Analysis of common defects of injection parts and improvement measures

A, lack of material

1. Reasons for defects:

The small parts and corners of the finished products can not be fully formed, because the mold processing is not in place or the exhaust is not smooth, the molding due to the injection dose or pressure is not enough and other reasons, design defects (insufficient wall thickness).

2. Mold improvement measures:

Revise the mold where the material is missing, take or improve the exhaust measure, increase the material thickness, improve the gate (increase the gate, increase the gate).

3, molding improvement:

Increase the dose and pressure of injection.

Second, the shrinking

1. Reasons for defects:

Often happen at take shape taste wall thick or material thick uneven place, because hot melt plastic cooling or solidify contraction is different and send, if the back side of rib, the edge that has side wall, BOSS column.

2. Mold improvement measures:

Reduce the material thickness, but retain at least 2/3 of the material thickness; Coarser runner, increase gate; Add the exhaust.

3, molding improvement:

Increase material temperature, increase injection pressure, prolong pressure holding time, etc.

Three, surface bright printing

1. Reasons for defects:

It often occurs on the back of the BOSS column or rib after reducing the thickness of the material, or because the core and thimble are designed too high, resulting in pressure marks.

2. Mold improvement measures:

Lower craters; Modified core and thimble; The parent die surface is sandblasted to reduce the brightness of the die surface.

3, molding improvement:

Reduce injection speed and pressure.

Fourth, gas lines

1. Reasons for defects:

Occurred at the gate, due to the mold temperature is not high, injection speed, pressure is too high, the gate setting is improper, when pouring plastic encounter turbulence structure

2. Mold improvement measures:

Change the gate, runner lighting, runner cold material area increase, increase the gate, the surface of the bite flower (by adjusting machine or repair mold drive line can also be).

3, molding improvement:

Increase mold temperature, reduce injection speed, reduce injection pressure, etc.

Five, the combination line (water stripe)

1. Reasons for defects:

Occurs at the confluence of two feed flows, such as two feed flows into the gate, around the core of the feed flow, due to temperature drop, poor exhaust.

2. Mold improvement measures:

Change the gate, add cold well, open exhaust groove or male mold surface bite flower, etc.

3, molding improvement:

Increase material temperature, mold temperature, etc.

Six, rough edge (Batch peak)

1. Reasons for defects:

Often occur at the joint of male and female die, due to poor die closing, or improper processing of the die surface and corners, forming often due to insufficient clamping force, material temperature, pressure is too high.

2. Mold improvement measures:

Revise the die and re-close the die.

3, molding improvement:

Increase the clamping force (check whether the tonnage of the injection machine is enough), reduce the material temperature, reduce the injection pressure, reduce the holding time, reduce the holding pressure, etc.

Seven, deformation

1. Reasons for defects:

Elongated parts, large area of thin wall parts, or asymmetric structure of the larger finished product due to uneven cooling stress or ejection force is not the same when forming.

2. Mold improvement measures:

Modified thimble; Set up a tensioning pull pin, etc.; When necessary, the male mold is added to adjust the deformation.

3, molding improvement:

Adjust the mold temperature of male and female molds, reduce and maintain pressure, etc. (The adjustment of small deformation mainly depends on the pressure size and time, and the adjustment of large deformation generally depends on the mold temperature)

Eight, the surface is unclean

1. Reasons for defects:

The mold surface is rough, for PC material, sometimes due to the mold temperature is too high, the mold surface has residual glue, oil stains.

2. Mold improvement measures:

Clean the die surface and polish it.

3, molding improvement:

Reduce the mold temperature, etc.

9, white

1. Reasons for defects:

It is easy to occur at the corner of thin wall of forming products or at the root of thin wall ribs. Due to the bad force caused by demolstering, the thimble is set improperly or the inclination of drawing mold is not enough.

2. Mold improvement measures:

Increase R corner; Increase the release Angle; Add a thimble or increase its cross-sectional area; Die surface lighting; Thimble or diagonal pin glazing

3, molding improvement:

Reduce the rate of fire, reduce the injection pressure, reduce the pressure and time.

10  and die

1. Reasons for defects:

Performance is demoulding bad or die injury, pull flower, mainly because pull die slope is not enough or die surface is rough, forming conditions also have an effect.

2. Mold improvement measures:

Increase the drawing Angle; Die surface lighting; Stick mother mold surface can increase/change the pull pin, pay attention to the horn feed diameter, male mold plus bite flower.

3, molding improvement:

Reduce injection pressure to reduce pressure retention and time.

11. Stomata

1. Reasons for defects:

Transparent finished PC material forming is easy to appear, because the gas is not exhausted in the injection process, improper mold design or improper molding conditions have an impact.

2. Mold improvement measures:

Add exhaust, change gate (gate increase), PC material runner must be polished.

3, molding improvement:

Strict drying conditions, increasing injection pressure, reducing injection speed, etc.

Twelve, segment difference

1. Reasons for defects:

Occurs in the male and female die block/slider/inclined pin and other joints, the performance of the combined surface is not uniform, due to improper die or die itself.

2. Mold improvement measures:

Revise the die and re-close the die.

3. Molding improvement: None

13. Out of dimensional tolerance

1. Reasons for defects:

Mold itself problems, or improper molding conditions caused by improper molding shrinkage rate is not appropriate.

2. Mold improvement measures:

Modify the mold, such as adding glue, reducing glue, or even in extreme cases (improper shrinkage rate resulting in excessive size deviation) to reopen the mold.

3, molding improvement:

Generally, changing the pressure holding time and injection pressure (the second stage) has the greatest influence on the size. For example, increasing the injection pressure and increasing the pressure holding and feeding effect can obviously increase the size, reducing the mold temperature can also, increasing the gate or increasing the gate can improve the adjustment effect.