Before a new mold is injection-molded or when the machine is replaced with another mold, the test mold is an essential part. The quality of the test results will directly affect whether the factory's subsequent production is smooth. Therefore, it is necessary to follow reasonable operating steps and record useful technical parameters in the mold test process in order to facilitate the mass production of the product.
Precautions before tryout
1. Understand the relevant information of the mold:
It is best to get the design surface of the mold, analyze it in detail, and ask the mold technician to participate in the mold test.
2. First check its mechanical cooperation action on the workbench:
Pay attention to whether there are scratches, missing parts, looseness, etc., whether the movement of the mold slide is correct, whether there are leaks in the waterway and trachea joints, and if there is a limit on the mold's starting distance, it should be marked on the mold. If the above actions can be done before hanging the mold, you can avoid the waste of man-hours that occur when the problem is found during the hanging of the mold.
3. When it is determined that each part of the mold is in proper action, it is necessary to choose a suitable test mold injection machine. When selecting, pay attention to:
(a) What is the maximum injection amount of the injection molding machine?
(b) Whether the lower die of the tie rod is placed
(c) Whether the maximum moving stroke of the movable template meets the requirements
(d) Whether other relevant test tools and accessories are ready
After confirming that there are no problems, the next step is to hang the mold. When hanging, you should pay attention not to remove all the clamps before locking and opening the mold to prevent the clamps from loosening or breaking and the mold falling. After the mold is installed, you should carefully check the mechanical actions of each part of the mold, such as the slide, thimble, retracting structure and limit switch. And pay attention to whether the injection nozzle and the feeding port are aligned. The next step is to pay attention to the mold clamping action. At this time, the mold closing pressure should be reduced. In manual and low-speed mold clamping actions, pay attention to see if there are any unsmooth movements and abnormal sounds. The process of hoisting the mold is actually relatively simple. The main thing to be careful about is the difficulty of calibrating the center of the mold gate and the nozzle. You can usually adjust the center by using a test paper.
4. Increase the mold temperature:
According to the performance of the raw materials used in the finished product and the size of the mold, an appropriate mold temperature control machine is used 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 inspected again, because the steel may cause the mold clamping phenomenon due to thermal expansion, so it is necessary to pay attention to the sliding of each part to avoid the occurrence of strain and chatter.
5. If the experimental plan rule is not implemented in the factory, we recommend that only one condition be adjusted at a time when adjusting the test mold 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 proper baking of the original ravioli.
7. Trial mold and future mass production use as much raw material as possible.
8. Do not try the mold completely with inferior materials. If you need color, you can arrange the color test together.
9. Internal stress and other problems often affect the secondary processing. After the mold is tested, the finished product should be stabilized and then the secondary processing mold should be added. After the mold is closed at a slow speed, the mold closing pressure should be adjusted and acted several times to check whether it is closed. Uneven mold pressure to avoid burrs and mold deformation in the finished product.
After the above steps are checked, lower the mold closing speed and mold closing pressure, and set the safety lever and ejection stroke, and then adjust the normal mold closing and mold closing speed. If the limit switch of the maximum stroke is involved, the mold opening stroke should be adjusted slightly shorter, and the high-speed mold opening action should be cut off before the maximum stroke of the mold opening. This is because during the entire mold opening stroke during the mold loading, the high-speed action stroke is longer than the low-speed stroke. On the plastic machine, the mechanical ejector must also be adjusted to act after the mold is opened at full speed to prevent the ejector plate or the peeling plate from being deformed by the force.
Please check the following items before making the first shot
(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.
To prevent short shots, fractures, deformation, burrs and even damage to the mold. If the processing cycle is too short, the ejector pin will push through the finished product or peel the ring to crush the finished product. This kind of situation may make you spend two or three hours to take out the finished product. If the processing cycle is too long, the thin parts of the mold core may be broken due to the shrinkage of the rubber. Of course you can't anticipate all the problems that may occur during the mold trial process, but taking full consideration of the timely measures in advance will help you avoid serious and expensive losses.
The main steps of trial
In order to avoid unnecessary waste of time and trouble during mass production, it is indeed necessary to pay patience to adjust and control various processing conditions, and to find the best temperature and pressure conditions, and to formulate standard test procedures and can be used Establish daily work methods.
1. Check whether the plastic material in the barrel is correct and whether it is baked according to regulations. (If different raw materials are used for test mold and production, different results are likely to be obtained).
2. The cleaning of the material tube must be thorough to prevent the inferior rubber or miscellaneous materials from being injected into the mold, because the inferior rubber and miscellaneous materials may seize the mold. Check whether the temperature of the tube and the temperature of the mold are suitable for the raw materials for processing.
3. Adjust the pressure and injection volume to produce a finished product with a satisfactory appearance, but do not run away the burrs, especially if some finished products of the cavity are not completely solidified, you should think about it before adjusting various control conditions, because A slight change in the rate may cause very large filling changes.
4. Wait patiently until the conditions of the machine and mold have stabilized. Even medium-sized machines may have to wait more than 30 minutes. Use this time to view possible problems with the finished product.
5. Screw advance time should not 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 lengthened to compact the finished product.
6. Reasonably adjust and reduce the total processing cycle.
7. Run the newly adjusted condition for at least 30 minutes to be stable, and then continuously produce at least a dozen full-mold samples, indicate the date and quantity on the container, and place them separately according to the mold cavity to test the stability of its actual operation And derive reasonable control tolerances. (Especially valuable for multi-cavity molds).
8. Measure and record the important dimensions of the continuous sample (should wait for the sample to cool down to room temperature before measuring).
9. To compare the size of each mold sample, pay attention to:
(a) Whether the size of the product is stable.
(b) Whether certain dimensions 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, you need to observe whether the quality of the finished product of each cavity is acceptable and its size is within the allowable tolerance. Write down the number of cavities measured continuously or larger or smaller than the average to check whether the size of the mold is correct
Record the parameters obtained during the mold test
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 time longer to stabilize the melt temperature and hydraulic oil temperature.
2. Adjust the machine conditions according to the oversized or undersized of all finished products. If the shrinkage is too large and the finished product appears to be insufficiently shot, you can also refer to it to increase the gate size.
3. If the size of each cavity is too large or too small, modify it. If the cavity and door dimensions are still correct, then you should try to modify the machine conditions, such as mold filling rate, mold temperature, and pressure of each part, and check some molds. Acupoint filling is slow.
4. According to the matching situation of the finished mold cavity or the displacement of the mold core, it should be corrected separately. It is also possible to adjust the filling rate and mold temperature again in order to improve its uniformity.
5. Inspect and modify the malfunction of the injection machine. Defects such as oil pumps, oil valves, temperature controllers, etc. will cause changes in processing conditions. Even a perfect mold cannot perform well in poorly maintained machines. After reviewing all recorded values, keep a set of samples to check whether the corrected samples have improved. Keep a proper record of all sample inspections during the mold test, including various pressures in the processing cycle, melt temperature and mold temperature, tube temperature, injection operation time, screw feeding period, etc. In short, all future It can be used to successfully establish data of the same processing conditions in order to obtain products that meet quality standards.
At present, the mold temperature is often ignored in the factory mold test, and the mold temperature is the easiest to grasp in the short-term test and future mass production. The incorrect mold temperature is sufficient to affect the sample size, brightness, shrinkage, flow, and missing materials. If you do not use the mold temperature controller, it may be difficult to hold it in mass production in the future.