Six Sigma Methodology (SSM) for developing new process or product consists of five steps: a) define,b) measure, c) analyze, d) design and e) verify (DMADV). SSM allow developing or improving processes that measure how many defects or failures any process has, in order to find ways to systematically eliminate them. This paper focuses on implementing DMADV to compare the performance of two designs of an experimental heat transformer. We have analyzed the temperature behaviour during the heat transformer operation. The results have been used as information to apply the SSM as follow: a) define; using statistical process control (SPC) to establish whether the temperature is “in control or out of control”. The objective is found out the opportunity areas. b) measure; we define initially a tolerance error of ±0.5 % over temperature as operation process defect. Then, the process behaviour was monitored in two stages: 1) from the first performance, data was recollected to be analyzed and, 2) another performance was monitored after implemented improvements (the objective is to compare the results). c) analyze; the result was examined in order to calculate the process capability (Cp) and the process capability index (Cpk). d) design; in this step we have used average control charts, as tools for evaluating the first design to respect the second. Finally, e) verify; the objective of the verify step is found out if the second design of the heat transformer is better than the first one. The results show that the second design of the heat transformer is better than the first design, because it has an enhanced process operation.