HEFEI PRE-WORLD Shares with You: Tips on Extrusion Mold Molding

Extruder is a type of PVC Foaming Machine Accessories, which can produce plastic products of various shapes. Each shape and different specifications of plastic products must have a set of special molds that can form specific shapes and sizes when extruding and molding, so there are many types of molds for extruders to mold plastic products, such as various specifications of pipes, rods, profiles, plates (sheets), films, wires, nets and flat belts. There are special molding molds of different sizes and specifications.

The design and manufacturing quality of the molding mold have a significant impact on the quality of plastic molded products. If the structure and size selection and design are unreasonable, sometimes it is even impossible to produce. The requirements for molding mold manufacturing and working technical conditions are as follows.

1) Requirements for steel used in molding mold manufacturing.

① Good heat resistance, small deformation in high temperature working environment.

② Strong wear resistance.

③ Corrosion resistance, working in a molten material environment with corrosive gas for a long time, not easy to be corroded, rusted and oxidized.

④ Good machining performance.

⑤ The oxide layer is thin and the deformation is small during heat treatment.

⑥ In addition to the above conditions, the alloy steel used to manufacture the die lip and the flow control strip should also have good elasticity. Commonly used steels for mold parts manufacturing include: 45, 40Cr, 65Mn, T8A, T10A, 2Cd3, 3Crl3 and 38CrMoAlA, etc.

2) When molding plastic products with different raw materials, a mold structure that is more suitable for its molding should be selected. For example, when PVC resin is used to produce molded pipes, a straight-through mold structure should be selected; when PE or PP resin is extruded into film, a mold structure with a spiral groove core rod and a right angle to the extruded melt flow direction should be selected.

3) In the molding mold body, the inner cavity of the melt flow should be streamlined, and the transition between sections of different diameters should be connected by arc lines, that is, there should be no dead corners or stagnation in the flow section of the melt.

4) The cross section of the melt flow cavity in the mold body to the cross section of the melt molding die mouth should be gradually reduced, with a certain compression ratio, so as to eliminate the melt bonding seam caused by the diverter cone bracket and make the product dense. This compression ratio refers to the ratio of the cross-sectional area of the flow at the outlet of the diverter cone bracket to the cross-sectional area of the die flow at the die outlet of the mold. According to the different raw materials used for the molded products, the compression ratio is generally taken in the range of 3 to 10.

5) The mold components should be as few as possible, the structure should be compact, and the shapes of the parts should be symmetrical to facilitate installation, disassembly and heater layout. 6) Each part in the mold should have sufficient working strength. The main parts should be tempered, and the die working surface should have a higher hardness, generally not less than 40-45HRC.