SMED Rapid Changeover: Slashing Changeover Time from 4 Hours to 30 Minutes

Scenario

Die changeovers in a stamping plant take 4 hours. The production manager complains: "Each changeover means half a day of lost production. So we try to produce large batches to reduce the number of changeovers."

The result: 3 weeks of inventory piled up, urgent customer orders cannot be delivered, and small orders cannot be accepted.

If changeover time is not reduced, large batches will only serve to cover up problems.

What is SMED

SMED (Single Minute Exchange of Die) = Single-Digit Minute Die Changeover

Goal: To compress any changeover time to less than 10 minutes ("single-digit minutes").

Not all processes can achieve 10 minutes, but the SMED methodology can reduce any changeover by 30-70%.

Four Steps of SMED

Step One: Record Current State (Record)

Use a video camera to fully record the entire changeover process.

Purpose: To identify all changeover actions, including parts you thought were "quick."

Common findings: A lot of time is spent looking for tools, waiting for the crane, or walking to fetch parts.

Time Breakdown:

• Disassembling old die: 45 minutes
• Finding new die + transportation: 60 minutes
• Installing new die: 75 minutes
• Adjustments and trial run: 60 minutes
• Total: 240 minutes (4 hours)

Step Two: Separate Internal and External Setups (Separate)

Internal Setups: Operations that can only be performed when the machine is stopped.

External Setups: Operations that can be prepared while the machine is still running.

Common findings:

• Finding new die (60 minutes) → Could have been prepared while the machine was running the previous batch → External setup
• Transporting tools (20 minutes) → Prepare a tool cart in advance → External setup

Step Three: Convert (Convert)

Convert internal setups to external setups as much as possible.

Typical conversion effects:

• Pre-heating the new die before changeover: Saves warm-up waiting time after shutdown.
• Prepare spare parts and material kits in advance.
• Verify the new die specifications are correct before changeover (not discovering the wrong die after shutdown).

Remaining internal setups after conversion: Disassembling old die + Installing new die + Basic adjustments = Approximately 130 minutes

Step Four: Streamline (Streamline)

Streamline the remaining internal and external setups:

• Standardize bolt sizes: Unify wrench sizes to reduce tool change time.
• Quick clamps: Replace bolts with quick clamps, saving 80% of tightening time.
• Positioning marks: Mark installation positions on the machine and die, eliminating the need for realignment.
• Two-person operation: Simultaneous disassembly and assembly.

Goal after streamlining: 60-75 minutes

Actual Results Comparison

A 72% reduction, without purchasing any new equipment.

Key Takeaway

"The most critical insight of SMED is: long changeover times are not because the operations themselves are slow, but because you only begin preparing tasks after the machine has stopped, tasks that could have been done in advance. By shifting preparatory work to before the machine stops, changeover time is naturally cut in half."