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5 kinds of injection molding machine tuning skills you should master

writer:LI SONG Share

Adjusting the injection molding machine is an indispensable skill for injection molding personnel. Although many adjustment techniques are based on theory, they rely on experience as indispensable. For the mould people to learn and refer to:

1. Mold transparency method
When we adjust the machine, we often sigh: If the mold is transparent, it will be fine! In this way, we can see all the filling process of the melt and see how and when the defects are generated. of. When we design a certain glue injection process, whether the glue injection process is actually completed according to the envisaged requirements, whether the starting point position is set correctly, etc., we hope to be able to see a series of questions.

 
In fact, it is impossible to directly see the melt filling process without high-tech equipment. But there is an indirect method. Using this technique, every operator who adjusts the machine can be as clear as he saw the filling process, and the method is very simple. The injection time can be increased from one second to one second! We only need to increase the injection time one second by one second, and each additional second beer is one beer, and then the unmatched beer pieces are arranged in order, so that You can clearly see the filling process of the melt until the cavity is filled. If you want to take a closer look at a key position, only 0.1 second per beer will increase at this key position, so you can see clearly.
injection molding machine
It’s even simpler if you just want to see if the starting point is not accurate. You only need to adjust the pressure and speed of the next level to 0, and you can see where the starting point is, instead of using a second-by-second increase method to slowly observe.

It should be reminded here that, since the melt will have a little inertial expansion after the injection stops, the actual shape of the beer part when the injection is stopped will be slightly different from the moment when the injection is stopped. The actual starting point should be earlier than the beer that you see.

It can be said that every injection molding technician must learn to use this technique, otherwise it is impossible for the adjustment technology to be greatly improved, let alone reach the level of advanced technology.

2. Positioning injection method
The so-called "positioned shot glue" method is a tuning method that evolved from our commonly used fast shot glue to lower-level slow shot glue. This method is to adjust the slow speed and pressure of the latter stage to zero, so that the fast glue injection of the previous stage stops immediately when it reaches a certain set starting position, and the pressure stored in the cavity is naturally released. For the final filling of the cavity and holding pressure. Usually the starting point is set at the point where it just fills the cavity, and then adjusts to move forward and backward according to the actual situation.

In the commonly used "fast-turn and slow-shot glue method" adjustment technique, the three levels of slow speed, fast speed, and starting point are all related to each other and affect each other, so those with inexperience are not easy to hold.

What are the advantages of the "positioned injection" method?
1). "Positioning glue injection" method because the pressure and speed of the latter stage are cancelled, and two influencing factors are missing. Therefore, only the pressure and speed of the previous stage need to be adjusted and the starting point is moved back and forth appropriately, and the machine is changed. It’s easier and can be set more accurately, making it easier for beginners to hold.
2). In production, when we encounter some raw materials and parts that cannot be produced at a slow speed from the next stage, such as large parts, thin-walled parts, large PC parts, etc., once they start slow injection, injection molding The parts will be uneven, or there will be clamping lines or vibration lines, so it must be shot to the end quickly, and the "positioning shot glue" method is a good choice. Therefore, the injection molded parts will not cause problems such as cracking, topping, and sticking due to excessive injection of glue. On the contrary, in order to prevent problems such as criticizing and disapproving, we can use this tuning technique to help solve the problem.
3). In fact, this technique can solve many problems if used well. When there is a shrinkage problem in injection molded parts, as long as the front pressure is appropriately increased and the starting point is slightly moved forward, the general shrinkage problem can be solved. Unless the shrinkage problem is quite serious, there will be no problems such as criticism and disapproval.

What are the limitations of the "positioning shot glue" method?
Of course, it is not a panacea, and it cannot completely replace the tuning technique of "fast-turn and slow-shot glue". For example, when air is trapped, it is difficult to solve the problem by using the "positioned injection" method, but it is much easier to use the "fast turn and slow injection method". In any case, being able to use it flexibly will surely become another magic weapon for you to solve difficult problems.

3. Slow first and then fast shot glue method
Slow first and then fast injection, that is, first-stage slow injection, when it reaches a set position, second-stage fast injection, the starting point is usually set at the beginning of injection into the cavity In the early stage of filling. According to different problems, sometimes it is necessary to switch to the second stage when a small part of the glue (about 10-15MM) is inserted, and some need to be transferred to the second stage when the glue is a little bit (about 3MM), and sometimes It must be transferred to the second stage before the glue is added.

With the first-level slow-spraying glue, the melted glue can be filled smoothly from the beginning, which is beneficial to prevent air trapping, gas lines and explosion-proof shots, spiral or folding (snake-shaped) shots. The second-level rapid injection is beneficial to overcome the resistance to ensure filling, reduce the temperature drop of the melt, and prevent the dull color and material shortage of the injection molded parts.

What problems can it solve?
The use of this tuning technique can often be used to solve many problems such as water breath marks and cow feces patterns, or to solve some conflicting problems, as follows:

1). It is used to solve the problem of bull dung patterns and water trapping patterns of thick and large pieces. For example, the number one problem in toy injection molding is the bullshit pattern and water trapping pattern of thick PVC parts.
2). It is used to solve the problem of easy to produce air lines or jet lines at the water inlet. For example, the problem of the water inlet breath pattern of PC parts.
3). Solve the problem of burnt glue and dull color around the water inlet.
4). It is used to prevent other problems when it is necessary to fill the mold quickly to be able to mix the materials. For example, the problem of air lines or shooting lines around the water inlet and so on.

Of course, in the production, the adjuster can also increase the number of injection levels in the process in order to solve some other problems that arise during the injection process according to the actual situation. For example, when there is a gas pattern in a certain position in the middle of the injection molded part, it is necessary to add a slow injection level during the rapid injection process, and then switch back to the fast injection after filling the position where the gas pattern is generated. Since rapid injection is easy to cause air trapping, scorching and frontal problems, a slow and low pressure filling and pressure holding process is required in the later stage of injection.

This tuning technique can be said to be one of the several commonly used tuning techniques that are indispensable in injection molding production. Whether it will be used or not, whether it is used well or not, there are essential differences in terms of the level of technology.

4. Fast and slow shot glue method
Fast first and then slow, that is to say, use the first level of fast injection, and when it reaches a certain set position, then the second level of slow injection. This secondary starting point is generally set at the late stage of injection and filling, that is, close to the end of filling.

What problems can it solve?
The use of the first-level quick glue injection can maintain the melting temperature, overcome the cavity resistance, and facilitate smooth filling. The second-level slow-spraying glue is beneficial to exhaust and melt glue to solve the trapped air and prevent the problem of cracking and shrinking. Using this technique can also solve many difficult and conflicting problems for us:

1). It can be used to solve the air trapping problem of injection molded parts. Including "dead corners" trapped air and "backpack" trapped air problems.
2). It is used to solve the problem that the same mold is caused by the imbalance of the water in the cavities of the mold.
3). It can also be used to solve problems such as front-end, white-out or shrinkage.
4). It can also be used to solve the problem of difficult filling.

Of course, the adjuster in production can also add several injection levels to the injection process of "fast first and then slow" according to the actual situation, in order to solve other problems in the filling process, or before the fast injection Adding a slow speed level to solve problems such as the air mark of the nozzle position, all of which are higher and more advanced applications of this technique.

In fact, in a complex multi-stage glue injection process, the two techniques of "slow first and then fast" and "fast first and then slow" may actually be combined into one, but each is still working on its own. When there are relatively few problems, there are actually more obvious differences and emphasis, so they are divided into two techniques to discuss, so that we can distinguish and understand and use them in a conflicting way.

5. Pressure and speed fine-tuning method
Sometimes, when solving problems such as piping, water trapping, and bull dung piles, there will always be such a situation: lowering the pressure or speed by one level, the piping or bull dung patterns can be solved, but at the same time, there will be dislocations. New problems such as uneven materials; up to the first level of pressure or speed, old problems will reappear, and problems such as uneven materials will no longer exist. At this time, I really hope that the pressure or speed of the injection molding machine can be fine-tuned by half.

How to achieve fine-tuning?
The actual half-level adjustment is impossible, but we found that the purpose of fine-tuning can be achieved by adjusting the melt temperature of plus or minus 2-5 degrees. When the temperature is increased, the fluidity of the melt will become better, and the filling will be faster, which has the same effect as increasing the pressure or speed; on the contrary, reducing the temperature is like reducing the injection pressure and speed.

When using this method to debug the injection molding machine, pay attention to the difference of the day and night shift voltage, or the instability of the daily voltage, the product will be unstable, and the melt temperature needs to be adjusted in time.

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