Intelligent Mold Technology Research and Application

In the plastic mold trial mold tuning and actual production, there are due to different machines, different tuning personnel brought about by the waste of materials, product qualification rate is low, etc., injection molding process can not accurately grasp the cavity pressure and temperature and other parameters, pressure preservation switching and adjusting the hot runner valve, the tuning of the master’s experience is more dependent on the tuning of the machine, the tuning time is long, and the quality of products produced by the product is not stable.

To ensure the good appearance of the molded plastic requirements and fast and stable production, it is necessary to optimize from the development of plastic parts, simulation, and analysis to the injection production, improve the efficiency of the mold production, and adapt to the rapid development of changing market demand.

Design Ideas

Sensors are added to the mold to monitor the pressure and temperature of the injection material flow to each position of the mold cavity, and to determine the process parameters of different machine tools and different times by monitoring the change curve of the pressure and temperature values in the cavity.

Figure 1 shows the air conditioner shell mold’s gate position and sensor arrangement. Two sensors (Sensors 1 and 2) are arranged near the hard-to-inject area to detect the pressure situation and assist in solving the defects of the products in this area.

Two sensors (sensors 3 and 4) are arranged at the front of the product to detect the pressure and solve the deformation problem at the front.

Fig. 1 Sensor arrangement of air conditioner face shell mold

Injection molding verification process

(1) Fig. 2 and Fig. 3 show the test pressure curve of the injection molding machine during the adjustment of the injection molding machine.

Figure 2 shows the pressure distribution curves of four pressure sensors in one injection molding cycle. The test results show that the pressure of the four sensors starts to increase at different times, which is caused by their different distances from the hot nozzle.

Fig. 2 Pressure distribution curve in one injection molding cycle

Among them, the pressure of sensor 2 starts to increase at the earliest time, which indicates that it is the closest to the hot nozzle, which is in line with the actual arrangement.

After the injection pressure reaches the maximum value and starts to hold pressure, the pressure at each position does not remain constant as analyzed in the simulation. Still, it shows a decreasing trend, indicating that there is a pressure loss in the cavity during the pressure holding process.

Figure 3 shows the pressure distribution curve of 10 injection molding cycles for Sensor 2 after fixing the injection parameters: it can be seen that the general trend of the pressure is the same, but the overlap is not very good, which is mainly due to the adjustment of the machine in the old injection molding machine bed, and the stability of the injection molding machine is poor.

(2) Fig. 4 and Fig. 5 are the pressure curves of the test molds tuned on the new machine bed.

Figure 4 shows the pressure curve distribution of the four sensors during an injection molding cycle. The starting point of the pressure rise and the change trend in the holding pressure stage are somewhat similar to those of the Zhende machine bed, but the overall profile is different.

Figure 5 shows the distribution of the pressure curves of the four sensors during 10 injection molding cycles after fixing the injection molding parameters. The pressure curves of the sensors overlap well, and the stability of the machine tool is relatively good.

Therefore, a machine with good stability must use the sensors to monitor the mold’s stable production.

Fig. 3 Pressure distribution curve of sensor 2 ten injection molding cycles in the mold

Fig. 4 Pressure distribution curve of 1 injection molding cycle

Fig. 5 Pressure distribution curve of 10 injection molding cycles

(3) Fig. 6 and Fig. 7 are the pressure curves of the test mold in another older Haitian machine.

Figure 6 shows the distribution of pressure curves of 4 sensors in one injection molding cycle, and Figure 7 shows the distribution of pressure curves of 4 sensors in 10 injection molding cycles after fixing the injection parameters.

It can be seen that the starting point of pressure rise is basically the same as that of the other two machine tools, but in the holding phase of the machine tool, it is obvious to see the relatively smooth pressure curve, which is similar to the theoretical analysis, indicating that the sensor is more sensitive and requires more stability of the machine tool.

This indicates that the sensor detection is more sensitive, and the machine tool’s stability must be higher.

Fig. 6 Pressure distribution curve of 1 injection molding cycle

Fig. 7 Pressure distribution curve of 10 injection molding cycles

Analysis and Summary

Verification from the same brand of new and old machine tools, but also from the comparison between different brands of machine tools, resulting in the following summary:

Technical difficulties:

① How to determine the monitoring position point;

② How to realize the visualization of the injection process, accurately grasp the process of filling the melt plastic;

③ Optimization of the injection molding process;

④ Monitoring and evaluation of the injection machine;

⑤ Control of the injection molding parameters;

⑥ Detection of the injection molding process;

⑦ How to quickly adjust the machine to get qualified products after mold transfer.

Solution:

① Find out the location of the product that is difficult to be injected by CAE simulation analysis;

② Increase sensors on the mold, and feedback the information of solute plastic filling to the computer display through the sensors;

③ Visualize the whole injection molding process, and accurately reflect the state of solute plastic filling;

④ Optimize the injection molding process;

⑤ Monitor and evaluate the injection molding machine;

⑥ Detect the injection molding process, judge the goodness of the product and automatically separate the defective products;

⑦ control injection molding, holding pressure switching control, hot runner valve needle control, etc.;

⑧ simplify the mold transfer, has been unchanged (process curves) should be changed (injection molding machine, environment, materials, adjusting personnel, auxiliary machinery, etc.);

⑨ production data recording, archiving, analysis; ⑩ injection plant big data management.

Validation results

(1) The experiment proves that by introducing sensors into the mold, rapid machine adjustment, monitoring production stability, and automatic screening of defective products can be realized. The specific reasons for the generation of nonconforming products can be quickly identified and solved.

(2) Real-time monitoring of the actual pressure state in the mold cavity during injection production.

(3) Monitor the distribution of cavity pressure and determine its regularity for injection adjustment and stable production.

(4) The stability of the injection pressure is similar to that of the qualified products in different machines.

(5) has accumulated experience in the use of sensors, for the subsequent solution of mold production problems to provide reference.

Conclusion

By using the pressure sensor to monitor the injection pressure, it can realize quick machine adjustment, reduce burr, stabilize production, improve the qualified rate of products, so that the qualified rate of products reaches more than 99%, and provide reference for the development of similar products.