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Injection molding staff must master the eighteen knowledge points!

01. shoot Tsui
 
    The melt usually flows from the nozzle into the nozzle, but some of the mold,Injection Plastics the nozzle is part of the mold, because it extends to the bottom of the mold. There are two main types of nozzle: open shot and closed mouth. Injection molding should be used more open nozzle, because they are both cheap and less likely to stay.
 
    If the injection molding machine is equipped with a depressurization device, this nozzle can be used even for viscous low melt. Sometimes must use a closed nozzle, the nozzle as the role of the throttle, the plastic in the shot in the plastic ring to block. Make sure that the nozzle is properly inserted into the spout, and the top hole is slightly smaller than the spout, which makes the nozzle easier to withdraw from the mold. Note that the hole in the mouth is larger than the shot 1mm, that is, the radius of the nozzle is 0.5mm smaller than that of the nozzle sleeve.
 
    02. Filter and combination nozzle
 
    Plastic impurities can be removed with an extension of the nozzle filter, that is, melting and plastic flow through a channel, the channel is divided into a narrow space. These narrow and gaps remove impurities and improve the mixing of plastics. So extend the opening, you can use a fixed mixer to line to better mixing effect. These devices can be installed between the shot cylinder and the nozzle, the separation and remixing of the work of the melt, the majority of the melt flow through the stainless steel channel.
 
    03. Exhaust
 
    Some plastic in the injection molding need to exhaust in the cylinder, so that the gas discharge. In most cases these gases are only air, but it may be melted and released from the moisture or monomolecular gases. If these gases can not be released, the gas will be squeezed by the melt and brought to the mold, it will expand and the formation of bubbles in the product. To remove the gas before reaching the nozzle or die, reduce or reduce the diameter of the screw can be in the casting cylinder for the melt pressure.
 
    Here, the gas can be discharged from the holes or holes in the shot cylinder. The root diameter of the screw is then increased and the melt of the volatiles is applied to the nozzle. The injection molding machine equipped with this facility is called an exhaust type injection molding machine. The top of this exhaust type injection molding machine should have a good gasifier for the gas burner, which may remove harmful gases.
 
    04. increase the role of back pressure
 
    In order to obtain high quality melt, the plastic should be heated or melted consistently and mixed thoroughly. Use the correct screw to properly melt and mix, and have sufficient pressure (or back pressure) in the shot cylinder to achieve mixing and thermal consistency.
 
    Increase the resistance to oil can be generated in the shooting cylinder back pressure. But the screw to use a longer time to reset, so the injection molding machine drive system has more wear and consumption. As far as possible to maintain the back pressure, and air isolation, but also need to melt the temperature and the degree of mixing.
 
    05. Stop valve
 
    Regardless of the type of screw, the tip is usually equipped with a throttle valve, in order to prevent the plastic from the nozzle outflow, will be equipped with decompression (cable) device or special shooting mouth. If the use of stop production and supply and marketing, must be regularly checked, because it is an important part of the shooting cylinder. At present, the switch-type nozzle is not commonly used, because the shooting nozzle equipment easy to leak plastic and decomposition. At present, each plastic has a suitable type of firing mouth.
 
    06. screw back (down cable)
 
    Many injection molding machines are equipped with a screw back or suction device. When the screw is stopped, it is withdrawn by hydraulic pressure to suck the plastic at the tip of the nozzle. The device allows the use of an open nozzle. The amount of time to take the suction may be reduced, because the air will give some plastic problems.
 
    07. Screw gasket
 
    Most of the injection cycle are required to adjust the rotation of the village, so that when the screw injection is completed, the majority will be a small amount of padded plastic, so you can ensure that the screw to achieve effective propulsion time and maintain a fixed firing pressure. Small injection molding machine of the gasket is about 3mm; large injection molding machine was 9mm. Regardless of the amount of screw material used, be sure to remain the same. Now the size of the screw pad can be controlled within 0.11mm.
 
    08. Rotation speed of screw
 
    The rotational speed of the screw significantly affects the stability of the injection molding process and the heat acting on the plastic. The faster the screw rotation, the higher the temperature, when the screw to high-speed rotation, the transfer to the plastic friction (shear) energy to improve the plasticizing efficiency, but also increased the melt temperature unevenness. Due to the importance of the speed of the screw surface, the screw rotation speed of the large injection molding machine should be less than that of the small injection molding machine because the shear heat generated by the large screw is much higher than that of the small screw. The speed of the screw is different due to the difference in plastic.
 
    09. shot amount
 
    The evaluation of the syringe press is usually based on the amount of PS that can be injected per injection, and may be measured in ounces or grams. Another sorting system is based on the volume of the melt injected into the injection molding machine.
 
    10. plasticizing capacity
 
    The evaluation of the injection molding machine is usually based on its 1 hour can be evenly melt the amount of PS material, or heated to the uniform melt temperature of the amount of PS (in pounds kg), which is called plasticizing capacity.
 
    11. Estimation of plasticizing capacity
 
    To determine whether the quality of the product can be maintained throughout the production process, a simple formula for yield and plasticization can be used as follows: t = (total injection volume gX3600) ÷ (plastic injection molding machine kg / hX1000) t is the minimum cycle time, such as mold cycle time is lower than the value of t, the injection molding machine can not be fully plastic plastic, in order to achieve uniform melt viscosity, so often appear deviation of injection molded parts. In particular, attention to injection of thin-walled or precision tolerances of the system quality, the amount of material and plastic volume must meet each other.
 
    12. Feeding tank retention time
 
    The decomposition of the plastic is the rate that depends on the temperature and time. For example, plastic at a high temperature after a period of time will be decomposed; but in a lower temperature environment, it will take a long time to break down. It is important that the residence time of the plastic in the shot cylinder is very important.
 
    The actual residence time can be determined experimentally by measuring the time required for the colored plastic to pass through the shot cylinder, which can be roughly calculated by the following formula: t = (the rated time of the shot cylinder gX cycle time S) ÷ (shot The amount of gX300) Please note that some plastic in the shot tank in the retention time longer than the calculation of the time, because they can be gathered in the shot tank.
 
    13. Calculate the retention time and importance
 
    According to the general practice, should calculate a plastic in a specific injection molding machine on the residence time. In particular, large injection molding machines use less amount of material, the plastic is easy to break down, and this is not detectable from the observation. If the residence time is short, the plastic will not be evenly plasticized; the residence time will be diminished.
 
    It is necessary to maintain the consistency of residence time. Method: Ensure that the plastic injection molding machine has a stable composition, consistent size and shape. If there is any abnormality or loss of the parts of the injection molding machine, it shall report to the maintenance department.
 
    14. Injection tank temperature environment
 
    It should be noted that the melt temperature is very important, and the temperature of any shoot cylinder used is only instructive. If you have not had any experience with a particular plastic, start with the lowest setting. Usually the first zone temperature is set to a minimum, preventing the plastic from melting and sticking prematurely in the feed port.
 
    The temperature of the other zones is then gradually increased until the nozzle is reached. To prevent dripping, the temperature at the tip of the nozzle is often slightly lower.
The mold is also heated and cooled, due to the size of many molds, the mold is also distinguished, but unless otherwise stated, the zones should be set to the same size.
 
    15. Melt temperature
 
    Measurable nozzle or air spray measurement. When using the latter to measure, care must be taken to ensure that there is no accident when cleaning hot melt plastics, because hot melt plastic heat will burn the skin, and even corrode the skin. In the injection molding workshop, burns are accidental.
 
    Therefore, gloves and masks should be worn when handling thermoplastic or in danger of splashing hot melt. To ensure safety, the tip of the thermosensitive needle should be preheated to the plastic injection molding cost temperature to be measured. Each plastic has a specific melt temperature, to achieve this temperature injection of the actual injection cylinder adjustment depends on the rotation speed, back pressure, injection volume and injection cycle may be.
 
    16. Mold temperature
 
    Always check whether the injection molding machine is set and run at the temperature specified on the record sheet. This is very important. Because the temperature will affect the surface roughness and production of injection molded parts. All measured values ​​must be recorded and inspected at the specified time.
 
    17. Uniform cooling
 
    Injection molded parts must be uniformly cooled, that is, different parts of the mold must be cooled at different rates, so that the whole product will be evenly cooled. The injection molded parts must be cooled at the fastest speed while ensuring that no defects are present, such as uneven surfaces and changes in physical properties. The cooling rate of each part of the injection part must be equal, but it means to cool the mold in an uneven manner, for example by introducing cold water into the core part of the mold, while the outside of the mold is cooled with warmer water. This technique should be used when the flattened products of the syringe are made of precision flat products or large water fountains.
 
    18. Temperature and cooling check
 
    Always check whether the injection molding machine is set and run at the temperature specified on the record sheet. This is very important. Because the temperature will affect the surface roughness and production of injection molded parts. All measured values ​​must be recorded and inspected at the specified time.

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