Scrap Rate
Scrap rate is the percentage of material that is wasted during a manufacturing process and cannot be used in a finished product.
Scrap rate is a key performance indicator (KPI) that measures manufacturing inefficiency. It quantifies the amount of raw material that is discarded or rejected during production. This material cannot be reworked or repaired, representing a direct loss of resources.
Tracking scrap rate is important for cost control and quality management. Every scrapped part carries the cost of its raw materials, the labor invested, and the machine time used. A high scrap rate directly reduces a factory's profitability. It can also indicate underlying problems with equipment, processes, or operator training.
On the shop floor, supervisors monitor scrap rates to identify issues in real time. For example, a sudden increase in scrap at a CNC machining station could signal a worn tool. In an injection molding facility, tracking scrap helps diagnose problems like incorrect temperature settings or material contamination. This data allows teams to take immediate corrective action.
Manufacturers implement scrap tracking by physically separating and counting or weighing rejected parts at each production stage. This data is entered into a Manufacturing Execution System (MES) or a quality management system (QMS). Analyzing this information over time helps identify trends, perform root cause analysis, and focus continuous improvement efforts.
A metal fabrication shop uses 1,000 kilograms of sheet steel for a production run. After shearing and stamping, 85 kilograms of material are left as unusable offcuts and defective parts. The scrap rate for this run is (85 kg / 1,000 kg) * 100, which equals 8.5%.
What is a good scrap rate for a manufacturer?
A good scrap rate varies by industry and process. Precision industries like medical device manufacturing may target rates below 1%, while other sectors might consider 3-5% acceptable. The primary goal is always continuous reduction.
How is scrap different from rework?
Scrap is material that is permanently discarded because it cannot be repaired. Rework is the process of correcting a non-conforming part so it meets quality specifications.
What are the most common causes of a high scrap rate?
Common causes include incorrect machine setups, worn tooling, poor raw material quality, and operator error. A systematic root cause analysis can identify the specific drivers.
How can we reduce our scrap rate?
Begin by accurately tracking scrap to find which processes generate the most waste. Use root cause analysis tools to find the source of the problem. Implement corrective actions like improved operator training, statistical process control (SPC), or a preventive maintenance schedule.
Does scrap rate include planned material waste like offcuts?
Yes, the calculation typically includes all material that does not become part of the final product. This includes both planned waste (e.g., skeletons from a stamping press) and unplanned waste (e.g., defective parts).
First Pass Yield
First Pass Yield is the percentage of products that meet quality standards after a single process step, without needing any rework or repair.
Root Cause Analysis
RCARoot Cause Analysis (RCA) is a structured method used to find the underlying reason a problem occurred to prevent it from happening again.
Cost of Goods Sold
COGSCost of Goods Sold (COGS) represents the direct costs of producing the goods sold by a business.
Quality Management System
QMSA Quality Management System (QMS) is a set of documented policies, processes, and procedures for achieving consistent product quality.
Continuous Improvement
Continuous improvement is the practice of making small, ongoing changes to manufacturing processes to increase efficiency and quality.