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Jun 17.2020

The experience of the mold master, how to improve the success rate of mold test!

When we receive a new set of molds for proofing, we are always eager to try out a result earlier and pray for a smooth process to avoid wasting time and causing trouble. But here we must remind two points:




First, mold designers and manufacturing technicians sometimes make mistakes. If we are not alert when we try molds, small mistakes may cause great damage.


Second, the result of the trial mode is to ensure the smooth production in the future.


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


2. Matters needing attention before trial


1. Understand the relevant information of the mold:


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


2. First check its mechanical coordination on the workbench:


Pay attention to whether there are phenomena such as scratches, missing parts and looseness, whether the movement of the mold to the skateboard is true, whether there is leakage in the waterway and trachea joints, and if the opening of the mold is limited, it should also be marked on the mold. If the above actions can be done before the mold is hung, you can avoid discovering problems when hanging the mold and then wasting the man-hours when disassembling the mold.


3. When it is determined that the various parts of the mold are moving properly, it is necessary to select a suitable trial mold injection machine, and pay attention when selecting


(a) Injection capacity


(b) Width of guide rod


(c) The largest journey


(d) Accessories


Is it complete? After everything is confirmed that there is no problem, the next step is to hang the mold. When hanging, you should pay attention not to remove the hook before locking all the clamp templates and opening the mold, so as to prevent the clamp template from loosening or breaking and causing the mold to fall.


After the mold is installed, you should carefully check the mechanical movements of each part of the mold, such as the movement of the skateboard, thimble, withdrawal structure and limit switch. And pay attention to whether the injection nozzle and the inlet 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 manual and low-speed mold clamping actions, pay attention to whether there are any irregular movements and abnormal sounds.






4. Increase the mold temperature:


According to the performance of the raw material 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 increases, the movement of each part must be checked again, because the steel may cause a mold clamping phenomenon due to thermal expansion, so pay attention to the sliding of each part to avoid the occurrence of 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 trial test conditions, in order to distinguish the impact of a single condition change on the finished product.


6. According to different raw materials, do a proper roasting of the original lees used.


7. Trial mode and future mass production use the same raw materials as much as possible.


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 secondary processing should be carried out after the finished product is stabilized. After the mold is closed at a slow speed, the mold closing pressure should be adjusted and moved several times to see if there is any Uneven mold pressure to avoid burrs and deformation of the mold.


After checking the above steps, lower the mold closing speed and mold closing pressure, and set the safety buckle 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 this mold opening maximum stroke. This is because the high-speed action stroke is longer than the low-speed one in the entire mold opening stroke during the mold installation. On the plastic machine, the mechanical ejector rod must also be adjusted after full-speed mold opening to prevent the thimble plate or peeling plate from being deformed by 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) Is the filling speed too fast or too slow?


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


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


If the processing cycle is too short, the thimble will push through the finished product or peel the ring to crush the finished product. Such a situation may cause you to spend 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 compound.


Of course, you can't anticipate all the problems that may occur during the mold trial process, but adequate consideration of timely measures in advance will certainly help you avoid serious and expensive losses.


Third, the main steps of trial mode


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, find out the best temperature and pressure conditions, and formulate standard mold trial procedures, which can be used in Establish daily working methods.


1. Check whether the plastic material in the barrel is correct and whether it is baked according to the regulations. (If different raw materials are used for trial mold and production, different results are likely to be obtained).


2. The cleaning of the material tube should be thorough to prevent the bad degumming material or miscellaneous materials from being injected into the mold, because the bad degumming material and miscellaneous materials may catch the mold ※. Test whether the temperature of the material tube and the temperature of the mold are suitable for the raw materials processed.


3. Adjust the pressure and injection quantity to produce a finished product with satisfactory appearance, but it is not allowed to run off the edging, especially when there are some mold cavity finished products that have not been completely solidified, you should think about it before adjusting various control conditions, because the mold filling A slight change in the rate may cause very large mold changes.


4. Wait patiently until the conditions of the machine and the mold stabilize, that is, the medium-sized machine may also wait more than 30 minutes. You can use this time to view possible problems with the finished product.


5. The time for the screw to advance should not be shorter than the time for the gate plastic to solidify, otherwise the weight of the finished product will be reduced and the performance of the finished product will be damaged. And when the mold is heated, the screw advance time also needs to be lengthened 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 to make it stable, and then at least continuously produce 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 actual operation And derive reasonable control tolerances. (Especially valuable for multi-cavity molds).


8. Measure the continuous sample and record its important dimensions (it should be measured when the sample is cooled to room temperature).


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


(a) Whether the size is stable.


(b) Are there any trends in the increase or decrease of certain dimensions that indicate 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 much and the processing conditions are normal, you need to observe whether the quality of the finished product of each cavity can be accepted, and its size can be within the allowable tolerance. Write down the number of mold cavities that are measured continuously or larger or smaller than the average value in order to check whether the mold size is correct.


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


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


2. Adjust the machine condition according to the size of all finished products is too large or too small. If the shrinkage rate is too large and the finished product seems to be insufficient in shot, you can also refer to increase the size of the gate.


3. The size of each mold cavity is too large or too small to be corrected. If the size of the mold cavity and the doorway are still correct, you should try to change the machine conditions, such as mold filling rate, mold temperature and pressure of each part, and check some molds. Whether the cavity filling is slow.


4. According to the matching situation of the finished product of each cavity or the displacement of the mold core, it can be corrected separately, and it may be possible to readjust the mold filling rate and mold temperature in order to improve its uniformity.


5. Check and modify the faults of the injection machine, such as the failure of 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 in the poorly maintained machine.


After reviewing all recorded values, keep a set of samples for proofreading and comparing whether the modified samples have improved.


4. Important matters


Keep all the records of sample inspection during the mold trial process, including various pressures during the processing cycle, the temperature of the melt and the mold, the temperature of the material tube, the injection action time, the screw feeding time, etc. In short, all future contributions should be saved The data of the same processing conditions can be successfully established to obtain products that meet the quality standards.

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