How do you get sharp corners on a galvo laser with the Polygon delay?
Your fiber laser marks a square and the corners come out rounded, like someone sanded them. Or they’re crisp but scorched. That’s the EZCAD Polygon delay, the pause the galvo mirrors take at every change of direction. Too short rounds the corner. Too long burns it.
Applies to
- Process
- Galvo lasers: fiber, UV, CO₂ galvo
- Software
- EZCAD 2, EZCAD 3, LightBurn for galvo
- Range
- 0 and up (Polygon can’t go negative)
Why it matters
EZCAD treats a whole outline as one curve, whatever its shape. Its start and end corner belong to Start TC and Laser Off TC. Every other corner belongs to Polygon.
At each corner the mirrors have to stop and change direction. Polygon sets how long they wait. Too long and the laser sits in the corner burning. Too short and they swing around early, so a 90° corner becomes a soft curve.
On text and logos this is the difference between crisp and mushy. A lot of corners, all at once.
What good looks like
- True right angles on the test squares
- No dark spot or bulge at the corner
- Squares stacked so neighbouring corners sit side by side
How to apply it
- Finish Start TC and Laser Off TC first.
- Draw a 20 × 20 mm square and label it with the Polygon value.
- Mark at Polygon 1000. Move the next square slightly up and to the right, so the top-right corners cascade.
- Repeat at 500, 250, 100, 50 and 0.
- Judge only the top-right corners under a USB microscope. The bottom-left one belongs to Start/Laser Off TC.
- Find the pair that brackets the answer (burn on one side, rounded on the other) and run a second cascade between them in 25 µs steps.
Test it on your setup
- On Alex’s machine, 250 and up burned, 100 and below rounded off. The 25 µs cascade put the sweet spot at 150 µs: sharp corner, no burn-in. Use the method, not his number.
Exceptions & tradeoffs
Above about 4,000 mm/s, most stock galvo heads stop tracking accurately and timing that looked right starts to drift. Tune Polygon at a sane speed.
Common mistakes
- Judging Polygon at the bottom-left cornerThat corner is Start/Laser Off TC; read the top right
- Spacing the test squares far apartCascade them so the corners you compare sit together
- Tuning Polygon before the TC valuesSet Start TC and Laser Off TC first
Frequently asked questions
- What does the Polygon setting do in EZCAD?It sets how long the galvo mirrors pause at each corner of a curve. Too long burns the corner; too short rounds it off.
- Why are the corners rounded on my fiber laser engraving?The Polygon delay is likely too short, so the mirrors turn before they finish the corner. Raise it in small steps on a test card.
- Can Polygon delay be negative?No. It starts at 0, so the test runs from 1000 down to 0.
The contour is one curve; the start corner is TC, the rest are Polygon — The COMPLETE Guide to Timing and Delay for Galvo Lasers ↗ at 08:20.
What Polygon does: too long burns the corner, too short rounds it — The COMPLETE Guide to Timing and Delay for Galvo Lasers ↗ at 11:56.
Cascading 20 × 20 mm squares, read at the top-right corner, 1000 to 0 — The COMPLETE Guide to Timing and Delay for Galvo Lasers ↗ at 13:00.
Bracketing between 250 and 100, a 25 µs second cascade, landing at 150 — The COMPLETE Guide to Timing and Delay for Galvo Lasers ↗ at 14:56.
The cascading-squares test is Alex’s, and it’s a clever one. Lining the corners up beside each other turns a guessing game into a side-by-side comparison.