In the production process of hot-formed products, the mold needs continuous water cooling to ensure that the mechanical properties of the parts meet the requirements during continuous production. The pressure, flow rate, and flow volume of the cooling water in the mold directly affect production efficiency and quality. To ensure the quality of the products produced, the water tightness of the mold must be effectively guaranteed, and the flow rate and flow volume in the water circulation system need to be monitored. Therefore, the mold's water channel sealing must be tested during mold assembly.

1. Functional Requirements

The watertightness testing device can simulate the state of the cooling system during production, used to detect the watertightness and leaks in the mold's water channels for filling, and to clean impurities in the mold's water channels. This device can perform simulated testing procedures in the assembly area, is highly mobile, reduces press time, improves press utilization efficiency, makes the location of mold watertightness testing flexible, improves overall work progress, and shortens the assembly cycle.

According to production process requirements, when a hot-formed mold enters the production line, the production line sets the water pressure entering the mold's water channel to 8 MPa. Therefore, during mold assembly, it must be ensured that there is no leakage at a slightly higher pressure to meet the production line's requirements.

2. Structure

The water testing device and the mold are independent entities. The entire device consists of a water storage unit, a control and detection unit, a connection unit, and a mobile unit. The water storage module includes a water tank, a filter screen, and a magnet. The control and detection unit includes a water pump, a throttle valve, a pressure gauge, and a flow meter. The connection unit includes water pipes and quick connectors. The mobile unit includes a flatbed cart that carries the entire device. The device diagram is shown in Figure 1. When using the module device, it needs to be connected to the mold through the inlet and outlet pipes to form a closed loop with the water channels in the mold. Therefore, in the early stage of mold design, corresponding connection ports need to be designed on the mold. In actual operation, for convenient disassembly of water pipes, quick connectors are designed and installed to achieve quick connection with the water testing device. The functions and specifications of the structural components are shown in Table 1.

3. Principle

In the hot-formed mold design stage, to meet the cooling requirements of actual mold production, the process design uses calculation and simulation to specify specific set values for the flow rate and flow volume of the mold's water channels. Only when the actual values are greater than or equal to the set values can the mold's production process and products meet the quality requirements of the products themselves. Therefore, to ensure that the simulated state in the test is the same as the actual production state, during the manufacturing of the testing equipment, there are certain range requirements for the selection of the water pump, and a water pump with a flow rate range that meets the requirements needs to be selected. The device experiment is shown in Figure 2.

During the water channel processing of hot-formed molds, a small amount of metal debris will remain in the water channel, and it is also difficult to avoid dust and impurities entering the water channel during assembly. Over time, this can easily lead to blockage of small-diameter water channels, resulting in poor water flow, seriously affecting the cooling effect of the mold during actual production. Therefore, before the mold enters the production line for formal production, the mold's water channels need to be cleaned to ensure smooth water flow and the cooling effect of the mold during actual production.

4. Usage

After connecting the device to the mold, the water pump feeds cooling water into the mold and applies pressure. The throttle valve [12] seals the water into the mold, keeping the water pressure above 8 MPa. After 10 minutes, the pressure drop is checked to confirm the sealing effect. If the pressure drop change is subtle, and there is no water leakage in the overall mold, it proves that the mold's water channel sealing meets the production line's production requirements; if the pressure drops significantly, or there is water leakage in the mold, it proves that the mold's watertightness does not meet the requirements.

After connecting the device to the mold, the water pump injects water into the mold to form a cooling water system circulation. The actual values of the water flow rate and flow volume are measured using the electronic flow meter and flow meter on the equipment to ensure that the mold's water channel sealing meets the process design requirements.

Using an aqueous solution with a certain concentration of cleaning agent circulating in the mold's water channels can effectively remove residual oily iron filings and impurities from the water channels. A filter screen and an electromagnet device are designed in the device's water tank. The filter screen collects non-metallic impurities and large-particle metal impurities, and the electromagnet collects small-particle metal impurities. After cleaning, the collected impurities are concentrated and cleaned.

Because the storage location of the mold during assembly is not fixed, the water testing device needs to be independent and easy to move and use, with a small footprint. Therefore, a mobile unit is added in the design, allowing the device to move flexibly, making the location of the mold water channel watertightness simulation testing procedure flexible, allowing for flexible selection of the simulation testing location.

5. Conclusion

The watertightness testing device can simulate the state of the cooling water channels in a hot-formed mold during production, used to detect the watertightness and leaks in the hot-formed mold's water channels for filling, and to clean impurities in the mold's water channels. This device can ensure that the hot-formed mold's water channel sealing is qualified before entering the production line, allowing it to be smoothly debugged and produced on the production line. During the design and manufacturing process, it greatly expands the effective utilization of the pilot line press capacity, reduces the time spent on mold press testing watertightness, makes the water testing procedure location flexible, allowing for flexible selection of the water testing location, improves the efficiency of mold watertightness testing, saves mold manufacturing costs, shortens the mold assembly cycle, and improves overall work progress. This device has a wide range of applications, suitable for water channel sealing testing during the mold manufacturing stage, and also suitable for later maintenance and inspection of the mold's sealing and maintenance.