A complete tolerance charting system in assembly

Abstract

The process of assigning tolerances in product design, more often than not, will a ect the functionality and cost of the product. An unnecessarily tight tolerance leads to higher cost while an excessively loose tolerance may lead to malfunctioning of the product. Traditionally, this important phase of tolerance allocation is done intuitively to satisfy design constraints based on the skills and experience of the designers. In most cases, the result is not optimum and modi® cation of the allocated tolerances is required. After the tolerances are allocated, the next step is to ensure that the assembly can be manufactured with the resources available. This can usually be veri® ed by performing tolerance charting for the assembly.However, if the result shows that the blueprint (B/P) tolerances speci® ed are too tight, the entire process of tolerance allocation and tolerance charting has to be repeated. This paper presents an e cient method of integrating the process of allocating optimum B/P tolerances in product design with the process of tolerance charting in process planning. This method ensures that the assembly is manufactured with optimum working dimensions and tolerances and yet satis® es all the assembly requirements. Two models are constructed. One based on process sequence and another based on the relationship between each component. Using the models coupled with unique algorithms, sets of linear equations are formulated based on the design constraints and assembly requirements. With another set of equations derived in terms of the process capabilities, the optimum B/P tolerances, working dimensions and tolerances can be determined by solving the equations.

Simultaneous optimal selection of design and manufacturing tolerances with different stack-up conditions using genetic algorithms

“…These tolerances are called manufacturing tolerances. Authors including Ahluwalia and Karolin (1984), Irani et al (1989), Mittal et al (1990), Ji (1993a, Ngoi and Teck (1993), Ngoi and Fang (1994), Ngoi and Tan (1995), Ngoi and Seow (1996), Jeang (1998), Ngoi and Ong (1999) and Li et al (2000) have researched this area considering different aspects with varying approaches.…”

Framework of an integrated tolerance synthesis model and using FE simulation as a virtual tool for tolerance allocation in assembly design

“…Feature-based tolerance charting methodology was also investigated to evaluate the different ways of tolerance allocation [14,15]. Comparative evaluation of composite tolerance specifications in robotic assembly [16], influence of sequence in assembly parts in tolerance chain detection [17], tolerance charting [18] and influence of design process in assembly were also investigated [19]. Aspects such as design for quality, quality improvement and cost reduction, asymmetric quality losses, charts for optimum quality and cost, minimum cost approach, cost of assemblies, development of cost tolerance models [20][21][22][23][24][25], have been explored in the quality area of tolerance synthesis.…”

An alternative method to tolerance transfer for parts with 2D blueprint

“…Other working lines regarding tolerances are related to tolerancing algebra (Hong and Chang 2003), tolerancing in assembly (Jayaraman and Srinivasan 1989, Ngoi and Cheong 1998, Ngoi and Ong 1999, kinematic tolerance analysis (Joskowicz et al 1997), tolerance information models (Kulkarni and Pande 1996, Shah and Yan 1996, Serré et al 2001, Zhou et al 2002 and quality and cost tolerance chart optimisation (Jeang 1998).…”