1. Transparent Mold Method
When we adjust the machine, we often sigh: It would be great if the mold was transparent! In this way, we can see the entire filling process of the molten glue, and see how and when the defects are generated. When we design a certain injection process, we hope to see whether the injection process is actually completed according to the requirements, whether the starting point position is set correctly, and a series of other issues.
Transparent injection mold model.
In fact, it is impossible to directly see the molten glue filling process without high-tech equipment. But there is an indirect method. Using this technique, every machine adjuster can see the filling process as clearly as if he saw it, and the method is very simple to say.
Increase the injection time second by second!
We only need to increase the injection time second by second, and add one beer for each second, and then arrange the beer parts that are not aligned in order, so that we can clearly see the filling process of the molten glue until the cavity is filled. If you want to see more carefully at the key position, just increase each injection by 0.1 second at this key position, and you can see it clearly.
If you just want to see whether the starting point is accurate, it is even simpler. Just adjust the pressure and speed of the next level to 0, and you can see where the starting point is, without using the method of increasing it by one second at a time to observe slowly.
It should be noted that since the molten glue will have a little inertial expansion process after the injection stops, the actual molded beer part will be slightly different from the shape of the beer part at the moment when the injection stops. The actual starting point should be earlier than the beer part you see.
This skill can be said to be something that every injection molding technician must learn to use, otherwise the machine adjustment technology cannot be greatly improved, let alone reach the level of advanced technology.
2. Positioning injection method
The so-called "positioning injection" method is a machine adjustment technique that has evolved from the common fast injection to the next level slow injection. This method is to adjust the slow speed and pressure of the next stage to zero, so that the fast injection of the previous stage stops immediately when it reaches a certain set starting position, so that the pressure stored in the cavity is naturally released, and the cavity is finally filled and pressure maintained. Usually, the starting point is set at the point where the cavity is just filled, and then the adjustment is made to move forward and backward according to the actual situation.
In the commonly used "fast turn slow injection method" machine adjustment technique, the three factors of slow speed, fast speed and starting point are interrelated and affect each other, so it is not easy for those with insufficient experience to grasp it.
What are the advantages of the "positioning injection" method?
1. Since the "positioning injection" method cancels the pressure and speed of the next stage, there are two fewer influencing factors. Therefore, it only needs to adjust the pressure and speed of the previous stage and move the starting point slightly forward and backward appropriately. The adjustment becomes easier and can be set more accurately, which is easier for beginners to grasp.
2. In production, when we encounter some raw materials and parts that cannot be produced by slow injection, such as large parts, thin-walled parts, large PC parts, etc., once they are injected slowly, the injection molded parts will be uneven or have clipping or vibration lines, so they must be injected quickly to the bottom. The "positioning injection" method is a good choice. Therefore, the injection molded parts will not have problems such as burrs, top whitening, and mold sticking due to excessive injection. On the contrary, in order to prevent problems such as burrs and top whitening, we can use this machine adjustment technique to help solve them.
3. In fact, this technique can solve many problems if used well. When there is a shrinkage problem in the injection molded parts, as long as the front stage 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 burrs and top whitening.
What are the limitations of the "positioning injection" method?
Of course, it is not omnipotent and cannot completely replace the "fast-turn slow injection method" as a machine adjustment technique. For example, when there is trapped air, it is difficult to solve the problem by using the "positioning injection" method, while it is much easier to use the "fast-to-slow injection method".
3. Slow-first-fast-later injection method
First-slow-later-fast injection, that is, first use the first-level slow injection, and when it is injected to a certain set position, start the second-level fast injection. The starting point is usually set at the early stage of filling when the injection is just started. Depending on different problems, sometimes it is necessary to switch to the second level when a small part of the glue is injected (about 10-15MM), sometimes it is necessary to switch to the second level when the glue is injected a little bit (about 3MM), and sometimes it is necessary to switch to the second level before the glue is injected.
Using the first-level slow injection, the melt can be filled smoothly from the beginning, which is conducive to preventing trapped air, gas lines and explosion-proof injection, spiral or folding (snake-shaped) injection. The second-level fast injection is conducive to overcoming resistance to ensure filling, reducing the temperature drop of the melt, and preventing problems such as dull color and lack of material of injection molded parts.
What problems can it solve?
This machine adjustment technique can often be used to solve many problems such as air marks and cow dung marks at the water inlet, or to solve some contradictory problems, as follows:
It is used to solve the cow dung marks and water inclusion marks of thick and large parts. For example: the number one problem of toy injection molding is the cow dung marks and water inclusion marks of thick and large PVC parts. 2. It is used to solve the problem of air marks or injection marks that are easy to appear at the water inlet. For example, the problem of air marks at the water inlet of PC parts. 3. Solve the problems of oil spraying, burning and dull color in the water inlet area. 4. It is used to prevent other problems when fast filling is required to complete the material. For example, the air marks or injection marks in the water inlet area, etc.
Of course, in production, the machine adjuster can also add several injection stages in this process according to the actual situation in order to solve some other problems generated in the injection process. For example, when air marks are generated at a certain position in the middle of the injection molded part, a slow injection stage should be added in the fast injection process, and the position where the air marks are generated should be filled and then switched back to fast injection. Since fast injection can easily cause air entrapment, burning and bursting problems, a slow and low-pressure filling and pressure holding process is required in the later stage of injection.
This machine adjustment technique can be said to be one of the several common machine adjustment techniques that are indispensable in injection molding production. Whether it can be used or not, whether it is used well or not, has an essential difference in terms of the level of technology.
4. Fast-first-slow-later injection method
Fast-first-slow, that is, first use the first-level fast injection, and when it reaches a certain set position, start the second-level slow injection. This second-level starting point is generally set at the end of injection filling, that is, close to the end of filling.
What problems can it solve?
Using the first-level fast injection can maintain the temperature of the melt, overcome the resistance of the cavity, and facilitate smooth filling. The second-level slow injection is conducive to exhaust and melt suction to solve the problem of air entrapment and prevent bursting and shrinkage. Using this technique can also solve many difficult and contradictory problems for us:
It can be used to solve the problem of air entrapment in injection molded parts. Including the problem of trapped air in "dead corners" and "back pockets". 2. Used to solve the problem of both batching and shrinkage or uneven material flow in the same mold caused by unbalanced water entry in each cavity of the mold. 3. It can also be used to solve the problems of batching, top whitening or shrinkage. 4. It can also be used to solve the problem of difficult filling.
Of course, in production, the machine adjuster can also add several injection stages in this "fast first and slow later" injection process according to the actual situation to solve other problems in filling. It can also add a slow stage before fast injection to solve problems such as air marks at the water outlet. All of these are higher and more advanced applications of this technique.
In fact, in a complex multi-stage injection process, the two techniques of "slow first and fast later" and "fast first and slow later" may actually have been combined into one, but each still plays its own role. When there are fewer 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 competitive manner.
5. Fine-tuning method of pressure and speed
Sometimes, when solving problems such as batching, water lines, and cow dung piles, the following situation often occurs: if the pressure or speed is reduced by one level, the batching or cow dung lines can be solved, but at the same time, new problems such as uneven material flow will appear; if the pressure or speed is increased again by one level, the old problems will appear again, and the problems such as uneven material flow 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 a level.
How to achieve fine-tuning?
It is actually impossible to adjust half a level, but we found that the purpose of fine-tuning can be achieved by adjusting the melt temperature by 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, just like the effect of increasing the pressure or speed; on the contrary, lowering the temperature is like reducing the injection pressure and speed.
