Low pressure injection foaming molding machine
DATE：2022/4/20 8:55:50 / READ： / SOURCE：This station
Low pressure injection foaming molding machine
The molding process and equipment structure of the low-pressure injection foaming machine are basically the same as those mentioned above. It needs to go through the processes of plasticization measurement, mold closing, injection foaming, cooling and shaping, mold opening and product stripping. The waiting point is that during injection, the amount of plastic melt (including foaming agent) injected into the mold cavity is only 60% ~ 80% of the volume of the mold cavity, and then the mold cavity is filled by melt foaming expansion. The mold cavity is always in a low pressure state, so it is called low-pressure method. The injection part shown in Figure 6-8 is the low-pressure method device of Beloit company. The locking force of the mold of low-pressure method only needs to overcome the expansion force of melt foaming in the mold cavity, generally 1.4 ~ 4MPa, When designing the mold locking mechanism, the mold cavity pressure can be taken as 5.5mpa for safety. Hollow board production lineAs early as the late 1950s and early 1960s, foaming injection molding with thermoplastic plastics such as polystyrene began to appear. The relatively famous low-pressure injection foaming molding machine of United carbide company (UCC) is shown in Figure 6-9. This model has been industrialized since 1966. Later, UCC developed physical foaming agent (n), as shown in Figure 6-9. The raw material department makes granular materials according to the formula, and the hopper is added into the plasticizing material barrel for heating and plasticizing. The foaming agent N2 is intermittently and continuously injected into the plasticized plastic melt by the high-pressure quantitative conveying device. After the injected low-pressure natural hair image is evenly mixed, it is pressed into the storage barrel for storage. One or more storage materials can be set. When the busy storage amount reaches the injection amount, the storage material is simply opened to the valve of the mold, Driven by the transmission system, the plunger of the busy material supplier quickly presses the stored melt into the mold, and then our door is closed. The plastic melt containing NZ foams and expands in the mold cavity, fills the mold cavity, and then goes through cost-effective setting. Finally, the mold is opened and the product is removed. The mold light pressure in the injection foaming expansion process in the mold cavity is 1.4 ~ 2.4Mpa. Sometimes, in order to improve the injection speed, the multi nozzle structure is adopted, and the mold cavity pressure may be as high as 7 ~ 10MPa. The mold locking mechanism of this machine is generally designed according to the mold cavity pressure of 5.5mp. The screw in the plasticizing barrel only rotates and cannot move along the axial direction. The foaming agent is injected into the plasticized melt at the front end of the plasticizing barrel, and N2 is mixed evenly in the melt through the special mixing element on the screw. In order to prevent the plastic melt from foaming in advance in the barrel, the back pressure to be maintained in the storage barrel and plasticizing barrel is 15 ~ 25MPa and 2 ~ 4mp respectively: the chemical capacity is 2000kg / h, the injection speed is 1 ~ 5kg / s, the one-time injection amount is 55-68kg, the mold locking force is 0.49 ~ 39mn, the template area is 7 ~ 10m2, the molding cycle is 2 ~ 10min, the cooling time is 2 ~ 8min, the product density is 250 ~ 950kg / ㎡, and the minimum thickness of the product is
4.5~6.4mm。 When the thickness is 6~6.4mm, when the thickness of the cortex is 0.5~0.8mm, the strength is the best. The mold temperature is generally 20~40 degrees. Polyolefin, PS and PC can be processed by UCC.
ISG thermoplastic injection foaming molding machine proposed by kraccss maflei of Germany is widely used in Europe. The structural principle of its injection part is similar to that shown in Figure 6-8. The injection power comes from the energy storage system of NZ. The injection pressure is higher than that of UCC method, which can achieve the purpose of high-speed injection of 268. The injection volume is large, and the height of the injection nozzle can be adjusted by a special height adjustment device to meet the needs of different mold locking devices. The plasticizing screw is driven by the motor through the gear reducer and can be adjusted to 8 speeds. The material added by the hopper can be powder or granular. In order to prevent the plastic melt in the plasticizer and storage Jane from foaming in advance in the cylinder, the back pressure and temperature in the cylinder and storage cylinder must be strictly controlled. Both plasticizer and storage Jane are equipped with multi-stage heating devices to improve the temperature control accuracy. The injection nozzle adopts a locking nozzle, and the locking core rod of the nozzle is controlled by the hydraulic system. The gap of the nozzle mouth can be adjusted as needed, and the back pressure is controlled by the pressure regulating valve in the hydraulic system. During injection, the back pressure in the storage cylinder shall be converted into injection pressure, which is controlled by the servo valve. In order to prevent early injection, it is necessary to control the switching time from back pressure to injection pressure and the time of opening the nozzle, which can only be slightly ahead or equal, and can not be delayed, that is, opening the nozzle mouth too early, so that the melt flows into the mold cavity at a low initial speed, affecting the foaming quality. In the process of injection foaming molding, the mold cavity pressure is relatively low, so the required mold locking force is relatively small, and the template size of TSG is large, which can form large products. The mold locking device is provided with a device for rotating the orientation of the template, and the template can be placed vertically or horizontally. For low-pressure injection foaming molding, it is more advantageous to use the horizontal template, because the mold is placed horizontally, the plastic melt in the mold cavity is in the same horizontal plane, and the gravity is relatively uniform, which is conducive to obtain a uniform foam. At the same time, it is convenient to place inserts and some stacked molds. Vertical template, the mold cavity is in the vertical plane, and the melt is easy to gather in the lower part of the mold cavity under the action of gravity, which affects the uniformity of the foam, but the production process is relatively easy to realize the automatic operation process. The orientation of the TSG is provided with this orientation of the TSG.
TSG low pressure injection foaming molding can process almost all thermoplastics. Its models mainly include tsg350, tsg700 and tsg600.
Author：admin