Lean and waiting

[ashishdevikar]

Waiting is one of the important wastes identified in lean manufacturing. What is actually waiting in the context of lean? If the customer has to wait to receive what they want it is known as waiting in the context of lean. The customer can be internal or external. So lean manufacturing proposes not to make any of your customers wait when they have a requirement. But how to stop waiting?

When it comes to manufacturing, lean works according to the pull concept. That is products are manufactured when there is a requirement for them or what we know as JUST IN TIME (JIT). If this process is interrupted the flow of value will stop hence will create wastes. Creating a manufacturing environment which is smooth and will not have any stops and waiting is the challenge faced by many manufacturers. In lean manufacturing context waiting is the second largest contributor to the work in progress is what i understand.

Lean doesn’t propose to have a higher inventory levels to eliminate waiting time. But the system should be fine-tuned and quipped to supply products when there is s a demand without making the requester waiting. This is where the system is really challenged. In lean manufacturing there will be frequent changes to the models manufactured, quantities are smaller and there is no inventory to level out the production. This requires robust systems. SMED techniques, careful layout planning, training and work cells are some of the techniques used to stop the interruptions to the flow of value hence the waiting time.

In lean office and lean service contexts waiting can be people who are waiting to get their documents done, people waiting for the information, people waiting for the reply for their email or a document waiting to be processed. Although this is not very much visible, offices and services have very high degree of waiting and higher cycle times. Have a think about it, how many times we have come across the similar situation in our office.

Carefully mapping and identifying the value stream will make it possible to identify wastes in the office (or in your service). When these are identified we can remove these wastes from the system.

Even in software development waiting is mainly due to the development model. If the projects are planned to develop larger pieces of software then the customers have to wait till the full thing is done. Internal customers like testing people will have to wait till the full piece of software to come out to complete testing. When it comes to testing it will take lots of time to complete the testing these large software pieces. If errors are identified it will take more time to correct them and retest them. The result is end customer will have wait for longer without seeing anything. Once the software is delivered he might have a different set of requirements and expectations which are evolved with time.

This can be avoided by developing software in small pieces putting them together subsequently. It takes lesser time to develop small pieces of software and it is less complicated to test them individually. Once the minimum requirements are met product can be delivered to the end customer after an integration testing. This will make customer happy since he has to wait only for a short while.

In lean manufacturing there is one very important theory. If we waste time in the process we can not catch up to that time again. No matter how hard we work, no matter how fast we work if we have already lost one minute of time it will be lost for ever. Waiting is the main contributor to longer cycle times. Waiting means longer lead times.

Summarizing the above,"Lean" is never subjected to factories and shop floor. Waiting is the muda or waste present everywhere around us; if we want organization to be lean we must be be lean in our approach.

[kvasudevan]

Ashish,

I agree with the overall theme of the post. But, from my references, waiting in lean refers to parts waiting for a process. Not the process waiting for a part.

Can you tell me where you found this perspective? I would like to read it.

Karthik, PMC

[ashishdevikar]

Which part of the post made that confusion? Please clarify; so that i could clear that out..

[kvasudevan]

Quote from above: "What is actually waiting in the context of lean? If the customer has to wait to receive what they want it is known as waiting in the context of lean"

That is the part that I would like to read more about. This describes waiting as process being starved (i.e. waiting for a part).

My idea on lean is that the waiting in lean is part waiting for a process (blocking).
[According to the lean manufacturing article in Wikipedia: Waiting means waiting for the next production step]

-Karthik, PMC

[ewilliams]

I interpret "waiting" very broadly as the enemy of lean. If machine X waits for the next part Y to arrive, conceptually X is the customer of the part Y flow, and X is losing time that can never be recovered. That matters IF operation X is a bottleneck in the broader scheme of things. It does not matter in the situation where, if X never had to wait, it could produce more product than the marketing department could sell. If part Y waits for machine X, conceptually Y is the customer of X, and Y is losing time it cannot recover in its urgency to reach the end of the supply chain. Again, that does not matter in the situation, where Y never has to wait, it would reach the end of the supply chain faster than it could be sold or consumed.