It turns out that the injection molding machine needs to be tested like this?

2021-03-23 14:34:48 admin

When our injection mold factory receives a set of new molds that require proofing and testing, we are always eager to try a result earlier and pray for a smooth process so as not to waste man-hours and cause trouble.


But here we must remind two points:


1. Injection mold designers and manufacturing technicians sometimes make mistakes. If we do not raise our vigilance when we try the mold, we may cause big damages due to small mistakes.


2. The result of mold trial is to ensure smooth production in the future. If reasonable steps and proper records are not followed during the mold trial process, the smooth progress of mass production cannot be guaranteed. We emphasize that if the mold is used smoothly, the profit recovery will be increased quickly, otherwise the cost loss caused will be more than the cost of the mold itself.


Precautions before mold trial


1. Understand the relevant information of the mold:


It is recommended to obtain the design drawing of the mold, analyze it in detail, and ask a mold technician to participate in the trial work.


2. First check the mechanical coordination action on the workbench:


Pay attention to whether there are scratches, missing parts, looseness, etc., whether the movement of the mold toward the slide plate is correct, whether there is any leakage in the water channel and air pipe joints, and if there are restrictions on the mold opening, it should also be marked on the mold. If the above actions can be done before hanging the mold, it is possible to avoid the waste of man-hours when the problem is found when hanging the mold and then the mold is disassembled.


3. When it is determined that the various parts of the mold move properly, it is necessary to select a suitable test mold injection machine, and pay attention to the selection


(a) Injection capacity


(b) The width of the guide rod


(c) The start of the first major


(d) Accessories


Is it complete? After everything is confirmed that there is no problem, the next step is to hang the mold. When hanging, be careful not to remove all the clamping templates and before opening the mold, so as to prevent the clamping template from loosening or breaking and causing the mold to fall.


After the mold is installed, carefully check the mechanical movements of each part of the mold, such as the movement of the sliding plate, thimble, withdrawal structure, and limit switch. And pay attention to whether the injection nozzle and the feed port are aligned. The next step is to pay attention to the mold clamping action. At this time, the mold closing pressure should be lowered. In the manual and low-speed mold clamping action, pay attention to see and hear whether there are any unsmooth movements and abnormal noises.


4. Increase mold temperature:


According to the properties of the raw materials used in the finished product and the size of the mold, an appropriate mold temperature control machine is selected to increase the temperature of the mold to the temperature required for production.


After the mold temperature is increased, the movement of each part must be checked again, because the steel may cause a jam phenomenon after thermal expansion, so pay attention to the sliding of each part to avoid strain and vibration.


5. If the experiment plan rule is not implemented in the factory, we suggest that only one condition can be adjusted at a time when adjusting the test conditions in order to distinguish the impact of a single condition change on the finished product.


6. According to the different raw materials, do a moderate baking of the raw materials used.


7. Try to use the same raw materials as much as possible for mass production in the future.


8. Do not try the mold completely with inferior materials. If there is a color requirement, you can arrange the color test together.


9. Problems such as internal stress often affect the secondary processing. After the mold is tested, the finished product should be stabilized, and then the secondary processing should be performed. After the mold is closed at a slow speed, adjust the closing pressure and perform several actions to check whether it is closed. Unequal mold pressure to avoid burrs and mold deformation in the finished product.


After checking the above steps, lower the mold closing speed and pressure, and set the safety hook and ejection stroke, and then adjust the normal mold closing and closing speed. If it involves a large-stroke limit switch, the mold opening stroke should be adjusted slightly shorter, and the high-speed mold opening action should be cut off before the first large stroke of the mold opening. This is because the high-speed movement stroke is longer than the low-speed stroke in the entire mold opening stroke during mold loading. On the plastic machine, the mechanical ejector rod must also be adjusted to act after the full-speed mold opening action to prevent the ejector plate or the peeling plate from being deformed by force.


Please check the following items again before making the first mold injection:


(a) Whether the feeding stroke is too long or insufficient.


(b) Whether the pressure is too high or too low.


(c) Whether the filling speed is too fast or too slow.


(d) Whether the processing cycle is too long or too short.


In order to prevent the finished product from short shot, fracture, deformation, burrs and even damage to the mold.


If the processing cycle is too short, the thimble will penetrate the finished product or squeeze the finished product by peeling the ring. This type of situation may cost you two or three hours to take out the finished product.


If the processing cycle is too long, the weak parts of the mold core may be broken due to the shrinkage of the rubber material.


Of course, you can't predict all the problems that may occur in the trial mold process, but full consideration and timely measures can help you avoid serious and expensive losses.


The main steps of tryout


In order to avoid unnecessary waste of time and trouble in mass production, it is indeed necessary to pay patience to adjust and control various processing conditions, find relatively good temperature and pressure conditions, and formulate standard test procedures, which can be used in Establish daily working methods.


1. Check whether the plastic material in the barrel is correct, and whether it has been baked in accordance with the regulations (if different raw materials are used for trial and production, different results may be obtained).


2. The material pipe should be cleaned thoroughly to prevent inferior rubber or miscellaneous materials from being injected into the mold, because inferior rubber and miscellaneous materials may jam the mold*. Test whether the temperature of the barrel and the temperature of the mold are suitable for the raw materials to be processed.


3. Adjust the pressure and injection volume to produce a finished product with a satisfactory appearance, but do not run off the burrs, especially when some mold cavity products are not completely solidified, you should think about it before adjusting various control conditions, because the mold is filled A slight change in the rate may cause a large change in the filling of the mold.


4. Wait patiently until the conditions of the machine and mold stabilize, even for medium-sized machines, it may take more than 30 minutes. You can use this time to view possible problems with the finished product.


5. The advancing time of the screw cannot be shorter than the solidification time of the gate plastic, otherwise the weight of the finished product will be reduced and the performance of the finished product will be impaired. And when the mold is heated, the screw advance time needs to be prolonged in order to compact the finished product.


6. Reasonably adjust to reduce the total processing cycle.


7. Operate the newly adjusted conditions for at least 30 minutes until they are stable, and then continuously produce at least a dozen full mold samples, mark the date and quantity on the container, and place them according to the mold cavity to test the stability of the actual operation And derive reasonable control tolerances. (Particularly valuable for multi-cavity molds).


8. Measure and record the important dimensions of the continuous sample (we should wait for the sample to cool to room temperature before measuring).


9. Compare the measured size of each mold sample, you should pay attention to:


(a) Whether the size is stable.


(b) Are there certain dimensions that have a tendency to increase or decrease indicating that the machining conditions are still changing, such as poor temperature control or oil pressure control.


(c) Whether the size change is within the tolerance range.


10. If the size of the finished product does not change and the processing conditions are normal, it is necessary to observe whether the quality of the finished product of each cavity is acceptable and its size can be within the allowable tolerance. Note down the number of cavities that are continuous or larger or smaller than the average to check whether the size of the mold is correct.


Record and analyze the data as the need to modify the mold and production conditions, and as a reference for future mass production.


1. Make the processing operation time longer to stabilize the melt temperature and hydraulic oil temperature.


2. Adjust the machine conditions according to the size of all finished products that are too large or too small. If the shrinkage rate is too large and the finished product appears to be insufficient for injection, you can also refer to it to increase the gate size.


3. If the size of each cavity is too large or too small, correct it. If the size of the cavity and the door is correct, try to modify the machine conditions, such as the filling rate, the temperature of the mold, and the pressure of each part, and check some molds. Whether the cavity fills the mold slowly.


4. According to the matching situation of the finished products of the mold cavity or the displacement of the mold core, it will be modified separately. It is also allowed to try to adjust the filling rate and mold temperature to improve its uniformity.


5. Check and modify the faults of the injection machine, such as the oil pump, oil valve, temperature controller, etc., will cause changes in the processing conditions, even the perfect mold can not play a good work efficiency on the poorly maintained machine.


After reviewing all the recorded values, keep a set of samples for proofreading to compare whether the corrected samples have improved.


Important matters


Properly keep all the records of sample inspection during the mold trial process, including various pressures during the processing cycle, melt and mold temperature, barrel temperature, injection action time, screw feeding period, etc. In short, you should save everything that will help in the future It can be used to successfully establish the data of the same processing conditions in order to obtain products that meet the quality standards.


At present, the mold temperature is often neglected during mold trial in the factory, and it is difficult to grasp the mold temperature during short-term mold trial and future mass production. Incorrect mold temperature can affect the size, brightness, shrinkage, flow pattern, and lack of material of the sample. , If the mold temperature controller is not used for mass production in the future, there may be difficulties.