: PT. Denapella Lestari is a company engaged in metal stamping, machining parts, and the engineering industry. This company products car and motorcycle parts. PT. Denapella Lestari itself continuously checks the products produced, one of the products of PT. Denapella Lestari is a Ring CVT. However, the production process cannot be separated from errors that cause defective products and do not meet general standards to be sent to customers. Therefore, quality control analysis is needed to maintain the quality produced using the DMAIC and Root Cause Analysis method consisting of five stages: define, measure, analyze, improve, and control. One of the problems that exist in the company is the number of defective Ring CVT products, especially in 2020, as many as 2262 pieces with 14 types of defect and are the value of 4.50 sigma.