01 nozzle
The melt usually flows into the nozzle the nozzle, but there are some molds, the nozzle is part of the mold because it extends to the bottom of the mold. There are two main types of nozzle: open firing nozzle closed nozzle. In the production of plastic injection, open nozzle should be used more frequently because they are cheaper less likely to stay.
If the injection molding machine is equipped with a pressure removal device, then even the lower viscosity melts can be used. Sometimes it is necessary to use a closed nozzle, which acts as a stop valve, blocking the plastic in the cylinder. To ensure that the nozzle is properly connected to the nozzle sleeve, the top hole is slightly smaller than the nozzle sleeve, which makes the nozzle easier to withdraw the mold. The hole of the nozzle sleeve is larger than the 1mm of the firing nozzle, that is, the radius of the nozzle is 0.5mm smaller than the radius of the nozzle sleeve.
02 filter combined nozzle
Impurities in plastics can be removed by filters with extended nozzle, that is, melt plastic flow through a channel, which is separated into narrow space by inserts. These narrow gaps can remove impurities improve the mixing of plastics. As a result, the fixed mixer can be extended to better mixing effect. These devices can be installed between the ejection cylinder the nozzle to separate remelt the glue, most of which is to melt the channel through the stainless steel.
03 exhaust
Some plastics need to vent in the ejection cylinder when they are injected. In most cases, these gases are only air, but it may be molten water single molecule gas. If these gases can be released, the gas will be compressed by the melt glue taken into the mold. It will expand form bubbles in the product. To discharge the gas before it reaches the nozzle die, reducing reducing the screw root diameter can reduce the pressure of the melt in the cylinder.
Here, the gas can be discharged the holes holes in the ejection cylinder. Then the diameter of the screw root increases, the melt of the volatiles is applied to the nozzle. The injection molding machine equipped with this facility is called exhaust injection molding machine. Above the exhaust injection molding machine, there should be a good smoke extractor to remove potentially harmful gases.
04 increase the role of back pressure.
In order to obtain high quality melts, plastics should be uniformly heated melted must be fully mixed. The proper screw can be properly melted mixed, there is enough pressure ( back pressure) in the ejection cylinder to achieve consistency of mixing heat.
Increasing the resistance to return oil can generate backpressure in the firing cylinder. But the screw needs to be reset for a longer time, so there are more wear consumption in the injection machine drive system. Keep back pressure as far as possible, separate air, also need consistency of melt temperature mixing degree.
05 stop valve
No matter what kind of screw is used, its tip is usually equipped with stop valve. To prevent plastic flowing out of the nozzle, there will be a pressure reducing device special firing nozzle. If you use abortion, you must check regularly because it is an important part of the firing cylinder. At present, the switch nozzle is widely used because it is easy to leak plastic decompose. At present, each type of plastic has a suitable type of firing nozzle.
06 screw back (reverse cable)
Many injection molding machines are equipped with a screw back suction device. When the screw is stopped, it is withdrawn by hydraulic pressure to absorb the plastic at the tip of the nozzle. The device allows the use of an open nozzle. The size of the intake can be reduced because air entry can cause problems for some plastics.
07 screw padding
Most of the injection cycles need to adjust the rotational speed of the screw village, so that when the screw is finished, a small amount of cushion plastic will be left behind, so that the screw can achieve effective advance time maintain a fixed firing pressure. The size of the small injection molding machine is about 3mm, while the large injection molding machine is 9mm. No matter how much screw pad value is used, it must be kept unchanged. Now the size of the screw pad can be controlled within 0.11mm.
Rotation speed of 08 screw
The rotational speed of the screw significantly affects the stability of injection molding process the heat on the plastic. The faster the screw rotates, the higher the temperature. When the screw rotates at high speed, the friction (shear) energy transmitted to the plastic increases the plasticizing efficiency, but at the same time increases the inhomogeneity of the melt temperature. Because of the importance of the screw surface speed, the screw rotation speed of the large injection molding machine should be less than that of the small injection molding machine. The reason is that at the same rotation speed, the shear heat generated by the large screw is much higher than that of the small screw. Because of different plastics, the speed of screw rotation is also different.
09 gel dosage
The evaluation of injection molding machines is usually based on the amount of PS injected in each injection, which may be measured by ounces grams. Another kind of displacement system is determined by the volume of the melt injected by injection molding.
10 plasticizing capacity
The evaluation of injection molding machines is usually based on the amount of PS that can be melted evenly within 1 hours, the amount of PS heated to a uniform melt temperature, which is called plasticizing capacity.
11 estimation of plasticizing capacity
To determine whether the quality of LV can be maintained throughout the production process, a simple formula for yield plasticizing capacity can be used as follows: t= (total injection volume gX3600) (injection molding machine plasticizing quantity kg/hX1000) t is cycle time, for example, the mold cycle time is below T value, the injection molding machine can plasticate the plastic sufficiently to achieve the same goal. Uniform melt viscosity, so injection parts often deviate. In particular, attention should be paid to the quality of injection molded thin walled precision tolerances, the amount of injection plasticization must be matched with each other.
12 detention time of ejection cylinder
The decomposition rate of plastics depends on temperature time. For example, plastics decompose at a high temperature for a period of time, but in a relatively low temperature environment, it takes a long time to decompose.Therefore, the detention time of plastic in the cylinder is very important.
The actual detention time can be determined by experiments. The method is to measure the time required for the coloured plastics to pass through the cylinder. The following formula can be roughly calculated: t= (material charge gX, cycle time S) (gX300). Please note that the retention time of some plastics in the cylinder is longer than the time required for calculation, because they can be gathered in the cylinder.
13 calculation of detention time importance
In general, the residence time of a plastic on a specific injection molding machine should be calculated. Especially when a large injection molding machine uses less amount of material, the plastic is easily decomposed, which is observed observation. If the residence time is short, the plastic will be plasticized evenly, the residence time will decrease if the length of the plastic is prolonged.
Therefore, we must maintain the consistency of detention time. Methods: ensure that the injection molding machine has stable composition, uniform size shape. If there is any aberration loss in the parts of the injection molding machine, it should be reported to the maintenance department.
14 temperature environment of cylinder
It should be noted that the temperature of the melt is very important, the temperature of any cylinder used is only instructive. If you don't have experience in processing a particular plastic, start with a low setting. Usually the temperature is set to a low value to prevent premature melting adhesion of plastics in the feed port.
The temperature in other areas gradually increased until the nozzle was reached, the temperature at the tip of the nozzle tended to be slightly lower to prevent dripping. The mold is also heated cooled. Due to the size relationship of many molds, the die is also distinguished, but unless specified, the zones should be set to the same size.
15 melt temperature
The nozzle can be measured measured by air injection. When making use of the latter, care must be taken to ensure that no accidents occur when hot melt plastics are cleaned, because the high temperature of hot-melt plastics will burn the skin even corrode the skin. In injection workshop, burns are accidental.
Therefore, gloves masks should be worn when dealing with dangerous plastics danger of splashing with hot melt plastics. To ensure safety, the tip of the needle should be pre heated to the temperature to be measured. Each plastic has a specific melt temperature. To achieve this temperature, the actual injection cylinder adjustment must depend on the rotational speed, back pressure, injection volume injection cycle.
16 mold temperature
Check regularly whether the injection molding machine is set run at the specified temperature on the record sheet. This is very important. Because temperature affects the surface finish output of injection molded parts. All measured values must be recorded checked by the specified time.
17 uniform cooling
Injection molded parts must be uniformly cooled, that is to say, different parts of the mold must be cooled at different rates, so that the whole product will be cooled evenly. Injection molded parts must be cooled at the fastest speed, while ensuring no defects, such as uneven surface changing physical properties. The cooling rate of each part of the injection part must be equal, but it means that the mold is cooled in an uneven way, for example, the cold water is poured into the inner part of the mold, the outside of the mold is cooled by warm water. This skill should be applied when the injector is plastic tolerances, the precise straight products the large products with long melting points.
18 temperature cooling check
Check regularly whether the injection molding machine is set run at the specified temperature on the record sheet. This is very important. Because temperature affects the surface finish output of injection molded parts. All measured values must be recorded checked by the specified time.
