LightBurn rotary settings
Split, Line Interval and effective diameter for engraving inside a ring on a fiber laser with a chuck rotary. Every value in whole motor steps.
An approximation to verify on metal
This tool is in beta. It computes from geometry and from the motor step count, but the chuck calibration factor is empirical: it depends on the tilt angle, the jaw geometry and where the beam lands. Treat the result as a starting point, run the two-line test from the calibration section and a trial on a marker-blackened steel ring before you touch gold. If something does not add up, write to us: that is the shortest route out of beta.
The values below are an approximation from formulas. Verify them on a marker-coated steel test piece before setting them on the final ring, and use the calibration section below.
In the mm system, type the inner diameter directly in the field below.
Measure with a caliper if you have the ring in hand, the field stays editable after picking a size.
Don't know the size? Printable ring sizer
The same number has to be set on the driver (DIP switches) and in LightBurn.
Source: no data, k=1 by default
The calibration factor has not been measured yet for this angle and side. Until the test in the Calibrate the diameter section, the values below are an approximation with k=1.
ChuckONONON640018.94059.500.40910.0000X5002000400OFFON75.000Fill0.037290ONOFFOFFOFFOFFall shapes at onceCheck with the Frame button in LightBurn whether the frame covers the engraving spot on the ring.
Goal: find the calibration factor k for the current tilt angle and engraving side. A stretched text means the diameter must be INCREASED, not decreased.
- 1. Set the calculator values for the starting k.
- 2. Engrave two vertical marks on the marker-coated ring, 40.00 mm apart along the rotation direction, 0.5 mm tall.
- 3. Measure the gap on the metal, a strip of paper pressed into the mark works well against a ruler.
- 4. Enter the measured value below.
This tool does not pick laser power or speed. Power and speed selection: laser parameters calculator
Diameter calibration in four steps
- 1Enter the calculator values
Type Object Diameter, Split, Overlap and Line Interval computed for the starting factor into LightBurn.
- 2Engrave two lines
On a steel ring blackened with a marker, engrave two vertical lines 40.00 mm apart in the direction of rotation, 0.5 mm tall.
- 3Measure the gap on the metal
A paper strip pressed into the ring, laid against a ruler. Note the gap to a tenth of a millimetre.
- 4Enter the measurement
The new diameter is the current one multiplied by measured over designed. A stretched text means a larger diameter, not a smaller one. The calculator recomputes Split and Line Interval and stores the factor for this angle.
Questions about ring engraving with a rotary
Why does the text inside the ring come out stretched or squeezed?+
Usually for two reasons at once. First, Object Diameter in Rotary Setup holds the measured inner diameter, while it should hold the effective diameter: the measured one multiplied by the chuck calibration factor; with a tilted chuck the difference reaches several percent. Second, Split and Line Interval do not land on whole motor steps, so the rounding accumulates over hundreds of slices. The calculator handles both: the diameter from calibration and every value as a multiple of the step.
Why do the letters overlap or come out chopped into vertical stripes?+
Stripes usually mean the wrong rotation direction: for engraving inside the ring, Reverse Rotary Direction must be on, otherwise the slices land on the wrong side. Overlapping letters most often come from Run Whole Shapes being on in Rotary Marking, which makes LightBurn draw a whole letter within one slice and exposes the gear backlash. Set Run All Shapes in Each Slice and turn Whole Shapes off.
Why must the rotation direction be reversed when engraving inside a ring?+
The beam hits the inner wall from the inside, so for the same chuck rotation the surface moves under the beam in the opposite direction than on the outer surface. Without Reverse, each slice steps backwards instead of forwards and lands on what has already been engraved.
How many microsteps should the rotary driver be set to?+
Usually 32 microsteps, which is 6400 pulses per revolution with a 1.8 degree motor. At 1600 the rotary moves in jerks and the slices smear in the direction of rotation. Above 12800 the torque drops and the motor may lose steps. The same number must be set on the driver DIP switches and in Steps per rotation in LightBurn, and the 360 degree test must return exactly to the mark.
Can I test the settings directly on a gold ring?+
No. Gold reflects about 97 percent of the 1064 nm beam, and the concave ring wall focuses the reflection back towards the source. Test on a steel ring blackened with a marker: the two-line test for diameter calibration and a block-letter F, which must come out legible and not mirrored. A rectangle around the full circumference is not a scale test, because it closes at any diameter.
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Would you rather we engrave it?
Settings are theory. We engrave inside rings in-house, on our own chuck.
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