Thermoforming and springback suppression mechanism of laser assisted multi-point forming method

Abstract

Multi-point forming (MPF) has unparalleled advantages in forming small-lot parts. However, the method has the disadvantage of large springback, which seriously affects the forming efficiency and accuracy. For this reason, a method of adding a laser into MPF (laser assisted MPF-LAMPF) is proposed. A numerical simulation model of LAMPF is established, and the forming and springback mechanisms of LAMPF are analyzed. In addition, the effects of different temperature values on the forming and springback of LAMPF are investigated. The results show that LAMPF can improve the forming value by 1.6 times and reduce the springback value by 67.3 % compared to the traditional MPF. The plastic zone of MPF is the load zone, and the springback zone is the transition zone and heat source zone. In contrast, the plastic zone of LAMPF is the load zone and heat source zone, and the springback zone is the transition zone. The laser has two roles in the LAMPF. One is that the heat generated by the laser can be directly involved in the plastic forming of the heat source zone so that the heat source zone is transformed from the elastic area to the plastic area. The other is that the laser heat lowers the yield strength threshold of the entire azimuthal section, which results in more elastic strain that can be easily converted into plastic strain. Further elevation of temperature can increase the forming value of LAMPF by a factor of 1.7 and suppress the springback value by 95.6 %. This is because elevating the temperature further expands the plastic strain area in the heat source and load zones and further compresses the elastic strain area in the transition zone. This method presents a new idea of thermally lowering the yield strength threshold to increase efficiency and reduce springback, which can provide a theoretical reference for the research of MPF in the field of thermoforming.