1. Defect characteristics of injection parts
The change of weight and size during the injection process exceeds the production capacity of mold, injection molding machine and plastic combination.
2. Possible causes of problems
(1) Uneven plastic in the injection cylinder.
(2) The range of injection cylinder temperature or fluctuation is too large.
(3) The capacity of injection molding machine is too small.
(4) Unstable injection pressure.
(5) The screw reset is unstable.
(6) The variation of operating time and inconsistent solution viscosity.
(7) The injection speed (flow control) is unstable.
(8). The plastic varieties that are not suitable for the mold are used.
(9). Consider the influence of mold temperature, injection pressure, speed, time and holding pressure on the product
3. Remedies
(1) Check whether there is sufficient cooling water flowing through the hopper throat to maintain the correct temperature.
(2). Check for inferior or loose thermocouple.
(3). Check whether the thermocouple used with the temperature controller is of the correct type.
(4). Check the injection volume and plasticizing capacity of the injection molding machine, and then compare it with the actual injection volume and the amount of plastic injection per hour.
(5). Check whether there is a stable molten hot material in each operation.
(6). Check the backflow preventer for leaks and replace it if necessary.
(7). Check whether the feeding setting is wrong.
(8). Ensure that the screw is stable in the return position during each operation, that is, not more than 0.4mm change.
(9). Check the inconsistency of operation time.
(10). Use back pressure.
(11). Check whether the hydraulic system operates normally and whether the oil temperature is too high or too low (25 -- 60oC).
(12). Select the type of plastic suitable for the mold (mainly from the shrinkage and mechanical strength consideration).
(13) Readjust the whole production process
Accept night mark
1. Defect characteristics of injection parts
This is usually associated with surface marks (see the "holes" section) and is caused by the plastic contracting off the mold surface.
2. Possible causes of problems
(1) The melting temperature is either too high or too low.
(2) Insufficient plastic in mold cavity.
(3) during the cooling stage, the surface in contact with the plastic will overheat.
(4) Unreasonable runner and too small gate section.
(5) Whether the mold temperature is suitable for the characteristics of plastics.
(6) Unreasonable product structure (too high, too thick, obviously different thickness).
(7) The cooling effect is not good, and the product continues to contract after demoulding.
3. Remedies
(1) Adjust the temperature of the injection cylinder.
(2). Adjust the screw speed to obtain the correct screw surface speed.
(3) Increase the injection volume.
(4). Ensure the use of correct padding materials;Increase screw forward time;Increase injection pressure;Increase injection molding speed.
(5). Check whether the check valve is properly installed, as abnormal operation may cause pressure loss.
(6). Reduce the mold surface temperature.
(7). Correct the flow passage to avoid excessive pressure loss;According to the actual needs, appropriately expand the section size.
(8) Properly control the mold temperature according to the characteristics of the plastics used and the product structure.
(9). Improve the product structure where allowed.
(10). Try to cool the product sufficiently.
Stain marks and injection marks
1. Defect characteristics of injection parts
Usually associated with the gate area: the surface is dull, sometimes with streaks.
2. Possible causes of problems
(1). Too high melting temperature.
(2) Mold filling speed is too fast.
(3) The temperature is too high.
(4). Related to the characteristics of plastics.
(5) There is cold material in the nozzle.
3. Remedies
(1). Reduce the temperature in the front two areas of the injection cylinder.
(2). Reduce injection molding speed.
(3). Reduce injection pressure.
(4). Reduce the mold temperature.
(5). Most of the parts produced by PE have injection marks, and the position of the feeding port can be modified according to the requirements of use.
(6). Avoid producing cold material as much as possible (control the nozzle temperature well).
Sprue stick
1. Defect characteristics of injection parts
The nozzle is held by the nozzle sleeve.
2. Possible causes of problems
(1) There is no correspondence between the injection muzzle and the injection nozzle.
(2) Excessive plastic stuffing in the mouth cover.
(3). The nozzle temperature is too low.
(4) The plastics are not completely solidified in the injection port, especially the injection port with large diameter.
(5) The circular arc of the injector bushing and the circular arc of the injector nozzle are improperly matched, leading to the emergence of a runner resembling "mushroom".
(6). The runner is not sufficiently inclined to pull out.
3. Remedies
(1) Re-align the injection nozzle and the injection nozzle sleeve.
(2). Reduce injection pressure.
(3). Reduce the screw forward time.
(4). Increase the nozzle temperature or heat the nozzle with an independent temperature controller.
(5). Increase the cooling time, but a better solution is to replace the original nozzle sleeve with a smaller nozzle.
(6). Correct the mating surface of the injection muzzle and the nozzle.
(7). Appropriately expand the pull out slope of the runner.
The cavity
1. Defect characteristics of injection parts
It can be easily seen in the "air trap" of a transparent molded piece but can also appear in opaque plastics.This is related to thickness and is often caused by the plastic shrinking away from the center of the injection piece.
2. Possible causes of problems
(1) The mold is not fully filled.
(2) abnormal operation of the check valve.
(3) The plastic is not thoroughly dried.
(4) Too fast pre-molding or injection.
(5) Some special materials should be produced with special equipment.
3. Remedies
(1) Increase the amount of injection.
(2). Increase injection pressure.
(3). Increase the screw forward time.
(4). Reduce the melting temperature.
(5). Reduce or increase the injection molding speed.(For example, increase the speed by 45% for non-crystalline plastics).
(6). Check whether the check valve is cracked or unable to operate.
(7) should be based on the characteristics of plastic to improve the drying conditions, let the plastic thoroughly dry.
(8) Appropriately reduce the screw rotation speed and increase the back pressure, or reduce the injection speed.
Injection piece bending
1. Defect characteristics of injection parts
The injection piece is similar in shape to the cavity but is a distorted version of the cavity shape.
2. Possible causes of problems
(1). Bending is due to excessive internal stress in the injection parts.
(2) Mould filling speed is slow.
(3) Insufficient plastic in mold cavity.
(4). Plastic temperature is too low or inconsistent.
(5) Injection parts are too hot when ejecting.
(6). The cooling is insufficient or the temperature of moving and fixed mode is inconsistent.
(7). Unreasonable structure of injection parts (such as stiffeners concentrated on one side, but far apart).
3. Remedies
(1). Reduce injection pressure.
(2). Reduce the screw forward time.
(3). Increase cycle time (especially cooling time).Immediately after ejecting from the mold (especially for thicker parts), cool the parts slowly by immersing them in warm water (38oC).
(4) Increase the injection molding speed.
(5). Increase the plastic temperature.
(6). Use cooling equipment.
(7) Properly increase the cooling time or improve the cooling conditions to ensure as much as possible the consistent mold temperature of the moving and fixed molds.
(8). If permitted according to the actual situation.
Common defects of injection molding products:
Phenomenon:
1. Insufficient injection speed.
2. Plastic shortage.
3. There is no screw pad at the end of the trip.
4. Variation of running time.
5, the temperature of the injection cylinder is too low.
6. Insufficient injection pressure.
7. The shooting mouth is partially sealed.
8. The heater outside the nozzle or injection cylinder cannot operate.
9. Injection molding time is too short.
10. Plastic is attached to the throat wall of the hopper.
11. Capacity of injection molding machine is too small (i.e. injection weight or plasticizing capacity).
12. The mold temperature is too low.
13. The anti-rust oil of the mold was not cleaned.
14, check ring damage, molten material backflow phenomenon.
Causes:
The melting temperature is either too high or too low.
2. Insufficient plastic in mold cavity.
3, the cooling stage when the surface contact plastic overheating.
4. Unreasonable runner and too small gate section.
5. Whether the mold temperature is suitable for the plastic characteristics.
6. Unreasonable product structure (too high, too thick, obviously different thickness).
7. The cooling effect is not good, and the product continues to shrink after demoulding.
Handling Measures:
1. Increase the injection speed.
2. Check the amount of plastic in the hopper.
3. Check whether the injection schedule is set correctly and make changes if necessary.
4. Check whether the check valve is worn or cracked.
5. Check whether the operation is stable.
6, increase the melt temperature.
7. Increase back pressure.
8. Increase the injection speed.
9. Check the nozzle hole for foreign bodies or unplasticized plastics.
10. Check all heater outer layers with ammeter to verify energy output is correct.
11. Increase the screw forward time.
12. Increase the throat area of the hopper or reduce the temperature of the rear area of the injection cylinder.
13. Use a larger injection molding machine.
14. Increase the mold temperature appropriately.
15. Clean the anti-rust agent in the mold.
16. Check or replace the check ring.
Product shortage:
1. Check whether there is sufficient cooling water flowing through the hopper throat to maintain the correct temperature.
2. Check for inferior or loose thermocouple.
3. Check whether the thermocouple used with the temperature controller is of the correct type.
4. Check the injection volume and plasticizing capacity of the injection molding machine, and then compare with the actual injection volume and the amount of plastic injection per hour.
5. Check whether there is a stable molten hot material in each operation.
6. Check the backflow preventer for leakage and replace it if necessary.
7. Check whether the feeding setting is wrong.
8. Ensure that the screw is stable in the return position of each operation, that is, no more than 0.4mm change.
9. Check for inconsistencies in operating hours.
10. Use back pressure.
11. Check whether the hydraulic system operates normally and whether the oil temperature is too high or too low (25-60℃).
12, choose suitable for the mold of plastic varieties (mainly from the shrinkage and mechanical strength consideration).
13. Readjusting the whole production process.
Fill dissatisfaction:
1. Adjust the temperature of the injection cylinder.
2. Adjust the screw speed to obtain the correct screw surface speed.
3. Increase the injection volume.
4. Ensure the use of correct padding materials;Increase screw forward time;Increase injection pressure;Increase injection molding speed.
5, check whether the check valve is properly installed, because abnormal operation may cause pressure loss.
6. Reduce the mold surface temperature.
7. Correct the flow passage to avoid excessive pressure loss;According to the actual needs, appropriately expand the section size.
8. Properly control the mold temperature according to the characteristics of the plastics used and the product structure.
9. Improve product mix where possible.
10. Try to cool the product sufficiently.
Size difference of injection parts
1. Uneven plastic input in the injection cylinder.
2. The range of temperature or fluctuation of the injection cylinder is too large.
3. The capacity of injection molding machine is too small.
4. Unstable injection pressure.
5. The screw reset is unstable.
6. The variation of operation time and inconsistent solution viscosity.
7. Unstable injection speed (flow control).
8, the use of the mold is not suitable for plastic varieties.
9. Consider the influence of mold temperature, injection pressure, speed, time, and holding pressure on the product.
How to simply distinguish the pros and cons of products:
Look at the appearance
1, to see whether the product is complete, deformed or not
2. Whether the color is uniform, whether there is obvious color difference, whether the color is bright and transparent
Touch products
1. Touch the surface of the product with your hands to see if it is smooth and whether there are burrs around and on the handle
2. Whether the assembly parts are appropriate and stacking is safe
3. Whether the product has been aging naturally, which is reflected in the fact that the product has become hard and brittle, while the high-quality product feels soft and tough
According to the weight
1, weigh the weight, from the raw material polymerization process and physical properties, specific gravity light means low crystallinity, high purity, less impurities
2. Products with the same structure and the same wall thickness are produced with the same raw materials and processes. In addition to the above two characteristics, the light weight is better