Thanks to Gary Tucker for a question regarding standard work and standardized time values:
How do you get your time values and how do you know that they are standardized? You sure can’t just take any observed time. There are all kinds of factors that have to be considered. I would think that MOST might work here, but I have not seen anything that supports this requirement for Standard Work in any article yet.
MOST works quite well in assigning predetermined time values by specific motion elements, or in determining how long certain tasks should take when starting up a new product or a pilot line when there is limited ability to observer actual processes, much less improve them.
The point of standard work is not to find the single best times for individual motion elements but the best overall combination of manpower, material and machinery. This is based on takt time calculated from net available time divided by customer demand, with the aim of matching supply to demand through continuous flow production and multi-process handling by workers.
In some cases this means that there is waiting time built into standard work, or that machines are idled for part of each cycle on purpose so as to get the best out of the overall system rather than a specific asset or a unit of labor. MOST can be used together with standard work but the aims are different and in my opinion it is not necessary. It’s an odd thing to say but actually the spirit of standard wok is that the standard need not be “standardized” as in normalized to take various loss factors into account.
Taiichi Ohno said, “The standard time should be the shortest time” because the shortest time should be the easiest way. His argument was that if the fastest way is not be repeatable due to fatigue or variation in material or machine factors during the day, these are not immutable conditions but areas for improvement. Standard work is not to “standardize” and determine a “best” time but rather to find a baseline for improvement. The shortest time is the “standard” but it is not necessarily a “standardized” time that takes into account various allowances. While standard work should not be unattainable, it can and should be a stretch that creates an urgency to do kaizen rather than a very safe standard that takes into account various loss factors.
Ohno also said, “Speaking of standards, time study is another thing everyone gets wrong.” Typically time studies require 30 measurements or more to be statistically valid according to textbooks. Setting an average time as the standard is very bad according to Ohno because if you observe someone repeating a process 10 times and they are doing it differently each time you should stop immediately to correct the process. In the Toyota Production System the twin cornerstones are standard work and kaizen. Standard work answers the question, “What is easiest known method?” while kaizen answers the question “What will it take to follow this standard work every time?”
“Some say that is harsh, but what’s harsh about it?” asks Taiichi Ohno. “The shortest time is the easiest method.”
This idea that the standard is not the normalized or standardized time does not sit well with a lot of people. Sometimes it’s bad enough getting people to accept that standards are good things, and then you tell them that the standard is not only the shortest time, but it’s ever-changing. Without understanding kaizen it can be very hard to explain standard work in a way that makes sense.