How to do a good job in plastic mold trial


Before the injection molding of new mold or the replace […]

Before the injection molding of new mold or the replacement of other molds on the machine, the trial mold is an essential part. The quality of the test results directly affects whether the follow-up production of the factory is smooth. Therefore, it is necessary to follow reasonable operation steps and record the useful technical parameters in the process of mold test, so as to facilitate the mass production of products.
1. Precautions before mold test
(1) Understand the mold related information: it is best to obtain the mold design drawing, analyze in detail, and invite mold technician to participate in the mold test work.
(2) First, check the mechanical cooperation action on the workbench: pay attention to whether there are scratches, missing parts and looseness, whether the movement of the sliding plate towards the die is correct, whether the water channel and air pipe joints have leakage, and if the opening distance of the mold is limited, it should also be marked on the mold. If the above actions can be done before hanging the mold, it can avoid the waste of working hours caused by dismantling the mold when problems are found during hanging the mold.
(3) When determining the appropriate action of each part of the mold, it is necessary to select a suitable trial injection machine
① What is the maximum injection volume of injection molding machine table;
② Whether the inner distance of the pull rod can put down the mold;
③ Whether the maximum moving stroke of movable template meets the requirements;
④ Whether other related tools and accessories for mold test are ready.
After everything is confirmed that there is no problem, the next step is to hang the mold. When hanging, pay attention not to take off the hook before locking all clamping templates and opening the mold, so as to prevent the clamping template from loosening or breaking, resulting in the mold falling. After the mold is installed, the mechanical actions of all parts of the mold, such as slide plate, thimble, tooth withdrawal structure and limit switch, should be carefully checked to see if they are correct. And pay attention to whether the injection nozzle is aligned with the feed inlet.
The next step is to pay attention to the mold closing action. At this time, the mold closing pressure should be lowered. During the manual and low-speed mold closing actions, attention should be paid to see and listen for any unsmooth movements and abnormal sounds. In fact, the process of lifting the mold is relatively simple, and the main thing to pay attention to is that it is difficult to calibrate the center of the mold gate and nozzle. Generally, the method of test paper can be used to adjust the center.

(4) Improve the mold temperature: according to the performance of the raw materials used in the finished product and the size of the mold, select the appropriate mold temperature control machine to increase the mold temperature to the required temperature during production. After the mold temperature increases, the movement of each part must be checked again, because the steel may cause die clamping phenomenon due to thermal expansion, so it is necessary to 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, it is suggested that only one condition can be adjusted at a time in order to distinguish the influence of single condition change on the finished product.
(6) According to different raw materials, the original used to do moderate baking.
(7) As far as possible, the same raw materials should be used for trial mold and mass production in the future.
(8) Do not test the mold completely with the secondary material. If there is color requirement, you can arrange the color test together.
(9) The internal stress and other problems often affect the secondary processing. The mold should be processed again after the mold test until the finished product is stable. After closing the mold slowly, adjust the mold closing pressure and act several times to check whether there is uneven mold closing pressure, so as to avoid burr and mold deformation of the finished product.
After the above steps are checked, lower the mold closing speed and mold closing pressure, and set the safety buckle rod and top travel distance, and then adjust the normal mold closing and closing speed.

If the limit switch of the maximum stroke is involved, the opening stroke should be adjusted a little shorter, and the high-speed opening action should be cut off before the maximum opening stroke. This is because during the whole mold opening stroke, the high-speed movement stroke is longer than the low-speed one. On the plastic machine, the mechanical ejection must also be adjusted after the full speed mold opening action, so as to avoid the deformation of the ejector plate or stripping plate due to stress.
Before the first mock exam is launched, please check the following items:
① Whether the feeding stroke is too long or insufficient;
② Whether the pressure is too high or too low;
③ Whether the filling speed is too fast or too slow;
④ Whether the processing cycle is too long or too short. In order to prevent the finished product from short shot, fracture, deformation, burr and even damage to the mold.
If the processing cycle is too short, the thimble will pierce the finished product or strip the ring and crush the finished product. It may take two or three hours for people to take out the finished product. If the processing cycle is too long, the fine and weak parts of the mold core may be broken due to the rubber shrinkage. Of course, it is impossible to predict all the possible problems in the process of mold test, but serious losses can be avoided by taking full consideration in advance.

2. Main steps of mold test
(1) Check whether the plastic raw materials in the barrel are correct and baked according to the regulations (if different raw materials are used for mold test and production, different results are likely to be obtained).
(2) The cleaning of the material pipe should be thorough to prevent the injection of inferior rubber or miscellaneous materials into the mold, as the inferior rubber and miscellaneous materials may block the mold. Check whether the temperature of material pipe and mold is suitable for processing raw materials.
(3) Adjust the pressure and injection rate in order to produce a satisfactory appearance of the finished product, but do not run the burr, especially when some die cavity products have not completely solidified, we should think about it before adjusting various control conditions, because a slight change in the mold filling rate may cause a great change in mold filling.
(4) Wait patiently for the machine and mold conditions to stabilize, even medium-sized machines may have to wait more than 30 minutes. You can use this time to see possible problems with the finished product.
(5) The advance time of screw shall not be shorter than the solidification time of gate plastic, otherwise the weight of finished product will be reduced and the performance of finished product will be damaged. Moreover, when the mold is heated, the screw advance time shall be appropriately extended to compact the finished product.
(6) Reduce the total processing cycle reasonably.
(7) Run the newly transferred condition for at least 30 minutes until it is stable, and then continuously produce at least a dozen full mold samples, mark the date and quantity on the container, and place them separately according to the mold cavity, so as to test the stability of the operation and derive reasonable control tolerance (especially for multi hole mold).
(8) Measure and record the important dimensions of continuous samples (it should be measured when the samples are cooled to room temperature).
(9) To compare the dimensions of each sample, it should be noted that:
① Whether the product size is stable;
② Whether there is a trend of increase or decrease in some dimensions, indicating that the machining conditions are still changing, such as poor temperature control or oil pressure control;
③ Whether the dimensional change is within the tolerance range.
(10) if the first mock exam is not changed and the conditions of processing are normal, it is necessary to observe whether the quality of the finished products of each mold cavity can be accepted and whether the size of the products can be within tolerance. Note down the hole number of continuous or large or less than the average value, so as to check whether the mold size is correct.