Common problems in automobile injection molding

The defects and abnormal phenomena of automobile injection molding are ultimately reflected in the quality of injection molded products. The defects of injection molded products can be divided into the following points: (1) Insufficient injection of products; (2) Overflow of products; (3) Dents and bubbles of products; (4) Joint marks of products; (5) Brittle products; (6) Plastic discoloration; (7) Silver streaks, streaks and flow marks of products; (8) Turbidity at the gate of products; (9) Warping and shrinkage of products; (10) Inaccurate product dimensions; (11) Products stick to the mold; (12) Materials stick to the runner; (13) Nozzle drooling.

The following describes the causes and solutions to overcome them one by one. ⒈ How to overcome insufficient injection of products Insufficient injection of products is often caused by the solidification of materials before filling the cavity. Of course, there are many other reasons. ⑴ Equipment reasons: ① The material is interrupted in the hopper; ② The hopper neck is partially or completely blocked; ③ The amount of material added is not enough; ④ The feeding control system is not operating properly; ⑤ The plasticizing capacity of the injection molding machine is too small; ⑥ The injection cycle is abnormal due to the equipment.
Injection molding condition reasons: ① The injection pressure is too low; ② The injection pressure loss is too large during the injection cycle; ③ The injection time is too short; ④ The injection full pressure time is too short; ⑤ The injection rate is too slow; ⑥ The material flow in the mold cavity is interrupted; ⑦ The filling rate is not uniform; ⑧ The injection cycle is abnormal due to operating conditions.
Temperature reasons: ① Increase the barrel temperature; ② Increase the nozzle temperature; ③ Check the millivoltmeter, thermocouple, resistance electric heating coil (or far-infrared heating device) and heating system; ④ Increase the mold temperature; ⑤ Check the mold temperature control device.
Mold reasons ① The runner is too small; ② The gate is too small; ③ The nozzle hole is too small; ④ The gate position is unreasonable; ⑤ The number of gates is insufficient; ⑥ The cold material hole is too small; ⑦ Insufficient exhaust; ⑧ The injection cycle caused by the mold is abnormal;
Material reasons: The material fluidity is too poor. ⒉ How to overcome product flash overflow: Product overflow is often caused by mold defects. Other reasons include: injection force greater than clamping force, material temperature is too high, insufficient exhaust, excessive feeding, foreign matter on the mold, etc.
Mold problems: ① The cavity and core are not closed tightly; ② The cavity and core are offset; ③ The template is not parallel; ④ The template is deformed; ⑤ Foreign matter falls into the mold plane; ⑥ Insufficient exhaust; ⑦ The exhaust hole is too large; ⑧ The injection cycle caused by the mold is abnormal.
Equipment problems: ① The projected area of ​​the product exceeds the maximum injection area of ​​the injection molding machine; ② The injection molding machine template is not installed and adjusted correctly; ③ The mold is not installed correctly; ④ The clamping force cannot be kept constant; ⑤ The injection molding machine template is not parallel; ⑥ The tie rod is deformed unevenly; ⑦ The injection cycle is abnormal due to the equipment
Injection molding condition problems: ① The clamping force is too low ② The injection pressure is too high; ③ The injection time is too long; ④ The injection full pressure time is too long; ⑤ The injection rate is too fast; ⑥ The filling rate is not uniform; ⑦ The material flow in the mold cavity is interrupted; ⑧ The feed amount is too large; ⑨ The injection cycle is abnormal due to operating conditions.
Temperature problems: ① The barrel temperature is too high; ② The nozzle temperature is too high; ③ The mold temperature is too high.
Equipment problems: ① Increase the plasticizing capacity of the injection molding machine; ② Make the injection cycle normal;

Cooling condition problems: ① The parts are cooled in the mold for too long to avoid shrinking from the outside to the inside, shorten the cooling time of the mold; ② Cool the parts in hot water.
How to avoid product dents and pores Product dents are usually caused by insufficient force on the product, insufficient material filling, and unreasonable product design. Dents often appear in the thick wall part close to the thin wall. The pores are caused by insufficient plastic in the mold cavity, cooling and solidification of the outer ring plastic, and shrinkage of the internal plastic to form a vacuum. Most of them are caused by hygroscopic materials that are not dried well, and residual monomers and other compounds in the material. To judge the cause of pores, just observe whether the bubbles of plastic products appear instantly when the mold is opened or after cooling. If they appear instantly when the mold is opened, it is mostly a material problem. If they appear after cooling, it is a problem with the mold or injection molding conditions. ① Dry the material ② Add lubricant ③ Reduce the volatile matter in the material (2) Injection molding condition problems ① Insufficient injection volume; ② Increase injection pressure; ③ Increase injection time; ④ Increase full pressure time; ⑤ Increase injection speed; ⑥ Increase injection cycle; ⑦ Abnormal injection cycle caused by operation reasons. (3) Temperature problem ① Excessive shrinkage caused by material being too hot; ② Insufficient compaction caused by material being too cold; ③ The mold temperature is too high, causing the material at the mold wall to not solidify quickly; ④ The mold temperature is too low, causing insufficient mold filling; ⑤ The mold has local hot spots; ⑥ Change the cooling plan. (4) Mold problem; ① Increase the gate; ② Increase the branch channel; ③ Increase the main channel; ④ Increase the nozzle hole; ⑤ Improve mold venting; ⑥ Balance the filling rate; ⑦ Avoid interruption of the filling material flow; ⑧ Arrange the gate feed at the thick wall part of the product; ⑨ If possible, reduce the wall thickness difference of the product; ⑩ Abnormal injection cycle caused by the mold. (5) Equipment problems: ① Increase the plasticizing capacity of the injection molding machine; ② Make the injection cycle normal; (6) Cooling condition problems: ① The component is cooled in the mold for too long to avoid shrinkage from the outside to the inside and shorten the cooling time of the mold; ② Cool the part in hot water. ⒋ How to prevent product joints (seam lines) Product joints are usually caused by low temperature and low pressure at the seam. ⑴ Temperature problems: ① The barrel temperature is too low; ② The nozzle temperature is too low; ③ The mold temperature is too low; ④ The mold temperature at the seam is too low; ⑤ The temperature of the plastic melt is uneven. ⑵ Injection molding problems: ① The injection pressure is too low: ② The injection speed is too slow. (3) Mold problems: Poor venting at the seam; Poor venting of the component; The runner is too small; The gate is too small; The inlet diameter of the three-runner is too small; The nozzle hole is too small;