Cutting Metal on Fiber: Filled Offset Rings
A galvo fiber cuts sheet metal well, jewelry charms, silver blanks, slide cutouts, but not the way a gantry laser does. Line mode is the trap: a single-line kerf on fiber re-welds itself shut behind the beam. The working method is a filled ring around the cut path, engraved down through the material. Numbers below are starting points for a 60W JPT MOPA-class source.
The cutting recipe (all metals, including gun slides)
| Speed | 450 mm/s (window 400-600) |
| Power | 90% (the only job class that runs 90) |
| Frequency | 55 kHz |
| Line interval | 0.03 |
| Hatch | Cross-hatch, even + odd angle discipline |
| Mode | Fill on the offset ring, no sublayers, no preset pass count |
Save it to its own layer color (red is the convention) so every cut job is one click.
Building the offset ring
- Select the cut path, then Tools → Offset Shapes.
- Ring width: 0.4mm per 1mm of material thickness. 1mm sheet = 0.4mm ring, 2mm = 0.8mm.
- Offset direction: OUTSIDE for jewelry (the piece you keep is inside the ring, so it stays dimensionally true), INSIDE for firearms cutouts (the slide is what you keep, so the ring eats the waste side). Never both.
- Corners: always Round.
- Fill the ring with the cutting layer. Tiny holes (jump rings, hardware holes): skip the ring and fill the whole circle.
Running the cut
- Workholding: bridge the sheet across two 1-2-3 blocks so the beam exits into air, with a business card or sacrificial steel below to catch it. Frame first to confirm you're clear of the block edges.
- Interior cutouts before the exterior ring, so the part stays held while the detail work happens.
- Run Continuously (no preset pass count) and watch the underside of the kerf.
- Stop condition: consistent bright white light all the way around the outline, light showing through the kerf from the far side, then give it one to two more minutes for insurance.
Pop it out with a pencil, never let it drop
Don't run until the part falls free. A dropping part can flash back at the lens or fall crooked into the kerf. Stop at the white-light condition, then push the part out with a pencil. If it fights back, a section isn't cut through, run another minute and try again.
What never to use
- Line mode: the kerf re-welds behind the beam on fiber. Always a filled ring.
- Wobble: shrinks cut dimensions and leaves ugly edges.
Time and margin benchmarks
- Thin brass jewelry charm cutout: roughly 9-15 minutes on a 60W-class source.
- 1mm sterling silver: roughly 6 minutes, and silver jewelry blanks are one of the highest-margin lanes a fiber shop has. Keep silver power at or below ~75%.
- Fresh cuts are gritty on top from slag: flat-sand the top face, light-sand the pop-out edge, Scotch-Brite overall. See Darkening & Finishing for the full finishing rules.