In last month's column, I described the common wastes of excessive inventory, overprocessing and motion. This month, I will describe other wastes that need to be addressed to improve the effectiveness of a manufacturing operation.
Waiting Waste: Have you ever seen an operator standing around waiting for something to happen? There are many causes of waiting, but one of the most common is an unbalanced workload. When the workload is unbalanced, an operator may be forced to wait for one operation to be completed before starting the next.
Another cause of waiting is unplanned machine downtime. Although there may be something else for an operator to work on, he or she is typically forced to wait until the extent of the problem is determined.
Upstream quality problems can also result in waiting. Perhaps a part produced in a previous operation was machined oversize and as such, the part cannot fit in the subsequent operation's fixture. Often, the operator will have to wait until the problem is solved.
Finally, first piece inspection is often cited as a major cause of waiting, as policy often mandates that the second piece cannot be made until the first one is checked and approved by inspection.
Remedies for waiting waste include an evaluation of the manufacturing process to be sure all operations and employees are balanced; a total productive maintenance effort, in which key equipment is evaluated and a maintenance schedule developed; and a modification of the quality system from inspecting for quality to building quality into the product.
Transportation Waste: Waste occurs any time we transport a part through the shop. Many companies have so much in-plant transportation that they employ full-time material handlers. In-plant handling is often caused by poor product flow. Production processes are not organized effectively, which causes parts to travel a great distance from one operation to another. Transportation waste is often proportional to the size of the production run: The larger the batch size, the more difficult the handling effort and the greater the need for hand trucks or even motorized fork trucks.
Unfortunately, the result is longer lead times, because when a part is transported, a queue time accompanies it. The queue time is generated at the point the parts are dropped off and does not end until they are picked up for processing at the next workstation. Transportation waste is often characterized by multiple handlings of products, temporary storage locations, lots of work in process inventory, and numerous motorized vehicles, conveyor belts and hand pallet trucks.
A remedy for this waste is a factory organization that groups together all processes required to complete a part or product, thus reducing the need for transportation. Batch size reduction efforts also reduce the amount of transportation necessary.
Defects: Defects are often a result of the wastes previously mentioned, but they can also result from poor process control, poor product designs, improperly selected machines and poor communication of requirements.
Nobody wants to produce defective parts, so it is reasonable to assume that defects are caused by system weaknesses. Perhaps the needs of customers (both external and internal) are not really understood, and we produce parts the way we think customers want them rather than as they truly want them. Defects can be attributed to many other causes, including improper employee training, non-standard manufacturing practices and a lack of tools and gages. Defects are the worst type of waste, as they often involve wasted material, labor, machine hours and time.
The key way to eliminate defects is to develop a manufacturing system that supports standardization. Processes, tools, fixtures and equipment must be designed to promote part-to-part consistency and contain sufficient documentation to assure that consistency is maintained from one run to the next. Just as importantly, employees must receive adequate training, not just in the "hard" skills of production, but also in "soft" skills such as print reading, communication and problem solving.
Wastes cost companies money. The more wastes that can be eliminated or reduced, the greater the opportunity to create an effective and profitable manufacturing operation.blog comments powered by Disqus