Value Stream Map Example: Steering Bracket Step by Step
The steering bracket example from "Learning to See" is the classic of value stream mapping. This lesson builds a version based on it step by step and recalculates it with the metrics of ValueStreamMapping.app. It is deliberately a partly improved current state: some pull elements are already in place, so that every symbol appears once.
Setting
Product family: steering brackets, left and right. Customer: vehicle assembly plant with 920 pieces per day, daily shipment. Working time: two shifts, 460 net minutes per shift. Supplier: steel mill, delivers coils twice a week (Tuesday and Thursday).
Processes and data boxes
- Stamping: C/T 1 s, C/O 60 min, uptime 85%, batch size 1,000, EPEI 3 days. A batch of 1,000 pieces covers a bit more than one day of demand; with two variants, each one comes up about every three days, which matches the supermarket of 2.5 days.
- Welding 1: C/T 39 s, C/O 10 min, uptime 100%, one operator.
- Welding 2: C/T 46 s, C/O 10 min, uptime 80%, one operator.
- Assembly: C/T 62 s, C/O 0, uptime 100%, scrap rate 2%, one operator.
- Shipping: loading with no significant cycle time.
Inventory and timeline
Between the processes there are coils for 5 days, stamped parts for 2.5 days, a FIFO lane with 40 assemblies (under one hour), welded parts for about 1.7 days and finished goods for 2 days. The timeline adds up the inventory days to a production lead time of 11.3 days (5 + 2.5 + 0.04 + 1.74 + 2); processing time is 2.6 minutes (153 s). Value-added ratio: 0.02%. On top of that, 3,000 purchased parts sit in a side branch; they count toward the total inventory of 13,380 pieces but not toward lead time. The exact values are in the template you can open below.
What the map shows
The bottleneck is assembly: a 62 s cycle time with 2% scrap gives 63.3 s effective, above takt. Welding 2 is also tight at 46 ÷ 0.8 = 57.5 s. Scheduling happens at three points: stamping by kanban from the supermarket, assembly through the heijunka box, but welding 2 still by a weekly schedule from production control. That is where material is pushed, and 1,600 welded parts (1.7 days) pile up in front of assembly.
In the future state, welding 1, welding 2 and assembly become one flow cell, stamping supplies a supermarket by kanban, the cell is the pacemaker with a daily schedule, and coils arrive daily. Production lead time drops to 4.0 days (coils 1.5 + stamped parts 1 + finished goods 1.5), and inventory without purchased parts drops from 10,380 to 3,680 pieces, about two thirds less. Both states are available as templates in the editor and can be set side by side in the current/future comparison.
Practice in the editor
Load the demo, check the metrics above, and compare them with the "Steering bracket (future state)" template using the current/future comparison.
Open the template in the editor Start blankFrequently asked questions
Where does the steering bracket example come from?
From "Learning to See" by Mike Rother and John Shook (Lean Enterprise Institute, 1999), the standard book on value stream mapping. The German edition is titled "Sehen lernen".
Can I work through the example with my own numbers?
Yes. You can change the demo in the editor as you like; the timeline, takt time and bottleneck are recalculated immediately.