In this guide 6 sections
Stamping changeovers run long because one clock hides four delays: lifting the old die out, setting up the new one, first off approval, and waiting for people or parts. Time each stage separately per press. The biggest loss shows itself.
One number hides four problems
Most press shops record one changeover time, from the last good part of the old job to the first good part of the new one. That figure is honest. It says nothing about what to fix.
Split it into four clocks. Die lift is removing the old die and fitting the new one with the crane or forklift, while setup covers clamping, shut height, feeder and coil alignment. First off approval is the check and signoff of the first part, and wait time is everything else that holds the press still.
Identical totals hide different stories. One press may lose its hours to a crane queue while another loses them to repeated trial parts, yet a supervisor who sees only the total will guess.
- Die lift out and die lift in
- Setup: clamp, shut height, feeder, coil
- First off approval by quality
- Waiting: crane, material, tools, people
Wait time is usually the largest hidden piece
Watch one changeover with a stopwatch. Note every moment the press crew stands idle, whether they wait for the crane, a missing clamp, a coil still in the store or a quality inspector elsewhere.
These pauses are not the crew’s fault. They are planning gaps, and each one repeats on every changeover until somebody writes it down and assigns an owner to close it. Stage the next die, coil and clamps beside the press before the last part of the old job comes off, so nothing waits on a forklift.
Ask the crew what holds them up. They already know.
First off approval deserves its own clock
First off approval starts when the first part leaves the press and ends when quality signs it, and in many shops this stretch alone holds a press idle. An inspector walks over with a gauge.
Measure how long the part waits for the inspector, how long the check takes and how many trial parts were needed before the signoff. Repeated trials point to setup problems. Shut height and die alignment come first.
A fixed check sheet for each part number, listing the critical dimensions, the gauge to use and the reading expected, shortens the check and removes arguments.
Record the same fields every time
Use a short form with press number, die number, job in and job out, and a timestamp for each of the four stages. Scan the die tag at the press.
Add a reason code for any wait longer than a few minutes, and keep the list short: no crane, no coil, no clamps, no inspector, die repair needed.
After a few weeks, rank presses and reasons. Sort by total lost hours rather than the worst single day, because one bad Monday should not outrank a crane queue that repeats on every shift.
- Press, die and job numbers
- Start and end time of each stage
- Wait reason from a short list
- Number of trial parts before approval
Fix the largest piece first
If lift time dominates, look at crane access, die carts and quick die change clamps, and if setup dominates, standardise shut heights and die heights. If waiting dominates, stage material and tools ahead.
Change one thing at a time. Watch the numbers for two weeks on that press, keep the change that shortened the stage you targeted and drop any change that left the total unmoved.
Start with one press this month. Time ten changeovers before you change anything.
Changeover timing sheet
Each row of this sheet is one changeover. Columns hold press, die in and out, lift time, setup time, first off approval time, wait time, wait reason and trial count. A summary strip at the foot ranks wait reasons by total hours, so the first fix is obvious at a glance.
Open a blank worksheet to printQuestions owners ask
What is a good changeover time?
It varies with press size, die weight and part. Compare each press with its own history first, then with similar presses in your shop that run comparable die weights and part sizes.
Who should record the times?
The press crew, with the inspector confirming approval. Times written by a supervisor after the fact tend toward rounded numbers, and rounded numbers hide the very waits you are trying to find.
Does this apply to progressive and transfer dies alike?
Yes, the four stages exist in both, though transfer dies often add finger and transfer setup to the setup stage, so time that part separately if it dominates.
How long before the data is useful?
Two to four weeks of changeovers on one press usually show a clear pattern in the wait reasons, provided the crew fills the form every time. Ten timed changeovers is a fair start.