Also, same case : you have for example, 2 types of pieces that go through the same process but the operation done is not the same, how do you represent it on the VSM ( 2 process boxes ?) and also how do you calculate the “value add time” (C/T(1) + C/T(2)) ?

I hope i’ve been clear enough and thanks you in advance for your answer.

As it relates to VSM… we normally note this C/O time for that process as you suggest. One thing to keep in mind is that a VSM is only a snap shot of the process. There are other tools like the Process Capacity Table that can and should be used in harmony with VSMs.

As a small commercial (sorry) we do cover all of these topics (VSM, Changeover, Standard Work, and much more) in our Gemba Academy courses. You can register for a free trial account to get a flavor of what it’s all about at http://www.gembaacademy.com/amember/signup.php.

I hope this helps! Great question.

While collecting the first data for my current state map I’m confused by the different definitions of ‘C/O’ that I find on the internet. It is not really important for understanding vsm, but I want to understand completely in order to explain others correctly in the future.

C/O, to me, is likely to be ‘Change Over time’ which I would define as the time needed to change your machine settings in order to start producing a product from a different product group (for example this website: http://www.strategosinc.com/value-stream-mapping-3.htm confirms this thought).

In practice, and also in your example, I see the space tagged ‘C/O’ in the databox used for the time it takes one product to walk through the specific process linked to that databox.

It seems to me that the second definition is the one to use making the current state map. I just don’t see how this has anything to do with change over time.

I hope you can help me clarify this vsm-mystery.

Kind regards,
Joost
The Netherlands

Now i came with a conclusion to map all the part numbers (i.e. 12 VSM’s ), So that i can derive different lead time for different part numbers and accordingly I can suggest the inventory to be maintained between the work stations. Am I correct?

That depends on the purpuse of your VSM. If you want to compare lead time between all part Nos. then you have to map all part nos. However, if you want to compare the 6 part nos. going through the 10 operations with the other 6 part nos. going through other operations, then you can settle with an average. Then you have grouped in product families.

But dont forget that a VSM has a lot of limitations. For example, it does poorly in visualizing monuments (operations that multiple part nos. share)

If you have to operators instead of one at one station, then the incoming inventory will everything equal be lowered. This will therefore decrease inventory days at that specific place of inventory. However, if the subsequent work station is/becomes a bottleneck then the inventory will instead pile up in front of that next work station.

The consequence and the morale is that total lead time will not go down if you dont elevate the bottleneck activity.

I was thinking of days of supply for the next process. Hence I thought that the inventory will deplete faster if there are more operators consuming the inventory.

BUT

Since the customer is only going to buy so much (through takt time), it doesn’t matter how many operators consume the inventory. The days of supply for the customer will remain the same.

Right?