Development Prospect and Introduction of 3D Blow Molding

Development Prospect and Introduction of 3D Blow Molding

With the automotive industry's demand for the production of complex and tortuous transportation pipelines, the development of off-axis extrusion blow molding technology has been promoted. This technology is called 3d blow molding or three-dimensional blow molding (also known as multidimensional extrusion blow molding (MES) in some countries). Because the waste flashes generated during the process of 3D blow molding are greatly reduced, and even no waste flashes are generated, it is also called less waste or no waste flash blow molding.

A more commonly used molding method of three-dimensional (3D) extrusion hollow blow plastics is that after extruding the plastic parison, it is pre-blown and pressed against the side of the mold wall, and the extrusion head or mold is carried out according to the molding process. The rotation of the second or third axis, when the intestine-like parison fills the film cavity, the other side of the mold closes and holds the parison to separate it from the subsequent parison. This is the entire parison which is blown and tightly formed on the wall of the membrane cavity. In this way, air ducts or oil pipelines are produced which are similar to those in automobiles, not only have few flashes, but also have no mold line on the product, moreover 3D blow molding not only makes many parts with complex shapes processed very easily, but also makes the products extruded in sequence.

The second molding method mainly adopts the sequential opening and closing mold and negative pressure molding process. The upper and lower ends of the mold are used as sliding blocks that can be opened and closed separately. The mold is closed first during production, the tubular parison is sucked in by negative pressure air and moves along the curve of the internal cavity inside the mold. After the parison is in place, the above and below sliders of the mold are closed and blow-molded; This molding method is suitable for molding pipes with regular shapes.

The third molding method mainly adopts a robot or a manipulator to hold the plastic parison and attach it to the mold, blows it into shape, and it can also realize three-dimensional blow molding. If the curved pipe fitting is produced by the conventional blow molding production process, as the flat-folded width of the parison is much larger than the projected width of the product, so a large number of waste flashes will be generated (some of the height is more than 50%), and the blank joint is long, which not only affects the appearance, but also affects the strength of the product.

Due to the special processability of three-dimensional blow molding, compared with the conventional blow molding process with waste flashes, it has the following advantages.

I.From the selection formula of clamping force, clamping force P clamping = 1.2P, P = qs, then we can know that the projection area of 3D blow molding is much smaller than the flat-folded width of the standard blow molding, P is the mold expansion force, q is the blowing pressure, and s is the projected area on the mold clamping surface, so the mold clamping force is much smaller than that required by the conventional blow molding process.

II.The workload of cutting off the flashes is greatly reduced.

III.No need to redress the outer diameter of the molded article.

IV.The quality of molded articles has been improved, because of the wall thickness distribution design, no less clamping strength.

V.Due to the reduction of scraps and less extrusion time, the degradation probability of heat-sensitive materials is reduced.

VI.Since the waste flash is greatly reduced, smaller extruder can be used for production.

Because of the above characteristics of 3D blow molding, this type of method is an ideal technology for manufacturing curved long pipes and pipes for automobiles. Parts that can be made by 3D blow molding include: air ducts for supercharged diesel engines, special cooling medium ducts, and fuel supplements. In some developed countries, 3D blow molding technology has replaced other technologies in some application areas to make parts such as oil injection pipes and seamless door handles. In addition, 3D blow molding technology is used in off-road vehicle parts and furniture(Chair backs and chair legs), large water pipe devices and other fields also have potential application value; 3D blow molding technology has very attractive development prospects.

The three-dimensional blow molding technology is suitable for manufacturing complex plastic pipe parts, and the manufactured parts will not have a parting line that can easily cause damage, there is no flash, and it can also improve the uniformity of the wall thickness of the hollow blown parts. Plastic molding technology can promote the integration of parts without assembly parts, thereby reducing costs. At present, the technology is making products with sequential structure and sandwich structure, improving product quality and production efficiency, and reducing product cost. This molding technology will have a large application and development space.