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K. Martinsen et al.
21.1 Introduction
Tolerance Engineering (TE) is the process of specifying allowed variations a.k.a.
tolerances to components and products. This is usually an activity in the product
development phase, with a major goal to ensure interchangeability of parts and to
ensure that the product quality and function will meet the customer demands. The
selected tolerances will, however also impact manufacturing and inspection processes
and thus manufacturing costs. Too tight tolerances “to be on the safe side” regarding
assembly and product function which do not take manufacturing capabilities into
consideration might lead to selection of an over-qualified manufacturing process
leading to more expenses than necessary. In contrast, under-qualified processes could
lead to problems to meet the quality requirements increasing scrap production. Literature reports many examples on this; Zhang (Zhang and Wang 2007) states that “many
parts and products are certainly over-toleranced or haphazardly toleranced, with
predictable consequences”. Singh (Singh 2002) point at the negative effects of inappropriate tolerances of increased cost and lacking product quality. Ali et al. (Durupt
and Adragna 2013) and Krogstie and Martinsen (Krogstie and Martinsen 2013) point
at the costs and efforts to change tolerances at a later stage. Watts (Watts 2007) states;
“all industry is suffering, often unknowingly, of the lack of adequate academic attention on tolerances”. Srinivasan et al. states that tolerancing has been “kept in a high
degree of technical focus” with focus on norms and standards (Srinivasan 2008;
Srinivasan 2012) and thus a lack of attention to organizational challenges.
Nevertheless, there are many different product development methodologies and
approaches where TE are addressed, such as Robust design (Zhang et al. 2010),
Design for Manufacturing (or DfX) (Holt and Barnes 2010; Zhang et al. 1992) as
well as digital twins for TE (Söderberg et al. 2017). A comprehensive listing of
models and management control of product development shows, however, a lack of
focus on TE (Brown and Eisenhardt 1995; Horváth 2004; Richtnér and Åhlström
2010). Moreover, only few of these models take the whole lifecycle of the product
and the concept of circular economy (Wang et al. 2018; Nagel and Meyer 1999)
into consideration. The CIRP keynote by Shu et al. (Shu et al. 2017) do mention
the importance of TE for reduced resource consumption, but on the other hand
is TE only briefly mentioned by Tolio et al. (Tolio et al. 2017) on their keynote
paper on demanufacturing and remanufacturing systems. Umeda et al. (Umeda et al.
2012) does not mention TE or variation management in their keynote on Life Cycle
Engineering. The authors of this paper claims that with a future circular economy
(CE) and increased reuse and remanufacturing of products and components, future
TE models need to reflect on the circularity paradigm. This paper will address this
challenge.
K. Martinsen et al.
21.1 Introduction
Tolerance Engineering (TE) is the process of specifying allowed variations a.k.a.
tolerances to components and products. This is usually an activity in the product
development phase, with a major goal to ensure interchangeability of parts and to
ensure that the product quality and function will meet the customer demands. The
selected tolerances will, however also impact manufacturing and inspection processes
and thus manufacturing costs. Too tight tolerances “to be on the safe side” regarding
assembly and product function which do not take manufacturing capabilities into
consideration might lead to selection of an over-qualified manufacturing process
leading to more expenses than necessary. In contrast, under-qualified processes could
lead to problems to meet the quality requirements increasing scrap production. Literature reports many examples on this; Zhang (Zhang and Wang 2007) states that “many
parts and products are certainly over-toleranced or haphazardly toleranced, with
predictable consequences”. Singh (Singh 2002) point at the negative effects of inappropriate tolerances of increased cost and lacking product quality. Ali et al. (Durupt
and Adragna 2013) and Krogstie and Martinsen (Krogstie and Martinsen 2013) point
at the costs and efforts to change tolerances at a later stage. Watts (Watts 2007) states;
“all industry is suffering, often unknowingly, of the lack of adequate academic attention on tolerances”. Srinivasan et al. states that tolerancing has been “kept in a high
degree of technical focus” with focus on norms and standards (Srinivasan 2008;
Srinivasan 2012) and thus a lack of attention to organizational challenges.
Nevertheless, there are many different product development methodologies and
approaches where TE are addressed, such as Robust design (Zhang et al. 2010),
Design for Manufacturing (or DfX) (Holt and Barnes 2010; Zhang et al. 1992) as
well as digital twins for TE (Söderberg et al. 2017). A comprehensive listing of
models and management control of product development shows, however, a lack of
focus on TE (Brown and Eisenhardt 1995; Horváth 2004; Richtnér and Åhlström
2010). Moreover, only few of these models take the whole lifecycle of the product
and the concept of circular economy (Wang et al. 2018; Nagel and Meyer 1999)
into consideration. The CIRP keynote by Shu et al. (Shu et al. 2017) do mention
the importance of TE for reduced resource consumption, but on the other hand
is TE only briefly mentioned by Tolio et al. (Tolio et al. 2017) on their keynote
paper on demanufacturing and remanufacturing systems. Umeda et al. (Umeda et al.
2012) does not mention TE or variation management in their keynote on Life Cycle
Engineering. The authors of this paper claims that with a future circular economy
(CE) and increased reuse and remanufacturing of products and components, future
TE models need to reflect on the circularity paradigm. This paper will address this
challenge.