Defects Waste in Lean Manufacturing occur when a product is found to have flaws in it after production occurs. The affected parts must be replaced or reworked completely resulting in additional costs, delays and possible safety issues.What is waste in a manufacturing setting? Waste is activity that absorbs resources such as time, money or material that produces no, or negative, business value. This means that waste destroys value by using more resources than should be required, by using resources that produce parts or components that are not useable or by producing end products that are not salable.
In Lean Manufacturing, waste is called Muda, waste in the Japanese language. Two types of waste have been identified, Obvious and Hidden.
Obvious Waste is waste that is easily seen, such as producing too many parts than what is needed, or producing parts which do not meet specifications.
Hidden Waste is work that is necessary to produce a manufactured product that is also work that could be eliminated by using an alternative process or technology to produce product, one which requires less resources.
In our eight part series of the 8 Wastes of Lean Manufacturing, we review each type of waste that has been identified within Lean.
The first form of Waste in Lean Manufacturing we consider is Defects Waste.
An obvious waste in Lean Manufacturing is defects. Defects include parts, assemblies or products that don’t meet specifications and therefore are unusable or that require rework. Defects are often one of the most costly forms of waste because they can snowball into other forms of waste such as additional Transportation, Overproduction or Overprocessing.
Lean Manufacturing consultants often recommend four steps to deal with defects in manufacturing.
First, identify the most costly, numerous or frequent defects in your production (in that order). Picking one defect to focus on, you then (second) add the ability to detect the defect such that defects don’t move to the next step in the manufacturing process compounding the loss of value. Then (thirdly) redesign the process so that it doesn’t lead to defects. Fourth, ensure that the process is standardized so that the new process consistently produces defect free products.
In general, as you’re analyzing the process to eliminate defects you’ll often find that there is:
- a lack of standards or poor documentation
- poor quality controls
- a lack of a defined process altogether
- poor or un-manufacturable product design
- undocumented design changes that don’t marry to related parts
- poor inventory control leading to ad-hoc manufacturing process adjustments
This means that you should:
- review the part or product design for ‘designed-in’ defects
- check for standardized work plans and QC job aids such as checklists
- check for a full understanding of product requirements and consider training
- ask the people in that area!
Often the people with their hands on the parts can tell you a lot about what is creating issues.
An example of how Smart Factory Analytics can be used to minimize or eliminate defects is presented in this smart baker case study:
The eight wastes of lean manufacturing can be remembered with the acronym DOWNTIME: