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Cylinder Correction

Cylinder Correction warps the output of your design to correct for distortion caused by engraving cylindrical objects without using a rotary. This tool is currently only available for Galvo lasers. EZCAD users may already be familiar with this tool by the name ProjectMark.

Screenshot of results

Using Cylinder Correction

Open the Cylinder Correction Setup window by going to Tools → Cylinder Correction Setup. Make sure Enable Cylinder Correction is turned on.

Cylinder Correction Setup screenshot

From the setup window, you'll adjust the Mirror Distance, Object Diameter, axis to curve around, and direction of the curve.

LightBurn will calculate the Cylinder Correction assuming the design to be output is centered on the object. If you are unable to place the item you're engraving at the center of the laser's working area, move your design to match the actual location of the object.

Mirror Distance

Warning

This is not the focus distance between the object and the lens, but the distance to the galvo mirrors themselves. Keep reading for help measuring this.

To use Cylinder Correction, you'll need to identify where your mirrors are. The mirrors are typically centered along a tube connecting the galvo head to the laser source. In the image below, a horizontal line marks the center of this tube.

Galvo mirror location example

Measure the vertical distance from this line to the bottom of the lens — shown with a vertical line in the image above — and add this to your focus distance to find the mirror distance. We recommend saving this measurement so you don't have to keep re-measuring.

Object Diameter

Measure the diameter of the object and enter it into this box.

X or Y Axis

Select whether the object curves along the X (horizontal) axis or Y (vertical) axis. Only one of the two can be selected. The images below the options show a simplified representation of what each option would look like.

Convex or Concave

Select whether the object is Convex — curving outwards to make up the outer surface of a cylinder — or Concave — curving inwards to make up the inner surface of a cylinder. As with the X and Y axis, the images show a simplified representation of Convex and Concave curves.

Show Valid Boundary

There are limits to where on a given object your laser can actually reach. The Show Valid Boundary button will insert a rectangle on the T1 Tool layer into your design to show the area that can be engraved.

Cylinder Correction Impossible Boundaries screenshot

If you try to Preview or run a cylinder-corrected engraving while a portion of your design is outside of the valid area, LightBurn will pop up a warning asking you whether you'd like to continue anyway, show the valid boundary, or cancel. If you engrave anyway, LightBurn will automatically cut off the portions of the design outside the valid boundary area, as shown below.

How It Works

Galvo lasers project the laser from a single point above your object. When marking a cylindrical object, the increased travel distance for the laser as the surface of the object curves away causes the shape to widen and bend, similarly to the uncorrected rectangle in the diagram below.

Cylinder Correction alters the output to warp your design in the opposite direction, negating the warping caused by the curve of the object. If your measurements are correct, this produces clean, undistorted output like the result shown in the diagram above.

Lens Selection

When using Cylinder Correction, you'll be marking across a larger range of focal distances than is typical when marking flat surfaces. For instance, if you have a 75 mm diameter tumbler and are engraving a 50 mm wide graphic, there will be about 10 mm difference in focal distance across your design.

For best results, use a lens with a larger field (working area) if possible. Wider field lenses have a lower power density but a longer focal range. To take advantage of the full focal range, focus your lens below the upper surface of the cylinder, as shown in the diagram below.

Troubleshooting

  • If the outer parts of your design are missing, make sure that it's fully within the valid boundaries.
  • If the placement of your engraving is wrong, check that the location of your design matches the actual location of the object you're marking. Confirm that the placement is right by framing before running the job.

For more help using LightBurn, please visit our forum to talk with LightBurn staff and users, or email support.