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Injection Mold Test Method And Precautions
Jun 30, 2018

Core Tip: Trial molds are an essential part of new molds before injection molding or the replacement of other molds. The quality of the test results will directly affect whether the subsequent production of the factory is smooth. Therefore, it is necessary to follow reasonable operation steps and record useful technical parameters in the trial mould process in order to facilitate the mass production of the product.

Pre-moderation considerations

1. To understand the relevant information of the mold:

It is best to obtain the design surface of the mold, analyze it in detail, and get the mold technician to participate in the mold test.

2. First check its mechanical cooperation on the workbench:

Attention should be paid to the phenomenon of scratches, missing parts, looseness, etc., whether the movement of the die plate is reliable, whether there is leakage of the water channel and the air pipe joint, and whether the opening of the die is limited should be marked on the die. If the above action can be done before hanging the mold, it can avoid the problems found when hanging the mold, and then the man-hour waste that occurs when the mold is removed.

3. When it is determined that the various parts of the mold are properly moved, a suitable test die injection machine must be selected. When selecting the parts, attention should be paid to:

(a) What is the maximum injection volume of injection molding machines?

(b) Whether the distance between levers is a lower mold

(c) Whether the maximum movement schedule of the activity template meets the requirements

(d) Whether or not other related tools and accessories for trial moulding are ready

After confirming that there is no problem, the next step is to hang the mold. When hanging, care should be taken not to remove the hook before locking all the clamp plates and opening the mold to prevent the clamp plate from loosening or breaking so that the mold will fall. After the mold is installed, the mechanical actions of each part of the mold should be carefully checked, such as whether the movements of the slide plate, the ejector pin, the retraction mechanism, and the limit switch are correct. Pay attention to whether the shooting nozzle and 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. Attention should be paid to seeing and listening to any phenomenon such as whether it is smooth or unnatural. The process of lifting the mold is actually quite simple. The main thing to be careful is that the mold gate and the center of the nozzle are more difficult. Usually, the center can be adjusted by means of a test strip.

4. Improve mold temperature:

Based on the properties of the raw materials used in the finished product and the size of the mold, an appropriate mold temperature controller is used to increase the temperature of the mold to the temperature required for production. After the mold temperature is raised, the movements of each part must be reviewed. Because the steel plate may be stuck after thermal expansion, attention must be paid to the sliding of each part to prevent strain and chatter.

5. If the factory does not implement experimental planning rules, we suggest that only one condition can be adjusted at a time in order to adjust the test conditions so as to distinguish the impact of single condition changes on the finished product.

6. According to different raw materials, moderate baking is performed on the used raw materials.

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

8. Do not try the mold completely with a second material. If there is a color requirement, try the color together.

9. Internal stress and other problems often affect the secondary processing. After the mold is to be tested, after the mold is stabilized, the secondary mold is closed at a slow speed. After the mold is closed at a slow speed, the pressure of the mold is adjusted and the tube is moved several times to check whether there is any contact. Mold pressure is not equal, so as to avoid burrs and mold distortion.

After the above steps are checked, the mold closing speed and the mold closing pressure are lowered, and the safety buckle and the ejection stroke are set, and then the normal closing mold and the closing mold speed are adjusted. If the limit switch is involved in the maximum stroke, the mold opening stroke should be adjusted slightly, and the high-speed mold opening action should be cut before the maximum stroke of this mold opening. This is because during the entire mold opening stroke during the mold loading, the high-speed stroke is longer than the low-speed stroke. The mechanical ejector rod on the plastic machine must also be adjusted after full-speed mold-opening action to prevent deformation of the ejector plate or stripper plate due to force.

 

 Please check the following items before making the first shot:

(a) Whether the feeding schedule is too long or not sufficient.

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

(c) whether the filling rate is too fast or too slow.

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

To prevent short shots, fractures, deformations, burrs, and even mold damage. If the processing cycle is too short, the ejector pin will go through the finished product or peel the ring to crush the finished product. This type of situation may take you two or three hours to remove the finished product. If the processing cycle is too long, the weak part of the mold core may be broken due to shrinkage of the rubber material. Of course, you cannot expect any problems that may occur during the trial process, but full consideration of timely and timely measures will help you avoid serious and costly losses.

 

 The main steps of the test model

In order to avoid unnecessary waste of time and problems in 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 a standard test mode program, which can be used for Establish daily work methods.

1. Check whether the plastic material in the cylinder is correct and whether it has been baked according to the regulations. (It may be possible to obtain different results if the trial mold and production use different raw materials.)

2. The cleaning of the feed pipe should be thorough so as not to inject the rubber or miscellaneous material into the mold, because the plastic material and miscellaneous material may jam the mold. Check whether the temperature of the feed pipe and the temperature of the mold are suitable for the processed raw materials.

3. Adjust the pressure and shot volume in order to produce a finished product with satisfactory appearance, but you can't run burrs, especially if there are some cavity products that have not yet completely solidified, you should think about it before adjusting the various control conditions. A slight change in the rate may cause very large mold changes.

4. Be patient and wait until the conditions of the machine and the mold are stabilized, that is, the medium-sized machine may have to wait for more than 30 minutes. You can use this time to view possible problems with the finished product.

5. The screw advancement time must 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 also needs to be lengthened in order to compact the finished product.

6. Make reasonable adjustments to reduce the total processing cycle.

7. Operate the newly adjusted conditions for at least 30 minutes until they are stable. At least one full dosing sample is then continuously produced. Mark the date and quantity on the holding device and place them on the mold cavity so that they can be tested for stability. And derive reasonable control tolerances. (Especially valuable for multi-hole molds).

8. Measure and record the important size of the continuous sample (the amount should be allowed to cool when the sample is cooled to room temperature).

9. Compare the size of each model sample and note that:

(a) Is the size of the product stable?

(b) Whether there is a tendency for some sizes to increase or decrease shows that the machining conditions are still changing, such as poor temperature control or oil pressure control.

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

10. If the finished product dimensions do not change and the processing conditions are normal, it is necessary to observe whether the quality of the finished product of each cavity can be accepted, and its size can be within the allowable tolerance. Record the number of the cavities that are continuous or large or smaller than average to check if the dimensions of the mold are correct.

  

Record the parameters obtained during the test

Record and analyze data as a need to modify molds and production conditions, and provide reference for future volume production.

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

2. According to the size of all finished products is too large or too small to adjust the machine conditions, if the shrinkage rate is too large and the finished product appears to be insufficient shot, it can be used as a reference to increase the gate size.

3. If the size of the mold cavity and the door are correct, correct the machine conditions such as mold filling rate, mold temperature, and pressure of each part, and check certain molds. Whether the filling point is slower.

4. According to the situation of each mold cavity or the mold core shift, to be individually amended, perhaps try again to adjust the mold filling rate and mold temperature, in order to improve its uniformity.

5. Check and modify the failure of the injection machine, such as the oil pump, oil valve, temperature controller, etc. will cause changes in processing conditions, even if the perfect mold can not play a good work efficiency in poorly maintained machines. After reviewing all recorded values, retain a set of samples in order to check if the corrected samples have improved. Safekeeping of all records of sample inspections during the trial moulding process, including various pressures in the processing cycle, melt and mould temperature, feed pipe temperature, injection action time, screw feed time, etc. In short, all future help should be preserved It is possible to successfully establish data for the same processing conditions in order to obtain products that meet quality standards.

 

At present, the mold temperature is often neglected during the test of the mold, and the mold temperature is the least easy to grasp in the short-term mold test and future mass production. The incorrect mold temperature can affect the size, brightness, shrinkage, rhythm and under-charging of the sample. If you do not use a mold temperature controller to grasp future mass production, difficulties may arise.