and nozzle.

For raw material: material pollution, decomposition of colorant, high content of volatile matter.

12. Fusing marks

Process conditions: low injection pressure, short injection time, low material temperature, too much clamping force, unsuitable release agent.

Mold: low mold temperature, small runner, incorrect gate position, poor exhaust.

Equipment: poor plasticization.

Material: poor fluidity, too much lubricant, foreign matter in material.

13. Glossy defects

Process conditions: low material or mold temperature, too low injection pressure, too large or too small injection speed, too short cooling time.

Mold aspect: mold roughness becomes large, gate is too small, runner is too thin, poor exhaust.

Equipment: insufficient material supply.

For raw materials: raw materials are not dried and treated or contain volatile substances, raw materials are easily degraded, too much additives or mold release agents or bad quality, containing foreign substances.