Three-dimensional freeforming technology has revolutionized the field of plastic forming in recent decades. This innovative technique combines advanced multi-axis servo control with plastic forming processes, enabling the one-time integral forming of complex components with high precision and efficiency. It has found extensive applications in aerospace, rail transportation, automotive, petrochemical, and construction industries.
The aim of this study was to investigate the three-dimensional freeforming technology for the production of a complex aluminum alloy skeletal structure used in the front window glass installation of a certain type of high-speed train locomotive. The skeletal structure, composed of JIS H 4100A5083 H112 AL-Mg deformed aluminum alloy extruded solid profiles, presented significant challenges due to its intricate three-dimensional geometry.
To reduce construction complexity and improve production efficiency, the manufacturing process was divided into several stages. First, the front window skeletal structure was segmented into two parts. After three-dimensional forming, the segments were assembled, welded, and subjected to mechanical processing for gap fitting. The individual component length was approximately 4500mm, with the segmented lines located at both ends. Specialized molds were designed and fabricated based on the solid extrusion profile section of the CRH2 locomotive’s front window skeletal structure. These molds were installed on the equipment control head, with the notch shape on the mold aligning with the bent profile section. This allowed the profiles to be smoothly and accurately bent during the forming process. To enhance formability and precision, the aluminum alloy extruded profiles were treated to achieve the mechanical properties specified by the H112 standard.
Process Observations and Control
The accompanying diagram illustrates the process and the main body of the mold during the three-dimensional forming of the segmented front window skeletal structure using extruded profiles and the three-dimensional freeforming system. It provides insight into the installation and configuration of the specialized molds, the interaction between the profiles and the molds during bending, and the control of the forming process based on the desired geometry.
Measurement and Quality Assurance
During the fabrication process, a manual coordinate measuring device was used to measure and collect data from the test specimens. The measurement data was imported into the control system and compared with the three-dimensional models using analysis software. By refining the control program, the dimensional accuracy of the three-dimensional freeforming of solid aluminum profiles was improved, resulting in the production of qualified components.
Through this technical research, it has been demonstrated that three-dimensional freeforming technology can meet the requirements for one-time integral three-dimensional forming of both hollow and solid complex-axis and complex-section aluminum alloy extruded profiles with high precision.