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  • Problems to be noted for new mold trial

Problems to be noted for new mold trial

Before injection molding, a new mold, or when the machine is replaced by another mold for production, mold trial is an essential part. The result of the mold trial will directly affect the smoothness of the subsequent production in the factory. Therefore, it is necessary to follow reasonable operation steps and record the useful technical parameters during the mold trial for the mass production of products.

Understand the relevant information of the mould.

It is better to get the design drawing of the mold, analyze it in detail and get the mold technician to participate in the mold trial.

Firstly, check the mechanical action on the table.

Pay attention to whether there are scratches, missing parts, and looseness, whether the action of the mold to the slide is true, whether there are leaks in the water and air joints, and whether the opening range of the mold should be marked on the mold if there are restrictions. If the above actions can be done before hanging the mold, it can avoid the waste of time when hanging the mold to find the problem and then disassemble the mold.

After determining that all the actions of the mold are appropriate, we should choose a suitable injection molding machine to test the mold.

What is the maximum injection volume of the injection molding machine?

Whether the inner distance of the tie bar can accommodate the mold

Whether the maximum moving stroke of the movable template meets the requirements

Whether other related tools and accessories are ready for the mold test

The next step is to hang the mold after everything is confirmed to be OK. When hanging, attention should be paid to not taking down the hanging before locking all the clamping plates and opening the mold, to avoid loosening or breaking the clamping plates and dropping the mold.

After the mold is installed, we should carefully check the mechanical action of each part of the mold, such as the slide plate. Thimble. The action of the ejector structure and the restriction switch are sure. And pay attention to whether the injection nozzle and the feed port are aligned. The next step is to pay attention to the mold closing action, at this time, the mold closing pressure should be turned down, in the manual and low-speed mold closing action, pay attention to see and hear whether there is any uneven action, and strange sound and other phenomena.

The process of lifting the mold is relatively simple, but the main thing that needs to be carefully done is that it is difficult to adjust the center of the mold gate and injection nozzle.

Increase the mold temperature.

According to the performance of the raw materials used in the finished product and the size of the mold, choose the appropriate mold temperature control machine to raise the temperature of the mold to the temperature required for production. After the mold temperature is raised, the action of each part must be checked again, because the steel may cause jamming after thermal expansion, so the sliding of each part must be paid attention to avoid strain and chattering.

If there is no experimental plan implemented in the factory, we recommend that only one condition be adjusted at a time when adjusting the test mold conditions to distinguish the effect of a single condition change on the finished product.

Depending on the raw material, the raw material used should be baked appropriately.

Use the same raw material for the trial mold and future mass production as much as possible. Do not try the mold entirely with inferior materials. If there is a demand for color, you can arrange a color test together. Internal stress and other problems often affect the secondary processing, should be after the mold test to be stable after the finished product that is the secondary processing mold in the slow speed closed, to adjust the mold pressure, and action several times to check whether there is uneven closing pressure and other phenomena, to avoid the finished product generated burr and mold deformation.

After the above steps are checked, the closing speed and closing pressure will be lowered, and the safety lever and ejector stroke will be set, and then the normal closing speed and closing speed will be adjusted. If the maximum stroke limit switch is involved, adjust the mold opening stroke slightly shorter and cut off the high-speed mold opening action before the maximum stroke.

This is because the high-speed action stroke is longer than the low-speed one during the whole opening stroke of the mold loading. In the plastic machine, the mechanical ejector rod must also be adjusted to the role of the full-speed mold opening action after the ejector plate or peel plate to avoid deformation by the force.

The main steps of mold trial.

1. To avoid unnecessary waste of time and trouble during mass production, it is indeed necessary to be patient to adjust and control the various processing conditions and to find out the best temperature and pressure conditions, and to develop a standard mold trial procedure that can be used to establish a daily method.

2. check if the plastic material in the barrel is correct and baked according to the regulations (test mold and production with different raw materials are likely to yield different results).

3. Clean up the barrel thoroughly to prevent bad plastic or miscellaneous materials from being shot into the mold, because bad plastic and miscellaneous materials may seize the mold. Check whether the temperature of the material tube and the temperature of the mold are suitable for the material to be processed.

4. Adjust the pressure and shot volume to produce a satisfactory appearance of the finished product, but do not run rough edges especially when there are still some mold cavities where the finished product is not fully solidified, think before adjusting the various control conditions, because a slight change in the filling rate may cause a large change in the filling.

5. Be patient until the machine and mold conditions stabilize, even for medium-sized machines it may take more than 30 minutes. This time can be used to check for possible problems with the finished product.

6. the screw advance time should not be shorter than the gate plastic solidification time, 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 should be extended to compact the finished product.

7. adjust reasonably to reduce the total processing cycle.

8. Run the new condition for at least 30 minutes to stabilize, then produce at least one dozen full mold samples in a row and mark the date and quantity on the container. Place them separately by dying cavity to test the stability of their operation and to derive reasonable control tolerances. (Especially valuable for multi-cavity molds). 9.

9. Measure and record the important dimensions of the successive samples (the samples should be measured when they have cooled to room temperature).

10. Compare the dimensions of each mold sample, noting.

A. Whether the dimensions of the product are stable.

B. Whether there is a tendency for some dimensions to increase or decrease while the machine processing conditions are still changing, such as poor temperature control or oil pressure control.

C. Whether the dimensional changes are within tolerance. 11.

11. If the finished product does not vary much in size and the machining conditions are normal, observe if the quality of the finished product in each die cavity is acceptable and the dimensions are within tolerances. Make a note of the cavity numbers that are continuously larger or smaller than the average to check the correct size of the mold. Record the parameters obtained during the mold test, and analyze the data to modify the mold and production conditions, and as a reference for future mass production.

Problems that should be noted during the mold test.

  • Make the processing running time longer to stabilize the melt temperature and hydraulic oil temperature.
  • Adjust the machine conditions by the oversize or undersize of all finished products. If the shrinkage is too large and the finished product seems to be undershot, it can also be used as a reference to increase the gate size.
  • If the die cavity and gate size are still correct, then the machine conditions such as the filling rate, mold temperature, and pressure of each department should be adjusted and some die cavities should be checked to see if they are filling slowly.
  • Depending on the fit of each die cavity or the displacement of the die pistons, each should be corrected and perhaps the filling rate and mold temperature should be adjusted to improve the uniformity.
  • Check and modify the malfunction of injection machines, such as oil pumps. Oil valve. Even the most perfect mold cannot perform well in a poorly maintained machine. After reviewing all the recorded values, keep a set of samples for comparison of the corrected samples for improvement.
  • Keep a record of all samples tested during the mold trial, including the various pressures of the cycle. Melt and mold temperatures. Tube temperature. Injection action time. In short, all data that will help to establish the same processing conditions in the future should be kept to obtain products that meet quality standards.
  • At present, the mold temperature is often neglected during mold trials, and it is not easy to control the mold temperature during short mold trials and future mass production, and an incorrect mold temperature is enough to affect the size of the sample. Brightness. Shrinkage. If we don't use the mold temperature controller, it may be difficult to grasp the mold temperature in future mass production.
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