  Citation: Apaolaza, U.; Orue, A.; Lizarralde, A.; Oyarbide-Zubillaga, A. Competitive Improvement through Integrated Management of Sales and Operations. Sustainability 2022, 14, 2722. https://doi.org/10.3390/ su14052722 Academic Editors: José L. Yagüe Blanco and Vanesa Gladys Lo Iacono Ferreira Received: 3 January 2022 Accepted: 12 February 2022 Published: 25 February 2022 Publisher’s Note: MDPI stays neutral with regard to jurisdictional claims in published maps and institutional affil- iations. Copyright: © 2022 by the authors. Licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license (https:// creativecommons.org/licenses/by/ 4.0/). sustainability Article Competitive Improvement through Integrated Management of Sales and Operations Unai Apaolaza 1, * , Aitor Orue 1 , Aitor Lizarralde 1 and Aitor Oyarbide-Zubillaga 2 1 Mechanics and Manufacturing Department, Mondragon Unibertsitatea, 20500 Mondragon, Spain; aorue@mondragon.edu (A.O.); alizarralde@mondragon.edu (A.L.) 2 Department of Mechanics, Design and Organization, University of Deusto, 48007 Bilbao, Spain; aitor.oyarbide@deusto.es * Correspondence: uapaolaza@mondragon.edu Abstract: Several authors agree on the importance of integrating sales and operations (S & OP) when it comes to improving the management of organisations. Thus, the relationship between S & OP can be critical from a competitive point of view, and therefore strategic. However, most of the literature on this topic focuses on the field of repetitive manufacturing. Consequently, this work aims to enhance the scarce literature related to S & OP in organisations that produce make-to-order (MTO). The present study is an analysis of cases of two industrial companies managed according to the theory of constraints. In both cases, the relationship between sales and operations was initially poor. Their approaches were mainly founded on their experience and intuition, as well as on simple data. The development of a new approach, integrating S & OP, has demonstrated the potential advantages of integrated management. As a result, we have identified some aspects of interest from a managerial perspective. Furthermore, we consider the findings of this study to be relevant to improving the competitiveness of this kind of organisation. Keywords: project management; sales and operations; drum-buffer-rope (DBR); theory of constraints (TOC); demand-driven adaptive enterprise (DDAE); demand-driven MRP (DDMRP) 1. Introduction The evolution of the business environment has led to an increase in both the com- plexity and competitiveness of organisations [1]. Bennet and Lemoine [2] defined the entrepreneurial space as being volatile, uncertain, complex, and ambiguous (VUCA). In these conditions, adaptiveness to change is an essential quality for companies to survive today. Customer satisfaction is a factor that has acquired growing influence in terms of competitiveness, and three aspects define it: product variety, speed and compliance relia- bility [3]. To maintain their competitiveness, companies must improve their competence in these for the long term [4,5]. The sustainable enterprise capital management approach [6,7] suggests, “the faster an enterprise achieves and maintains a balance between its capitals” (namely tangibles, financial capital, structural capital, market capital, human capital, and social capital). Con- sequently, the efficiency of management is a balance between goal achievement efficiency or the “point of balance between capitals” [7]. The authors warn that the search for objectives often hinders the balance between the capitals. So, often, a goal is strived, and only later does the search for the balance between the capitals begin. The demand-driven adaptive enterprise (DDAE) model arose in response to the VUCA environment to provide a complete model for management [8]. It is composed of three components that together cover operational, tactical, and strategic levels of management. The DDAE approach aims to address all three managerial levels consistently through configuration-feedback-reconciliation cycles, and S & OP is a key process within this framework. Importantly, DDAE incorporates a flow-based method for the operational Sustainability 2022, 14, 2722. https://doi.org/10.3390/su14052722 https://www.mdpi.com/journal/sustainability