Key takeaways
- Ask for the maintenance schedule, the trigger for a die pull and the last three records, not a verbal assurance.
- Spare punches, inserts and springs are a capacity decision. A die that waits for a part is a line that waits.
- Maintenance is a cost line. If it is invisible in the piece price, it is either deferred or charged later.
- A rising burr, more slugs and a longer setup are early warning signs that the die is drifting.
Why a buyer should care about the die
A progressive die is a production asset with a wear life. It cuts, forms, trims and often assembles a part in one stroke, and every stroke takes a small amount of life out of the cutting edges, the bend inserts, the guides and the springs. Maintenance is the process that keeps the die inside its working window.
When maintenance is done well, the part stays within tolerance, the press runs at rate and the die lasts for the planned volume. When it is deferred, the first symptom is usually a burr or a dimensional drift, and the second is a wreck: a broken punch, a jammed strip or a damaged die section. A wreck can take days to repair and can put a programme behind for weeks.
For a buyer, the question is not whether the supplier has a maintenance plan. Most will say yes. The question is whether the plan is written, resourced and recorded, and whether the commercial model pays for it.
What a real maintenance plan contains
A progressive die plan has four layers. The first is the shift check: strip lubrication, slug clearance, sensor function, air pressure, die height and a visual check for loose or damaged components. The second is the stroke based service: a die pull at a defined interval for cleaning, inspection and a check of punch lengths and spring pressures.
The third is sharpening and repair. Cutting edges are ground back by a controlled amount, worn punches and inserts are replaced, and the die is re-set and trialled. The fourth is the record: what was found, what was replaced, how much was ground and what the first-off result was.
A plan that only covers the first layer is a cleaning routine, not maintenance. A plan that covers all four, with named responsibility and a spare parts list, is one that can survive a busy quarter.
The maintenance cycle
The cycle below is the one to ask a supplier to describe. If they cannot walk through it in order, the plan is probably informal.
- 01
Check at the press
Lubrication, slug path, sensors, air pressure, die height and a visual check for damage or looseness at the start of each shift.
- 02
Count the strokes
A stroke counter triggers the next level of service. The interval is set from the die design and the material, not from convenience.
- 03
Pull and inspect
The die comes out for cleaning and inspection of punches, inserts, guides, springs and strippers. Findings are recorded.
- 04
Sharpen or replace
Cutting edges are ground by a controlled amount. Worn punches, inserts and springs are replaced from the spare list.
- 05
Set and trial
The die is re-set, the shut height checked, and a first-off part inspected before the run restarts.
- 06
Review the record
Burr, grind depth, downtime and scrap are reviewed against the previous cycle to spot a trend before it becomes a failure.
The questions that get a useful answer
The same question can produce a reassuring answer or a real one. The table pairs each question with the kind of answer that tells you the plan is under control.
| Question | Weak answer | Good answer |
|---|---|---|
| What is the maintenance schedule? | We maintain as needed | A written schedule by shift, stroke count and calendar, with named owners |
| What triggers a die pull? | When quality drops | A stroke interval, a burr limit, a tonnage trend or a sensor event, whichever comes first |
| Who does the work? | The press operator | A toolroom with the drawings, the spare list and the grinding records |
| What spares are held? | We can order them | A defined spare list on site, with minimum quantities for the wear parts |
| How is sharpening controlled? | We sharpen when it needs it | A maximum grind per event, a total allowance and a replacement trigger |
| What records exist? | We can check | A die history with dates, findings, parts replaced, grind depth and first-off results |
| Is maintenance in the price? | It is included | A stated maintenance allowance per 1,000 strokes or per year, visible in the cost breakdown |
Ask for the last three records, not a sample from a good month. A trend is more useful than a single entry.
Spare tooling and the capacity question
Spare tooling is often treated as a toolroom detail. It is really a capacity decision. A die with no spare punch waits for a replacement to be made, and the press sits idle while the delivery date moves. A die with a spare punch is back in production in an hour.
The spare list should cover the parts that wear or break: punches, die inserts, guide pins and bushings, springs, stripper bolts and sensors. The quantity depends on the wear rate and the lead time. For a long programme, a second set of critical inserts is cheap insurance compared with a week of downtime.
Ask where the spares are held and who owns them. If the die is customer owned, the spares should usually be part of the tooling package and should transfer with it. If the supplier owns the die, the spare list is still a legitimate question in a supplier review, because it affects your delivery.
A useful test is to ask how long the die would be down for the most likely failure. If the answer is measured in weeks because a punch has to be made, the spare list is too thin for the volume. If the answer is measured in hours, the programme has a buffer.
Warning signs in the data
Maintenance problems rarely appear without warning. They show up in the production data before they show up in a failure.
Review these signals at the same meeting as delivery and quality. A maintenance trend that is discussed only in the toolroom is a trend the buyer sees first as a late shipment, a price increase or a missed launch.
- Burr height trending up across successive lots at the same material and die
- More slugs or short stops for slug removal than in the previous quarter
- Setup time creeping up after each die pull
- Scrap rate rising on one feature rather than across the part
- Tonnage or punch load drifting at the same stroke rate
- Sharpening frequency increasing without a change in material
- The same punch or insert failing repeatedly
Putting maintenance in the commercial model
Maintenance has to be paid for somewhere. It can sit in the piece price as an allowance, be charged as a separate service, or be absorbed by the supplier and recovered through volume. Each model can work, but the buyer should know which one is in use.
A quote that separates tooling, maintenance and piece price is easier to compare than a single number. Ask for the maintenance allowance per 1,000 strokes or per year, the assumed volume and the replacement trigger for wear parts. If the volume falls below the assumption, the allowance per part rises, and the piece price should reflect that.
Agree what happens at the end of the programme. A die that has been maintained to a known standard is worth more at transfer, and a die history makes the transfer easier. If the die is customer owned, ask for the records to be handed over with the tooling, not reconstructed afterwards.
The cheapest quote can be the one that skips maintenance
A price that assumes no die pulls and no spares is not a lower cost. It is a cost that arrives later, with interest, as a line stop.
Frequently asked questions
How often should a progressive die be maintained?
It depends on the die, the material and the stroke rate. Most plans combine a shift check with a stroke based die pull, and a sharpening interval set from the wear rate. The supplier should be able to state the interval and show the records that support it.
What spare parts should be held for a progressive die?
At minimum, the wear and break parts: punches, die inserts, guide pins and bushings, springs, stripper bolts and sensors. The quantity depends on the wear rate and the replacement lead time. Critical inserts are often duplicated for a long programme.
Should maintenance be included in the piece price?
It can be, but it should be visible. Ask for the maintenance allowance, the assumed volume and the replacement trigger. A price that hides the allowance is hard to compare and easy to cut when a supplier is under pressure.
What records should a buyer ask to see?
The die history: dates, findings, parts replaced, grind depth, first-off results and any unplanned stops. The last three records are more useful than a single example, because they show whether the die is stable or drifting.
Sources and further reading
- ISO 9001:2015, Quality management systems, requirements for control of production and service provision
- IATF 16949:2016, Automotive quality management system, maintenance and tooling requirements
- Qumek tooling and supplier review notes for progressive dies
Qumek Engineering Desk
Engineering team
The engineering team behind Qumek drawings, DFM notes, tolerances and inspection standards. Every guide is reviewed against the drawings and processes used on live programmes.
Reviewing a supplier's die maintenance?
Send the die list and the annual volume. The engineering desk will reply with a maintenance questionnaire and the records to request before you place the order.
Ask for a review