Tuesday, February 4, 2014

Lean Manufacturing - How to reduce wait times

We've all seen sales persons on the floor of a retail store standing around doing nothing when there are no customers to service. In my previous company, employees used to wait for the response from their client. So, they weren't able to move on to the next step of their work. These are examples of the lean waste of waiting. It’s wasteful because the paid time is simply going to waste. Their is a loss of revenue for non-productive work. This kind of waste is often not realized because when you go to an office you'll actually see people "working".

Waiting can be caused by a few things. Most often there are bottle-necks involved. Lets say, there are two resources R1 and R2 processing items one after another. After R1 has done processing an item, it goes to R2 for further processing. Suppose R1 takes 40 mins to process an item and R2 takes 30 mins to process the same item; R2 has to wait for 10 mins doing nothing! So the actual time taken by the whole process is actually 40 mins and not 35 or 30 mins. So, the management should focus on identifying such bottle-necks rather than trying to boost the efficiency of each and every resource.

Another cause of wait time is variability in inter-arrival times. To illustrate this, let us take an example.Think of a restaurant which operates from 6 PM to 11 PM. Generally, most of the customers arrive between 8PM to 10 PM (dinner time), leaving time windows 6 PM - 8 PM and 10 PM to 11 PM with less customer arrival rates. In these time windows, the resources ( chef, caterers) are under utilized which in turn means wait time shows its face again . On the other hand, during peak times, the resources might be over-loaded. This could also mean that customers could turn away as they had to wait for long. So how to solve this problem?  A simple solution would be to move the customers from peak load times to under-utilized hours. Nowadays, restaurants are giving "early-bird" offers to their customers just to accomplish this.

The above methods have proved effective in reducing wait times but there are still many other solutions/tactics which are not covered under this blog. Can you think of any other?


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