Scrap and rework in manufacturing are generally seen as an unavoidable and expensive part of doing business. But with careful planning, manufacturers can minimize the bottom-line impacts of materials costs and wasted labor.
But first, some definitions: “scrap” refers to materials left over from product manufacturing and may range from metal shavings to whole parts. Scrap is different from “waste” in the sense that it is recyclable and therefore has some monetary value. “Rework” happens when an inspected part is found to be non-conforming, defective, or failed and must be disassembled, repaired, replaced, or reassembled.
1. Minimize Human Error
Damage to parts can occur during transit or whenever manual handling occurs, so it’s a good idea to use automation to limit physical contact with parts as much as possible – particularly delicate parts that will be damaged if dropped.
Mike Lynch, the founder of CNC Concepts, points out that “excessive scrap-causing mistakes should be a signal that your people need more training.” Better training reduces the chances of human error; well-trained teams are more likely to use software applications correctly and will not have to go through as many trial-and-error stages.
2. Improve Change Management and Communication
Scrap is often the outcome of poor or incomplete communication about production changes. For example, if a decision is made by the engineering team to change a part in order to improve the overall product, this needs to be communicated rapidly and clearly not only internally but also throughout the supply chain. Failure to do so may result in the company being left with a stockpile of the old part, which may be non-cancellable and non-returnable and will have to become scrap.
3. Document Everything
Standard operating procedures (SOPs), CAD drawings, and bills of materials (BOMs) should all be documented digitally and filed correctly to ensure scrap and rework aren’t caused by someone referring to an outdated document. Documentation is a key part of change management, particularly in terms of information sharing and version control.
Arena Solutions, a PLM software provider, advises manufacturers to create and maintain a BOM for each product as CAD drawings alone do not capture important information such as design changes after production has begun. Third-party contract manufacturers should be provided with a complete suite of documentation including BOM records, CAD sheets, details of changes, datasheets, and work instructions.
4. Optimize Manufacturing Processes
Perhaps the most important part of the process in terms of its potential to generate scrap is the design phase. Good communication and collaboration between engineers, production team members, and materials suppliers are key, along with the use of simulation software to minimize the number of prototypes required.
Regular inspection of the manufacturing line is critical to understanding where errors are introduced. Ill-fitting, damaged, or poorly-made tools can be a source of scrap, not to mention safety risks. Ensure you are using the right tools, right techniques, and right materials.
Use design practices that minimize scrap. For example, “nesting” in metal stamping means having more than one part type per die by inserting smaller parts into what would have otherwise been the scrap areas. Stamping shops can use offal dies (otherwise known as recovery dies) that use scrap to produce other parts, stitching or fastening scrap together to create a continuous strip.
5. Have a Plan for Scrap
It’s important to have a plan in place for those times when scrapping is unavoidable. Ask yourself if scrap can be reused or recycled internally before exploring scrap recycling options outside your organization.