Abstarct: ABSTRACT Friction stir welding (FSW) is a solid-state joining process as well as a proven technique for mextals welding that has recently been applied to polymers with favorable results. In this research, the process of designing, manufacturing and testing of FSW equipment including fixture, tool, thermal shoes equipped with cartridge elements and other components for the butt welding of Teflon plates with the possibility of placing alumina microparticles are presented. For this purpose, the response surface methodology (RSM) and Box-Behnken design (BBD) were chosen as the experimental design method. In the following, statistical analysis of the data obtained from tensile, hardness and impact tests was carried out in order to investigate the effect of input variables (tool rotational speed, welding speed and size of the reinforcing microparticles) on the mechanical properties of the welded joints, and the regression equations were extracted separately. Also, the optimal conditions of the input variables to achieve desirable mechanical properties were extracted using the desirability function. The SEM images confirmed the proper distribution and dispersion of alumina microparticles in the welded zone. The ANOVA results showed that the competence of the regression models in order to predict the response parameters (maximum tensile force, maximum engineering stress, MHD parameter and impact strength) can be confirmed baxsed on the monitoring of normal probability and residuals diagrams. The maximum tensile force and impact strength that can be tolerated by the welded joint (rotation speed: 1000 rpm, welding speed: 50 mm/min and microparticle size: 20 microns) are 11.57% and 16.22% higher than the raw Teflon (unwelded), respectively. In addition, the tool rotational speed, the product of the microparticle size and the rotational speed, and the second-order exxpressions of the microparticle size, rotational speed, and welding speed were effective on the MHD parameter (deviation from the microhardness of the baxse Teflon) and were recognized as the significant exxpressions. On the other hand, the values of the desirability function resulting from the optimization processes for maximum tensile force, maximum engineering stress, MHD parameter and impact strength were obtained as 88.3%, 100%, 100% and 100% respectively. In the following, verification tests confirmed the values of the maximum tensile force and impact strength resulting from the optimization process with a difference of 9.61% and 12.73%, respectively.