What is “waste” in Lean?
In Lean manufacturing, “waste” is commonly defined as any action that does not add value to the customer. Essentially, waste is any unnecessary step in a manufacturing process that does not benefit the customer, therefore, the customer does not want to pay for it. Lean manufacturing is centered around eliminating waste from a manufacturing process. When you remove wastes, you are left with only the steps that are required to deliver a satisfactory, now high-valued, product to the customer.
Henry Ford and his team at Ford Motor Company discovered Lean along with the assembly line, even though they didn’t use that term specifically. Dr. Taiichi Ohno and Toyota perfected and popularized Lean through their creation of the Toyota Production System (TPS), or the original seven wastes: Transportation, Inventory, Motion, Waiting, Overproduction, Extra-Processing and Defects. The 8th waste of non-utilized talent was later included in the 1990s after TPS was adopted in the Western World.
Below is a brief description of the 8 Wastes of Lean Manufacturing, and ways to combat these issues in your facility. A good way to remember these wastes is through the acronym DOWNTIME.
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Any aberrations of a product found during inspection, causing that product to be scrapped completely or sent back for rework. Defects represent non-productive time, and reducing them allows for that saved time to be spent on value added activities.
Example: Poor or no on-line quality inspection processes fail to catch a crucial flaw in a machined part early in the process. By the time it reaches completion, it’s still unusable and wasted time that could have been spent making a good part. If it can be re-worked, then you add more time/cost that you cannot recoup.
Solution: Implement quality at the source so that every operator has well-defined check points.
Producing more than is needed. Not only has time been wasted producing too much product, but personnel could be better used on other tasks and it often leads to the Inventory waste.
Example: 20 parts have been made over demand. Now someone has to deal with the excess parts, they may get mis-placed or obsoleted before they can be sold. All these extra non-value-added tasks just add to overhead and lost opportunities.
Solution: Follow the schedule and work on something else when the demand quantities have been met, even if it is just cleaning up.
Waiting as a waste involves activities like idle time and queues. When time is spent not producing it’s considered a waste. Furthermore, queues often cascade exponentially to more waste the longer they build up. Note that waiting is preferred to overproducing.
Example: The process flow isn’t properly timed. An etching station takes longer to process a part than the parts take to arrive at the station, building up a backlog. Each part that arrives must wait longer and longer to be processed.
Solution: Work on the bottleneck and then balance or pace the line to the remaining bottleneck pace as appropriate.
This waste involves not fully using people’s knowledge, skill, and abilities. You need to involve people in the process so they can identify issues and generate improvement ideas.
Example: A person has been at a station for 5 years. They are a diligent worker, but there is an on-going issue with not meeting production rates which has resulted in OT. Management finally asks the employee why they think they cannot make the established rate. They point out a problem with the fixture that takes them extra time. This leads to fixing the fixture versus blaming the employee for something out of their control.
Solution: Make sure that the operators are involved in any problem solving or improvement to make sure nothing is overlooked. After all, they are the experts of what they do.
Moving materials and parts around the plant can lead to waste, especially if they’re poorly planned. Unnecessary trips lead to wasted time and opportunity.
Example: A plant layout was built up over time, but as machines were added the old ones weren’t moved in regard to flow. Multiple back and forth trips have to be made to complete a flow. Rearranging based on need could reduce the time it takes for a part to be completed.
Solutions: Do a Spaghetti diagram to visualize possible flows of people, tools, inventory, equipment, or products through systems. Then work on streamlining the flow over time, and not over-producing work-in-process items.
Any supply in excess of one-piece flow or the areas that hold raw materials and/or Finished Goods. Space is needed to hold overproduction (Work-in-Process and Finished Goods), mentioned earlier, leading to space that could be better used.
Example: The 20 overproduced parts must now be moved to storage, adding up to 20 separate trips. Now someone needs to manage the excess material and it takes up room that could be used for other product.
Solution: Set up Kanban signals to manage the material flow and storage limits, such as only purchasing raw materials when needed and in the quantity needed and creating a queue system to prevent overproduction.
Any action that does NOT add value to the product. This can take the form of part movement from the machine, or from personnel working on the part. More motion than is necessary coupled with poor ergonomics can lead to literal pain.
Example: A poorly optimized process requires the operator to bend down to pick up material. Raising the material to waist level to eliminate the bending motion.
Solutions: Watch the operator at work and relocate any materials that cause the operator to stretch or strain. Organize the workstation so equipment and tools are near the production locations, and place materials at an ergonomic position.
This waste involves any effort that adds no further value to the product. The biggest impact from this waste is that it can lead to many of the above wastes, taking non-value-added work to an increased level.
Example: A bumper was being painted on the inside even though the material had been changed to plastic. The original metal bumper needed to be painted on the inside for corrosion resistance, but now the plastic takes care of that and makes painting the inside redundant. Removing this step saves time and materials.
Solutions: Whenever a process change is made, question the need for any of the current steps so that you take full advantage of the full impact of the change.
Eliminating the 8 Wastes
The first step to reducing waste is recognizing that they exist and having an effective process for identifying them. Value Stream Mapping (VSM) is a Lean management method for analyzing the current state and designing a future state. The purpose of a value stream map is to view the entirety of a process flow from start to finish and create a plan to remove wastes and optimize efforts in getting the company to its desired outcomes.
To identify wastes, use VSM and document instances of the 8 wastes in the processes and develop a plan for eliminating or reducing them. Continue challenging your team to find more wastes and continuously improve your processes. A good way to achieve this is to involve your frontline workers and include their input for improvement. Overtime, reducing waste will become part of their daily routine.