3 Ways to Adjust the Focus of Your Laser Cutting Machine

1. NC point locating of laser focus position

To determine the laser focus position, place a flat, smooth piece of white cardboard on the workbench and position the laser cutting head above it.

The height of the focusing lens from the cardboard should be approximately 10mm, which is less than the focal length of the lens. For example, if the focal length of the lens is 127mm, the lens should be set to about 117mm from the cardboard.

The NC system sets the cutting head to move every 10mm along either the X or Y axis, and the Z axis rises by 1mm with each movement. The distance for 20 consecutive movements can be set.

At each movement, 20 holes are punched 20 times, and the Z-axis height is increased by 20mm. By observing the 20 holes, the diameter of the holes can be seen to gradually change from large to small and then from small to large.

Locate the position where the aperture is the smallest and record it. The distance from the cardboard to the lens at this position is the actual laser beam focus position.

2. Bevel focus cautery method

The method is as follows:

Place a straight wooden board diagonally on the workbench with a slope of approximately 10 degrees.

Set the cutting head at Point A, with the height dimension from the focusing lens being 20mm smaller than the focal length of the lens.

The NC system sets the cutting head to continuously move along either the X-axis or Y-axis for a distance of 230mm.

The laser outputs 200W of continuous laser when the movement begins and stops when the cutting head stops.

At this point, a laser beam burn trace can be seen, which changes from wide to narrow and then from narrow to wide.

Take the narrowest point of the trace as the focal position and record it.

At this position, the distance of the wooden board from the lens is the actual laser beam focus position.

3. Laser cutting direct cauterization method

To determine the laser beam focus position, hold a straight wooden board at an angle of 85 degrees on the cutting table. Raise the cutting head so that the focusing lens is about 1.5 times in focus from the surface of the table.

Open the laser shutter and continuously output a 200W laser beam. Move the wooden board horizontally under the focusing lens.

The surface of the wooden board will have a burn trace that changes from wide to narrow and narrow to wide before and after the laser beam is focused. This trace closely resembles the change in the laser beam’s focusing process.

Take the narrowest point of the trace as the focal position and record it. The distance of the wooden board from the lens at this position is the actual focus position of the laser beam.

Please note that this method requires manual operation and special attention must be paid to safety to avoid injury.