Injection mold trial management
Injection molding trials are a critical step in new product development or mold commissioning. Their purpose is to verify mold design rationality, determine optimal process parameters, and test whether the plastic part meets quality requirements, providing a reliable basis for mass production. Mold trial management involves the systematic planning, organization, coordination, and control of the entire process, ensuring efficient and orderly trials and avoiding the time and cost waste caused by improper trials. For example, when a new energy company was developing an automotive battery casing, due to disorganized mold trial management and unclear trial objectives and processes, it took as many as eight trials to meet qualified standards, taking two months longer than planned and delaying the product’s launch.
The preparation work before the mold trial is the basis of the mold trial management and directly affects the mold trial effect. First of all, the mold trial objectives need to be clarified, such as verifying the mold structure, optimizing process parameters, detecting the size or appearance of the plastic parts, etc., and a detailed mold trial plan should be formulated, including the mold trial time, participating personnel, required equipment and materials, etc. Secondly, the mold should be fully inspected to ensure that all mold components are installed in place, move smoothly, and the cooling system and exhaust system are working properly. For example, check whether the guide pins and guide sleeves are well lubricated, whether the ejection mechanism is flexible, and whether the gates and runners are unobstructed. A mold factory did not check the mold cooling water circuit before the mold trial, resulting in uneven cooling of the plastic parts during the mold trial, resulting in warping and deformation. The mold trial had to be suspended for maintenance, wasting 4 hours.
Raw material preparation and process planning are also crucial tasks before mold trials. Qualified raw materials must be prepared according to the part design requirements and thoroughly dried (for example, PC materials must be dried at 120°C for at least 4 hours) to prevent bubbles in the molded part caused by excessive moisture content. Furthermore, a preliminary process parameter plan, including melt temperature, mold temperature, injection speed, injection pressure, and hold time, is developed based on the material properties and mold structure. Multiple parameter combinations are prepared for commissioning. During a mold trial at a power plant, the POM raw materials were not thoroughly dried, resulting in numerous bubbles in the molded part. The raw materials had to be re-dried before the mold trial, increasing mold trial costs.
Data recording and monitoring during the mold trial process are core to mold trial management. A dedicated person should be assigned to record various parameters during the mold trial, such as actual injection pressure, temperature, and time, as well as the quality of the plastic part (such as dimensions, appearance, and mechanical properties). Any problems (such as flash, missing material, and sink marks) should be described in detail and photographed for archiving. Furthermore, mold operation status should be monitored in real time, such as for abnormal noises, oil leaks, or jamming, to ensure mold safety. During a mold trial, a precision instrument manufacturer failed to record process parameters promptly, making it impossible to trace the cause of the part’s dimensional deviations. Consequently, the mold had to be repeated three times, increasing mold wear and material consumption.
Post-trial analysis and summary are key aspects of trial mold management, and their results directly guide subsequent production. After the trial mold is completed, technical personnel are organized to analyze the trial mold data, assess mold performance (such as smooth filling and proper venting), and the rationality of process parameters. Improvement measures are then proposed based on the part inspection results. For example, if a part exhibits sink marks, the holding pressure may need to be increased or the holding time extended. If flash is present, the injection pressure may need to be reduced or the mold clearance adjusted. A mobile phone casing manufacturer, through analysis of trial mold data, identified the optimal melt temperature of 230°C and an injection speed of 50 mm/s. The resulting mass production process has increased the part qualification rate from 75% during the trial mold to 98%.
The preparation and filing of mold trial reports is the finishing touch to mold trial management, providing a basis for subsequent production and mold improvements. The mold trial report should include the purpose of the mold trial, the mold trial equipment and materials, mold trial parameters, plastic part inspection results, existing problems and solutions, and include relevant images and data charts. The report must be signed and confirmed by relevant personnel before being archived for easy reference and traceability. An automotive parts company has established a comprehensive mold trial report filing system. When quality issues arise in subsequent batch production, they can quickly identify the cause by reviewing the mold trial report, reducing downtime from 8 hours to 2 hours. Furthermore, mold trial management should also include mold trial cost accounting (such as raw material consumption, equipment depreciation, labor costs, etc.) to provide a reference for product cost control.
