Auto Plastic B Pillar Low Pressure Injection Molding

What is the A/B/C pillar in automoblie?

The A-pillar is between the engine compartment and the cockpit, and above the left and right rear-view mirrors, it will obscure part of your turning horizon, especially the left turning, so it is discussed more. The B-pillar is between the front and rear seats of the cockpit, which is the longitudinal bar between the two doors on both sides. It extends from the roof to the bottom of the car. From the inside, the seat belt is on the B-pillar. The C-pillars are on both sides of the rear seat headrest.

The characteristics and design points of auto pillar injection molding

1. Spots and gate marks are not allowed on the appearance of plastic parts, and defects such as shrinkage dents, weld marks, and flashes are not allowed too.

2. Plastic parts are interior molding parts, which are typical high-demand interior parts.

3. The appearance of plastic parts is complex, and the appearance of the clamp line is high. The appearance of the plastic parts needs to be treated with skin texture.

4. As the appearance surface of the plastic part needs to be texture, the draft angle of the appearance surface of the plastic part is designed to be at least 5 degrees or more to prevent the plastic part from sticking to the fixed mold after the texture and have some drag marks.

5. The parting line of the plastic part is complicated, and a curved surface shape is required.

6. Check the mold draft angle of the appearance surface of the plastic part before designing the mold: especially whether the area that needs to be added the texture finishing to be 7º, and the fixed mold must be checked too; Polished plastic part area is 5º.

7. Due to the high requirements for the appearance of plastic parts, the rib thickness of the plastic parts and the wall thickness of the main body of the plastic parts must be reasonably designed. Therefore, check the size and ribs size on the plastic part before the design of the mold: the big end must not be greater than 1/3 of the corresponding main wall thickness, otherwise there will be shrink marks on the surface; the small end must not be less than 0.6MM, which is too small for processing and injection molding forming maybe have the problem too.

8. There are many ribs. All the plastic parts and ribs must be proportional to the wall thickness of the plastic parts, if not, the surface of the plastic parts will have some shrinkage marks.  all the ribs also need to be designed as the mold opening or moving direction, if not, it will have some undercut here too. 

New technic of making auto pillar mold--- Low-Pressure Injection

For more medium and high-grade automobiles, there is a special and soft cloth on the plastic pillar, showed like the above picture, which can highly increase the decorative, feeling, and aesthetic function in the automotive part.

This is made by a new injection technic.

A low-pressure double-layer injection mold, also called a low-pressure injection mould, is a new injection technology for mold. The previous way is using manual coating and vac-sorb the component to cavity & core, now it can be worked directly on the injection procedure. 

The main principle is: when opening the mould, putting fabric/cloth to the front mould pin, then die assembling, injecting, and at last taking out the pieces.  This special technology is usual applied to the skeleton of the map bag and pillar part in the auto part.