Laser Marking & Engraving on Machined Parts

What it is and when to specify it

Laser marking leaves a mark with no measurable depth; laser engraving cuts one 0.025 mm to 0.13 mm deep. Choosing between the two is the first decision on any marked part, and they are not interchangeable — one leaves the surface intact, the other removes material from it.

Both are used for the same family of requirements: part numbers, serial numbers, logos, traceability codes and data matrix codes. Marking is the default where the surface must stay intact, and engraving is chosen where the mark must survive abrasion or where a tactile, recessed mark is wanted. The process is arranged and managed by us through our vetted partner network, managed under one quality process, so your artwork and position callouts are handled under one process. The right approach is usually settled by whether the mark must sit below the surface or simply be visible and permanent. For the wider range, see surface finishes.

Laser marking is four different processes

“Laser marking” covers four distinct ways of putting a mark on metal, and they cannot be substituted for one another. The same part number can require different processes on different materials, so specifying which one you need is the first decision on this page.

Annealing, or oxide marking, is the default on stainless steel. The fibre laser heats the surface without melting it, and a thin oxide layer forms that reads dark against the metal. Depth is effectively zero — the mark is a surface condition measurable in microns, and the part dimensions are untouched.

Engraving removes material. The laser vaporises a shallow pocket, typically 0.025 mm to 0.13 mm deep, which is 0.001 in to 0.005 in. This is the choice when the mark has to survive aggressive cleaning, when it must be felt, or when a paint fill will be added. It is a real cut, and on a thin wall or a sealing face that matters.

Contrast marking works on anodised aluminium, coated parts and some plastics, where the laser changes the coating rather than the substrate. On clear anodise the mark reads white; on black anodise it reads light grey or white depending on the setting.

Ablation removes a coating — paint, ink or plating — to expose what is underneath. It is used for marks that have to sit under a later coating, and for stripping a small area of a cosmetic finish so a mark can be applied after coating.

A mark that anneals cleanly into 304 stainless produces almost no contrast on plain aluminium, and a mark that engraves well into aluminium will not colour stainless at all.

What “mark the part” actually has to specify

By the time a drawing reaches a machine, “laser mark the part” has usually lost most of the information needed to make the mark correctly. Seven things decide it, and a callout that names all seven comes back right the first time.

The content is the obvious one — part number, revision, lot, date code, a two-dimensional code or a logo. Give the exact string, including separators and leading zeros, because a mark is not the place for interpretation.

The location has to be dimensioned from a datum rather than described. “On the shank” is not a location. “On the shank, 5 mm from the shoulder face, centred on the axis” is.

Character height sets readability. For human-readable text on machined parts, 1 mm to 3 mm is the working range; below 0.5 mm the mark becomes an inspection-equipment feature rather than a label. An operator reading a part number at arm’s length needs at least 1.5 mm.

Depth applies only to engraving, and it is a tolerance rather than a wish. State it as a range — 0.05 mm to 0.10 mm deep — because a single value cannot be held on a laser.

Contrast is what makes the mark legible. State whether the mark must be readable under normal shop lighting or is required only for machine vision; the two need different settings and different inspection.

Grade applies to two-dimensional codes. A data matrix code that scans once on the bench and fails on the line is a grade problem rather than a printer problem, and the practical answer is to name the required grade in the callout.

Post-processing is the one most often forgotten. If the part is stainless and will be passivated, say whether the mark is applied before or after, because that answer changes the procedure rather than the mark.

What each material does under a fibre laser

The mark is a reaction between the beam and the surface, so the material sets the result before any setting is chosen.

Stainless steel anneals well. Grades 303, 304, 316 and 17-4 PH all take a dark, high-contrast mark at low power, the oxide is stable, and the mark survives normal handling. It is the easiest material on this list.

Aluminium does not anneal into contrast. Marks are made by a controlled melt or by ablation of the oxide layer, and the result is grey rather than black. On anodised aluminium the coating does the work and the contrast is excellent.

Brass and copper reflect the beam and conduct heat away quickly, so they need more power for less contrast. Marks are usually light on dark and shallower than on steel.

Titanium takes a mark by controlled oxidation, and the colour varies with the energy applied — useful where a mark has to be distinguishable from a decorative finish on the same part.

Plated and coated parts are the trap. Marking through a zinc or nickel plate can breach it locally and start a corrosion cell at the mark. Either mark before plating, or mark after plating at settings that colour the plate without breaking it, and say which on the drawing.

Plastics are a separate case. A fibre laser does not mark most of them usefully, and the marks that do work are made with a different wavelength or with a laser-sensitive additive compounded into the resin.

Marking and corrosion: the passivation question

Laser marking a stainless part disturbs the passive oxide layer that makes the material corrosion-resistant, and the disturbance sits exactly where the mark is. That is why the sequence matters more than the setting.

Two things happen at the mark. The heat of the beam changes the local structure, and surface contamination is driven into the surface rather than removed. Both reduce the local resistance to corrosion, and both are partly recovered by passivation after marking. On parts destined for outdoor, marine or wash-down service, mark first and passivate afterwards — the alternative is a mark that becomes the place corrosion starts.

Where the part cannot be re-passivated, the options are to engrave to a depth that is then mechanically cleaned, to mark in a location that is never wetted, or to accept an annealing mark with the oxide left intact, which is the least disruptive of the three.

The same logic applies to plated parts. A mark that breaches a zinc plate leaves bare steel at the mark, and on a part that sees condensation the mark becomes the first rust. Mark before plating, or mark after plating within the coating.

Where not to put a mark

A mark is a feature. It changes the surface it sits on, and there are places where that change costs more than the mark is worth.

Keep marks off sealing faces — O-ring grooves, gasket lands and any surface that has to seal against fluid. Even an annealed mark changes the surface condition, and on a face that seals under pressure that change is a leak path.

Keep them off bearing and sliding surfaces where the mark would sit inside the contact zone. Outside the wear track, on a shoulder or an end face, the same mark is harmless.

Keep them off threads, both because the mark disturbs the flank geometry and because a mark inside a thread is unreadable in service anyway.

Keep them off stress-critical fillets and section changes, where a shallow engraved pocket can act as a stress riser on a part that cycles.

Keep them off cosmetic surfaces unless the customer has accepted a mark there. On a visible face a mark is branding, on a hidden face it is traceability, and the two callouts are different documents.

The good locations are usually the same on every part: an end face, a shoulder, a machined flat, or the head of a fastener. Making that the default removes an entire class of questions at quotation stage.

How laser marking compares with the alternatives

Laser marking is not the only way to put a permanent mark on a machined part, and it is not always the right one.

Ink stamping is fast and inexpensive and rubs off. It suits a mark that only has to survive the assembly line, and it is the wrong choice for anything that has to stay legible after a year in service.

Dot peen produces a deeper, rougher mark by impact and is very durable, but the characters are larger and the surface damage is greater. It is common on castings and on parts where the mark is struck into a rough surface.

Chemical etching gives an even, shallow mark and needs masking, chemicals and a stencil per change. It is slower per part and better suited to flat plates than to turned parts.

Electrochemical etching uses a stencil and an electrolyte to mark without heat, which is the advantage on thin or heat-sensitive parts, at the cost of a stencil for every content change.

Laser marking wins on turned and milled parts because it needs no tooling, no mask and no consumable, it can change content between parts without a setup, and in its annealing form it leaves the part dimensionally untouched. For low and medium volume work with a variable mark, that combination is hard to beat.

Putting laser marking on the drawing

A callout that comes back right the first time reads like a short paragraph rather than a word. It names the process, the content, the place, the size and the sequence.

Write the process together with the material reaction: “laser anneal mark” on stainless, “laser contrast mark” on anodised aluminium, “laser engrave 0.05–0.10 mm deep” where a paint fill follows. Then state the content exactly as it must appear, in the case it must appear in.

Dimension the location from a datum the shop already uses, and state the character height. For a machine-readable code, name the symbology and the required grade rather than leaving the choice to the marking program.

Finally, state the sequence relative to any surface treatment. “Mark after passivation” and “mark before passivation” are different instructions, and on stainless parts that see moisture only one of them keeps the mark from becoming the place the part fails.

Send the drawing with the mark called out this way and the marking is quoted as a line item with the depth, the sequence and the inspection method included. Where the mark is the only open question, we come back with a proposal rather than a guess.

Specifications

Depth and contrast are the two levers that define a mark, and both are specified rather than assumed. Engraving depth is set from the drawing and confirmed per part. Contrast is specified by appearance on each material — from a dark mark on stainless steel and aluminium to an annealed tone on titanium — and it is judged by legibility rather than a measured number.

Fibre lasers cover most metals and are the usual choice for steel, stainless steel, aluminium, brass and copper. Other laser types are available where the material and the mark call for them. Content such as logos and data matrix codes is produced from artwork you supply, so fonts, formats and cell sizes match your specification. For logos and fine text, we work from your vector artwork so the mark reproduces cleanly at small sizes.

Parts ship with a material certificate (MTR) and pre-shipment photos. Lead times follow our standard schedule: samples in 5–10 days and production in 25–35 days after sample approval, with the MOQ from 50 pieces and samples from 1 piece.

Which materials and parts it suits

Laser marking suits the full metal range we machine. We arrange it on aluminium 2024, 5052, 6061 and 7075, stainless steel 303, 304, 316 and 316L, carbon and alloy steel 1045, 1215 and 4140, and brass, bronze, copper and titanium. The beam is tuned to each material so the mark is legible and stable rather than burnt or shallow.

The finish is used wherever a part must be identified in service — serialised housings, brackets, shafts and electrical components that carry a part number or a data matrix code for traceability. It also covers logos and branding on visible surfaces. Because the mark is permanent and does not rely on ink or labels, it survives handling, cleaning and long-term use. A data matrix code, for example, can carry a serial number, batch or date code that travels with the part from machining through assembly and field service. See the full materials list to confirm substrate options.

Corrosion, wear and dimensional impact

Marking has a small surface impact that is worth planning around. A contrast mark leaves the surface essentially unchanged, while engraving removes a small amount of material, so engraved marks are placed away from critical surfaces and specified with a depth that stays within the part’s tolerance envelope. Where a part is plated or anodised, the mark is usually applied after finishing so it reads through or on top of the coating as the drawing requires.

The dimensional impact is minimal for contrast marks and limited to the recess for engraved marks. We machine precision features to ±0.01 mm and hold ISO 2768-m as a general tolerance, and we confirm mark position and depth against the drawing. Every order starts with a quote within 24 hours that includes DFM feedback.