{"id":623,"date":"2023-02-06T16:27:09","date_gmt":"2023-02-06T08:27:09","guid":{"rendered":"https:\/\/www.fuhrung.com\/technical-blog\/?p=623"},"modified":"2023-02-06T16:27:09","modified_gmt":"2023-02-06T08:27:09","slug":"injection-mold-technician-18-knowledge","status":"publish","type":"post","link":"https:\/\/www.fuhrung.com\/technical-blog\/injection-mold-technician-18-knowledge.html","title":{"rendered":"As an injection mold technician, do you know all these 18 knowledge"},"content":{"rendered":"\n

01 nozzle<\/strong><\/p>\n\n\n\n

Melts usually flow from the nozzle into the nozzle, but in some molds, the nozzle is part of the mold because it extends to the bottom of the mold. There are two main nozzle types: open nozzle and closed nozzle. In injection production, open nozzles should be used more, because they are cheap and less likely to stay.<\/p>\n\n\n\n

If the injection molding machine is equipped with a pressure relief device, this nozzle can be used even for low viscosity melts. Sometimes it is necessary to use a closed nozzle, which acts as a stop valve to block the plastic cathode in the injection cylinder. Ensure that the nozzle is correctly connected to the nozzle sleeve, and the top hole is slightly smaller than that of the nozzle sleeve, so that the nozzle can be easily removed from the mold. The hole of the nozzle sleeve is 1mm larger than that of the nozzle, i.e. the nozzle radius is 0.5mm smaller than that of the nozzle sleeve.<\/p>\n\n\n\n

02 filter and combined nozzle<\/strong><\/p>\n\n\n\n

The impurities in the plastic can be removed by the filter of the extensible nozzle, that is, the melting and plastic flow through a channel, which is divided into a narrow space by the inserts. These narrow and interstitial spaces 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 injection cylinder and the injection nozzle to separate and remix the melts, most of which make the melts flow through the stainless steel channel.<\/p>\n\n\n\n

03 exhaust<\/strong><\/p>\n\n\n\n

Some plastics need to be vented in the injection cylinder to let the gas out. Most of the time these gases are just air, but they may be water or monomolecular gases released by melting. If the gas can’t be released, it will be compressed by the glue and brought into the mold, it will expand and form bubbles in the product. To discharge the gas before it reaches the nozzle or die, reduce or reduce the screw root diameter can reduce the pressure of the melt in the injection cylinder.<\/p>\n\n\n\n

Here, the gas can be discharged from the holes or holes in the injection cylinder<\/strong>. The diameter of the screw root is then increased, and the melt adhesive of the devolatilization is adapted to the nozzle. The injection molding machine equipped with this facility is called exhaust injection molding machine. The exhaust injection molding machine should be equipped with a good smoke exhaust device of catalytic combustion device to remove the harmful gas.<\/p>\n\n\n\n

04 effect of increasing back pressure<\/strong><\/p>\n\n\n\n

In order to obtain high-quality melts, plastics should be uniformly heated or melted and fully mixed. The correct screw can be used to properly melt and mix, and there is enough pressure (or back pressure) in the injection cylinder, so as to achieve the consistency of mixing and heat.<\/p>\n\n\n\n

Increasing the resistance of return oil can produce back pressure in the firing cylinder. But the screw needs to be reset for a longer time, so there is more wear and consumption in the driving system of injection molding machine. Keep the back pressure as far as possible, isolate from the air, and also need the consistency of the melt temperature and mixing degree<\/p>\n\n\n\n

05 stop valve<\/strong><\/p>\n\n\n\n

No matter which screw is used, its tip is usually equipped with a stop valve. In order to prevent plastic from flowing out of the nozzle, a pressure relief (rewire) device or a special nozzle will also be installed. If you use stop abortion supply and marketing, you must check it regularly, because it is an important part of the shooting cylinder. At present, the switch type nozzle is not widely used, because the nozzle equipment is easy to leak plastic and decompose. At present, each type of plastic has a list of applicable nozzle types.<\/p>\n\n\n\n

06 screw backward (reverse cable)<\/strong><\/p>\n\n\n\n

Many injection molding machines are equipped with screw backward or suction device. When the screw rotation stops, it is withdrawn by hydraulic pressure to suck back the plastic of the nozzle tip. The device allows the use of an open nozzle. It is possible to reduce the number of aspirates, as air can cause problems with some plastics.<\/p>\n\n\n\n

07 screw pad<\/strong><\/p>\n\n\n\n

In most injection molding cycles, it is necessary to adjust the rotation of screw village so that when the screw injection is completed, most of them will have a small amount of cushion plastic, which can ensure that the screw can achieve effective propulsion time and maintain a fixed firing pressure. The padding of small injection molding machine is about 3mm, while that of large injection molding machine is 9mm. No matter how much screw padding value is used, it must be kept unchanged. Now the size of screw pad can be controlled within 0.11mm.<\/p>\n\n\n\n

08 screw rotation speed<\/strong><\/p>\n\n\n\n

The rotational speed of the screw significantly affects the degree of knowledge stability and the heat acting on the plastic during the injection molding process. The faster the screw rotates, the higher the temperature is. When the screw rotates at a high speed, the friction (shear) energy transmitted to the plastic improves the plasticizing efficiency, but also increases the non-uniformity of the melt temperature. Because of the importance of screw surface speed, the screw rotation speed of large-scale injection molding machine should be less than that of small-scale injection molding machine, because the shear heat energy produced by large-scale screw is much higher than that of small-scale injection molding machine at the same rotation speed. Because of different plastics, the speed of screw rotation is also different.<\/p>\n\n\n\n

09 glue injection quantity<\/strong><\/p>\n\n\n\n

The evaluation of syringe molding machines is usually based on the amount of PS that can be injected in each injection, which may be measured in ounces or grams. Another positioning system is determined by the volume of the melt injected by the injection molding machine<\/p>\n\n\n\n

10 plasticizing capacity<\/strong><\/p>\n\n\n\n

The evaluation of an injection molding machine is usually based on the amount of PS that can be melted evenly within one hour or heated to a uniform melt temperature (in pounds and kilograms), which is called plasticizing capacity<\/p>\n\n\n\n

11 plasticizing capacity estimation<\/strong><\/p>\n\n\n\n

To determine whether the LVQ can be maintained in the whole production process, a simple formula about the output and plasticizing capacity can be used, as follows: T = (total injection blow amount gx3600) \u00f7 (plasticizing amount kg \/ hx1000) t is the minimum cycle time. If the cycle time of the mold is lower than t value, the plastic can not be fully plasticized by the injection molding machine to achieve the average The viscosity of the melt glue is even, so the injection parts often have deviation. In particular, pay attention to the injection thin-walled or precision tolerance of the product quality, the injection quantity and plasticizing quantity must match each other.<\/p>\n\n\n\n

12 injection cylinder retention time<\/strong><\/p>\n\n\n\n

The decomposition rate of plastics depends on temperature and time. For example, plastics decompose at a high temperature for a period of time, but at a lower temperature for a longer period of time. Therefore, the retention time of plastic in the injection cylinder is very important.<\/p>\n\n\n\n

The actual retention time can be determined by experiments. The method is to measure the time required for colored plastics to pass through the injection cylinder, which can be roughly calculated by the following formula: T = (rated material quantity of injection cylinder GX cycle time s) \u00f7 (material quantity gx300). Please note that the retention time of some plastics in the injection cylinder is longer than the calculation time, because they can gather in the injection cylinder.<\/p>\n\n\n\n

13 calculation of detention time and importance<\/strong><\/p>\n\n\n\n

According to the general practice, the residence time of a certain plastic on a specific injection molding machine should be calculated. In particular, when a large injection molding machine uses a small injection quantity, the plastic is easy to decompose, which is not observable. If the retention time is short, the plastics will not be plasticized evenly; if the retention time is long, the properties of the plastics will decline.<\/p>\n\n\n\n

Therefore, the retention time must be the same. Methods: to ensure that the plastic input into the injection molding machine has stable composition, consistent size and shape. Any abnormality or loss of the injection molding machine parts<\/strong> shall be reported to the maintenance department.<\/p>\n\n\n\n

14 temperature environment of injection cylinder<\/strong><\/p>\n\n\n\n

It should be noted that the melt temperature is very important, and any spray cylinder temperature used is only indicative. If you have no experience in processing a particular plastic, start with the lowest setting. Generally, the temperature of the first zone is set to the lowest value, which can prevent the plastic from melting and sticking prematurely in the feeding port.<\/p>\n\n\n\n

The temperature of other areas then increases gradually until it reaches the nozzle. In order to prevent leakage, the temperature at the nozzle tip is often slightly lower. Molds are also heated and cooled. Due to the size relationship of many molds, molds are also distinguished. However, unless otherwise specified, each area should be set to the same size<\/p>\n\n\n\n

15 glue temperature<\/strong><\/p>\n\n\n\n

It can be measured by nozzle or air injection method. When using the latter for measurement, care must be taken to ensure that there is no accident when cleaning the hot-melt plastic, because the high temperature of the hot-melt plastic can burn or even corrode the skin. In the injection workshop<\/strong>, the burn was an accident.<\/p>\n\n\n\n

Therefore, gloves and masks should be worn when handling hot plastics or when there is danger of splashing hot-melt plastics. To ensure safety, the tip of the heat control needle should be pre heated to the temperature to be measured. Each kind of plastic has a specific melt temperature. To reach this temperature, the actual injection cylinder adjustment value depends on the screw village rotation speed, back pressure, injection quantity and injection cycle.<\/p>\n\n\n\n

16 mold temperature<\/p>\n\n\n\n

Always check whether the injection molding machine is set and operated at the temperature specified on the record sheet. This is very important. Because the temperature will affect the surface finish and production of injection parts. All measured values must be recorded and the injection molding machine checked at the specified time.<\/p>\n\n\n\n

17 uniform cooling<\/strong><\/p>\n\n\n\n

The injection finished parts must be cooled evenly, that is to say, different parts of the mold must be cooled at different rates, so that the whole part can be cooled evenly. The injection molded parts must be cooled as fast as possible, and at the same time, defects shall not be produced, such as the surface is not smooth, the physical properties change, etc. The cooling speed of each part of the injection molding part must be equal, but it means that the mold is cooled in an uneven way, for example, cold water is input into the inner core part of the mold, while the outside of the mold is cooled by warmer water. This technique should be applied to the flat products with precise plastic tolerance of syringe or the large products with long melting flow in the gate.<\/p>\n\n\n\n

18 temperature and cooling check<\/strong><\/p>\n\n\n\n

Always check whether the injection molding machine<\/a><\/strong> is set and operated at the temperature specified on the record sheet. This is very important. Because the temperature will affect the surface finish and production of injection parts. All measured values must be recorded and the injection molding machine checked at the specified time.<\/p>\n","protected":false},"excerpt":{"rendered":"

01 nozzle Melts usually…<\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"closed","ping_status":"open","sticky":false,"template":"","format":"aside","meta":{"footnotes":""},"categories":[1],"tags":[28],"class_list":["post-623","post","type-post","status-publish","format-aside","hentry","category-technical","tag-injection-molding-machine","post_format-post-format-aside"],"_links":{"self":[{"href":"https:\/\/www.fuhrung.com\/technical-blog\/wp-json\/wp\/v2\/posts\/623","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/www.fuhrung.com\/technical-blog\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/www.fuhrung.com\/technical-blog\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/www.fuhrung.com\/technical-blog\/wp-json\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/www.fuhrung.com\/technical-blog\/wp-json\/wp\/v2\/comments?post=623"}],"version-history":[{"count":1,"href":"https:\/\/www.fuhrung.com\/technical-blog\/wp-json\/wp\/v2\/posts\/623\/revisions"}],"predecessor-version":[{"id":624,"href":"https:\/\/www.fuhrung.com\/technical-blog\/wp-json\/wp\/v2\/posts\/623\/revisions\/624"}],"wp:attachment":[{"href":"https:\/\/www.fuhrung.com\/technical-blog\/wp-json\/wp\/v2\/media?parent=623"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.fuhrung.com\/technical-blog\/wp-json\/wp\/v2\/categories?post=623"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.fuhrung.com\/technical-blog\/wp-json\/wp\/v2\/tags?post=623"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}