In production process of thermoformed products, mold needs to be continuously cooled by water to ensure that mechanical properties of parts meet requirements during continuous production process. Pressure, flow rate, and flow rate of cooling water in mold have a direct impact on production efficiency and quality. In order to ensure quality of products produced, water tightness of mold must be effectively guaranteed, flow speed and flow rate in water circulation system need to be monitored. Therefore, mold water tightness needs to be tested during mold assembly process.

Water tightness detection device can simulate state of cooling system during production process, is used to detect water tightness of mold waterway, leak points for plugging, and clean impurities in mold waterway. This device can carry out simulation inspection process in assembly area. It has strong mobility, reduces working hours of press, improves use efficiency of press, makes mold water tightness inspection work site flexible, improves overall work schedule, and shortens assembly cycle.
According to production process requirements, when thermoforming mold enters production line, water pressure of production line is set to 8 MPa. Therefore, during mold assembly process, it is necessary to ensure that there is no water leakage at a pressure slightly higher than this in order to meet production line production requirements.

 

Water test device and mold are independent entities, rectification device is composed of a water storage unit, a control and detection unit, a connection unit, and a mobile unit. Water storage module includes a water tank, a filter screen, and a magnet. Control and detection unit includes a water pump, a throttle valve, a pressure gauge, and a flow meter. Connection unit includes water pipes and quick connectors. Mobile unit includes a flatbed truck that carries entire device. Schematic diagram of device is shown in Figure 1. When module uses device, it needs to be connected to mold through inlet and outlet pipes to form a closed circuit with waterway in mold. Therefore, in early mold design, it is necessary to design corresponding connection port on mold. In actual operation, it is convenient to disassemble and assemble water pipe, quick coupling is designed and installed to realize quick connection with water test device. See Table 1 for functions and specifications of structural components.

In hot forming mold design stage, in order to meet cooling requirements in actual production of mold, in process design, through calculation and simulation, there are specific set values for flow speed and flow rate of mold water circuit. Only on the premise that actual value is greater than or equal to set value, production process of mold and product can meet quality requirements of product itself. Therefore, in order to ensure that simulation state in test is same as actual production state, there is a certain range requirement for selection of pump during manufacturing process of test equipment, pump with flow range to meet demand needs to be selected. Device experiment is shown in Figure 2.
There will be a small amount of metal scraps in water channel during waterway processing of thermoforming mold, and it is difficult to prevent dust and impurities from entering waterway channel during assembly process, which can easily cause water channel with a small diameter to be blocked for a long time and water channel is not circulating, which seriously affects cooling effect of mold in actual production process. Therefore, before mold enters production line for formal production, mold waterway needs to be cleaned to ensure smooth flow of waterway to ensure cooling effect of mold in actual production process.

After connection between device and mold is completed, water pump passes cooling water into mold and applies pressure. Water is sealed into mold by throttle valve [12] to keep water pressure above 8 MPa. After 10 minutes, pressure drop is checked to confirm sealing effect. If pressure drop changes slightly and overall mold has no water leakage, it proves that mold waterway tightness meets production line production requirements; if pressure drops significantly or mold has water leakage, it proves that mold water tightness does not meet requirements.
After device and mold are connected, water pump injects water into mold to form a cooling water system circulation. Electronic flow meter and flow meter on equipment measure flow rate and actual value of water flow to ensure that mold waterway tightness meets process design requirements.
Use aqueous solution with a certain concentration of cleaning agent to circulate in mold waterway, which can effectively bring out oily iron filings and impurities in waterway. A filter screen and an electromagnet device are designed in water tank of device. Filter screen is used to collect non-metallic impurities and large particles of metal impurities, electromagnet is used to collect small particles of metal impurities. After cleaning is completed, collected impurities are cleaned up.
In mold assembly process, because storage site is not fixed, water test device needs to be independent, easy to move and use, small in area. Therefore, a movable unit is added in design, and device can be moved flexibly, so that location of mold watertightness simulation test process becomes flexible, simulation test location can be flexibly selected.

Water tightness detection device can simulate state of cooling water circuit of hot forming mold during production process, is used to detect water tightness of hot forming mold water circuit, leak points for plugging, and clean impurities in mold water circuit. This device can ensure that waterway tightness of thermoforming mold is qualified before entering production line, so that it can be smoothly debugged and produced on production line. In design and manufacturing process, effective use of production capacity of trial-production line press is expanded to the greatest extent, maximize effective use of production capacity of press in trial production line, reduce man-hours for testing water tightness, make location of water testing process flexible, can flexibly select water test location, improve work efficiency of mold water tightness testing, save mold manufacturing costs, and improve the overall work schedule. Device has a wide range of applications. It can be used for waterway tightness testing in mold manufacturing stage, as well as for post-mold maintenance, inspection and testing of mold tightness and maintenance.