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PurposeThe purpose of this study is to examine whether there is a difference between ISO 9001 certified and non‐certified companies in terms of performance.Design/methodology/approachIn order to determine the effect of certification on performance, motivations for certification and companies' quality practices have been considered as factors. A survey was carried out with 255 small to medium‐sized enterprises (SMEs) in Turkey. The differences between certified and non‐certified companies in terms of performance and quality practices were examined by one‐way analysis of variance (one‐way ANOVA).FindingsThe results showed no statistically significant difference between certified and non‐certified companies in terms of performance. Certification showed no direct effect on performance. Also it has been claimed that the quality practices of certified companies was higher than those of non‐certified companies, according to results it is showing a statistically significant difference, in the 0.01 level of significance. However, higher quality practice does not necessarily mean higher performance. Motivations for certification also affect performance; it was found that companies that are internally motivated for certification have partially higher performance than companies externally motivated.Originality/valueTo the authors' knowledge, this is the first study examining the effect of the ISO 9001 quality management system on the performance of SMEs in Turkey.

The problem dealt with in this study has job sequence-dependent setup times under suitable machine constraints and due date constraints. The performance criterion for this problem is to minimize the sum of makespan and total tardiness. In the literature, an application of ABC algorithm for the problems which includes all the properties that we have dealt has not been discussed. Because there is no appropriate test data, a real-life data was collected from a factory. In this study, a new approach has been proposed for the solution with meta-heuristics of unrelated parallel machine scheduling problems which is a combinatorial problem. This new neighborhood approach provides different machine assignments for every candidate job sequences. This approach is used by integrating into ABC and GA. To evaluate the performances of the algorithms, the real-life problem was solved by using ABC and GA algorithms under similar conditions. It was found that all jobs can be completed in two shifts without the need for a third shift. Computational results show that ABC algorithm has better performance than GA.

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