Blow mold and main auxiliary parts design points

Blow mold and main auxiliary parts design points

Mold usually only cavity part, no punch, mold surface generally do not need to do hardening treatment, cavity under the blowing pressure is much smaller than injection molding, generally 0.2~1.0MPG, the cost is lower.

Dongguan blow molding

1. Mold materials

Usually made of aluminum alloy, and for corrosive materials such as PVC and POM, beryllium copper or copper-based alloys are also used; For the higher life requirements of the mold, such as blowing engineering plastics ABS, PC, POM, PS, PMMA, etc. need to use stainless steel to make the mold.

Blow molding

Figure mold

2. Key points of mold design

1) Parting surface

Generally to be placed on the symmetrical surface, reduce the blowing ratio, such as elliptical products, parting surface in the long axis, distance shape products, then through the middle line.

2) Cavity surface

PE material should be slightly rough, fine sand surface is conducive to exhaust; While other plastics (such as ABS, PS, POM, PMMA, Nylon, etc.) blow molding, the mold cavity generally can not be sandblasted, can be made in the parting surface of the mold cavity exhaust groove, or in the cavity to do the vent, the general cavity of the vent diameter Φ0.1 ~ Φ0.3, the length of 0.5~1.5mm.

3) Cavity size

Cavity size design to consider the plastic shrinkage rate, specific can refer to common plastic shrinkage rate.

4) Cut off the cutting edge and tailings groove

In general, blow molding engineering plastics and more rigid plastics, cutting edge to use good wear resistance materials, such as beryllium copper, stainless steel, etc. For LDPE, EVA and other soft plastic products, general aluminum alloy can be;

Cutting edge to choose a reasonable size, too small will reduce the strength of the joint, too large will not be able to cut off and die parting surface at the clip is large, and under the cutting edge open tailings groove, tailings groove is designed into an Angle, cutting can be a small amount of melt extrusion into the joint, so as to improve the joint strength.

5) Injection blow molding mold

The design is different from the extrusion blow molding, the main difference is that the injection blow mold does not need to cut off the edge and tail feed groove, the injection blow parts of the blank design is very important, which is directly related to the quality of the finished product.

6) Injection and blowing mold -- design principle of billet

A. Length of long diameter ≤10/1;

B. Blowing ratio of 3/1 ~ 4/1(ratio of product size to billet size);

C. Wall thickness of 2 ~ 5.0mm;

D. According to the shape of the product, the wall thickness should be thick in the place where the blowing ratio is large, and the wall thickness should be thinner in the place where the blowing ratio is small;

E. For elliptical containers with an elliptical ratio greater than 2/1, the mandrel shall be designed to be elliptical. For elliptical products with an elliptical ratio less than 2/1, the circular mandrel can form an elliptical container.

7) Blow rod design

The structure of the blow rod is determined according to the mold structure and product requirements. The selection range of the aperture of the general intake rod is:

L<1: aperture Φ 1.5;

4>L>1: aperture Φ6.5;

200>L>4: aperture Φ 12.5(L: for volume, the unit is in litres)