Main content of Digital Mold Tryout
Digital Mold Tryout is not a popular discourse in the injection industry, but a production trend. It is changing the mindset of the injection molding industry. How to correctly determine the process and produce stable quality products based on scientific data will be the future standards of the injection molding industry. In the process of product development and production, to achieve the goal of “T0 Production” after the mold is completed, the prerequisite is that the injection processing conditions for the designed mold must be grasped at the early stage of the design, before the mold is put on the actual machine. Before injection, it is necessary to use scientific methods to estimate and evaluate the appropriate initial injection molding conditions, and the estimated processing conditions are almost the same as the final mass production conditions. Only in this way can we predict the potential problems and optimize the process in the early stages of design. The technical content of Digital Mold Tryout mainly includes the confirmation of the conditions and parameter settings in the injection molding process. The important process parameters include:
(1) Injection molding machine selection – Use scientific theory to estimate clamping force to determine suitable clamping force tonnage; Actual injection to verify reasonable clamping force setting value experiment; Estimate injection volume to determine suitable screw size; Confirm the difference between the set injection speed value and the actual response value of the machine.
(2) Plasticization conditions – Estimate the amount of melt with considering the melt density; Estimate the residence time in the barrel to determine the screw speed (rpm).
(3) Injection setting – Determine an appropriate injection speed by U-shaped curve experiment; Determine VP switching point; Determine multi-segment flow rate profile; Estimate the pressure loss in each area of the mold; Evaluate whether the flow pattern is balanced.
(4) Packing setting – Verify the gate freeze time to determine proper packing time and packing pressure.
(5) Cooling setting – Estimate the required cooling time by scientific theory.
(6) Other process conditions – Estimate the volume of hopper; Estimate the required flow rate of coolant.
Fig 1. Optimization of injection speed
In addition, in the actual machining process, some external resources are needed to obtain the actual machine response data. For example, CAE mold flow analysis and verification. We can observe the flow pattern in CAE filling analysis and compare with the actual short shot melt front. We can interpret the speed/pressure response curve of the injection machine and compare the difference between the set conditions and the response data of the actual machine. We can interpret the response statistics of the injection machine to observe the stability of the injection machine under continuous production. At the same time, we can conduct real-time detection of temperature and pressure data in the mold by using infrared thermal imaging equipment to measure the temperature distribution on the mold surface, and use in-mold pressure sensor to measure the pressure changes at a specific position in the mold.
Injection molding is a science rather than art. The development process must be based on facts and scientific data. Too many human subjective factors will affect the correct judgment. Traditionally, most mold manufacturing units focus on mold design, instead of looking at the molding process from the perspective of plastic flow, while the molding site focuses on the setting parameters of the molding machine. However, the actual performance data of the four control factors (actual speed, temperature, pressure, time) is the key to the success of the product. Appropriate technical training and certification for enterprises allow to carry out continuous professional talent development and allows enterprises to accumulate and inherit core technologies and internalize them into technical knowledge.