Author: mgg-Plastic bottle manufacturer
1. The shape and calculation of shrinkage such as heat shaped plastic formation shrinkage, which affects the formation shrinkage of thermoforming plastics is as follows. 1.1 During the heat-forming plastic molding of plastic varieties, from the volume change of the crystalline shape, strong inner stress, residual stress in the molding part, is frozen, molecular resistance, etc., compared to thermoset plastics, shrinkage large profitability The width and directionality of the range are obvious. The shrinkage rate after fire and the humidification treatment is generally larger than the thermoset plastic.
When the characteristics of the 1.2 statue are formed, the melting material and the surface of the cavity are immediately cooled immediately, and the low density solid housing is formed. Due to the difference in thermal conductivity of the plastic, the inner layer of the statue is slowly cooled to form a large high-density solid layer contracted. Therefore, the wall is thick, the cooling is slow, and the high density layer is large.
In addition, due to the configuration of the embedding and the landfill, the number directly affects the direction of the material flow, the size of the density distribution and the contraction resistance, etc., the characteristics of the statue are the size of the contraction, and the effect is very affected. 1.3 The form of the intake port, the size, distribution of these elements directly affect the flow direction, density distribution, pressure enhancement and molding time of the material. Direct access to material ports, the cross section of the mouth is large (especially the cross section of the cross section), but the directionality is very large, the width of the mouth is small and the length is short.
If close to the mouth of the material or in the direction of the material flow, the shrink will be large. 1.4 The temperature of the forming conditions is high, the melting material is cool, the density is high, the shrinkage is large, and the crystal crystallinity is high, the volume changes, and more shrinkage. Type temperature distribution and the homogeneity of cooling and density in the inside and outside of the statue are also related to the contraction and directionality of each part directly affect.
In addition, there is also an influence of affecting pressure and time shrinkage, the pressure is large, and the direction is also large. The pressure of the injection mold is high, the viscosity difference of the molten material is small, the cutting force between the layers is small, and the elasticity of the degree is large, and the contraction can also reduce the amount. Therefore, when molding, temperature adjustment, pressure, emitting forming speed, cooling time, and the like may appropriately change the condition of the statue shrinkage.
In the mold design, according to the contraction range of various plastics, the size of the plastics is experienced, and the shrinkage of the respective parts of the statue is experienced, and the dimensions of the plastics are experienced. In the case of a difficult picture and shrinkage, the mold is generally designed with the following method. 1 According to the small shrinkage ratio of the outer diameter of the statue, the inner diameter has a large shrinkage, and there is room for correction after the test type.
2 test type determine system form, size and molding conditions. 3 The size of the dimensional changes treated after treatment (after the measurement 24 hours after the measurement). 4 Correct the mold according to the actual contraction condition.
You can change the condition of the project. 2, fluidity 2.1 thermostat size of thermoplastics can generally analyze a series of indices such as size, melting index, flow length of the molten index, autumn leaf spiral, showing viscosity and flow ratio (flow length / plastic point wall thickness). . The molecular weight, the molecular weight distribution, the molecular structure is poor, the melting index is high, the length of the bastus, the viscosity is small, the fluidity is better than the fluidity, and the liquidity of the same product is suitable for injection molding must be confirmed.
According to the design of the mold, the flow of plastic can be divided into three. 1 Good fluidity PA, PE, PS, PP, CA, set (4) methyloni; 2 polyethylene resin (ABS, AS), PMN, force, polystyrene ether 3 fluidity Pc, Hard PVC, polystyl ether, polyester, polyester, fluorine plastic. 2.2 The fluidity of various plastics is also changed according to each forming element, and the main impact has the following points.
1 The temperature of the temperature is high, but depending on the different plastics, the PS (especially the impact resistance and MFR value), PP, PA, PMX, denathetic polyethylene (ABS, AS), PC, CA The fluidity of plastics is therefore greatly changing in temperature changes. PE, PM, the increase in temperature has little effect on its fluidity. Therefore, the former adjusts the temperature and controls the fluidity during molding.
2 When the pressure of the pressure is increased, the cutting of the melting material is very large, and the fluidity is also increased, in particular, PE, PM, which can be adjusted, and the pressure of the injection molding can be adjusted, and the fluidity is controlled. The form, size, configuration, cooling system of the 3-type structure, the design of the cooled system, the flow resistance of the melting material (eg, the surface cleaning degree, the material of the material, the shape, the shape of the cavity, the exhaust system) and other elements are directly The actual fluidity effect of the type of the molten material generally reduces the temperature of the melting material, increasing the fluidity of the fluid resistance drop. The mold design must select a reasonable structure according to the fluidity of the plastic.
When molding, the temperature can be controlled. Third, the crystalline thermoforming plastic does not cause crystalline phenomena, which can distinguish two sizes of crystalline plastic and non-crystalline (and no fixed type) plastics. The crystalline phenomenon means that the molecule is independently moved in the case where the plastic is fused, and the molecule is completely in a non-order state, and the molecule stops free movement, according to the slightly fixed position, there is a phenomenon of the molecule as a formal model.
As the appearance of these two plastics, the transparency of the thick-walled plastics of the plastic can be identified, and the general crystalline material is opaque, translucent (PM, etc.), and the amorphous material is transparent (PMX, etc.). However, the transparency of coalescence (4) methylideylene crystalline plastic is high, but ABS is not transparent as an amorphous fee. In the choice of mold design and injection molding machine, you must pay attention to the following requirements and precautions in crystal plastics.
1 The temperature of the material rises to the molded temperature, the amount of heat required, and the use of large use capacity. 2 The heat is high when cooling is high and cool. 3 Melting state and solid specific gravity, forming shrinkage, easy to generate shrinkage holes and air holes.
4 Cooling fast, low crystallinity, reduced, high transparency. The crystallinity is high, but the wall thickness is cool, high crystallinity, large shrinkage, good physical property. Therefore, the crystal material needs to control the temperature of the model as required.
5 is obvious to their respective anisotropy, and the internal stress is large. There is no undefiltrated molecule continuously after the release, the deformation, the curve is easily produced in the unbalanced state of energy. 6 The temperature range of the crystallization is narrow, and the mold can be injected on the basis of unmelted, and the door can be blocked.
4, thermosensitive plastic and water solution 4.1 heat sensitivity is thermist in a plastic, the heat is long, or when the dose is small, when the cutting effect is large, the material temperature is high, discolored, decomposed, decomposed, The tendency of the decomposition becomes high, and such a characteristic plastic is referred to as thermal plastic. For example, hard PVC, polyvinyl chloride, vinyl acetate, and copolymers, wave, polyvinyl chloride, and the like. The thermal plastic produces a by-product of monomers, gases, solids, especially for a decomposed gas, and has irritation, corrosion and toxicity in particular a decomposed gas.
Therefore, in the mold design, injection molding machine, it should be noted that the nut-type injection molding machine, the system is large, the mold and material must be chrome. In plastic (PC, etc.) of 4.2, even if a small amount of moisture is contained, it will be decomposed under high temperature and high pressure, which is referred to as hydrolysis. V. Vi-stress, the stress of the plastic of the melt 5.1 is very sensitive, and the internal stress is easily deteriorated, and the statue of the statue will occur immediately under the action of the external force. Phenomenon.
To this end, in addition to adding additives in the raw material, it is necessary to pay attention to dry, reasonably selectively select molding conditions, reducing internal stress and crack resistance. Also, the shape of a reasonable statue cannot be selected and the characteristics cannot be set. In the mold design, the slope of the trunk increases, selects a reasonable entry and the top out of the anterior mechanism, and adjust the temperature, temperature, adjustment pressure, and cooling time of the appropriate adjustment material when molded.
5.2 The melt of the polymer of the flow rate of the melt body must be fused, and after passing through the nozzle hole by the nozzle hole at a constant temperature, it is obviously transversely transversely in the surface of the melt, referred to as melt rupture. Therefore, select a polymer having a high speed of the melt stream or the like, eject, increase the upper road, increase the material incision, reduce the speed of the injection, and improve the temperature of the material. 6, thermal performance and cooling speed 6.1 Various plastics, heat, thermal conductivity, thermal deformation temperature and so on are different.
Thermal molding requires heat, and selects a large-scale injection molding machine. The cooling time of the thermal deformation temperature is short cooling time, quick release, but the cooling deformation is prevented. Since the cooling rate of the plastic with low thermal conductivity is slow (the cooling speed of the ionic polymer, the cooling speed is very slow), it must be sufficiently cooled.
Hot water molds are applied to plastics having high thermal conductivity. High heat, low thermal conductivity, low thermal deformation temperature, slow cooling rate, is unfavorable to high speed, and the appropriate injection molding machine and mold cooling must be strengthened. 6.2 Various plastics, depending on their characteristics and the shape of the statue, the appropriate cooling rate must be maintained.
Therefore, the mold must be provided with a molding requirement to maintain a certain temperature. Cooling according to the material at a high temperature, in order to prevent deformation of the diagram of the diagram, shorten the molding cycle, reduce the degree of crystallinity. When plastic is not sufficient to maintain a certain temperature, the mold is provided with a heating system, keeping the mold at a certain temperature, in order to control the cooling speed, ensure fluidity, improve the filling conditions, control the statue to cool, prevent thick walls No cooling inside and outside and increased crystallinity.
In the case where the fluidity, the molding area is large, the temperature is not uniform, and the status is formed, there is heating or cooling, or partially heated. To this end, the metal mold has a corresponding cooling and heating system. 7, hygroscopicity because there are various additives in the plastics, so because there is different kinds of moisture, plastics are generally moisturizing, absorbing moisture and water cannot attach moisture.
Foam, fluidity decline, appearance and mechanical properties are poor. Therefore, moisture absorbing plastics must be preheated with appropriate heating methods and specifications, and prevent moisture during use. Koopeng Plastic Focus on fourteen years, ordering hotline: 0752-3737979 mobile phone 13922888294 (WeChat).