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The Whole Process of Mold Test: 8 Steps about the Process Setting

Jun 01-2021     Views: 40

Improper mold tool design often causes defects in the final product. Before modifying the mold, try out the mold and evaluate it, optimize the mold tool design and process parameters, which can usually achieve a multiplier effect with half the effort, while meeting the high-quality requirements of mass production.

The eight steps of mold testing:

1. Set the temperature of the barrel

It should be noted here that the initial barrel temperature setting must be based on the recommendation of the material supplier. This is because the same materials of different manufacturers and different brands may have considerable differences, and material suppliers often have quite in-depth research and understanding of their own materials. Users can make basic settings according to their recommendations, and then make appropriate fine-tuning according to specific production conditions.

In addition, it is necessary to use a detector to measure the actual temperature of the melt. Because the barrel temperature we set is often due to the environment, the model of the temperature sensor, and the depth of the location, it cannot be guaranteed to be 100% consistent with the melt temperature. Sometimes due to the presence of oil pollution or other reasons, the actual temperature of the melt and the set temperature of the barrel are very different (previously, we have had examples where the temperature difference between the two is as high as 30°C)

2. Set the temperature of the mold

Similarly, the initial mold temperature setting must also be based on the recommended value provided by the material supplier. It should be noted that the mold temperature we are talking about refers to the temperature of the mold cavity surface, not the temperature displayed on the mold temperature controller. In many cases, due to the environment and improper power selection of the mold temperature controller, the temperature displayed on the mold temperature controller is not consistent with the temperature of the mold cavity surface.

Therefore, the temperature of the cavity surface must be measured and recorded before the formal trial. At the same time, you should also measure different positions in the mold cavity to check whether the temperature at each point is balanced, and record the corresponding results to provide reference data for subsequent mold optimization.

3. Set injection molding machine parameters

Based on experience, initially set the plasticization amount, the limit value of the injection pressure, the injection speed, the cooling time and the screw speed and other parameters, and appropriately optimize them. Check more details about 

4. Carry out filling test to find out the conversion point

The switching point refers to the switching point from the injection stage to the holding pressure stage, which can be the screw position, filling time, and filling pressure. This is one of the most important and basic parameters in the injection molding process. In the actual filling test, the following points need to be followed:

① The holding pressure and holding time during the test are usually set to zero;

②The product is generally filled to 90%~98%, depending on the wall thickness and the structural mold tool design;

③Because the injection speed will affect the position of the pressure transfer point, each time the injection speed is changed, the pressure transfer point must be reconfirmed.

Through the filling test, the user can see the flow path of the material in the mold cavity, thereby judging where the mold is likely to trap air, or where it needs to improve the exhaust, etc.

5. Find out the limit value of injection pressure

In this process, attention should be paid to the relationship between injection pressure and injection speed. For hydraulic systems, pressure and speed are interrelated. Therefore, it is impossible to set these two parameters at the same time to meet the required conditions at the same time.

The injection pressure set on the screen is the limit value of the actual injection pressure. Therefore, the limit value of the injection pressure should be set to always be greater than the actual injection pressure. If the injection pressure limit is too low, making the actual injection pressure close to or exceed the limit value of the injection pressure, the actual injection speed will automatically drop due to the power limit, which will affect the injection time and molding cycle.

6. Find out the optimized injection speed

The injection speed referred to here is to satisfy the requirements of making the filling time as short as possible and the filling pressure as small as possible at the same time. In this process, you need to pay attention to the following points:

①The surface defects of most products, especially those near the gate, are caused by the injection speed;

②Multi-stage injection is used only when one injection cannot meet the technological requirements, especially in the trial phase;

③When the mold is intact, the turning pressure point is set correctly, and the injection speed is sufficient, the injection speed has no direct relationship with the generation of flash.

7. Optimize the holding time

The dwell time is also the condensation time of the gate. Generally, the condensing time of the gate can be determined by weighing, so as to obtain different holding time, and the optimal holding time is the time when the product mold weight reaches the maximum.

8. Optimize other parameters, such as holding pressure and clamping force

Finally, it needs to be emphasized that the purpose and focus of mold trial is to optimize the mold and process to meet the production requirements, not just to test out good product samples.

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