Ask three shops to "engrave" a part and you may get three different processes. Fiber lasers mark metal three distinct ways, and the words are not interchangeable. Ablation removes a thin surface layer and stays microns deep. Engraving cuts into the metal, measured in thousandths of an inch. Stain marking heats the surface until an oxide layer forms, with almost no penetration at all. Each one suits different materials and different requirements, and choosing the wrong one is how parts get scrapped or fail a depth spec. Here is what separates them, and when each is the right call.
Quick answer:
A fiber laser marks metal three ways: ablation removes a surface coating or burnishes bare metal and stays microns deep, engraving cuts into the material and is measured in mils (thousandths of an inch), and stain marking (also called annealing) heats the surface to form a non-penetrating oxide layer. The right technique depends on the material and whether the mark needs depth.
The difference between the three is mostly a difference in depth and in what the laser is doing to the metal. Ablation and stain marking both stay at the surface, in the range of microns, while engraving deliberately goes deeper, into the thousandths. Ablation and engraving remove material. Stain marking removes nothing; it changes the surface chemistry with heat.
All three work on metals. Many plastics mark well too, but engraving into plastic usually melts it, so with plastics the goal is almost always a surface mark rather than depth. Once you know whether your part needs contrast, depth, or a clean non-contact mark, the technique chooses itself. If the terms speed, power, and pulse frequency are new to you, start with how the fiber laser marking process works and come back; the three techniques below are just different combinations of those settings.
Quick answer:
Laser ablation removes or vaporizes a thin surface layer, such as anodize off aluminum or the metallic film off coated plastic, to leave a contrasting mark without cutting into the part. It uses faster marking speed and lower power than engraving, and depths stay in the range of microns.
Ablation is the most common marking technique, and the cleanest example is anodized aluminum. The laser removes the anodize, exposes the base metal underneath, and textures that surface so it scatters light and reads as a stark white mark. Pull the metallic film off a piece of coated plastic and you get the same idea: a contrasting mark made by taking a layer away, not by digging in.
The settings are the opposite of engraving. Faster speed and lower power do the work, because the goal is to lift the coating and stop. Too much power for too long starts removing base metal or melting plastic, which defeats the purpose. Some materials are sensitive enough that a shorter pulse width is needed to keep heat from spreading. On anodized aluminum we often run two passes: a damage pass around 12 to 15 watts at 25 to 40 inches per second to clear the coating, then a lighter cleanup pass near 10 watts at 30 to 50 inches per second to brighten the mark. Aluminum has enough of its own variables, including anodize type and coating thickness, that we cover it separately in our guide to laser marking aluminum.
Anodized nameplates and panels are everyday work in our job shop, and ablation is the technique behind most of them.
Quick answer:
Engraving cuts into the metal itself, with depths measured in thousandths of an inch. It uses higher power and slower speeds, around 5 to 10 inches per second, with multiple passes. The practical limit for narrow line widths is about .020 inch, because past that the vaporized material cannot clear the trough.
You reach for engraving when the mark has to survive wear or abrasion, when it needs color fill, or when a spec demands depth. Firearms marking is the classic case, since some marks carry a minimum depth so they cannot be polished off. The trademarks of deep engraving are high power and slow speed, but the way you get a clean result is multiple passes, each taking a thin slice, with different fill angles between passes. Try to remove it all in one slow pass and you get a slaggy trough bottom and slag piled at the edges.
Focus sets the ceiling. Depths around .010 to .015 inch are reachable with the lens in one position; go deeper and you start moving the lens to keep the surface at the focal point. We have engraved past .025 inch into aluminum, but only by repositioning the lens many times, and it took real time. The other limit is the trough itself. As a narrow engraving gets deeper, the vaporized metal collects on the sidewalls instead of clearing, which puts a practical floor around .020 inch for narrow line widths. Past that, a rotary mechanical engraver is often the better tool.
Depth is one constraint; part geometry is another. Engraving a flat plate and engraving around a pen barrel are different jobs, and we cover the second one in laser marking curved and round parts.
Quick answer:
Stain marking, also called annealing, heats the metal surface with a properly sized beam until a dark oxide layer forms. It works on stainless steel, titanium, hard chrome, and a few similar metals. The mark is non-penetrating, only microns into the surface, which makes it well suited to medical instruments where no inks or chemicals can be used.
Stain marking heats the metal instead of removing it. Hold the right spot size on stainless steel or titanium and the heat grows an oxide layer that reads as a permanent dark mark. Run more passes and the layer gets darker, and with a variable pulse width MOPA laser you can push it into color shades like black, blue, red, and green by controlling that oxide thickness. The mark is attractive, permanent, and non-contaminating, which is why it shows up so often on surgical and dental instruments. It does have one limit: because it lives in the top few microns, it can be sanded or abraded off, so it is the wrong choice on a wear surface.
The secret to a good stain mark is spot size. Most fiber laser optics focus to a very small spot, too small for stain marking, so the beam removes material instead of gently heating it. You can defocus by moving the part away from the lens, but that gets subjective and falls apart on round or radiused parts as the beam drifts in and out of focus. The Jimani Hybrid fiber laser marking system handles this optically: a 1.5X reversible beam expander de-collimates the beam to produce the correct, larger focused spot and more depth of focus through the lens. That adds a little cost, and the stain-mark quality earns it back.
Quick answer:
Yes. Color marking controls the thickness of a stain-mark oxide layer and is best done with a variable pulse width MOPA laser. It is slow and temperamental, often 5 to 6 hours of setup per part, which is why Jimani does not offer color marking as a job shop service.
There are plenty of striking color-marked parts on the internet, and almost none of those photos mention the hours of setup behind them. Color is a balance of pulse width, power, speed, fill density, and frequency, and the right combination for one material rarely carries to the next. Dialing in a single part can take 5 or 6 hours, and the next part takes about the same.
We are honest about this in the job shop: we do not do color marking, because no one wants to pay for the setup time it really takes. If color is a hard requirement for your product, it is worth a direct conversation about whether it is practical for your volume.
Not sure whether your part needs ablation, engraving, or a stain mark? Send us a sample. We will mark it the right way for the material and the spec, and tell you which process we used and why.