What are the structural components of plastic molds?

The plastic mold consists of a moving mold and a fixed mold. The moving die is installed on the moving die plate of the injection molding machine, and the fixed die is installed on the fixed die plate of the injection molding machine. During injection molding, the movable mold and the fixed mold are closed to form a gating system and a cavity. When the mold is opened, the movable mold and the fixed mold are separated, and the plastic product is taken out.

Although the structure of plastic mold may vary with the variety and performance of plastic, the shape and structure of plastic products and the types of injection molding machines, the basic structure is the same.

First, the plastic mold structure is divided by function.

Mainly consists of: gating system, temperature control system, molding parts system, exhaust system, guiding system, ejection system, etc. Among them, the gating system and molding parts are the parts that are in direct contact with plastics and change with plastics and products, and they are the most complicated and changeable parts in plastic molds, which require the highest machining smoothness and accuracy. ?

1. Gating system: refers to the part of the runner before the plastic enters the cavity from the nozzle, including the main runner, the cold material hole, the shunt runner and the gate.

2. Molded part system: refers to the combination of various parts that make up the shape of the product, including moving die, fixed die, cavity (female die), core (male die), forming rod, etc. The core forms the inner surface of the product, and the cavity (female die) forms the outer surface shape of the product. After the mold is closed, the core and the cavity form the cavity of the mold. According to the requirements of technology and manufacturing, sometimes the core and die are composed of several pieces, and sometimes they are made into a whole. The inserts are only used in parts that are easy to be damaged and difficult to process. ?

3. Temperature control system: In order to meet the requirements of injection molding process for mold temperature, a temperature control system is needed to adjust the mold temperature. For the injection mold of thermoplastic, the cooling system is mainly used to cool the mold (or heat the mold). The common method of cooling the mold is to open a cooling water channel in the mold, and take away the heat of the mold with circulating cooling water; Cooling water can be used to heat the mold by hot water or hot oil, and electric heating elements can be installed inside and around the mold. ?

4. Exhaust system: it is designed to exhaust the air in the cavity and the gas produced by plastic melting during injection molding out of the mold. When the exhaust is not smooth, defects such as gas marks (gas marks) and burning will be formed on the surface of the product; The exhaust system of plastic mold usually opens a slot-shaped exhaust port on the mold to exhaust the air in the prototype cavity and the gas brought by the melt.

When the melt is injected into the mold cavity, the air originally stored in the mold cavity and the gas brought by the melt must be discharged from the mold through the exhaust port at the end of the material flow, otherwise, the product will have air holes, poor connection, insufficient mold filling, and even the accumulated air will burn the product due to the high temperature generated by compression. Generally speaking, the vent hole can be located at the end of the melt flow in the mold cavity or on the parting surface of the plastic mold.

The latter is to open a shallow groove with a depth of 0.03-0.2 mm and a width of 1.5-6 mm on one side of the female die. During the injection process, a large amount of molten material will not seep out of the exhaust hole, because the molten material will cool and solidify there and block the passage. Don't point the exhaust port at the operator to avoid accidental discharge of molten material and personal injury. In addition, the gap between the ejector pin and the top hole, the gap between the ejector block and the stripper plate and the core can also be used for exhaust.

5. Guide system: It is set to ensure the accurate alignment of the movable die and the fixed die when clamping, and guide parts must be set in the die. In the injection mold, four groups of guide posts and guide sleeves are usually used to form the guide part, and sometimes it is necessary to set mutually consistent inner and outer conical surfaces on the moving mold and the fixed mold to assist in positioning.

6. Ejection system: generally composed of thimble, front and rear thimble plates, thimble guide rod, thimble return spring and thimble plate locking screw. When the product is cooled in the mold, the front and rear molds of the mold are separated and opened, and the plastic product and its condensate in the runner are pushed out or pulled out of the mold cavity and runner by the ejector pin of the injection molding machine, so as to carry out the next injection cycle. ?

Second, according to the structure, the plastic mold is generally composed of a mold base, a mold core, auxiliary parts, an auxiliary system, an auxiliary setting, a dead angle processing mechanism and the like.

1. Mold base: Generally, it does not need to be designed, and it can be ordered directly from the standard mold base manufacturer, which greatly saves the time needed to design the mold, so it is called the standard mold base for plastic molds. It constitutes the most basic frame part of plastic mould. ?

2. Mold core: The mold core is the core part of the plastic mold and the most important part of the mold. The molding part of plastic products is in the mold core, and most of the processing time is spent in the mold core. But compared with some relatively simple molds, it has no core part, and the product is molded directly on the template. Most of the early plastic molds were so backward. ?

3. Auxiliary parts: The common auxiliary parts of plastic mold include locating ring, sprue sleeve, thimble, grab pin, support column, guide sleeve of ejection guide post, garbage nail, etc. Some are standard parts, which can be ordered directly together when ordering the mold base, and some need to be designed by themselves. ?

4. Auxiliary system: The plastic mold has four auxiliary systems: pouring system, ejection system, cooling system and exhaust system. Sometimes, because the plastic materials used need high temperature heating, some molds still have heating systems.

5. Auxiliary setting: The plastic mold is provided with an auxiliary ring hole and a KO hole (ejector pin hole). ?

6. Dead corner processing structure: When the plastic product has dead corners, the mold will also have one or more dead corner processing structures. Such as slide block, inclined top, hydraulic cylinder, etc. In most books in China, this mechanism for dealing with dead ends is called "core-pulling mechanism"?

In fact, plastic molds are not difficult. No matter how the plastic products change, the mold structure for molding this plastic product is nothing more than the above aspects. The difference between molds is whether the mold is big or small.

The position or mode of each auxiliary part, auxiliary setting and auxiliary system is different. The method, structure and size of dealing with dead corners have only changed. Of course, design experience is particularly important to make the designed mold simple in processing, convenient in assembly, long in service life, moderate in price and good in molded products. Good experience can deal with problems in design and processing, and you are more sure of design changes. ?

Third, the structure of the injection machine:

A general injection machine mainly includes injection device, clamping device, hydraulic transmission system and electrical control system. The main function of the injection device is to plasticize the plastic uniformly and inject a certain amount of molten material into the mold cavity with sufficient pressure and speed. The injection device is mainly composed of plasticizing parts (screw, barrel and nozzle), hopper, transmission device, metering device, injection and moving oil cylinder, etc.

Clamping device: its function is to realize the opening and closing of the mold, ensure the reliable closing of the molding mold during injection molding, and eject the product. The clamping device is mainly composed of front and rear fixed templates, moving templates, pull rods connecting the front and rear templates, clamping cylinders, linkage mechanisms, mold adjusting devices and product ejection devices.

Hydraulic system and electric control system: its function is to ensure that the injection machine works accurately and effectively according to the predetermined requirements (pressure, speed, temperature and time) and the action sequence of the process. The hydraulic system of injection machine is mainly composed of various hydraulic components and circuits and other auxiliary equipment, and the electrical control system is mainly composed of various electrical appliances and instruments. The hydraulic system and the electrical system are organically organized to provide power and control for the injection machine.