Plastic mould basic knowledge & technology application

Hits: Date:2011-9-22 Font Size:14px 12px
Our daily production, life to use all kinds of tools and products, to the base of the machine tool, the shell, small to an embryo head screw, and various buttons of home appliances, without exception, and mold shell have a close relationship. The shape of the mould depends on the shape of these products, mould processing quality and the precision has also decided on the quality of the products. Because all the material of products, appearance, specifications and different purposes of mold, divided into molding, forging die, die casting die, stamping mould and so on the plastic mold, and the plastic mould.
In recent years, with the rapid development of plastic industry and general and engineering plastics in strength and precision, rise ceaselessly, the plastic products application scope is expanding continually, such as: household electric appliances, instruments and meters, construction equipment, automobile industry, daily hardware, etc, plastic products is the proportion of increases rapidly. A reasonable design of plastic parts can often replace DuoGe traditional metal parts. Industrial products and daily product plastic trend of rising.
2, die, defined: in industrial production, with all sorts of press and put pressure on board in the specialized tools, through the pressure to put metallic and non-metallic materials needed for pointing out the shape of the parts or products, the special tools collectively referred to as mold.
Three, the injection molding process description: mold is a kind of production plastic products tools. It consists of several groups of parts, the combination is composed of the division were forming cavity. When we do the injection mould clamping, in the molding machine, molten plastic be injection moulding mold cavity, and in the chamber, and then the design lower die by ejector apart, the system will products from the mold cavity top left, and finally closed again on the next injection mould, the injection molding process is the cycle.
4, mould can be divided into the general classification: plastic mould and the plastic mould:
1) the plastic mould: molding, forging die, punching die, die casting die, etc.
A. molding-faucet, pig iron platform
B. forging die-car body
C. stamping dies-computer panel
D. die-casting die-super alloys, cylinder body
2) plastic mold production technology and production products according to the different and divided into:
A. the injection molding mould-TV shell, keyboard buttons (the most common application)
B. blowing die-water bottles
C. compression molding mould-bakelite switch, scientific profits in dish
D. transfer molding mould-IC products
E. extrusion die-glue tube, plastic bags
F. hot forming dies-transparent packaging shell moulding
G. rotation of forming dies-soft plastic dolls
The injection molding is the most widely used in plastic processing methods. This method is applicable to all thermoplastics and thermosetting plastic parts, system of plastic products the great number of other modeling method is deficits, as the injection molding process of main tool of injection mold, one of the quality precision, manufacturing cycle and injection molding process of production efficiency level, directly influence the quality of the products, production, costs, and the renewal of the products, at the same time also decide the enterprise in the market competition ability of response and speed.
Injection mold is by some steel plate with various parts, basic is divided into:
A forming device (concave die, the punch)
B positioning device (guide pin, guide set)
C fixed device (paper board, code mold pit)
D cooling system (the hole)
E thermostatic system (heating tube, hair hotline)
F runner system (clamorous tsui, flow, port DaoCao hole hole)
G ejector systems (thimble, top stick)
5, according to the different type gating system of the system can be divided into three categories: die
1) gate mould: port and in gate parting line, and products in the core, and design the parting with simple, easy processing, with low cost, so the DuoRen the gate system operation.
2) fine shuikou mould: port and gate not parting line, general directly in the products, so want to design a group more nozzle parting line, the design is relatively complex, processing is more difficult, in general to depending on the product requirements and use a fine nozzle system.
3) mould of hot flow path: the mould structure and fine nozzle is approximately the same, its biggest difference is the port in a DuoGe or constant temperature of heat flow and heat DaoBan piping mouth, no cold material, stripping flow channel and runner in the product, so the direct flow don't need, this system also called stripping without nozzle system, may save the raw material, suitable for raw materials, products more expensive higher requirements, design and processing difficulties, mould cost is higher.
Hot runner system, also called hot runnet system, mainly by hot runner set, hot water, electricity DaoBan temperature control box to form. Our common hot runner system has a single point hot runner and more hot runner two forms. Single point hot runner is to use a single hot runner set the molten plastic mold directly into a single cavity, and is a single runner of plastic mould; More hot runner is through the hot water DaoBan the molten material to each branch hot runner set to again into the cavity, it is suitable for single lumen more into the material or more mold cavity
The advantage of hot runner system
1) no shuikou material, do not need to make the whole processing after forming process is fully automated and save the working time, improve the work efficiency.
2) pressure wastage. Hot runner temperature and injection molding machine shoot mouth temperature equal, to avoid the raw materials in the runner of condensate in surface, injection pressure wastage.
3) shuikou material repeated use can make plastic performance degradation, while the use of hot runner system has no material, can reduce the nozzle of raw materials, so as to reduce the cost of product loss. In the cavity uniform temperature and pressure, plastic parts stress small, density, in smaller injection pressure, a relatively short period of time, the injection molding than the average injection molding systems better products. For transparent pieces, thin pieces, large plastic parts or high demand plastic parts can demonstrate its advantage, and with small models produce larger products.
4) hot spray nozzle to the standardization and serialization design, with various options for nozzle head, has good. The unique design of electric heating circle, processing to the heating temperature even, long service life. Hot runner system equipped with heat, temperature controller, etc DaoBan, the design is exquisite, are varied, easy to use, the quality is stable and reliable.
Hot runner system application deficiency
1) the whole mold closing high increase, because the hot water DaoBan etc, mould overall height increases.
2) thermal radiation is difficult to control, hot runner's biggest problem is the heat loss runner, is a need to address the major issue.
3) exist thermal expansion, heat bilges cold shrink is we design considerations.
4) mould manufacturing costs rise, hot runnet system standard accessories prices higher, affect hot runner mould popularization.