The composition of plastic mold structure

Updated: 2016-10-26

Mold injection molding is the mass production of some of the complex shape of parts used in a processing method.

Specific principles are: the melting of plastic raw materials by the injection molding machine screw into the high-pressure plastic injection mold cavity, after cooling and curing, the plastic molding products.

The plastic mold consists of movable mold and fixed mold. The movable mold is installed on the moving mold of the injection molding machine. The fixed mold is fixed on the fixed mold of the injection molding machine. In the injection molding, the movable mold and the fixed mold are closed to form the pouring system and the cavity. When the mold is opened, the moving mold and the fixed mold are separated to remove the plastic products.

Although the structure of plastic mold due to the variety and performance of plastic, plastic products, the shape and structure and the type of injection machine may vary, but the basic structure is the same.

First, the plastic mold structure by function, mainly by: pouring system, temperature control system, forming parts system, exhaust system, guidance system, the top of the system components.

One of the casting system and molding parts are in direct contact with the plastic part, and with the plastic and products and changes in the mold is the most complex, the largest change, requiring processing of the highest finish and accuracy of the part.

1. Gating system: refers to the plastic from the nozzle into the cavity before the flow channel parts, including the main channel, cold material hole, diversion channel and gate.

2. Forming parts system: refers to the composition of various parts of the shape of the product portfolio, including dynamic mode, fixed mode and cavity (die), core (punch), forming rods and other components. The core forms the inner surface of the article, and the cavity (female mold) forms the outer surface shape of the article. After the mold core and cavity will constitute a mold cavity. According to the process and manufacturing requirements, and sometimes the core and die by a combination of several blocks, sometimes made as a whole, only in the vulnerable, difficult to use parts of the inserts.

3. Temperature control system: In order to meet the injection process on the mold temperature requirements, the need for a temperature control system to regulate the temperature of the mold. For injection molding of thermoplastics, the cooling system is designed to cool the mold (and the mold can be heated). Die cooling is commonly used in the mold set up cooling water channel, the use of circulating flow of cooling water away mold heat; mold heating can be used in addition to cooling water through hot water or hot oil, but also within and around the mold installation Electric heating elements.

4. Exhaust system: It is to set the air in the cavity and the gas produced by the melting of the plastic to the outside of the mold during the injection molding process. When the exhaust is not smooth, the surface of the product will form gas marks, Poor; the plastic mold of the exhaust system is usually opened in the mold of a trough-shaped outlet, used to discharge the original cavity of the air and melt into the gas.

Melt into the cavity, the original stored in the cavity of the air and the melt into the gas must be at the end of the material flow through the exhaust port to the mold, otherwise it will make products with air holes, Filling mold dissatisfaction, and even the accumulation of air due to compression generated by high temperature products will burn. Under normal circumstances, the vent can be located in the cavity at the end of the melt flow can also be located in the mold parting surface.

The latter is in the concave side of the mold opening 0.03-0.2mm wide and 1.5-6mm shallow groove. In the injection, the vent does not have a lot of melt leakage, because the melt will be solidified in the cooling channel blocked. Do not open the exhaust port facing the operator, to prevent melt accidentally spray wounding. In addition, the ejection rod can also be used with the top hole with the gap, the top block and stripping plate with the core with the gap between the exhaust.

5. Guide system: in order to ensure that the dynamic mode and fixed mold in the mold can be accurately set up in the mold, the mold must be set guide parts. In the injection mold is usually used in four sets of guide pillars and guide sleeve to form guide parts, and sometimes need to move in the fixed mold and were set on each other to match the inner and outer cone to assist positioning.

6. Ejection system: generally include: thimble, front and rear thimble plate, thimble guide rod, thimble return spring, thimble plate locking screw composed of several parts. When the product is molded and cooled in the mold, the molds are separated before and after the mold is opened and the plastic products and their condensate in the flow channel are pushed out or pulled out of the mold cavity and the flow passage position by the ejector-ejector push rod of the injection molding machine , In order to carry out the next injection molding work cycle.

Second, the plastic mold according to the structure generally by the mold, die, auxiliary parts, auxiliary systems, auxiliary settings, dead bodies and other parts of the composition.

1, mold frame: generally do not need our design, can be ordered directly from the standard mold manufacturer, which greatly saves the time required to design the mold, so called plastic mold standard mold. It constitutes the most basic part of the plastic mold frame.

2, mold kernel: mold part is the core part of the plastic mold, which is the most important part of the mold. The molded part of the plastic product is inside the mold core, and most of the processing time is also spent on the mold. However, some relatively simple mold, it is not part of the mold, the product directly above the form in the template. Most of the early plastic mold so, relatively backward.

3, auxiliary parts: plastic mold commonly used auxiliary parts are positioning ring, nozzle bushing, thimble, grasping pin, support column, the top plate guide pin guide sets, garbage nails, etc., they are part of standard parts, can Order directly with the order form when the mold, there are some need to design their own.

4, auxiliary system: plastic mold auxiliary system has the following four: pouring system, ejector system, cooling system and exhaust system. Sometimes, because the use of plastic materials to be heated at a high temperature, so some mold will also exist in a heating system.

5, with help settings: plastic mold set with auxiliary ring hole, KO hole (top hole hole) and so on.

6, dead-end treatment structure: When the plastic products are dead, the mold will have one or more structures dealing with dead ends. Such as the slider, inclined roof, hydraulic cylinder and so on. In most domestic book describes the treatment of dead bodies known as the "core institutions."

In fact, the plastic mold is not difficult, no matter how the changes in plastic products, plastic products for the formation of this mold, its structure is nothing more than the above-mentioned aspects. The difference between the mold is that the mold is large or small? Each auxiliary parts, auxiliary settings, auxiliary system location or manner is not the same. Treatment dead ends of the method, structure, size, etc. have changed only. Of course, to make the design of the mold processing is simple, easy assembly, long life, affordable, forming a good product, design experience is particularly important. Good experience, you can handle the design, processing problems which occur, the treatment is also more sure to change.

Third, the structure of the injection machine: a general-purpose injection machine, including injection devices, clamping device, hydraulic drive system and electrical control system.

The main function of the injection device is to plasticize the plastic evenly and to a sufficient amount of pressure and speed to melt into the mold cavity. The injection device is mainly composed of plastic parts (screw, barrel and nozzle), hopper, transmission device, measuring device, injection and moving cylinder and so on.

Clamping device: The role of the mold is to achieve the opening and closing, to ensure that the injection mold to ensure a reliable tight, and prolapse products, clamping device mainly by the front and rear fixed template, mobile template, before and after the template used to connect the rod, , Connecting rod mechanism, modulating device and product ejecting device.

Hydraulic system and electrical control system: its role is to ensure that the injection machine according to the process requirements (pressure, speed, temperature, time) and the sequence of accurate and effective work. Injection machine hydraulic system consists of a variety of hydraulic components and circuits and other ancillary equipment components, electrical control system is mainly composed of a variety of electrical and instrumentation, hydraulic and electrical systems organically organized together to provide power and implementation of the injection machine control.