Lean practices are known to increase operational performance. Previous research has identified critical success factors for implementing lean practices. This research aims to examine the extent to which success factors are critical for various degrees of lean practice implementation. Using multiple-respondent self-assessments from 33 Dutch manufacturing small and medium-sized enterprises (SMEs), we conducted a Necessary Condition Analysis. Our findings indicated that the criticality of success factors is progression dependent. In the initial stages of the lean journey, SMEs could improve their lean practices in a bottom-up manner through local factors such as a learning focus, improvement training and support congruence. When lean practices are more advanced, some company-wide factors must be present: top management support, a shared improvement vision and a supplier link. Our findings question the universality of success factors such as strategic involvement and indicate the need for a more dynamic model of lean implementation.

Purpose-This paper examines whether and when improvement routines are critical for implementing lean practices in small-and medium-sized manufacturing enterprises (SMEs). Improvement routines such as "employees initiate and carry through improvement activities" are generally seen as an important means to achieve the full benefit of structural lean interventions. Womack and Jones (2003) suggest that these improvement routines should be developed as the company becomes more experienced in lean. The purpose of this paper is to explore the relative importance of individual improvement routines at various degrees of lean practice implementation. Design/methodology/approach-A Between-Case Comparison Analysis (Dul and Hak, 2012) and a Necessary Condition Analysis (Dul, 2016) were performed on self-assessment data from 241 respondents at 38 Dutch manufacturing SMEs. Findings-The importance of improvement routines depended on the degree of lean practice implementation. Lean practices could be implemented to some extend without developing specific improvement routines, yet certain routines were necessary for more advanced implementations of lean. These routines relate to employees conducting shared improvement activities and in the most advanced cases to aligning different improvement activities. Originality/value-These findings question existing lean implementation models that neglect improvement routines and indicate the need to integrate improvement routines into every lean transformation for it to be sustainable.

PurposeBuilding on the routine dynamics literature, this paper aims to expand our philosophical, practical and infrastructural understanding of implementing lean production. The authors provide a process view on the interplay between lean operating routines and continuous improvement (CI) routines and the roles of different actors in initiating and establishing these routines.Design/methodology/approachUsing data from interviews, observations and document analysis, retrospective comparative analyses of three embedded case studies on lean implementations provide a process understanding of enacting and patterning lean operating and CI routines in manufacturing SMEs.FindingsIncorporating the “who” and “how” next to the “what” of practices and routines helps explain that rather than being implemented in isolation or even in conjunction with each other, sustainable lean practices and routines come about through team leader and employee enactment of the CI practices and routines. Neglecting these patterns aligned with unsustainable implementations.Research limitations/implicationsThe proposed process model provides a valuable way to integrate variance and process streams of literature to better understand lean production implementations.Practical implicationsThe process model helps manufacturing managers, policy makers, consultants and educators to reconsider their approach to implementing lean production or teaching how to do so.Originality/valueNuancing the existing lean implementation literature, the proposed process model shows that CI routines do not stem from implementing lean operating routines. Rather, the model highlights the importance of active engagement of actors at multiple organizational levels and strong connections between and across levels to change routines and work practices for implementing lean production.

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