SMED Implementation Guide for CNC
Build a repeatable 90-day setup-time reduction program
What is SMED?
SMED (Single-Minute Exchange of Dies) is a lean manufacturing methodology developed by Shigeo Shingo at Toyota to reduce setup times to under 10 minutes (single-digit minutes, hence "single-minute").
For CNC machining, SMED focuses on reducing changeover time between jobs—from finishing the last good part of Job A to starting the first good part of Job B.
Why SMED Matters (illustrative model):
Before SMED:
- • Setup: 45 minutes average
- • 8-hour shift = 10 setups max
- • 420 minutes lost/day (87.5%)
After SMED (50% reduction):
- • Setup: 22 minutes average
- • 8-hour shift = 21 setups possible
- • 210 minutes saved/day
The Three Core Principles
- Separate internal and external activities - Do as much as possible while machine is running
- Convert internal to external - Move activities outside the critical path
- Streamline remaining activities - Eliminate waste in unavoidable downtime
Setup Time: Before vs. After SMED
Before SMED: 45 Minutes
After SMED: 22 Minutes (-51%)
Step 1: Classify Activities (Internal vs. External)
Internal Activities
Must be done while machine is stopped
- ✓ Remove finished part from machine
- ✓ Change workholding (vise, chuck, fixture)
- ✓ Install new part in fixture
- ✓ Touch off tools (tool length measurement)
- ✓ Set work zero (part origin)
- ✓ Run first article inspection
External Activities
Can be done while machine is running
- ✓ Gather tools and fixtures for next job
- ✓ Pre-set tool lengths on tool presetter
- ✓ Review and verify CNC program
- ✓ Prepare raw material (deburr, clean)
- ✓ Stage tooling at machine door
- ✓ Print job traveler and setup sheets
SMED Goal:
Move as many activities as possible from the Internal (red) column to the External (green) column. Every minute moved = one more minute of production capacity.
90-Day SMED Implementation Plan
Phase 1: Measure & Analyze
Week 1-2: Baseline Measurement
- • Film 5-10 complete setups with smartphone (get operator consent)
- • Time each activity with stopwatch: "Remove part: 3:45, Get vise: 2:30..."
- • Calculate average setup time and breakdown by activity
- • Identify top 3 time-consuming activities (Pareto analysis)
Week 3-4: Team Kickoff
- • Form SMED team: 1 supervisor, 2-3 operators, 1 programmer
- • Watch setup videos together, classify internal/external
- • Brainstorm improvement ideas (no idea too small!)
- • Set target: e.g., "Reduce 45-min avg to 22-min in 90 days"
Phase 2: Quick Wins Implementation
| Improvement | Action | Time-Saving Estimate |
|---|---|---|
| Pre-stage next job | Kitting: cart with tools, fixtures, material ready before current job ends | Validate onsite |
| Tool presetting | Measure tool lengths offline with presetter (not on machine) | Validate onsite |
| Quick-change vises | Install sub-plates with repeatable locating pins | Validate onsite |
| Standard work zero | Use same G54 offset for common fixture, eliminate re-touching | Validate onsite |
| Shadow boards | Tool storage with labeled outlines (wrenches, allen keys, etc.) | Validate onsite |
Expected total savings from quick wins: validate cumulative reduction with timed trials on your own setup families.
Phase 3: Standardize & Sustain
Create Standard Work Documents
- • Write setup procedure for each machine (with photos)
- • Include tool list, fixture setup, work offset procedure
- • Laminate and post at each machine
Train All Operators
- • 2-hour training session on new SMED procedures
- • Hands-on practice with presetter, quick-change fixtures
- • Certify each operator (skills checklist)
Measure and Improve
- • Track setup time weekly (plot on chart)
- • Monthly SMED review meeting: celebrate wins, address issues
- • Continuous improvement: set a quarterly reduction target from actual trend data
Top 10 SMED Techniques for CNC
Tool Presetting Station
Offline tool presetter measures tool lengths before job starts. Eliminates 6-10 min of on-machine touching.
Investment: Vendor-quote based for your presetter scope
Payback: Compute from measured setup-time recovery and loaded machine rate
Quick-Change Fixture System
Sub-plates with dowel pins allow fixtures to be mounted in exact same position every time. Zero re-indicating.
Example: System 3R, Erowa, Schunk VERO-S
Time saved: Validate per setup family with stopwatch data
Dedicated Fixture Library
Pre-build fixtures for common part families. Store on labeled shelves next to machine.
Strategy: Build 3-5 common fixtures (e.g., "4-inch vise," "angle plate 30°")
Result: Grab-and-go fixture selection (no custom build per job)
Work Offset Standardization
Use consistent work zero locations (e.g., G54 = vise jaw corner) across all jobs with same fixture.
Benefit: No touching work zero each setup—programmed offset is always correct
Time saved: Validate with pilot runs on repeat part families
Job Kitting / Setup Cart
Pre-stage all tools, fixtures, material, and paperwork for next job on a cart 30 minutes before current job ends.
Implementation: Simple rolling cart with checklist
Time saved: Measure in your environment after kitting standardization
Standardized Tooling
Keep common tools (e.g., 1/2" endmill, #7 drill) assembled in holders at all times. Don't disassemble after each job.
Tip: Buy duplicate holders for high-use tools after confirming handling bottlenecks in setup observation.
Visual Setup Sheets
Photo-based instructions showing exact fixture orientation, part location, tool list with pictures.
Format: Laminated A4 sheet: photo of setup + tool list + work offset values
Result: Less confusion = faster, error-free setups
Eliminate Adjustments
Replace adjustable fixtures with fixed, repeatable designs. No tramming, no dialing in.
Example: Replace adjustable angle plate with fixed 45° wedge fixture
Philosophy: "Set it once, use it forever"
Tool Crash Prevention
Use simulation software (Vericut, NCSimul) to verify programs before first part. Eliminates trial-and-error.
Benefit: Reduces trial-and-error during prove-out and improves safety margin for first runs.
Bonus: Lowers crash risk when simulation discipline is consistently applied.
Two-Operator Setup (Complex Jobs)
For large/heavy setups, assign 2 people. Parallel work = faster completion.
Example: Operator A loads material, Operator B stages tools simultaneously
When to use: Setups >30 min with 2+ people available
SMED Financial Impact Calculator
This section is an illustrative financial model. Replace all inputs with your measured setup times, rates, and staffing costs before making decisions.
Example Shop Scenario
| Setups per day | 10 |
| Avg setup time (before SMED) | 45 min |
| Avg setup time (after SMED) | 22 min |
| Time saved per day | 230 min (3.8 hrs) |
| Machine rate | Use your loaded rate |
| Working days/year | Use your production calendar |
Financial Benefits
| Daily capacity gain | From your measured delta |
| Daily value recovered | Capacity gain × loaded rate |
| Annual value | Daily value × working days |
| SMED implementation cost | Sum of your actual implementation items |
| (e.g., presetter, fixtures, training, standard-work development) | |
| Payback period | Implementation cost ÷ daily recovered value |
Common SMED Implementation Pitfalls
Skipping baseline measurement
Without timing current setups, you can't prove improvement or prioritize actions. Always measure first.
Operator resistance ("We've always done it this way")
Involve operators early in brainstorming. Their buy-in is critical—they know the pain points best.
Over-investing in automation too early
Start with low-cost fixes (shadow boards, kitting) before buying expensive quick-change systems.
No follow-up tracking
SMED gains erode without continuous monitoring. Track setup times weekly on a visible chart.
Trying to fix all machines at once
Start with one "pilot" machine. Perfect the process, then roll out to others.
SMED Success Metrics
Track these KPIs to measure SMED effectiveness:
Related Resources
Use our calculators to understand how SMED impacts overall equipment effectiveness: