How to Adjust the Focus of the Laser Cutting Machine? (3 Different Ways)

Laser Cutting Working Principle Drawing

1. NC point locating of laser focus position

Use a flat, smooth white piece of cardboard and tile it on the workbench. The laser cutting head will be set above it.

The height of the focusing lens from the cardboard is about 10mm, which is smaller than the focal length of the focusing lens.

For instance, if the focal length of the focusing lens is 127mm, then you should set the focusing lens to about 117mm from the cardboard.

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

Each time it moves into position, 20 holes are punched with 20 times, and the Z-axis height is increased by 20mm.

By observing the 20 holes, we can find that the diameter of the holes gradually changes from large to small, and then from small to large.

Find the location where the aperture is the smallest, and record it.

The distance from the cardboard to the lens when measured at this position is the actual laser beam focus position.

2. Bevel focus cautery method

The method is shown as follows.

A straight wooden board is placed diagonally on the workbench with a slope of about 10 degrees.

Set the cutting head at point A.

The height dimension of point A from the focusing lens is 20mm smaller than the focal length of the focusing lens.

The numerical control system sets the cutting head to move horizontally along the X-axis or Y-axis continuously for 230mm.

The laser outputs 200W continuous laser when the movement starts.

When the cutting head stops, the laser also stops.

At this time, you can see that there is a burning trace of the laser beam which changes from wide to narrow, then from narrow to wide.

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

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

3. Laser cutting direct cauterization method

To hold a straight wooden board at an angle of 85 degrees on the cutting table and raise the cutting head to a position where the focusing lens is about 1.5 times in focus from the surface of the table.

Then, open the laser shutter and continuously output a 200W laser beam.

Move the wooden board horizontally under the focusing lens.

You can see that the surface of the wooden board will have a burning trace changing from wide to narrow and narrow to wide before and after the laser beam is focused.

And this trace is very close to the change in the focusing process of the laser beam.

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

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

Because this method requires manual operation, so special attention needs to be paid to safety to avoid human injury.

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