Common Problems And Corresponding Solutions Of Bumper Mold Injection Molding

Common problems and corresponding solutions of bumper mold injection molding

(1) Pressure line

There are obvious pressure lines around the bumper fog lights, which affect the appearance and surface quality of the product. Since the bumper is part of the exterior surface of the car, there are strict requirements on the apparent quality, and crimping can seriously affect its apparent quality.

Possible cause analysis and improvement measures:

1)some kind of. Die: Set a door G5 near the hole around the fog light. When this gate is opened, the pressure on both sides of the hole will reach the equilibrium pressure line again due to the effect of the hole.

2) Solution: Minimize the pressure difference around the weld line, or make the pressure difference insufficient to move the solidified melt.

(2) Tigerskin pattern

Tigerskin pattern is a surface defect with wavy stripes, which is roughly perpendicular to the direction of melt flow, and forms markings with different gloss levels on the surface of the part, which are similar to the pattern on a tiger skin, commonly known as tiger pattern. Skin pattern.

How to improve tiger skin patterns?

1) In the mold design, increasing the diameter of the runner and expanding the thickness and width of the gate are effective measures to prevent the occurrence of tiger-skin patterns. The thickness of the gate is preferably 0.7 to 0.8 times the wall thickness, in order to reduce the pressure loss of the melt in the runner and gate and reduce the expansion effect when entering the cavity.

2) During the injection molding process, increasing the melt temperature and mold temperature and adjusting the injection speed will help to eliminate the occurrence of tiger skin lines. In general, using a lower rate of fire is beneficial in eliminating tiger stripes because the melt flow is more stable at lower velocities.

(3) Material flower

The flower-shaped cold material near the automobile bumper not only affects the apparent quality of the part but also affects its mechanical properties. A car bumper is a safety device that absorbs and mitigates external impacts and protects the front and rear of the body. Generally, it is better to choose PP with better mechanical strength.

Possible cause analysis and improvement measures:

As for injection molding, some needle valve gates may not be tightly sealed, there is residual cold material on the gate, and the air pressure to close the needle valve is very low, which cannot function as a sealant. Use an air pressure booster to increase the air pressure at the needle and the cold slug will go away when there is no leak around the hot gate.

(4) Peel off

Due to the large surface area and low defect rate of automobile bumper parts, spalling defects are difficult to find, but such defects seriously affect the surface quality of the parts.

Possible cause analysis and improvement measures:

1) Molding process: Due to manual picking in the production process, when the picking time is long, each hot nozzle will have different degrees of drooling. After shortening the pick-up time, it was found that the hot nozzle sprue phenomenon was effectively improved. As a result, cold stock from drool may flush into the cavity, causing delamination and spalling.

2) Solution: increase the injection distance of the injection molding machine, so that the hot nozzle no longer produces salivation.