The plastic mold is composed of a moving mold and a fixed mold. The moving mold is installed on the moving template of the injection molding machine, and the fixed mold is installed on the fixed template of the injection molding machine. During injection molding, the moving mold and the fixed mold are closed to form the gating system and cavity. When opening the mold, the moving mold and the fixed mold are separated to take out the plastic products. Although the structure of plastic mold may vary due to the variety and performance of plastic, the shape and structure of plastic products and the type of injection machine, the basic structure is the same.
1、 Plastic mold structure is divided by function
It is mainly composed of gating system, temperature regulating system, forming part system, exhaust system, guiding system, ejection system, etc. Among them, the pouring system and molding parts are the parts that directly contact the plastic and change with the plastic and products. They are the most complex and changing parts in the plastic mold, requiring the highest machining finish and precision.
1. Gating system:
It refers to the part of the flow channel before the plastic enters the mold cavity from the nozzle, including the main flow channel, cold material cavity, shunt channel and gate, etc.
2. Formed part system:
It refers to the combination of various parts that constitute the shape of the product, including moving mold, fixed mold, cavity (concave mold), core (punch), forming rod, etc. The core forms the inner surface of the product, and the cavity (die) forms the outer surface shape of the product. After closing the mold, the core and cavity form the mold cavity. According to the process and manufacturing requirements, sometimes the core and die are combined by several blocks, sometimes they are made into a whole, and inserts are only used in the parts that are easy to be damaged and difficult to process.
3. Temperature regulation system:
In order to meet the requirements of injection process for mold temperature, a temperature regulating system is needed to regulate the mold temperature. For injection molds for thermoplastics, the cooling system is mainly designed to cool the mold (the mold can also be heated). The common method of mold cooling is to set up cooling water channels in the mold, and use the circulating cooling water to take away the heat of the mold; In addition to using cooling water to supply hot water or hot oil, electric heating elements can also be installed inside and around the mold.
4. Exhaust system:
It is set up to exclude the air in the medium-sized cavity and the gas generated by the melting of plastic from the mold during the injection molding process. When the exhaust is not smooth, the product surface will form gas marks (gas lines), charring and other defects; The exhaust system of plastic mold is usually a groove shaped air outlet opened in the mold to discharge the air in the original mold cavity and the gas brought in by molten material.
When the melt is injected into the mold cavity, the air originally stored in the mold cavity and the gas brought in by the melt must be discharged outside the mold through the exhaust port at the end of the material flow, otherwise the product will have pores, poor connection, insufficient mold filling, and even the accumulated air will burn the product due to high temperature caused by compression. Generally, the exhaust hole can be set at the end of molten material 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 0.03-0.2mm and a width of 1.5-6mm on one side of the die. During the injection, there will not be a lot of molten material exuding from the exhaust hole, because the molten material will cool and solidify there and block the channel. The opening position of the exhaust port must not face the operator to prevent accidental ejection of molten material from hurting people. In addition, the fit gap between the ejector rod and the ejector hole, and the fit gap between the ejector block and the stripping template and the core can also be used to exhaust.
5. Guidance system:
It is set up to ensure that the moving mold and the fixed mold can be accurately aligned when closing the mold. Guide parts must be set in the mold. In the injection mold, four groups of guide posts and guide sleeves are usually used to form the guide parts. 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, it consists of thimble, front and rear thimble plates, thimble guide rods, thimble return springs, thimble plate locking screws, etc. When the product is molded and cooled in the mold, the front and rear molds of the mold are separated and opened, and the plastic products and their condensates in the flow channel are pushed out or pulled out of the mold cavity and the flow channel position by the ejector pin, which is the ejector mechanism, under the push of the ejector rod of the injection molding machine, so as to carry out the next injection molding work cycle.
2、 According to the structure, plastic molds are generally composed of mold base, mold core, auxiliary parts, auxiliary system, auxiliary setting, dead corner processing mechanism, etc.
1. Mold base:
Generally, we don’t need to design it. We can order it 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 of plastic mold. It constitutes the most basic framework of plastic mold.
2. Mold kernel:
Mold kernel part is the core part of plastic mold, which is the most important part of the mold. The forming part of plastic products is in the mold core, and most of the processing time is also spent on the mold core. However, compared with some relatively simple molds, there is no mold kernel part, and the products are directly formed on the template. Most of the early plastic molds were so backward.
3. Auxiliary parts:
Common auxiliary parts of plastic molds include locating ring, nozzle bushing, thimble, grab pin, support column, ejector plate guide column guide sleeve, garbage nail, etc. some of them are standard parts, which can be ordered directly when ordering mold base, and some of them need to be designed by themselves.
4. Auxiliary system:
There are four auxiliary systems of plastic mold: pouring system, ejection system, cooling system and exhaust system. Sometimes, because the plastic materials used need to be heated at a high temperature, some molds will also have a heating system.
5. Auxiliary settings:
The auxiliary of the plastic mold is set with lifting ring hole, Ko hole (top rod hole), etc.
6. Dead corner processing structure:
When plastic products have dead corners, the mold will also have one or more structures to deal with dead corners. Such as sliding block, inclined roof, oil cylinder, etc. This kind of mechanism dealing with dead ends is described in most domestic books as “pistil pulling mechanism”.
In fact, the plastic mold is not difficult. No matter how the plastic product changes, for the mold to form this plastic product, its structure is nothing more than the above aspects. The difference between molds is whether the mold is large or small? The location or mode of each auxiliary part, auxiliary setting and auxiliary system is different. The method, structure and size of dealing with dead corners have 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 forming products. With good experience, you can deal with problems in design and processing, and you are more confident in dealing with design changes.
3、 Structural composition of injection machine:
A general-purpose injection machine mainly includes injection device, clamping device, hydraulic transmission system and electrical control system. The main function of the injection device is to evenly plasticize the plastic 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 (composed of screw, barrel and nozzle), hopper, transmission device, metering device, injection and mobile oil cylinder, etc.
Mold closing device: its function is to realize the opening and closing of the mold, ensure the reliable closing of the molding mold during injection, and remove the products. The mold closing device is mainly composed of front and rear fixed templates, moving templates, pull rods for connecting the front and rear templates, mold closing cylinders, connecting rod mechanisms, mold adjusting devices, and product ejection devices.
Hydraulic system and electrical control system: their function is to ensure that the injection machine works accurately and effectively according to the predetermined requirements (pressure, speed, temperature, time) and action sequence of the process. The hydraulic system of the injection machine is mainly composed of various hydraulic components, circuits and other auxiliary equipment, while 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.
About Huizhou Dj Molding Co., Ltd
Dj Mold is a China mold maker of plastic molds- injection mold, die casting moulds, plastic blow molding, rotational molding, medical plastic injection molding, two shot plastic injection molding, insert molding, overmolding, metal injection molding, micro injection molding, powder injection molding, ceramic injection molding, liquid injection molding, husky injection molding, household mold, casting mold, die mold tool, custom molds, china moulds, rapid prototyping tooling, plastic prototyping tooling, punch press tooling, die and tooling for mobile/ cell phone parts, automotive parts, vacuum cleaners, rechargeable tools, telephones, copiers, computers, multimedia speakers, and many other electronic products and household appliances. And also a plastic product manufacturer, mold manufacturer China– plastic parts, plastic water tank, plastic balls, plastic containers, plastic buckle, plastic anchor, plastic hanger, plastic spoon, plastic pipe fitting, plastic tumble, plastic tableware, plastic cups, plastic bottles, plastic tray, plastic cosmetic container, plastic case, plastic food container, plastic chairs, plastic caps, plastic cap closure, plastic tubes, plastic water pipes, plastic knobs, plastic tubing, plastic utility boxes, plastic racks and so on.
Person: James Yuan
Company: Huizhou Dj Molding Company Limited
Add: LongGang Village,LongXi Town,BoLuo County,HuiZhou City,GuangDong Province, China
Email: [email protected]