Dot Peen Data Matrix Marking on Steel, Copper and Cast Iron

A dot peen Data Matrix code is a field of dents, not a printed square. That one fact decides which metals it suits, how it must be graded, and when a laser is the better answer.

Contents hide

1 What is a Data Matrix code?

2 How dot peen forms the code

3 Which metals does dot peen handle?

4 Dot peen or laser?

5 When a laser is the better answer

6 Where dot peen is used

7 Two machines that mark Data Matrix codes

8 FAQs

Short answer

Up to 60 HRC. Past that, carbide styli stop biting and wear out fast.
Best on rough, oily or cast surfaces. Shadow contrast copes with texture that a laser mark cannot.
Soft metals need less force. Copper, brass and aluminium pile up around each dent, which merges cells.
Graded under ISO/IEC 29158 at 30°, not under ISO/IEC 15415. Different lighting, different result.

Dot peen Data Matrix code and character line marked on a steel part — Each cell is an indentation. A verifier reads it by the shadow the dent casts under angled light.

What is a Data Matrix code?

A Data Matrix code stores a lot of data in a small square. On industrial parts it is formed directly in the metal rather than printed on a label, so it survives heat, solvent and abrasion.

One point matters more than any other here. A printed Data Matrix has ink, so a phone camera can read it. A dot peen code has no ink.

It is read by the shadow the dents cast under angled light. An industrial scanner handles that easily. A phone usually cannot. If someone tells you a direct part mark on metal reads from a phone, they are describing a printed label.

Marking to a customer specification and not sure which method it allows? Tell us the spec — our engineers will tell you whether dot peen meets it.

How dot peen forms the code

Dot peen makes contrast from shadow, not from colour. A carbide stylus drives a dent into the surface. Angled light falls into the dent and the verifier reads the dark spot.

That is why a dot peen code is graded under ISO/IEC 29158 with 30° lighting rather than under ISO/IEC 15415. It is also why the code holds up on dirty, oily or cast surfaces, where a laser mark loses contrast.

Dot peen stylus marking a Data Matrix code on a metal part — The stylus drives one dent per cell. Depth and spacing decide whether the code grades.

Dot peen forming a Data Matrix code, dent by dent.

Which metals does dot peen handle?

Up to 60 HRC. Past that, the stylus stops biting and wears out fast.

Below the hardness limit, the deciding factor is not how hard the metal is. It is how much it moves when the dent goes in.

The same dot peen Data Matrix code marked on stainless steel, aluminium, brass and cast iron — The same code, the same machine, four different metals. What changes is how much each one moves under the stylus.

How each metal behaves under a dot peen stylus
Metal	How it behaves	Watch out for
Steel and stainless	The default case. Clean dents, steady depth, reliable grade	Never use the same stylus on carbon steel and stainless. Iron particles stay in the dent and rust. A brushed or blasted face grades better than a polished one
Copper and brass	Soft. Start at roughly half the force you would use on mild steel	Pile-up. The raised ring around each dent merges neighbouring cells and cell fill leaves the 60–105% window
Aluminium	Soft, similar to brass. About 60% of steel force	Thin sections can dimple on the far side. Verify anodised parts after anodising, not before
Cast iron and bronze	Where dot peen wins. Rough, porous surfaces do not affect shadow depth	Cast bronze varies by tin content. Test your own alloy — two that look the same can grade a letter apart
Hardened steel above 60 HRC	Out of range. Carbide stops penetrating	Mark before heat treatment, or use a laser. Heat treatment then changes the code, so verify on the finished part

What pile-up looks like

On copper, brass and aluminium the dent is easy to make. The problem is the metal that gets pushed out of the way.

Dot peen Data Matrix code marked with correct force versus too much force, showing cell merging — Left: correct force, cells stay separate. Right: too much force, the raised ring around each dent merges neighbouring cells and the code fails grading.

Not sure how your alloy will behave? Send us one part. We mark it, measure the dent depth, and return it with a verifier grade report under ISO/IEC 29158.

Ask for a graded sample

Dot peen or laser?

Nine points decide it. Four of them favour laser, and pretending otherwise wastes your time and ours.

What actually separates the two processes
What decides it	Dot peen	Fiber laser
Hardness limit	60 HRC	None
How contrast is made	Shadow from dents	Oxide colour or melt texture
Graded under	ISO/IEC 29158 at 30°	ISO/IEC 29158 at 90° on-axis
Mark depth	0.1–1 mm; pneumatic to about 2 mm	Surface to under 1 mm
Dirty, oily or cast surfaces	Holds the grade	Contrast drops
Smallest usable code	Limited by stylus tip diameter	Much smaller
Survives shot blasting	Yes, if deep enough	Shallow marks wear away
Consumable	Carbide stylus	None in normal use
Noise	Pneumatic runs above 85 dB	Quiet

The fifth row is the one worth testing yourself. Laser suppliers point out, correctly, that a laser reaches higher grades on a smooth machined face. On a rough cast surface the result goes the other way.

Dot peen versus laser Data Matrix code on the same rough cast surface, with the verifier grade for each — The same rough cast surface, marked two ways. A laser needs an even surface to give even contrast. Shadow depth does not care about texture.

Still weighing the two? Send us the part drawing and the standard you are graded against — we will name the process, even when the answer is laser.

When a laser is the better answer

Dot peen is not the answer to everything. Four cases where a laser is simply the right tool:

Hardened parts above 60 HRC. A stylus cannot get in. A laser does not care.
Very small codes. The stylus tip sets a floor on cell size. A laser spot is far smaller.
Fatigue-critical or thin-walled parts. A dent is a stress concentration. Laser annealing removes no metal at all.
High grey-scale contrast on a smooth face. If your customer grades under 90° on-axis lighting and wants a high modulation score, a laser mark starts ahead.

If any of those describe your part

The honest answer is a laser. Our guide to choosing a Data Matrix marking machine compares both processes against the standard your customer grades against, and the fiber, MOPA and UV range covers the laser side.

Where dot peen is used

Metal fabrication marks sheets, pipes and structural parts for traceability. The energy sector marks valves, pipelines and meters, where the code carries installation date and maintenance schedule. Aerospace marks components that must stay identifiable through the life of the airframe.

What these have in common is the surface. Castings, forgings and weathered parts are exactly where shadow contrast beats colour contrast.

Dot peen Data Matrix code and engraved numbering on a circular metal plate — A code on a machined face. Depth and spacing stay consistent across the whole symbol.

Marking installed equipment, castings or parts that never come off the line? Describe the job and we will tell you which format reaches your part.

Two machines that mark Data Matrix codes

Which one you need depends on a single question: can the part come to the machine, or must the machine go to the part?

Handheld dot peen marking machine for Data Matrix codes

For parts you cannot move

Handheld dot peen marker

Take the marker to weldments, frames and installed equipment
Marks Data Matrix, serial numbers and logos
Carbide stylus is the only consumable

See specifications & price Or ask an engineer about your part

Electric desktop dot peen marking system for Data Matrix codes

For parts you bring to a station

Electric benchtop system

Motorised depth control keeps cell fill consistent across a batch
Runs from a touchscreen, no PC needed at the station
Suits repeat production where the grade must not drift

See specifications & price Or ask an engineer about your part

Neither of these quite fits? We also build pneumatic, portable and integrated systems. Tell us the part and the cycle time you need, and we will point you at the right format — or say so if none of ours suits.

Talk to an engineer

Send us your part. We will mark it and send you the grade.

Your alloy, your surface condition, your code content. A sample plate proves nothing about your part.

The part back, marked, with the settings we used
A verifier grade report under ISO/IEC 29158, showing every parameter
Measured dent depth
If a laser suits your part better, we will say so

Get a graded sample

Marking and report are free. Shipping both ways is yours. We reply within one business day.

FAQs

Can dot peen mark a Data Matrix code on copper or brass?

Yes, but drop the force. Both are soft, so a setting tuned for steel pushes metal up around each dent. That raised ring merges neighbouring cells and the code fails grading.

Start at about half the force you would use on mild steel, then adjust. Test your own alloy — temper and surface oxide both change the result.

Will a dot peen code work on stainless steel?

Yes, and stainless is one of the easier cases. Two things to get right.

Never share a stylus between carbon steel and stainless — transferred iron particles sit in the dent and rust, and your customer reads that as a failed part. And a brushed or blasted face grades better than a mirror polish, because polished stainless reflects the verifier's own light straight back.

What hardness can a dot peen machine handle?

About 60 HRC. Past that the carbide stylus stops penetrating reliably and wear accelerates sharply.

For harder parts, mark before heat treatment or use a laser. But heat treatment changes the surface, so verify the grade on the finished part, not the freshly marked one.

Can a phone read a dot peen Data Matrix code?

Usually not. A phone camera looks for colour contrast, and a dot peen code has none — it is read by the shadow the dents cast under angled light.

An industrial scanner with 30° lighting reads it reliably. If you need a code a phone can read, you need a printed label or a laser mark on a smooth face.

Will the code still read after the part is painted?

Only if the dents are deeper than the coating. Paint and powder coating fill shallow marks completely and the shadow disappears.

Two options: mark deep enough to survive the coating thickness, or move marking to after painting. Tell your supplier the coating thickness before you buy — it decides which machine you need.

Which standard grades a dot peen code?

ISO/IEC 29158, also called AIM DPM. It lights the code at 30° to catch the shadow of the dents, and grades at two aperture sizes, reporting the better one.

ISO/IEC 15415 was written for printed codes under fixed lighting. Grade a dot peen code under 15415 and it will score too low — the method is wrong, not your machine.

How small can a dot peen Data Matrix code be?

The stylus tip sets the floor. Each cell needs one clean dent, and the dent cannot be smaller than the tip that makes it.

In practice that puts dot peen behind laser on very small parts. Ask your supplier for the minimum cell size their tip can hold, not the smallest code they can attempt.