How to Implement Lean Manufacturing: Simplify and Solve – Value Stream Mapping and Team Problem Solving: Part 4
OK, so enough talk about boxes and arrows and lets put something on paper. We have a couple of decisions to make before we get started. First, we need to decide just which process to map. It might be that all the products in your operation go through the same process; that makes it easy to decide which process to map doesn’t it? In most cases, though, different products go through different processes. So, you have to pick one to map. (In many cases, you’ll have groups of products that go through a similar processes. If that’s your case, think of creating a process map for a group of products.) Now, I’ve read books that recommended an approach to picking a product or product group to map that involved lots of data gathering and calculations before making a decision. I don’t think it’s that hard. All you have to do is carry on a discussion that addresses these questions:
- Which products/product groups are high volume?
- Which products/product groups are high margin?
- Which products/product groups are important for some other reason, e.g., important new product?
- Which products/product groups are giving us the most problems?
If you have a product/product group that hits two or three of these criteria, go with that one. If none of your products hit more than one criterion, pick whichever product you want to start with, then move on to the others. Then do like we said last time, start with the customer and discuss their needs and the outputs that meet those needs. Then talk about the suppliers and your standards for what they provide.
OK, now you’re ready to connect those boxes and arrows.
You’re map probably looks something like this. Actually, your map probably has a bit more detail in it. That “Make It” step probably extends for a few more boxes. And, yeah, I left out the arrows between the triangles and the boxes because I didn’t want things to get too cluttered.
Now, it’s time to ask (and answer) some questions about some of the steps within the process. Again, let’s start at the end of the process and work our way backwards.
Ship It to Customer
How do we measure Customer service performance? What do our most recent measures show, e.,g. what is our on-time ship performance, shipment accuracy performance? What’s the best it ever gets? What’s the worst it ever gets?
How much inventory of the target product or products sits in Finished Goods? (I usually like to express this in either annual turns or days in inventory.)
What’s the Make It cycle time, i.e., how long does that process step take? What’s the setup/changeover time for the Make It step? What’s the scrap rate? What’s the machine uptime rate? What’s the throughput? What’s the typical batch size? Or what’s the typical length of a run?
Many value stream maps also document how many people are at the Make It step. I don’t like to do that. It sends the false message that the purpose of all this is to get rid of people.
Another value stream map measure folks sometime use is “efficiency” at each step. I’m not adamantly opposed to that but many organizations don’t measure efficiency well (I’ve talked with managers who swore by efficiency as a valid indicator of operations performance but who had no idea as to what the standard rates were or how they were determined) and they tend to use it wrong anyway.
As I said, you’ll probably have more than just one Make It step on your map; you’ll have several process steps here. That means you’ll also have triangles between those process steps that indicate Work In Process inventory. Be sure to document every instance where material sits. For example, you might have a staged inventory in front of a process step, inventory immediately after a process step, and stored inventory between process steps. Then staged inventory in front of the next process step. In other words, your Make It might actually look like this:
In this case, you’d want to document how much inventory is typically at each triangle. All this might seem like overkill but the above map would show that there’s lots of movement of material through the process. That’s important to know.
Supplier to Raw Materials
How do you measure Supplier performance? What do those measures show with respect to recent performance? How much inventory do you have on hand? What is the lead time for Raw Materials?
So, lots of data need to be gathered at this point. Let’s talk more about that in our next post.