Scrap rate
Scrap rate measures the percentage of materials or products that are discarded because they fail to meet specifications and cannot be reworked or salvaged. High scrap rates indicate process problems, quality issues, or material inconsistencies that waste resources and increase effective unit costs.
Examples
Manufacturing scrap: A machining operation produces 5% scrap due to dimensional nonconformances, tool wear, and material defects. This 5% scrap rate means material, labor, and machine time for those units are lost.
Supplier scrap factor: A supplier's quote includes an 8% scrap factor in material cost, reflecting expected waste from their manufacturing process. Understanding this factor enables discussion of whether scrap reduction could enable price improvement.
Material yield vs scrap: A stamping process uses sheet metal, producing parts and scrap from the remaining material. Material yield is the percentage of input material that becomes product; the complement is scrap, which may have salvage value as recycled material.
Definition
Scrap rate directly affects product cost. If scrap rate is 10%, producing one good unit requires 1.11 units of material input. This material premium compounds through the supply chain, affecting landed cost and profitability.
Scrap differs from yield loss in terminology: yield typically refers to process output (percentage good), while scrap rate refers to the waste (percentage bad). They're complementary measures: 90% yield means 10% scrap rate.
Scrap causes include process variability, equipment problems, material quality issues, operator errors, and design limitations. Reducing scrap requires understanding its causes and addressing root causes rather than just accepting waste as normal.
Scrap has value implications beyond direct material cost. Floor space for scrap handling, disposal costs, and the environmental impact of waste all matter. Some scrap can be sold for salvage or recycling, partially offsetting the loss.
Frequently asked questions
What is scrap rate?
Scrap rate measures the percentage of materials or products discarded because they fail to meet specifications and cannot be reworked or salvaged. High scrap rates point to process problems, quality issues, or material inconsistencies that waste resources and raise effective unit costs.
How does scrap rate affect product cost?
Producing one good unit at a 10 percent scrap rate requires 1.11 units of material input, and that material premium compounds through the supply chain into landed cost and profitability. Suppliers also build scrap factors into quotes: an 8 percent scrap factor in material cost is a discussable line item, since scrap reduction could support price improvement.
What is the difference between scrap rate and yield?
Yield typically refers to process output, the percentage good, while scrap rate refers to the waste, the percentage bad. The two are complementary measures: 90 percent yield means a 10 percent scrap rate.
What causes scrap in manufacturing?
Typical causes include process variability, equipment problems, material quality issues, operator errors, and design limitations. Reducing scrap requires understanding and addressing those root causes rather than accepting waste as normal, since the lost units carry material, labor, and machine time with them.
Does scrap have any residual value?
Some scrap can be sold for salvage or recycling, which partially offsets the loss; the material left over from a stamping process is a common example. Scrap also carries costs beyond the material itself, including floor space for handling, disposal costs, and the environmental impact of waste.
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