1) The design is difficult because the plastic melt belongs to the viscoelastic body, the melt flow process with shear stress, shear rate changes, the
flow of macromolecules in the direction of flow direction. After the cavity is full of the melt is partially compressed and in the cooling and curing process
of plastic? Very complex, all parts of the cavity, the shrinkage of the direction are different and different types of grades of resin to close? Rates
are also very different. All of the above is given to the design of injection mold has brought a lot of difficulties. This difficulty is not other mechanical products.
2) the high cost of manufacturing molds are specific to the shape of plastic products, specifications design, so a variety of mold structure very
different, it is not possible to buy in the market, can not be mass-produced. It is only possible in a special factory for single-piece production, and mold
life is longer, the possibility of repeated manufacturing mold is very small, so the mold manufacturing costs are higher.
3) short production cycle The current product is extremely competitive, who products can be put on the market, it is possible to grab the first business opportunities, therefore, each manufacturer in a race against time, as soon as possible on the market and makes every effort, which requires Injection from
the design, manufacture, production should try to shorten the time required to shorten the production cycle as far as possible in order to grab the market,
grab the benefits.
4) high technological content of injection molding products, some of the shape is very complex, the size, precision requirements are high, and mostly the main components, which to the design and manufacture of injection mold has brought great difficulty, in order to be able to press Quality mold manufacturing time, must be invested elite, must focus on advanced machinery manufacturing technology.
(1) the productivity is extremely high, the production process is easy to realize the mechanization and the automation. General cold chamber Die casting machine every eight hours can be 600 to 700 times the die-casting, hot-pressing die-casting machine every eight hours to die-casting 3 000 to 7 000 times. And a die-casting mold cavity often more than one, so that the number of die-casting production will also exponentially increased.
(2) high dimensional accuracy of the casting, the size of stability, consistency, and less processing allowance and a good assembly. Die-casting
of the accuracy of up to IT11 ~ IT13 level, and sometimes up to IT9 level. Surface roughness values ??are generally Ra0.8 ~ 3.2, the lowest up to
Ra0.4. General die castings only a few parts of the size of machining, and some parts without even mechanical processing can be directly assembled
to use. This high utilization of materials, up to 60% to 80%, the rough utilization rate of 90%.
(3) casting dense organization, with high strength and hardness. As the metal liquid is solidified under pressure, and because of high-speed filling,
the cooling rate is extremely fast, so that the casting surface to generate a layer of cold hard layer (about 0.3 ~ 0.8mm), the layer of metal grain is
small, dense organization. Therefore,high strength and hardness of die-casting, solid wear-resistant. When the die wall thickness is appropriate and
uniform, its strength is higher.
(4) can be complex casting shape, clear-cut thin-walled deep cavity casting, because the liquid metal under high pressure to maintain high mobility.
The minimum wall thickness of zinc alloy die-casting parts can reach 0.3 mm, aluminum alloy is about 0.5 mm. The minimum casting diameter is
0.7 mm and the minimum pitch of the castable thread is 0.75 mm.
(5) Inlay casting method eliminates the assembly process, simplify the manufacturing process. Parts of other materials such as magnets, brass sleeves
and insulating materials can be embedded directly into specific parts of the die casting to meet specific requirements, eliminating the need for assembly processes and simplifying the manufacturing process.
(6) casting the existence of porosity, but generally still meet the requirements. As the filling of liquid metal is extremely fast, it is difficult to completely
remove the gas entrained in the cavity during filling, which results in the presence of pores and oxidized inclusions in the die castings, thereby reducing the quality of the die castings.Therefore, the general die casting can not be heat treatment, and should not work at high temperatures. Similarly, do not want to mechanical processing, so as not to expose the pores under the casting surface.
(7) Die-casting machine pressure chamber and die casting mold cavity material limits the type of die-casting alloys. High melting point ferrous metal Die casting because of its short life and difficult to die in the actual production. In the same alloy, there are grades restrictions, it is because of the characteristics of the Die-casting process, such as chilling, shrinkage stress, filling conditions, such as molding.
(8) The size of die-casting die-casting machine by clamping force and size constraints mold, so the production of large-scale die casting production is
limited. At present,large-scale die-casting machine has been developed, large parts die casting problem is gradually being resolved.
(9) Die-casting process is only suitable for mass production. As the high price of die-casting machine, die casting mold manufacturing costs are high,
long hours,maintenance costs are high, so the total cost of production, not small batch production.