How to Implement Lean Manufacturing: Simplify and Solve – Value Stream Mapping and Team Problem Solving: Part 6
So, at this point, you have a pretty good value stream map of your current state. I doubt if it looks as neat as the one I included in my last post. In fact, it probably looks more like this:
Example Value Stream Map (Sorry it’s a link instead of an actual diagram. It’s a PDF, as you’ll see, and this is the only way I could include it.)
You’ll see the addition of the Tool Room and Purchasing, lots of places that material sits, lots of people who need to see the Production Schedule, and a “contingency routing” which was used when the equipment in the “preferred routing” was down. (You’ll also see a Future State VSM but don’t pay any attention to that for now.) That’s how these things go…they can get messy. This VSM team met twice a week for about six weeks to get just the current state map completed. Again, that’s how these things go.
The other thing you’ll notice is that there are some numbers next to many of the steps. Those represent activity and performance data and they’re what we need to attend to now.
Deciding exactly what data to gather can be the result of a number of discussions unto themselves. If you look at the VSM examples on the interwebs and in books about the topic, it seems pretty straightforward. But every manufacturing operation is different and so every VSM map will contain different information. That said, there are a few basic metrics that the VSM team needs to consider.
First, what’s the total throughput that the process produces in a given time period (week, month, year, whatever)?
Second, you’ll want to know something about customer needs and demands. How often are you shipping? In what quantities are you shipping? (Yeah, I know…these data can vary widely in many cases. So get a “typical” order quantity and frequency and a range of highest and lowest. All that data will give you insights into how robust the process needs to be.) Perhaps most important, what’s the process’ customer service performance, e.g., on time delivery rate, shipping error rate, etc.?
Now, work your way back through the VSM asking other questions. How much material is put into shipping staging areas? How often? How much is in the finished goods inventory? (Again, the numbers may vary widely. That’s OK. It’s important to know.)
When you get to the operations steps, there will be lots of questions to get answers to. What’s the historical throughput at that step? What’s the changeover time? How much unplanned downtime does that operation experience? How much scrap? What’s the typical batch size? What’s the cycle time for a typical batch? How many shifts does the operation work? How much scheduled time per shift? What’s the first pass yield? Some of these data might not be very germane to your operations. On the other hand, there might be other relevant data unique to your process that need to be gathered.
It’s been my experience that this work about data and, especially, the gathering of needed data are among the most difficult aspects of developing the VSM. In plain language, it’s boring. It’s like homework back in school. You won’t often hear it said quite this way, but often the underlying answer to many of the questions above will be some variant of “We don’t know and we don’t care.” It can be aggravating but, remember, the reason that they don’t know is that management never cared.
Put the data right on the VSM. Yes, this will make things a bit cluttered. I get it. But if it’s not right there on the map, you won’t pay any attention to it.
So, at this point, you have a map with lots of boxes and arrows and lots of data on it. What now? Well, the experts will tell you it’s time to create a “future state” VSM. I agree, but first…you need to study the heck out of that current state map. More about that in our next post.