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Knowledge Base/Comprehensive Guide to Drawing Value Stream Maps (VSM): From Current to Future State
Lean Production6 min read

Comprehensive Guide to Drawing Value Stream Maps (VSM): From Current to Future State

This highly practical article recounts a painful experience where a wafer fab's yield plummeted, causing widespread concern, and outlines how solutions were found. Upon reading, you will understand what a Value Stream Map (VSM) is and why it's more than just a flowchart, helping to visualize the time and value of every step from product inception to delivery. If you want to know where your production line is bottlenecked or how much time is wasted on waiting, this article will provide the answers.

That Day the CPK Report Came Out, the Entire Room Fell Silent for Three Seconds

I still remember many years ago, our factory had a new production line. Initially, the yield was acceptable, but after running for a period, one day when the yield report from the wafer fab came out, the CPK report had directly dropped to 1.08, and DPMO soared to 6210! The air in the conference room instantly froze, and everyone looked at each other. The boss's face turned ashen, and he directly asked: "Where exactly is the bottleneck? Who can explain the entire process clearly from start to finish?" At that moment, I thought to myself, how great it would be if we could lay out the entire process to see all the problem points at a glance. This is why we need a "Value Stream Map" (VSM).

Where the Problem Lies

Simply put, VSM charts your product from beginning to end—from customer order placement to delivery—depicting all steps involved, including personnel, machinery, and information flow, all on one map. It's not just as simple as drawing a flowchart; more importantly, it also marks the "time" and "value" of each step. Think about it, normally we only know which machine is broken or where there's insufficient manpower, but how much time in the entire process is spent "waiting"? How much time is spent "processing"? How many "non-value-added actions" do we perform? VSM is precisely about uncovering these hidden wastes. It will show you that what you perceive as a bottleneck might not be the real bottleneck at all.

How to Actually Do It

Frankly, when drawing a VSM, you start with a "Current State Map."

  1. Select a Product Family: Don't be greedy and try to map all products at once. First, choose a product line that has the greatest impact on company revenue or has the most severe problems.
  2. Trace Upstream from the Customer: Imagine you are the customer and have received the product. Trace backward: which machines did the product go through? Which departments? How was it shipped? Draw out all physical flow.
  3. Annotate Key Data for Each Step: This is the "real stuff." You need to spend time on-site, talk to senior OPs, and ask equipment engineers. For each process segment, please record:

* Cycle Time (CT): How long does it take to complete one product? (e.g., etching 120 seconds/piece)

* Changeover Time (CO): How long does it take to switch to a different product? (e.g., mask change 30 minutes)

* Yield: What is the yield for this step? (e.g., 98.5%)

* Uptime: What percentage of time is the machine actually running? (e.g., 85%)

* Work-In-Process (WIP): How much inventory is there between each step? (e.g., 50 pieces in the waiting area)

* Manpower: How many people are needed for this step?

* Available Working Hours: How many hours per day are available for production?

You will find that a lot of time is spent on "non-value-added" activities like waiting and moving. These are the areas where you should make changes.

  1. Draw the Information Flow: Who gives instructions? What system is used? Is it email, MES, or verbal instructions? These must also be drawn.

Once the "Current State Map" is complete, you will clearly see, wow, just waiting for materials, machines, and dispatching accounts for a large portion of the entire production cycle!

The Most Common Pitfalls

The most common pitfall I've seen is people "imagining" or "concocting" processes while sitting in a conference room. Engineers would offhandedly say, "This step probably takes about 5 minutes, right?" or "WIP is probably around 20 pieces?" The resulting map would be vastly different from the actual situation. To be honest, the biggest taboo in VSM is relying on "gut feeling." You must personally go to the site, follow the product through its journey, time it with a stopwatch, and ask frontline colleagues to obtain real data. We once had such an experience where we thought a certain process was a bottleneck, but upon inspecting the site, it wasn't the process time that was long; rather, there was an issue with the preceding manpower scheduling, causing machines to often run idle. Therefore, without data, anything you say is useless.

One Thing You Can Do Today

Choose one product you most want to improve, start from the shipping end, and draw the first step.

Want to try it yourself?

Every tool mentioned in this article is available on InsightFab — just upload a CSV to analyze.

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