Bumper Molding

As plastic injection is applied for most of plastic auto parts production, there are always defects such as tiger skin flow mark, sink mark, weld line, warpage and so on. For bumper molding, we need to pick up the supreme solutions for material, part construction design, mold tooling design and plastic injection molding process which are great factors to avoid defects. Here we are going to introduce some normal problems that maybe occur during bumper injection molding.

The diagram shows the rear bumper of one car that a swell came about at turning up area related to luggage cover,which happens sometimes and influences appearance after injection molding.

It is because air vent is not made at cold runner end,so when melt resin ejected,air remained in cold runner goes into product and here comes the bubble.Holes can be found at product section when cut out.Therefore,air vent is necessary at the cold runner end and valve tip be closed with runner to guarantee no air sneaks in.

In the above left figure splay marks on the bumper product which is definitely bad for appearance, the reason for which are two that hotrunner and coldrunner are both set in the bumper mold without cold slug well for coldrunner and the other is some of the valve gates are not sealed well while residual resin left on the gate. To use a inflator to guarantee the valve needle air pressure so hot gate would not leak melt resin any more could solve the splay marks problem.

Problem-see left figure above that tiger skin flow marks come about on gate area of product surface which is perpendicular to melt flow direction in actual bumper molding. It is because much drag force comes about when melt resin pass by little fillet transition as well as the construction on the melt flow vertical direction.Thus to enlarge the fillet transition can decrease the drag force.

Problem: bumper picture above is made with hidden parting line mechanism in mold, and in red circle there is hole covering push-pull block at turn-up area which will be effected during bumper pull warp that leads the hole fail to assembly.

Solution: to add red flash groove as picture below, to assist hole and enhance pull warp strength so the bumper warps successfully without hole deformation, plastic molding well..

Hot Tags: bumper molding, China bumper molding manufacturers, makers, Chair Injection Mold, gas assisted injection, household mold, Gas Assisted Molding, Bumper Injection Mould, Overmold