If you run a small job shop and need durable part IDs that won’t rub off, deep laser engraving steel with a 20–60W fiber galvo is a practical, repeatable path to 0.2–0.5 mm‑deep serials on tool steels. This guide walks you through setup, parameters, focus management, verification, and post‑processing so you can hit depth without drowning in burrs or heat tint. Use the steps as your baseline, then tune on coupons for your alloys and lens.
What You Need and Why It Matters
-
20–60W pulsed fiber galvo with an F‑theta lens (100–175 mm is common), an enclosed or interlocked work area, and a rigid Z stage.
-
Source capture fume extraction (pre‑filter + HEPA + carbon) positioned near the plume, plus non‑combustible beam stops.
-
Rigid fixturing: magnetic chuck, modular clamps, or a custom nest with a sacrificial backer.
-
Cleaners (solvent), wire brush, and optional vibratory tumbler; stainless work may require passivation or electropolishing.
-
PPE and shop controls for Class 4 lasers under an LSO program.
Class 4 controls—enclosures, interlocks, entry procedures, and eyewear selection—should align with the principles in the ANSI Z136.1 framework. For a readable overview, see the industry explainer on the safe use of lasers that summarizes ANSI Z136.1‑2022 requirements, and pair it with the OSHA Technical Manual’s Laser Hazards chapter for U.S. workplace program guidance.
-
According to the 2022 explainer on the safe use of lasers by ANSI, Class 4 systems require engineering‑first controls and LSO oversight, while the OSHA Technical Manual (Section III, Chapter 6) outlines program elements for hazard assessment and controls. Read the ANSI Z136.1‑2022 overview in the article Safe Use of Lasers and the OSHA Laser Hazards chapter for context.
Prep the Part and the Workspace
Clean the part to bare metal. Oils and oxide films steal energy, slow removal, and encourage recast. If glare is a problem, a light bead blast can even the surface finish without materially affecting depth. Mount the part in a rigid fixture that sets a repeatable Z reference; add a sacrificial backer under thin parts to damp vibration.
Stage the fume extraction nozzle close enough for source capture without disturbing the plume or risking collision. A concise vendor primer on capture methods explains why close‑in source capture protects people and optics; see the Purex guide to laser fume extraction for context.
Dialing Parameters for Deep Laser Engraving Steel
Deep laser engraving steel is a balancing act between fluence (energy per area), heat input, and material ejection. For tool steels (A2, D2, H13, etc.), start with these levers:
-
Power: Run near the source’s available max for roughing. You can taper power down slightly for finishing to limit heat tint.
-
Speed: 500–2000 mm/s on 30–60W systems for roughing is common; 20W may need slower speeds to maintain removal.
-
Frequency: 20–50 kHz concentrates energy per pulse for deeper removal. Higher frequency on cleanup passes can smooth edges.
-
Hatch spacing: 0.02–0.05 mm. Wider for roughing, tighter for finishing.
-
Pulse width: If adjustable, shorter pulses concentrate energy and can reduce burr; longer pulses may increase melt/ejection.
The patterns below reflect common shop practice and align with vendor tutorials on deep engraving metals (e.g., a stainless example that contrasts time‑ vs. quality‑optimized paths). Always confirm on coupons.
Starting recipes by power tier
Two to three pass “sets” are a unit of work; measure depth after each set. Use a cross‑hatch (0/90° or 45/135°) and bidirectional fill.
|
Power tier |
Roughing: power / speed / freq / hatch |
Finishing: power / speed / freq / hatch |
Notes |
|---|---|---|---|
|
20W |
100% / 600–900 mm/s / 25–35 kHz / 0.04–0.05 mm |
90–100% / 1200–1600 mm/s / 60–100 kHz / 0.02–0.03 mm |
Expect more passes; keep lens clean; consider smaller field for higher fluence. |
|
30–40W |
95–100% / 1000–1600 mm/s / 25–40 kHz / 0.03–0.05 mm |
85–95% / 1600–2200 mm/s / 60–120 kHz / 0.02–0.03 mm |
Good balance of time and quality for most serials. |
|
50–60W |
90–100% / 1400–2000 mm/s / 30–50 kHz / 0.03–0.05 mm |
80–90% / 2000–2600 mm/s / 80–150 kHz / 0.02–0.03 mm |
Watch heat tint on stainless; add cleanup sets as needed. |
Hatch and pass strategies
-
Rough with wider hatch spacing and lower frequency to maximize per‑pulse energy and chip out material. Run 2–4 sets.
-
Switch to 1–2 cleanup sets: tighten hatch spacing, increase frequency and speed, and optionally reduce power. This reduces burr and recast on character edges.
-
For characters and Data Matrix codes, keep quiet zones clear and avoid overburning corners by moderating overlap at direction changes.
A vendor stainless example illustrates the trade‑offs well: time‑optimized passes can be fast but create more distortion, while higher‑frequency finishing produces smoother cavities at longer cycle times. See the tutorial on deep engraving metal from Trotec for a concrete comparison.
Run the Job: Focus, Z‑Steps, and Pass Blocks
-
Make a coupon. Use the same alloy and finish as production parts. Engrave a 5×5 mm matrix of squares at varied speeds and frequencies while holding power constant. Record time and measured depth.
-
Zero and focus. Bring the surface to the lens’s nominal focus using your focus tool or autofocus routine. Verify on at least two points across the field.
-
Load the first roughing recipe. Run 2–3 pass sets with cross‑hatch (change angle between sets). Brush the cavity lightly and measure.
-
Adjust with intent. If depth is lagging, slow the speed or lower frequency to push per‑pulse energy. If burr is heavy, raise frequency and speed for a cleanup set and tighten hatch.
-
Manage focus as the cavity grows. For depths near 0.2–0.3 mm, most setups can stay at the original focus without dramatic loss. As you approach 0.4–0.5 mm, consider small Z‑steps into the cavity (e.g., −0.1 to −0.2 mm per set) to keep fluence up. Re‑verify focus at the surface plane between sets to understand your offset.
-
Finish cleanly. Shift to the finishing recipe for your power tier. Add one or two fast, higher‑frequency cleanup sets to knock down recast.
Think of Z‑stepping like keeping a flashlight beam tight as you walk into a tunnel—small adjustments preserve intensity on the spot you’re working.
Verify Depth and Readability
Aim for ~0.2–0.5 mm depth for rugged serials on tool steels unless a drawing or contract says otherwise. You don’t need a lab to measure:
-
Microscope focus method: Focus on the surface, note the stage position, then focus on the cavity bottom and subtract. With a calibrated stage, you can resolve ~0.01 mm.
-
Mechanical approximations: Pair thin feeler gauges or shim stacks with a fine‑tip depth indicator. It’s not pretty, but it’s consistent once practiced.
If you’re marking Data Matrix, grade with a verifier that supports ISO/IEC 29158 (AIM DPM). The DataMan verifier reference manual from Cognex explains the grading method, lighting, and report outputs; many shops target C/2.0 or better unless a higher grade is specified.
Post‑Processing That Preserves Depth
For tool steels, a light wire brush or short vibratory tumble is often enough. Clean with solvent to remove residues and oil the surface if corrosion is a concern in service.
On stainless, deep engraving can disturb the passive layer and leave heat tint. Industry practice follows a clean‑then‑passivate sequence per the ASTM A967 passivation standard (often after cleaning/descaling in ASTM A380). Where edges show persistent discoloration or burr, electropolishing per ASTM B912 can both smooth and repassivate the affected zones more effectively than passivation alone.
Troubleshooting and Quick Fixes
|
Symptom |
Likely cause |
What to change |
|---|---|---|
|
Shallow depth after many passes |
Fluence too low; lost focus; dirty optics |
Slow speed or lower frequency to boost per‑pulse energy; confirm focus; clean lens; verify output power. |
|
Heavy burr/recast or heat tint |
Too much melt; plume redeposition; low scan speed |
Add high‑frequency, faster cleanup sets; tighten hatch; reduce power slightly for finishing; improve fume nozzle position. |
|
Ghosting/double edges |
Part movement or vibration |
Increase clamping; add sacrificial backer; reduce acceleration or split the artwork. |
|
Inconsistent character legibility |
Overlap/angle issues; field non‑uniformity |
Verify hatch overlap and cross‑hatch angles; re‑calibrate field; check lens flatness across the work area. |
Throughput Reality Check and Power Scaling
Cycle time scales with removal rate, which depends on power, spot size, and settings. A well‑documented stainless example at 20W shows roughly 200–220 μm depth achieved two ways: a faster path with more distortion and a slower, smoother path at similar depth on a small 5×5 mm area. Tool steels are tougher, so expect longer times at similar depth. Higher power can reduce passes or increase speed, but watch burr and heat tint—especially on stainless.
Use these benchmarks to set expectations with customers: deeper than 0.5 mm is possible, but time and post‑processing effort rise quickly.
Wrap‑Up and Next Steps
Deep laser engraving steel for serialization comes down to a disciplined loop: prep and fixture well, rough with energy‑efficient settings, measure early and often, then finish with lighter, faster passes to clean edges. Document your recipes by alloy, lens, and target depth so future jobs start at pass three instead of pass zero. And before you scale to production, run a short pilot batch with verification and post‑process steps included—the small investment pays back in rework avoided.
