This is how to adjust the mirrors on the Exlas 1280 laser cutter at Ace Monster Toys. The general technique may be useful on other laser cutters but the details are specific to this particular machine.
There are 3 mirrors and one lens all of which must be properly adjusted for the laser to end up focused correctly on the material to be cut. The laser itself sits behind the cutting bed, pointing to the left, and immediately hits a stationary, 45° mirror which bends the beam 90° towards the front of the unit. There is a second mirror on a rail on the left side of the unit, which slides forwards and back, and turns the beam another 90° towards the right side. The beam then hits the third mirror which is mounted to the cutting head gantry and turns the beam 90° downwards to pass through the lens and intersect the material to be cut. All of these mirrors must be precisely angled so that the beam gets through the whole way to make a cut or etch where desired.
Step 1: Open the Case
The laser is accessed from the rear of the machine where there is a hatch cover that pivots out and down on a piano hinge.
It is helpful for this process to prop the lid open, although if you choose to do this you must take great care not to get in the way of the laser during its tiny bursts - the laser beam is invisible and can blind you. Protective glasses are advised. If you choose to prop the lid open, you must temporarily disable the interlock that prevents the laser from firing when the lid is open. It is an interlock lever on the right hinge.
Step 2: Align First Mirror
The first mirror is on a stand at the left rear corner of the machine. The mirror is enclosed in a case with a circular hole in front through which the mirror is visible, and adjustment screws behind. The second mirror is mounted on the Y axis rail on the left side of the laser bed along which it can be moved from the front of the unit to the very rear, only an inch or two from the first mirror. The Y axis rail, in fact, also supports the entire X axis rail and cutting head assembly. (There is a second rail on the right side of the bed which supports the other end of the X axis and the whole assembly moves together.)
- Align the first mirror by making sure a laser beam hits the second mirror, as follows:
- Cut a piece of paper 2-1/8" square. Mark the center of it with an X or + and tape it over the second mirror's case.
- Move the second mirror gantry to the far corner by the first mirror, using the control panel on the front of the machine (Y all the way back).
- Fire the laser once.
- Observe the paper on the mirror; there will be a small dot, or series of dots, somewhere on the paper. Ideally they should be in the middle. It's helpful to either mark these, or take a pic of them, so subsequent firings can be distinguished. If the dot is close to the middle, go on, otherwise turn the adjustment screws on the back of the first mirror to change its angle so the beam will hit more in the middle of the second mirror, and test again.
- Move the mirror gantry to the front position, as far from the first mirror as it will go.
- Fire the laser once.
- Observe the paper. There should be a second dot, or possibly if the mirror is perfectly aligned and clean, the first dot is bigger and/or darker (this is rare).
- Adjust the screws on the back of the first mirror, testing as you go, until the laser beam dot is very close to centered in both the front and rear positions. This may take another piece of paper or two.
You may find you need to adjust the laser's height, if the screws on the mirror don't have enough play to get the beam dot centered vertically.
Step 3: Align Second Mirror
The second mirror alignment is basically just like the first, only you have to move the third mirror back and forth to test its centeredness, and you have to do this process with the second mirror in the rear position and in the front position.
The third mirror is on the cutting head, above the lens assembly, and directs the beam down into the lens. It moves along the X axis of the laser (the whole X axis rail, as noted before, moves along the Y axis).
- Tape a 2" square paper target with an X in the middle over the third mirror.
- Move the axes so the second mirror is at the rear and the third mirror is in the far left, up close to the second.
- Fire the laser for one short burst.
- Observe the dot and adjust the second mirror's angle as necessary.
- Move the third mirror to the far right and fire the laser.
- Adjust the second mirror again.
- Repeat with the entire mirror assembly at the front of the unit.
- Move the assembly back again and check the rear position. You may have to make a compromise adjustment such that the average position of the laser dot is centered, but the corner positions may be off somewhat. As long as the beam hits the lens more or less in the middle, it should be able to focus.
Step 4: Align Third Mirror
The third mirror bends the laser beam downwards so it will pass through the lens and hit the material to be cut. If it does not hit the lens close enough to the center the beam will be deflected sideways and the cuts will not be focused or accurate.
- First tape a piece of heavy paper to the laser bed to make a target for the beam
- Move the bed (the Z axis) up so that the lens assembly is almost touching the paper, and draw a circle around the tip of the lens holder on the paper
- Move the bed down several inches for space
- Remove the lens assembly with the blower attachment and set it aside on the bed (you do not need to detach the blower)
- Fire the laser once. The unfocused beam should make a mark on the paper near the circle representing the tip of the lens assembly. When the mirror is properly angled, this mark will be centered in that circle, indicating that the laser beam will pass through the center of the lens and focus directly downwards without deflection.
- To adjust the mirror, use the adjustment screws on the top of the cutting head gantry assembly.
Repeat this entire process at various points on the bed to ensure the mirror angle is good for the whole bed. Once this is done, replace the lens assembly on the cutting head and fire the laser to verify the beam is now focused in the center of the target circle.
Close the rear cover and remove the tape over the hinge interlock, if you taped it.
Celebrate! That was a lot of work.