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  • Five kinds of injection molding tuning techniques

Five kinds of injection molding tuning techniques

Injection molding machine tuning is a necessary skill for injection molders. Although many tuning techniques are based on theory, reliance on experience is indispensable. In this article, we have collected 5 kinds of tuning techniques from Mr. Huang Rongsheng for injection molders to learn and refer to:

1. Transparent mold method

When we adjust the machine, we often exclaim: If only the mold was transparent! In this way, we can see the whole process of molten rubber filling, and see how and when the defects are produced. When we design a certain injection process, we want to see whether the actual injection process is completed according to the envisioned requirements, whether the starting point is set at the right position, and so on.
In fact, it is impossible to directly see the melt glue filling process without high-tech equipment. However, there is an indirect way. By using this technique, you can make every adjuster see the process of filling as clearly as you can, and the method is very simple to say.

Just increase the shot time second by second!
We just need to increase the shot time by one second, one beer per second, and then arrange each beer in order, so that we can clearly see the process of filling the melt until it fills the cavity. If you want to see more carefully in the key position, add only 0.1 seconds to each beer in this key position, so you can see clearly.
If you just want to see if the starting point is accurate, it is even easier. Just turn the pressure and speed of the next level to 0, you can see where the starting point is, instead of using a second-by-second method to slowly watch the check.
It is important to note that the actual molded part will have a little different shape from the moment when the injection stops because of the inertial expansion of the melt after the injection stops. The actual starting point should be a bit earlier than the seen beer.
This technique can be said that every injection molding technician must learn to use, otherwise, it is impossible to have a great improvement in machine tuning technology, much less to reach the level of advanced technology.

2. Positioning injection method

The so-called "positioning shot" method is a tuning technique evolved from our common fast shot to the next level of slow shot. This method is to adjust the slow speed and pressure of the next level to zero, so that the fast injection of the previous level will stop immediately when it reaches a certain set starting position, allowing the pressure stored in the cavity to be released naturally, through which the cavity is finally filled and the pressure is maintained. Usually, the starting point is set at the point where the cavity is just full and then adjusted to the actual situation by moving back and forth.
In the commonly used "fast to slow method", the slow speed and the fast and the starting position of the stage are the same. Fast and the starting position are all interrelated. Therefore, it is not easy for inexperienced people to hold it.
What are the advantages of the "positioning shot" method?
(1) "Positioning glue" method is easier to adjust the machine because the pressure and speed of the next level are eliminated and there are two fewer influencing factors, so it is only necessary to adjust the pressure and speed of the previous level and move the starting point a little bit back and forth appropriately.
(2) In the production, when we meet some raw materials and pieces that cannot be produced at a slow speed at the next level, such as large pieces. Thin-walled parts. PC large parts, etc., once they start to use slow injection, the injection parts will be uneven or have pinched or shock lines, so it must be shot quickly to the end, using the "positioning injection" method is a good choice. Therefore, the "positioning injection" method is a good choice. The injected parts will not have a sharp edge due to excessive injection. Whitetop. The problem of sticking to the mold. On the contrary, in order to prevent the problems such as sharp edges. We can use this tuning technique to help solve the problem.
(3) In fact, this technique can also solve many problems when it is used well. When there is a shrinkage problem of injection molded parts, as long as the appropriate increase in front pressure, the starting point of the stage slightly moved forward, the general shrinkage problem can be solved. Unless the shrinkage problem is very serious, it will not be followed by a batch front. Top white and other problems.
What are the limitations of the "positioning shot" method?
Of course, it is not a panacea, and it cannot completely replace the "fast to slow glue shooting" technique. For example, when there is trapped air, it is very difficult to solve the problem by using the "positioning shot" method, while it is much easier to use the "fast-slow shot" method.
Anyway, if you can use it flexibly, I believe it will become another magic weapon for you to solve the problem.

3. Slow and then the fast method

First slow and then a fast injection, that is, the first level of slow injection, shot to a set location, the second level of rapid injection, the location of the starting point is usually located at the beginning of the injection into the cavity when the pre-filling. Depending on the problem, sometimes it is necessary to turn to the second stage when a small part of the glue (about 10-15MM) is injected, sometimes it is necessary to turn to the second stage when a little bit of glue is injected (about 3MM), and sometimes it is necessary to turn to the second stage before the glue is injected.
With the first level of slow injection, you can make the molten glue fill smoothly at the beginning, which is conducive to prevent trapped air. Air pattern and explosion-proof shot. Spiral or folded (serpentine) injection. The second stage of fast injection is helpful to overcome the resistance to ensure the filling, reduce the temperature drop of the melt, and prevent the problems of matte color and lack of material in the injection molded parts.
What problems can it solve?
This technique is often used to solve many problems such as air and shit patterns at the water inlet, or to solve conflicting problems, as follows:
(1) It is used to solve the problem of cow shit pattern and water trap pattern of large and thick parts. For example, the number one problem of toy injection molding is the problem of bullsh*t pattern and water trap pattern of thick and large PVC parts.
(2) It is used to solve the problem of air or shot lines at the water inlet. For example, the problem of airlines at the water inlet of PC parts.
(3) To solve the problem of oil spraying and matte color in the area of the water inlet.
(4) It is used to prevent other problems when it needs to be filled quickly in order to go flush with the material. For example, the problem of air or shot pattern in the area of the water inlet, etc.
Of course, the production of the tuner can also be based on the actual situation, in order to solve some other problems arising in the injection process, you can add a few more injection stages to the process. For example, if there is an air pattern in the middle of the injection molded part, a slow injection stage should be added to the fast injection process, and then the injection should be turned back to fast injection after filling the air pattern. Since the fast injection is prone to air trapping, scorching, and batching problems, it is necessary to add a slow injection stage to the fast injection process. Burnt and batch front problems, so in the late injection molding need to have a slow low-pressure filling and pressure-holding process and so on.
This tuning technique can be said to be one of the several common tuning techniques essential to the production of injection molding, whether it will be used, used, or not, for the level of technology has the essence of the difference.

4. first fast and then slow injection method

First fast and then slow, that is, the first level of fast shooting glue, shooting to a set position, and then the second level of slow shooting glue. This second stage starting point is usually located at the late stage of glue filling, that is, near the end of the filling position.
What problems can it solve?
The first stage of fast injection can maintain the temperature of the melt and overcome the resistance of the cavity, which facilitates smooth filling. The second stage of slow injection facilitates exhaust and melt suction to solve trapped air and prevent batching and shrinkage problems. This technique can also be used to solve many difficult and conflicting problems:
(1) It can be used to solve the problem of trapped air in injection molded parts. Including "dead corner" trapped air and "backpack" trapped air problem.
(2) Used to solve the mold cavity water imbalance caused by the same mold both batch front, and shrinkage or uneven alignment of the shield problem.
(3)It can also be used to solve the problem of batching. Top white or shrinkage and other problems.
(4) It can also be used to solve the problem of filling difficulties.
Of course, the production of the tuner can also be based on the actual situation, in order to solve other problems in the filling, in this "fast and then slow" injection process to increase the number of injection levels, but also in the fast injection before the addition of a slow level to solve the problem of airlines at the mouth of the water, all of these are higher and more levels of the use of this technique.
In fact, in a complex multi-stage glue shooting process, the two techniques of "slow then fast" and "fast then slow" may actually be combined into one, but each is still working on its own effectiveness. When there are fewer problems, there are actually more obvious differences and preferences, so they will be divided into two techniques to discuss so that we can understand the difference and have the right to use them.

5. Pressure. Speed fine-tuning method

Sometimes, in solving the problem of sharpness. Water streak. If you lower the pressure or speed, you can solve the problem of batching or cow shitting, but at the same time, there will be new problems such as uneven material flow; if you raise the pressure or speed, the old problems will appear again, and the uneven material flow does not exist. At this time, you really want to have a half level of fine adjustment of the pressure or speed of the injection molding machine.
How to achieve fine adjustment?
But we found that we can adjust the melt temperature by plus or minus 2-5 degrees to achieve the purpose of fine-tuning.
When the temperature is raised, the melt flow will become better and the filling will be faster, just like the effect of raising the pressure or speed; on the contrary, lowering the temperature is like lowering the injection pressure and speed.
Using this method to adjust the machine, we should pay attention to the different voltages of day and night shift, or the daily voltage instability, the product will appear unstable situation, need to adjust the melting temperature in time.
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