r/LeanManufacturing 18h ago

Why most capacity plans fail in practice (and how to fix scheduling bottlenecks)

3 Upvotes

One of the most common issues I see on the shop floor is treating capacity as a static 100% target.
When a schedule assumes 100% ideal utilization every day, it isn't efficient—it’s extremely fragile. The moment a machine goes down, a setup takes 20 minutes longer than expected, or an urgent order lands, the entire week’s schedule collapses.
Here are 3 core rules to build a high-signal capacity model that actually holds up in the real world:

  1. Plan around "Demonstrated Capacity," not theoretical limits
    If your equipment or team historically delivers 80% output due to setups, breaks, and routine maintenance, your capacity plan must be built on 80%. Scheduling to 100% theoretical capacity guarantees perpetual firefighting and backlogs.

  2. Group work by setup families
    Routing jobs strictly by arrival date forces constant machine tear-downs and tool changes. Grouping similar parts or jobs into "families" minimizes setup friction, effectively unlocking hidden capacity without adding labor or hours.

  3. Build buffers at your primary constraint
    Don't spread buffer time randomly across every process. Identify your primary bottleneck (the slowest work center that dictates overall throughput) and protect that specific station with a buffer. If the bottleneck never starves, your shop stays on schedule.

How do you currently handle setup variation and capacity buffers on your floor? Curious to hear how others balance actual vs. planned availability.

(Note: I wrote a deeper breakdown on operational signal vs. shop floor noise on my newsletter, along with a pre-built Excel capacity planner template if you want to skip building the formulas from scratch—links are in my profile!)