The purposes of this study are, first, analyzing why the Capability Process (Cpk) index of Drop Impact Resistance (DIR) does not meet the customer requirement or below 1.33, second, finding out what improvements should be made to make it meet the specifications. Statistical Process Control (SPC) is a method used in this research with supporting other tools such as Cause and Effect Diagrams (CED), Nominal Group Techniques (NGT) and why, what, where, when, and how (5W1H) method. After improvement was made, the results of the study were satisfactory, the average of DIR test was increased by 26.21% i.e. from 20.41 cm to 25.76 cm, standard deviations reduced from 1.80 to 1.48, and the potential Cpk increased significantly from 0.48 to 1.79. The SPC supported by other statistical tools was effective and efficient to improve quality, so the process statistically can be categorized as in control. At the end of this research, the further discussion is still needed to maintain what has been achieved and also to make the research even better. It is recommended for further researchers to examine the chemical composition of aluminum M1 alloy 3104 influence on the strength of the drop impact resistance and to analyze data. It is recommended to integrate or combine SPC with Six Sigma or Engineering Process Control (EPC).