A worker scans the small square Data Matrix code on a steel part. The shop scanner reads it in a second. Then the customer checks the same part with a verifier, a device that scores barcodes from A to F. It gets a D.
A Data Matrix is a small square barcode, a bit like a QR code, made for parts. It can be as small as 2–3 mm across. It still reads with about 30% of it damaged.
But a code that scans on the line can still fail an audit. Three things decide that: the material, the code size, and the tool used to check it. This guide covers all three, plus how to mark a Data Matrix on 7 common metals.
The short version
- Parts get Data Matrix, phones get QR. Data Matrix reads at 2–3 mm. A phone QR code needs about 20 mm.
- Size the cells to the surface. 0.2–0.3 mm on smooth faces, 0.4 mm or more on castings.
- Pick the method by material. Fiber laser for smooth metal, dot peen for rough, oily or hot parts.
- “It scans” is not “it passes”. Audits grade Data Matrix codes A–F under ISO/IEC 29158.
Words used in this guide
- Cell
- One small square of the Data Matrix code. Also called a module.
- Quiet zone
- The blank border around the Data Matrix code.
- ECC 200
- The version of Data Matrix that every modern rule uses.
- Dot peen
- A hard pin hits the part and leaves small dents. Each dent is one cell.
- Verifier
- A reader that grades a barcode from A to F, not just reads it.
What Is a Data Matrix Code?
A Data Matrix is a square or rectangular 2D code. It stores up to 2,335 letters or 3,116 digits in a grid of small black and white squares. It still reads with about 30% of the code damaged. Almost every part today uses the version called ECC 200.
The rules for the code are in one standard, ISO/IEC 16022. Each small square is called a cell. A dark cell means 1. A light cell means 0.
A normal barcode stores data in one line, so it gets longer as you add characters. A Data Matrix stores data in rows and columns, so it stays small. That is why it was made in the late 1980s: for parts too small to carry a normal barcode.
Today you find it on engine parts, circuit boards, surgical tools and aircraft parts. In short, anywhere a part needs a permanent ID and has very little space for it.
DMC is short for Data Matrix Code. It means the same thing.
Data Matrix vs QR Code: Which One Belongs on a Part?
Use Data Matrix on parts. It reads at 2–3 mm across, needs only a one-cell blank border, and is the code named in military (MIL-STD-130), aerospace (AS9132) and medical device (UDI, the unique device ID) rules. Use a QR code when the public will scan it with a phone. That needs about 20 mm.
Data Matrix | QR code | |
|---|---|---|
How to spot it | One solid “L” on two edges | Three big squares in three corners |
Blank border it needs | 1 cell wide | 4 cells wide |
Smallest size that reads well | 2–3 mm, with an industrial reader | About 20 mm, with a phone |
Damage it can survive | About 30%, fixed | 7%, 15%, 25% or 30%. You pick; more means less data. |
Who scans it | Readers on the line, auditors | Customers with phones |
Where rules ask for it | Military, aerospace, medical UDI, automotive parts | Marketing, menus, packaging |
The blank border matters more than people think. A QR code needs four cells of empty space on every side. On a small bracket, that border alone can take more room than a whole Data Matrix.
A QR code holds more data at full size: up to 4,296 letters. But a part number, a date and a serial need 20–40 characters. A Data Matrix holds that in a code the size of a grain of rice.
So the rule is simple. If a machine reads it, use Data Matrix. If a person with a phone reads it, use QR.
Need to mark Data Matrix codes on your parts?
Tell us the material, the part size and what the Data Matrix must hold. HeatSign will suggest a marking machine and a cell size.
How Do You Spot a Data Matrix and Tell If It Is ECC 200?
Look for one solid “L” along two edges. A QR code has three corner squares instead. Then check the top-right corner cell. On ECC 200 it is always light, and the rows and columns are always even numbers. Older ECC 000–140 codes fail both checks.
Every Data Matrix has four parts:
Part | What it looks like | What it does |
|---|---|---|
Finder pattern | The solid “L” on two edges | Tells the reader where the code is and which way is up |
Timing pattern | Dotted light-dark line on the other two edges | Tells the reader how many rows and columns there are |
Data area | The cells in the middle | Holds your data plus backup data for repairs |
Quiet zone | Blank space, 1 cell wide, all around | Separates the code from the part around it |
Why care about ECC 200? Because every modern rule means ECC 200 when it says “Data Matrix”. That includes MIL-STD-130, AS9132, FDA UDI and GS1 (the global barcode standards body). The older versions only live on in old systems.
One warning. The 30% damage rule only covers the data area. It does not cover the “L” or the quiet zone. A scratch across the middle of the code is usually fine. A scratch along the “L” often kills the code, because the reader can no longer find it.
How Much Data Fits, and How Big Should the Data Matrix Code Be on a Part?
A 14-character serial number fits in a Data Matrix code of about 16 × 16 cells. Multiply by the cell size to get the code size: with 0.25 mm cells, the code is about 4 mm across. MIL-STD-130 allows cells from 0.19 to 0.635 mm. On rough castings, use 0.4 mm or more.
ECC 200 comes in fixed sizes. There are 24 square sizes, from 10 × 10 to 144 × 144 cells. There are 6 long, thin sizes, from 8 × 18 to 16 × 48 cells, for narrow spots like a shaft or a cable. The software picks the smallest size your data fits into.
The bigger question is the cell size. Here is the rule: each cell must be bigger than the bumps on the surface. If the surface is rough, the reader cannot tell a cell from a bump.
Surface | Cell size to start with | Why |
|---|---|---|
Smooth machined or ground face | 0.2–0.3 mm | Little texture, so small cells read well |
Normal machined part | 0.3–0.4 mm | Tool marks start to compete with small cells |
Die-cast or sand-cast face | 0.4 mm or more (in our experience) | Pores and texture swallow small cells |
Shot-blasted after marking | About 0.6 mm | Blasting wears down small cells. One laser maker’s tests found 0.6 mm cells held up best. |
For military parts, stay inside the MIL-STD-130 range: cells of 0.19–0.635 mm (0.0075–0.025 in), and the whole code no bigger than 25 mm (1 in) square.
A quick example. A die-cast housing needs to carry 20 characters. That fits in a 16 × 16 cell code. At 0.45 mm per cell, it is about 7 mm across, plus a thin blank border. Most housings have that much flat space if you plan it before the mold is made.
How Do You Mark a Data Matrix on Steel, Aluminum, Brass and Cast Parts?
Match the method to the surface. A fiber laser suits machined steel, stainless steel and bare aluminum. A MOPA laser turns anodized aluminum black. Dot peen suits cast, scaled or oily parts, and parts that later face heat above 200 °C. Rough castings need a cleaning pass or bigger cells.
Fiber Laser or Dot Peen: What Is the Difference?
- Fiber laser marking. A laser beam changes the top layer of the metal. It can heat it until it turns black (called annealing), or burn a little of it away (engraving). It gives sharp, high-contrast cells. It works best on clean, smooth metal.
- Dot peen marking. A hard carbide pin hits the part and leaves a row of small dents. Each dent is one cell. The dents are deep, so they survive paint, grit and heat. They read by shadow, not by color.
Which Method Works on Which Metal?
Here is how we match them to materials in our sample room:
Material | Best method | Watch out for |
|---|---|---|
Stainless steel (304 / 316) | Fiber laser black mark (annealing) or light engraving. Dot peen also works. | A black annealing mark fades above about 200 °C. For medical parts, check your cleaning process first. |
Carbon steel, machined | Fiber laser engraving or black mark. Dot peen for heavy parts. | Parts that rust need a deeper mark, so the code still shows under rust. |
Bare aluminum (6061, 5052) | Fiber laser. Gives a light grey or white mark. | Shiny metal reflects light. Use a reader with diffuse (soft, even) light. |
Anodized aluminum | Fiber laser removes the coating and leaves a white mark. A MOPA laser (a fiber laser with adjustable pulse length) can mark it black. | Don’t burn too deep. A shallow mark gives the best contrast. |
Die-cast aluminum (A380, ADC12) | Laser cleaning pass first, then mark with 0.4 mm+ cells. Or dot peen. | High-silicon alloys mark dull and grey. If you change metal supplier, test again. |
Brass, copper, bronze | Dot peen (the metal is soft, so dents form easily). Fiber laser also works with the right settings. | These metals reflect a lot of laser light. Old parts darken, which lowers contrast. |
Cast iron, forgings with scale | Dot peen. | Hard scale wears the pin faster and gives poor dark-light contrast. |
Two things from our own work stand out. First, the same “aluminum” behaves very differently. In our experience, 6061 and 5052 mark clean and bright, while high-silicon die-cast alloys like A380 mark dull. So if you change your metal supplier, test the code again. Don’t assume the old settings still work.
Second, the only real test is your own part. We have marked thousands of test parts in our sample room: stainless steel, aluminum, titanium, brass and anodized parts. The results still surprise us.
Not sure which method fits your part?
Tell us the material, the part size and what happens to it after marking. We will suggest a method and a cell size.
What Makes a Dot Peen Data Matrix Code Readable?
The dots must touch or nearly touch. A good target is a dot about 80% as wide as the space between dot centers. If the gap between dots is more than half a dot wide, the code gets hard to read.
Pin force matters too. Too much force makes dents that spread and merge into their neighbors. Then the reader can no longer count the cells. For settings on steel, copper and cast iron, see our dot peen Data Matrix guide.
The aerospace standard AS9132 checks three things on dot peen Data Matrix codes:
AS9132 check | Limit | What it means on the shop floor |
|---|---|---|
Dot size | 65–105% of the cell | Too big: lower the pin force. Too small: raise it. |
Dot center offset | Up to 20% of the cell | Dots out of line usually mean a loose fixture or a worn marking head. |
Angle of distortion | Up to 6° | The “L” must stay square. Clamp the part flat. |
Which Machine Should You Start With?
For most plants, one of these three covers it:
Desktop Fiber Laser, 20–50 WFor machined steel, stainless steel and bare aluminum. Sharp Data Matrix codes down to small cell sizes. $1,950–5,000.View machine →
MOPA Fiber Laser, 30–100 WFor black marks on anodized aluminum and thin parts that must not warp. $2,500–6,500.View machine →
Electric Desktop Dot PeenNo air compressor needed. For cast, scaled or oily parts, with a built-in touch screen. $1,900–2,900.View machine →Compare all models on our fiber laser markers and dot peen machines pages.
Will the Data Matrix Code Survive Paint, Blasting and Heat?
It depends on how the code was made. A laser annealing mark fades above about 200 °C. Shot blasting wears down shallow cells, so bigger 0.6 mm cells hold up better. Paint and zinc fill small cells. Deep laser engraving or dot peen survives most post-processing.
Think of the finish as a layer on top of your code. A thin black laser mark has no depth, so paint covers it and heat erases it. A dent 0.3 mm deep still shows under a coat of paint.
- Heat above 200 °C (heat treatment, hot casting): don’t use a black annealing mark. Use deep engraving or dot peen.
- Shot blasting after marking: use bigger cells, about 0.6 mm, and mark deeper.
- Galvanizing or thick paint: mark deep and big, or mark after the finish.
We tested this in detail in our guide on how deep to mark before paint, blasting or galvanizing.
Why Does a Data Matrix Code Scan on the Shop Floor but Fail the Customer’s Audit?
A shop scanner only needs to read the code once. An audit verifier grades it from A to F under ISO/IEC 29158, and many customers ask for grade C or better. Grading a part mark with ISO/IEC 15415, the standard for printed labels, can fail good codes.
“It scans” and “it passes” are two different things. A scanner tries many times until it gets a read. A verifier measures the code: contrast, cell size, how square the grid is, and more. The final grade is the lowest of those scores. One weak point is enough to fail.
The most common reason we see for a low grade is marking too fast. At high speed, the laser’s mirrors drift a little, so the grid stretches in one direction. Verifiers call this axial non-uniformity (ANU). In our experience, slowing the laser down by 10–20% often lifts a code from grade C to grade B.
If your customer audits Data Matrix codes, you can add an online verifier after the laser. It checks every part. If a code grades C or lower, the line stops and the part is marked again.
What you want | What to use |
|---|---|
Just read the Data Matrix code on the line | Industrial reader (any code that decodes is fine) |
Prove the code meets the customer’s grade | Verifier set to ISO/IEC 29158 (for part marks) |
Check printed labels | Verifier set to ISO/IEC 15415 (for print) |
Check dot peen Data Matrix codes for aerospace | AS9132 dot checks, plus an ISO/IEC 29158 grade |
For the full grading rules, read how ISO 29158 grading works. To see which machines hold a grade on your parts, see choosing a Data Matrix marking machine.
Need a Data Matrix code that passes your customer’s audit?
Tell us the part, the material and the grade your customer asks for. Our sales team will send the right machine setup and a full quote, shipping included.
How Do You Read a Data Matrix Code?
Use the right tool for the job. A phone app reads printed barcodes and QR codes. An industrial reader with angled or soft light reads codes marked into metal. A verifier grades the code against ISO/IEC 29158. Data Matrix codes marked into metal have no ink, so phones often fail on them.
Tool | Printed labels | Data Matrix codes marked into metal | Gives a grade |
|---|---|---|---|
Phone app | Yes | Often not | No |
Industrial reader | Yes | Yes | No |
Verifier | Yes | Yes | Yes (A–F) |
Why do phones fail? A dot peen Data Matrix code is just dents in bare metal. It only shows up when light hits it from the side, which makes shadows in the dents. A phone lights the part from the front, so the dents disappear. Industrial readers use side light or soft, even light for exactly this reason.
FAQ
Is a Data Matrix the same as a QR code?
No. Both are 2D codes, but a Data Matrix has one “L” border and a 1-cell blank border. A QR code has three corner squares and a 4-cell border. Data Matrix fits on smaller parts. QR holds more data and scans with any phone.
What does DMC mean?
DMC stands for Data Matrix Code. It is the same code. People in automotive and electronics often use the short form.
What is the smallest Data Matrix?
The smallest ECC 200 code is 10 × 10 cells. Its real size depends on the cell size. MIL-STD-130 allows cells from 0.19 mm, so a small code can be about 2 mm across.
How many characters can a Data Matrix hold?
Up to 2,335 letters and numbers, or 3,116 digits, in the biggest 144 × 144 size. Most Data Matrix codes on parts carry 15–40 characters and use a size of 14 × 14 to 22 × 22 cells.
Can I read a Data Matrix with my phone?
Yes, if it is printed on a label. Data Matrix codes marked into metal often won’t read on a phone. They need an industrial reader with side light.
Which machine marks a Data Matrix on metal?
A fiber laser for clean, smooth metal. A dot peen machine for rough, cast or oily parts, or parts that face heat or blasting later. Some plants use both.
Data Matrix Marking: Where Should You Start?
Most failed Data Matrix codes we see are not a problem with the code itself. They are a planning problem. Someone picked the machine first, then found out the part was die-cast, or got blasted, or was graded by a verifier.
So work in this order. First, the material and what happens to the part after marking. Then the cell size. Then the method. Last, the grade your customer checks.
If you already know your part and your customer’s grade, send us both. We will tell you which method and cell size to use.
Sources
- ISO/IEC 16022, Data Matrix bar code symbology specification
- ISO/IEC 29158, Direct Part Mark (DPM) quality guideline
- MIL-STD-130, Identification Marking of U.S. Military Property
- SAE AS9132, Data Matrix quality requirements for parts marking
- Keyence, “Data Matrix code vs. QR code: what is the difference?”
- Pryor, “How to Pass AS9132”
- Vision Systems Design, “Dot scribing ensures barcode readability”
- Laserax, “Data Matrix Code Laser Marking” and die-cast marking tests
- Trumpf, laser annealing application page
