Quality is a measure of how close a product is to a certain standard. Standards may relate to time, materials, performance, reliability, or quantifiable (objective and measurable) characteristics. Products will be declared quality if they comply with predetermined standards. PT XYZ is a manufacturing company that produces cables. During the production process, the quality of the cable is constantly monitored, and the cables will go through a final test carried out by the Quality Assurance department, which includes electrical tests and dimensional tests. The production process is certainly not free from mistakes and can result in defective products. Quality control must maintain the product quality using the DMAIC method, which consists of five stages: defining, measuring, analyzing, improving, and controlling with the object of observation is a low voltage cable. The purpose of this research is to find the cause of the defects and reduce the percentage of existing defects. The analysis results show that the biggest causes of the defect products are short cables and rough/wound/torn insulation with a DPMO calculation result is 279.4336811 and a sigma level that is equal to 4.951 sigma.