Warm Global Customers
With China Plastic Machinery
With China Plastic Machinery
Thermosetting plastic compression molds have no pouring system, which saves molding materials. A mold cavity or a feeding cavity is provided as a space to accommodate the molding material, and the material is preheated. The molding pressure is directly applied to the plastic part by the mold, which is suitable for molding plastics with poor fluidity or with various fillers. In addition, there are few oriented structures and low orientation degree in the plastic part, and the various directional properties are relatively uniform.
Thermosetting plastic molds are mainly used to mold thermosetting plastic products, that is, to process powdered thermosetting plastics into shape. There are three types: thermosetting plastic compression molds, thermosetting material transfer molds and thermosetting plastic injection molds. Among them, compression molds are the most widely used, and injection molds are less commonly used. Commonly used thermosetting plastics include phenolic plastics (i.e. bakelite), amino polyester, epoxy resin, polydiallyl phthalate (PDAP), silicone plastics, etc.
The working temperature of thermosetting plastic molds is generally between 160 and 250¡ãC. The unit pressure of the mold cavity is large, generally between 160 and 200 MPa. During operation, friction occurs between the cavity surface and the flowing powder, which makes the cavity surface easy to wear and bear certain impact loads and corrosion. When this type of mold is used to press various bakelite powders to make parts, a certain amount of low-grade powder filler is added to the raw materials and the parts are formed under hot pressing. Therefore, the thermal load and mechanical load are large, and the filler causes serious wear of the mold cavity.
(1) The size of the cavity and core of the compression mold is determined by the shape and dimensional accuracy required by the plastic part. Since the mold works under the heating state (60¡æ-150¡æ), the size will expand when heated, and the size will shrink again after the cavity cools down, alternating repeatedly. Therefore, when manufacturing the compression mold, in addition to carefully processing and manufacturing according to the drawing size, the wear of the cavity and core and the above-mentioned thermal expansion and contraction factors should also be taken into account to ensure the quality of the product when the mold is used for a long time.
(2) When manufacturing the compression mold, the core and cavity should be processed in coordination. After the coordination processing, paraffin or plasticine can be used to trim the edges. After passing the inspection, it is hardened and polished.
(3) In order to facilitate the removal of the product, the cavity and core should be processed with a demolding slope.
(4) The position accuracy of the upper and lower molds of the compression mold is generally guaranteed by the guide pins and guide sleeves. During processing, the installation holes of the guide pins and guide sleeves should be consistent, and the matching clearance should be appropriate. The forming holes, insert holes, core holes on the core fixing plate, etc. should maintain a certain position accuracy with the guide pins and guide sleeve holes so that the mold can move flexibly after assembly.
(5) The forming parts of the compression mold should be polished and chrome-plated to a surface roughness of 0.20¦Ìm or more.
(1) Scraping of the concave mold cavity. The processing of the compression mold concave mold cavity is often done by stamping and filing the fully processed and hardened stamping sample. The stamping and filing should be performed while stamping to ensure that the cavity die mating surface and each forming surface are processed to size and the dimensional accuracy and surface quality requirements are guaranteed. After the finely trimmed die is heat-treated and hardened, it is polished, ground or hard-chrome-plated to make the surface of the cavity die smooth.
(2) Before the die is heat-treated and hardened, the guide nail L should be drilled and reamed according to the markings.
(3) Trim the mold hole of the fixing plate. The fixed plate hole, upper die fixed plate, is repaired with the upper core stamping file; the lower die fixed plate hole is repaired with the lower concave die or stamping punch stamping file or processed to size according to the drawing. In addition, the slope of the forming hole and the guide radius of the punch must be trimmed.
(4) Press the core into the fixed plate. Press the upper core into the upper fixed plate and the lower core into the lower fixed plate, and ensure the verticality of the core to the plane of the fixed plate.
(5) Grinding. Grind the upper and lower planes of the concave die according to the actual height after the core and the fixed plate are assembled, so that the upper and lower cores and the upper core maintain a certain relative position with the feeding chamber.
(6) Re-drill and ream the guide pin hole. On the fixed plate, re-drill the guide pin hole and ream the hole to size according to the position of the drilled concave model cavity guide hole.
(7) Press the guide pin into the fixed plate.
(8) Grind the bottom plane of the assembled fixed plate.
(9) Chrome plating and polishing. Remove the pre-assembled concave mold, blocks, and core (after the mold test is qualified), chrome plating, and polishing.
(10) Reassemble the components and concave mold core according to the drawing requirements, and install all accessories to make it a complete mold.
(11) Check according to the assembly drawing, test the pressure with a press, and check the quality of the sample. And perform trimming while testing the pressure until a qualified part is pressed out.
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