Cost reduction, time to market, product quality improvement, and the support of technological evolution are all critical issues that software companies must face to be competitive in today?s market. Software Product Line Engineering (SPLE) is one approach to address these issues. This paper presents the experiences of Mondragon Sistemas de Informaci?n, a small-to-medium company, of introducing software product line engineering. The paper describes reports the benefits generated by deploying a software product line for developing Programmable Logic Controllers? programs for metal processing lines as well as lessons learned.