Causes of common injection molding defects and solutions.

Burr (or flash, overflow and material overflow)

Burr is caused by the overflow of molten injection resin from the parting surface of the mold, which is a bad state in the forming operation. Especially when the burr is firmly adhered to the parting surface of the die for die locking, it will damage the parting surface of the die. After the die is damaged, new burr will be generated in the formed product when it is re operated. At the same time, it also aggravates the damage of the die and makes it unusable. Therefore, special attention should be paid.

1.Do not use too high injection pressure

Make the molding machine act at the switching position of injection and pressure holding as soon as possible to reduce the injection volume and injection pressure. When the injection pressure of the injection molding machine reaches the set peak value, complete the resin filling process and switch to pressure holding pressure. When high injection pressure is still applied after the filling process, residual stress will be formed in the formed product and burr will occur.

2. improve the clamping force

The mold locking pressure can be increased by the mold locking pressure regulating valve, or the mold locking pressure can be set to 95%. However, the appropriate forming machine shall be selected according to the projected area of the formed product and the required forming pressure of the formed product.

3. keep the mold properly

When the parting surface of the die is damaged or foreign matters are sandwiched, so that the parting surface cannot fit closely, burrs will certainly occur. If the mold is not kept properly, the moving and fixed mold base plates of the mold will be damaged and rusted. Therefore, the die cannot be placed on the ground directly, otherwise it will cause burr during forming. We should form a good habit of keeping molds properly. The mold mounting surface of the horizontal injection molding machine should also be properly kept. Before the mold is installed into the injection molding machine, the mold mounting surface must be wiped clean with a rag. In case of corrosion, knock marks and dents, the fixed formwork and lock formwork shall be removed and processed and repaired with milling machine, drilling machine, etc.

4. adjust the injection volume and reduce the temperature

Burrs can also occur when the injection volume is too large or the temperature of the heating barrel is set too high. The injection volume should be set gradually.
It can also be adjusted by the following methods: select materials with high viscosity grade; Grind the die surface where the overflow occurs, and use harder die steel; Increase die support column to increase rigidity; Determine the size of different exhaust slots according to different materials.