Thermoplastics are characterized by expansion after heating and contraction after cooling. Of course, the volume will shrink after pressurization. In the injection molding process, the molten plastic is first injected into the mold cavity. After the filling is completed, the molten material cools and solidifies. When the plastic part is taken out of the mold, shrinkage occurs. This shrinkage is called forming shrinkage. During the period from when the mold is taken out to stabilize the plastic part, there will still be slight changes in size. One change is to continue to shrink. This shrinkage is called post-shrinkage.
Injection molds are parts that give plastic shapes and dimensions during molding. Although the structure of the mold may vary widely due to the variety and performance of plastics, the shape and structure of plastic products, and the type of injection machine, the basic structure is the same. The injection mold is mainly composed of three parts: the gating system, the molded parts and the structural parts. Among them, the pouring system and molded parts are the parts that are in direct contact with the plastic and change with the plastic and the product. They are the most complex and the most variable parts in the plastic mold, requiring the highest processing finish and precision.
In order to improve the quality of plastic molds, minimize mold quality complaints, and meet customer needs when producing molds, we summarize and summarize common problems in mold manufacturing, establish standards, and implement them as required. According to our production experience, we summarize the production of standard molds into the following 30 points: 1. For mold blanks smaller than 2020, a prying pit is required between the a and b plates; for mold blanks larger than 2020, all templates including thimble plates must be prying pits; 2. Exhaust grooves should be machined on the guide post and guide sleeve of the mold blank to prevent the guide post and guide sleeve from straining; 3. There should be no sharp corners on the mold, and chamfering is required. Except for specially specified places; 4. The inner mold and mold parts must not be welded without consent; 5. Exhaust grooves must be opened at the appropriate position on the periphery of the mold product. For the specifications of the exhaust grooves, please refer to the mold design manual;
Hot runner gating system can be understood as an extension of injection molding machinery. The function of the hot runner system is to deliver the thermoplastic melt to the vicinity of the molding die or directly into the die adiabatically. The hot runner can be heated independently, but thermally insulated in the injection mold, so that it can individually compensate for the heat loss caused by contact with the "cold" mold. Hot runner molds have been successfully used to process various plastic materials. Almost all plastic materials that can be processed with cold runner molds can be processed with hot runner molds.
The car bumper is one of the relatively large trim parts on the car. It has three main functions: safety, functionality and decoration. There are three main ways to reduce the weight of automobile bumpers: material lightweight, structural optimization design, and manufacturing process innovation. Material lightweight generally refers to replacing the original material with a material with a lower density under certain conditions, such as replacing steel with plastic; the structural optimization design of the lightweight bumper mainly includes thin-wall technology; the new manufacturing process includes micro-foaming New technologies such as materials and gas-assisted molding.
A wall plug, also named wall anchor or rawlplug, is a fibre or plastic insert used to enable the attachment of a screw in material that is porous or brittle, otherwise not support the weight of the object attached with the screw. There are many types of wall plugs, the most common is the plastic wall plugs.