Injection mold is installed on injection machine. When designing an injection mold, in addition to mastering injection molding process, you should also have a comprehensive understanding of relevant technical parameters of selected injection machine to ensure that designed mold is compatible with injection machine used.
Tag: plastic injection molding
As plastic parts are used in more and more industries, there is increasing pressure to reduce costs and shorten time to market. Against this background, demand for simulation tools has also increased. When it comes to plastic injection molding process, it’s never been more important to understand details and key points behind it. Moldflow software, as a professional plastic injection molding simulation tool, is like an experienced expert, helping us verify, optimize injection mold and injection molding process of plastic parts.
General principles of product structure design are basic ideas and rules to be followed in product structure design. These basic rules make product structure design more reasonable. Whether it is plastic products or hardware products, general principles of product structure design include rational selection of materials, selection of reasonable structure, simplify mold structure and cost control as much as possible.
Injection molding cycle, also known as molding cycle, refers to time required to complete an injection molding process. It includes all the time in injection molding process, and time composition of injection molding cycle is shown in Table 1.
Compression injection molding is a more traditional injection molding method Principle: First inject molten material into mold cavity, when molten material enters mold lung. Mold is opened a little under its pressure knife; after molten material fills cavity, mold is locked with high pressure to obtain desired product. Second step is compression molding. Since molten material enters cavity when mold has been slightly opened, required mold force is relatively small. When molding, screw no longer injects material into mold cavity, but mold is locked by high pressure so that force Lf is pressed against plastic to form, so orientation of product is small and internal stress is low. This method is especially suitable for products with small volume and high transparency requirements;
1 Seven Elements of Plastic Forming A pressure B speed C time D temperature E measurement F raw material G mold 2 Programmable control effects A. Improve appearance by controlling injection process According to experience, appearance of finished product is determined by the first half of molding process, that is, closure of resin filling injection outlet, etc., and size of resin injection rate is closely related to appearance of finished product, which is well known. Injection speed controls filling state of resin, in order to make quality of finished product excellent, especially to improve accuracy of appearance and size.
Injection pressure refers to pressure exerted on plastic melt by top of plunger or screw. Its function is to overcome flow resistance of plastic melt flowing from barrel to mold cavity, giving melt a certain filling rate, compacting and feeding melt. During injection process, pressure at nozzle of injection machine is the highest to overcome flow resistance in the whole process of melt. After that, pressure gradually decreases along flow length to front wave front of melt. If inside of cavity is well vented, final pressure at the front of melt is atmospheric pressure. On injection machine, gauge pressure is commonly used to indicate injection pressure, which is generally between 40 and 130MPa.
In the field of plastic injection molding, there is always a strange problem. Every time a mold is installed on machine, it takes tens of minutes or even half a day to adjust. It is difficult to produce according to mature parameters of other machines. In the era of standardized manufacturing, this phenomenon is unimaginable, but it comes in detail.
In plastic injection molding, injection mold is not only a molding equipment for plastic melt, but also acts as a heat exchanger. Mold temperature adjustment system directly affects quality and production efficiency of product. Due to different performance and molding process requirements of various plastics, requirements for mold temperature are also different. In particular, some injection molded parts are made of materials such as polycarbonate (PC), polymethyl methacrylate (PMMA) and glass fiber (glass fiber), and surface quality of product is strict.
Figure 1 shows a precision double plastic helical gear in an automobile potentiometer. Large and small gears are cylindrical helical gears with relative phase requirements. Gear accuracy is required to be Q-ISO1328 9-10. Difficulty of molding mainly includes following 3 points:: ① Coaxiality of large and small helical gears is relatively high, but it is difficult to guarantee due to influence of demolding mechanism; ② Due to limitation of processing technology of helical gear cavity, relative phase angle of two helical gears is difficult to accurately control; ③Helix angle β of pinion helical gear is 23°, which makes it difficult to demold.
Gud Mould 