The whole process of UG plastic mold design, it is recommended to collect
The various tools and products used in our daily production and life, ranging from the base of the machine tool, the body shell, to a screw, button and the shell of various household appliances, are all closely related to the mold. The shape of the mold determines the appearance of these products, and the processing quality and precision of the mold also determines the quality of these products.
In recent years, with the rapid development of the plastics industry and the continuous improvement of general engineering plastics in terms of strength and precision, the application range of plastic products is also expanding, such as: household appliances, instrumentation, construction equipment, automotive industry, daily use In many fields such as hardware, the proportion of plastic products is increasing rapidly.
A reasonably designed plastic part can often replace multiple traditional metal parts. The trend of plasticization of industrial products and daily-use products is on the rise. Let us understand some basic common sense about mold design!
1. General definition of mold
In industrial production, various presses and special tools installed on the press are used to make metal or non-metallic materials into parts or products of the required shape through pressure. Such special tools are collectively called molds.
2. Description of injection molding process
Injection mold is a tool for producing plastic products. It is composed of several groups of parts, and there is a molding cavity in this combination. During injection molding, the mold is clamped on the injection molding machine, the molten plastic is injected into the molding cavity, and is cooled and shaped in the cavity, then the movable and fixed molds are separated, and the product is ejected from the cavity and out of the mold through the ejection system. Finally, the mold It is closed again for the next injection, and the entire injection process is carried out in cycles.
3. General classification of molds
Can be divided into plastic molds and non-plastic molds.
(1) Non-plastic molds include: casting molds, forging molds, stamping molds, die-casting molds, etc.
(2) Plastic molds are divided into different production processes and products:
A. Injection molding mold-TV shell, keyboard buttons (the most common application);
B. Blow mold-beverage bottle;
C. Compression molding mold-Bakelite switch, scientific porcelain dishes;
D. Transfer molding mold-integrated circuit products;
E. Extrusion mould-glue pipe, plastic bag;
F. Thermoforming mold-transparent molded packaging shell;
G. Rotational mould-soft doll toy.
(3) The injection mold is composed of several steel plates with various parts, and is basically divided into:
A. Forming device (concave mold, convex mold);
B. Positioning device (guide post, guide sleeve);
C. Fixing device (I-shaped board, code mold pit);
D. Cooling system (water hole);
E. Constant temperature system (heating tube, heating wire);
F. Runner system (pump hole, runner groove, runner hole);
G. Ejection system (thimble, ejector, etc.).
5. According to the different pouring system, the mold can be divided into three types
(1) Large nozzle mold: The runner and gate are on the parting line, and they are demolded together with the product when the mold is opened. The design is the simplest, easy to process, and low cost, so more people use the large nozzle system to work.
(2) Fine nozzle mold: runners and gates are not on the parting line, generally directly on the product, so it is necessary to design an additional set of nozzle parting lines, the design is more complicated and the processing is more difficult, and generally depends on the product requirements. Fine nozzle system.
(3) Hot runner mold: The structure of this type of mold is roughly the same as that of the nozzle. The biggest difference is that the runner is in one or more hot runner plates and hot nozzles with a constant temperature. There is no cold material demoulding, runner and pouring. The port is directly on the product, so the runner does not need to be demolded. This system is also called a nozzleless system, which can save raw materials and is suitable for situations where raw materials are more expensive and products require higher requirements. Design and processing are difficult, and mold costs are higher.
6. Hot runner system
Also known as hot runner system, it is mainly composed of hot runner sleeve, hot runner plate, and temperature control electric box. Our common hot runner system has two forms: single-point hot gate and multi-point hot gate.
The single-point hot gate uses a single hot gate sleeve to directly inject molten plastic into the cavity. It is suitable for plastic molds with a single cavity and single gate. Multi-point hot gate is to branch the molten material into each sub-heat gate sleeve through the hot runner plate, and then enter the cavity. It is suitable for single cavity multi-point feeding or multi-cavity molds.
(1) Advantages of hot runner system
1) No nozzle material, no need for post-processing, so that the entire molding process is fully automated, saving working time and improving work efficiency.
2) The pressure loss is small. The temperature of the hot runner is equal to the nozzle temperature of the injection molding machine, which avoids the surface condensation of the raw materials in the runner, and the injection pressure loss is small.
3) The repeated use of the nozzle material will degrade the performance of the plastic, and the use of the hot runner system without nozzle material can reduce the loss of raw materials, thereby reducing product costs. The temperature and pressure in the cavity are uniform, the stress of the plastic part is small, and the density is uniform. Under a small injection pressure and a short molding time, better products can be injected than ordinary injection molding systems. For transparent parts, thin parts, large plastic parts or high-demand plastic parts, it can show its advantages, and can produce larger products with smaller models.
4) The hot nozzle adopts standardized and serialized design, equipped with various nozzle heads to choose from, and has good interchangeability. The uniquely designed and processed electric heating ring can achieve uniform heating temperature and long service life. The hot runner system is equipped with hot runner plates, thermostats, etc., with exquisite design, diverse types, convenient use, and stable and reliable quality.
(2) Shortcomings of hot runner system application
1) The closing height of the overall mold is increased, and the overall height of the mold has increased due to the addition of hot runner plates.
2) The heat radiation is difficult to control. The biggest problem of the hot runner is the heat loss of the runner, which is a major issue that needs to be solved.
3) There is thermal expansion, thermal expansion and contraction are issues that we must consider when designing.
4) The cost of mold manufacturing increases, and the price of standard parts of the hot runner system is higher, which affects the popularity of hot runner molds.