Laser-Cut Vent Patterns: Hole Size and Web Width
A laser-cut vent pattern lives or dies on web width between holes. How close holes can sit in thin steel, why dense patterns warp, and how to lay one out.
Hundreds of little holes in a fan panel look easy in CAD. Then the first laser-cut vent pattern comes off the table wavy, or with a few webs burned through.
How Close Can Airflow Holes Be in Thin Steel?
Keep the web between holes at least half the sheet thickness, and closer to 1–1.5 times thickness if the panel needs to be stiff and cut cleanly. On 0.9 mm sheet, that's roughly 0.5 mm as a floor and about 0.9–1.35 mm as a target.
The question came from r/lasercutting, about airflow holes in a 0.9 mm SPCC front panel for a PC case. One reply pointed out that SPCC is a Japanese spec that's basically cold rolled carbon steel, and that it needs a proper metal-cutting laser rather than a hobby machine.
Spacing a laser-cut vent pattern
SendCutSend's cut feature guide gives the numbers above. It recommends hole diameters and bridging widths of at least 50% of material thickness, but would "prefer" 1X to 1.5X for strength and cut quality. It also warns that undersized bridging can get burned away by the laser. That's one fabricator's guidance, and it says to check the material specs too.
Heat is the real enemy in a dense field. Each hole adds a little heat to the same patch of sheet, and thin webs can't carry it away. That's the same effect behind nesting parts too close together.
A few layout habits help:
Stagger the rows. A hex layout gets more open area for the same web width than a square grid.
Keep the hole size at or above sheet thickness. Our post on the smallest hole you can laser cut explains why.
Leave a solid border. Holes running right to the panel edge or a bend line make a floppy, distorted edge.
Think about finish. Paint or powder coat closes holes slightly, so a tight pattern loses airflow after coating.
Getting it cut
Cold Rolled Steel, Galvanized Steel and Aluminum 5052 are all on our materials page. The sheet metal page lists a cut tolerance of "±0.13 mm cut", which matters when the web is only a millimeter wide. A dense field also costs more to cut, since the page says pricing counts cut length and pierce count. For the minimum web we can hold in your material and thickness, ask us when you quote.
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