How to solve the flow mark on the surface of injection molded products

Flow mark is a common appearance defect of injection molded products. It will have a great impact on production, so how to solve it? Let’s talk about how to solve the flow marks on the surface of injection molded products?

Fault analysis and troubleshooting

1. Poor melt flow leads to annual ring wave flow marks centered on the gate on the surface of plastic parts. It can be adopted to increase the temperature of mold and nozzle, increase the injection rate and mold filling speed, and increase the injection pressure, pressure holding and pressurization time. A heater can also be set at the gate to increase the local temperature at the gate. The gate and runner area can also be appropriately expanded, and the gate and runner section is preferably circular, which can obtain the best mold filling. However, if the gate is set in the weak area of the plastic part, the square section shall be adopted. In addition, a large cold material cavity shall be set at the bottom of the injection port and the end of the diversion channel. The greater the influence of the material temperature on the flow performance of the molten material, the more attention shall be paid to the size of the cold material cavity. The position of the cold material cavity must be set at the end of the molten material along the flow direction of the injection port.

• The poor flow of molten material in the channel leads to spiral wave flow marks on the surface of plastic parts. When the melt flows from the narrow section of the flow channel into the cavity with large section or the mold flow channel is narrow and the finish is very poor, the material flow is easy to form turbulence, resulting in spiral wave flow on the surface of the plastic part. In this regard, the injection speed can be appropriately reduced or the injection speed can be controlled slowly, fast and slowly. The gate of the mold shall be set at the thick wall part or directly at the wall side. The gate form is preferably handle type, fan-shaped or diaphragm type. The runner and gate section can also be appropriately expanded to reduce the material flow resistance.

3. Volatile gas causes cloud like wave flow marks on the surface of plastic parts. When ABS or other copolymer resin raw materials are used, if the processing temperature is high, the volatile gas generated by resin and lubricant will produce cloud like wave flow marks on the surface of plastic parts. In this regard, it is necessary to appropriately reduce the temperature of the mold and barrel, improve the exhaust conditions of the mold, reduce the material temperature and mold filling rate, appropriately expand the gate section, and consider changing the lubricant variety or reducing its dosage.

The above is the fault analysis and troubleshooting methods listed on how to solve the flow marks on the surface of injection molded products. I hope it will bring you harvest.