Eighteen knowledge points that must be mastered by injection molding personnel!

1 shoots

The glue usually flows from the nozzle to the sprue, but there are some dies, which are part of the mold, because it extends to the bottom of the mold. There are two main types of nozzles: open firing nozzle and closed nozzle. More open nozzles should be used in injection molding because they are both cheaper and less likely to stay.

If the injection machine is equipped with a pressure relief device, the nozzle can be used even if the adhesive is of lower viscosity. Sometimes it is necessary to use a closed nozzle, the nozzle as a stop valve, will be in the delivery cylinder in the plastic shade to block. To ensure the correct access injection nozzle, the top hole than the injection sleeve slightly small, the nozzle can easily withdraw from the mold. Note the muzzle hole than shooting mouth 1mm, namely the injection nozzle radius than the muzzle radius of fine 0.5mm.

2 filter and combined nozzle

Impurities in plastics can be removed by filters with extended nozzles, that is, molten and plastic flows through a channel separated into narrow spaces by inserts. These narrow and gap can remove impurities and improve the mixing of plastics. Therefore, the fixed mixer can be used to achieve better mixing effect. These devices can be installed between the cylinder and the nozzle, separating and mixing the melt, most of which is molten through the stainless steel channel.

3 exhaust

Some plastics need to vent in the ejection cylinder to let the gas out during injection. In most cases, these gases are just air, but it may be water or single molecule gas released from the melt. If the gas can’t be released, the gas will be compressed by the melt and brought into the mold, and it will expand and form bubbles in the product. To remove the gas before reaching the nozzle or die, reducing or reducing the diameter of the screw root, it can be used in the cylinder to reduce the pressure of the melt.

Here, the gas can be expelled from the hole or hole in the cylinder. Then the screw root diameter increases, and the volatile adhesive is applied to the nozzle. The injection molding machine equipped with this facility is called an exhaust injection molding machine. The exhaust gas injection molding machine should have a catalytic burner, a good smoke extractor, and remove the potentially harmful gases.

4 increase the role of back pressure

In order to obtain high quality melt adhesive, the plastics should be heated or melted uniformly, and should be fully blended. The correct screw is used to properly fuse and mix, and sufficient pressure (or back pressure) in the injection cylinder is used to obtain the consistency of mixing and heat.

To increase the resistance of return oil, the back pressure can be produced in the firing cylinder. But the screw take longer to reset, the injection molding machine drive system wear and consume more. As far as possible to maintain the back pressure, isolated from the air, but also need to melt temperature and mixing degree of consistency.

5 stop valve

Regardless of the screw, its tip is usually equipped with stop valve, in order to prevent the plastic from the nozzle outflow, but also equipped with decompression (inverted rope) device or special shooting mouth. If you use the abortion, you must check it regularly, because it is an important part of the firing cylinder. At present, the switch nozzle is not widely used, because the nozzle equipment is easy to leak plastic and decomposition. At present, each type of plastic has a suitable type of shooting nozzle.

6 screw back (reverse cable)

Many injection molding machines are equipped with screw back or back suction device. When the screw rotates, it is withdrawn by hydraulic pressure to suck back the plastic at the tip of the nozzle. The device allows the use of an open nozzle. The number of returns may be reduced because air entry can cause problems for some plastics.

7 screw pad

Most of the injection molding cycle need to adjust the rotation of the screw village, so that when the screw is finished, most of the plastic will be a small amount of cushion plastic, so that the screw can achieve effective propulsion time and maintain a fixed firing pressure. The cushion of the small injection molding machine is about 3mm, and the large injection molding machine is 9mm. No matter how large the screw cushion value is, it must remain the same. Now the size of the screw pad can be controlled within 0.11mm.

Rotation speed of 8 screw

The rotational speed of the screw significantly affects the stability of the injection molding process and the amount of heat on the plastic. The rotation of the screw, the temperature is high, when the screw is rotated at high speed, transferred to the plastic friction (shear) energy improves the plasticizing efficiency, but also increases the melt temperature uniformity. Visit mymarvelousmaids.com website. Because of the importance of the screw surface speed, the screw rotation speed of the large injection molding machine sh uld be less than that of the small injection molding machine, because the shear energy generated by the large screw is much higher than that of the small screw at the same rotating speed. Because of the difference in the plastic, screw rotation speed is also different.

9 injection volume

Evaluation of syringe is usually determined by plastic injection molding can PS the volume of each injection, according to ounces measurement. Another ranking system is based on the injection molding function of the volume of adhesive injection.

10. plasticizing capacity

The evaluation of an injection molding machine is usually based on the amount of PS that can be uniformly melted within 1 hours, or heated to the amount of PS at the temperature of the homogeneous melt adhesive (weighing in pounds). This is called plasticizing capacity.

11. plasticizing capacity estimation

To determine the quality of products can be maintained in the whole production process, a simple formula can be combined on Yield and plasticizing capacity, as follows: t= (total injection hits gX3600) 83019 (plastics injection molding machine kg/hX1000 T) is the minimum cycle time, such as cycle time of die is lower than the value of t, injection molding it can not be fully plasticized plastic machine, to achieve uniform melt viscosity, the injection molding often appear deviation. In particular, attention should be paid to the quantity of injection and plasticizing quantity when the products of thin wall or precise tolerance are injected

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