The dimensional quality of sheet metal assembly with welding-induced internal stress

Abstract

The present paper is the first to propose a minimum stress criterion for the minimum dimensional variation during sheet metal assembly. The weld sequence affects the dimensional variation owing to the welding process. A case study illustrates the minimum stress criterion on dimensional variation. This paper proposes a generic design criterion for sheet metal products and processes that would produce minimal stress-induced dimensional variation for spot-welded sheet metal assemblies. The process design proposes a minimum strees build-up by using the ‘sheet metal ironing welding technique’ in the weld sequencing design. The product design proposes a minimum stress build-up design criterion to manage the accumulation of stress. The proposed product and process design methods enable automotive body design engineers to create a quality product with minimum dimensional variation caused by the manufacturing stress within the body-in-white structure. Moreover, this facilitates the industry's objective of building a high quality automotive body with minimum stress. This is an important factor in contributing to the superior quality of the body panel fits. It also helps to reduce the quality-related warranty costs. This paper primarily focuses on the development of a joint design guideline by exploring the relationship between the dimensional variation and the stress build-up. First, the automotive assembly process design will be introduced. A simple analysis of a one-dimensional assembly is produced. A three-dimensional structural analysis of a box assembly is investigated for the effect of stress build-up within a structure on the dimensional instability or variation. Then a three-dimensional finite element analysis of an assembly with weld sequencing of two imaginary parts is produced. An experimental industrial trial has confirmed the validity of the simulation methodology. Then a welding sequence design guideline is produced based on the previous simulation result, followed by a joint design guideline to help improve the design of dimensionally robust design.

Quality and productivity improvement through spot welding process optimisation in automobile body shop

“…Body assembly sheet metal dimension variations due to various welding sequences were studied and the author has recommended few design guide lines to the sheet metal designers to select the weld sequences to set appropriate Geometry. Design guide lines are provided to make stress free welding and stress relief patterns for different joineries (Shiu et al, 2000). The dimensional variation effects due to positional variation of spot weld was studied by Mali and Inamdar (2012) and he has concluded that, "spot weld position variation control is essential to maintain proper assembly dimensional accuracy".…”

“…There have been more than one research conducted in the past on the analysis of body assembly dimensional variations; and the two major focused areas are: 1 assembly processes 2 resistant spot welding process. Shiu et al (2000) stated that "the dimensional stability increases the productivity and reduces the quality related problems. Welding process failure and dimensional variation are some of the major factors for decrease in productivity".…”

Joining in Nonrigid Variation Simulation

“…There is some research done on optimization of spot welding sequences. Shiu et al [26] investigate the relationship between stress build-up due to different spot welding sequences and the resulting dimensional variation. General guidelines for welding sequences are also Figure 7.…”

An assessment of the robustness of gauge repeatability and reproducibility analysis in automotive components

“…In the automotive industry, body assembly is a crucial operation to evaluate the overall quality of body-in-white, typically in improving gap evenness and flushness [43][44][45][46][47]. It is also very important to achieve acceptable gauge R&R results from these types of panels because of their non-rigidity [44,48].…”