Development of Time and Area Dependent Forced Lubrication Technology in Hydroforming

We developed a forced lubrication technology that supplies high-pressure lubricant between a die and a tube during hydroforming process (Japanese patent application number: 2021–143672). In this study, we performed experiments on time- and area-dependent forced lubrication during tube hydroforming based on this technology. We obtained the following findings about time-dependent lubrication: 1) The thickness distribution can be controlled by lowering the lubricant pressure during forming. 2) Increasing the internal pressure at which the lubricant pressure is lowered tended to reduce the thickness in the vicinity of the lubricant supply port (center of the flat area) and increase the thickness of corners. In other words, there was a trade-off between the thickness of flat areas and corners. 3) Controlling the lubricant from the start to the middle stage of forming is important in controlling the thickness distribution. We obtained the following finding about area-dependent lubrication: 4) Lubricant flow can be held back by providing a level difference of 0.1 mm–0.2 mm at a position 5 mm–15 mm from the lubricant supply port. Product surface quality is improved when the level difference is small. These time- and area-dependent forced lubrication technologies will contribute to improved design freedom of products such as automotive parts. They will also be effective in reducing process and product design rework because they allow product performance to be controlled using manufacturing parameters.