Rabbit Laser Cleaning and Maintenance

Keeping laser mirrors and lenses clean are a very important part of maintenance for our laser systems.

The concepts from this guide are borrowed heavily from this page from omtech. There is also this Maintenance schedule from Rabbit Laser that we will get much of our guidance.

We need a clean and padded work area for cleaning the laser lens. Not appreciating this step may cause you to drop and break the laser lens, (ask Jeff over a beer sometime).

• Frequency: Weekly

This is the lens that is used to focus the laser beam. It is not possible to clean the lens while it is mounted in the focal tube. The laser beam alignment should be checked after cleaning is completed.

TODO: What should we get / have for the work pad here?

1. Lower the bed several inches.
2. Loosen the ring at the top of the focal tube so that it is loose to move in and out.
3. Rotate the focal tube while holding the nozzle unscrewing the nozzle from the tube. (This causes less wear on the air hose than removing the air hose from the nozzle.)
4. Slide the focusing tube down and out of the laser head assembly. It will now be free to take to a work table.

Now that the focal tube is removed from the laser head you could consider cleaning Mirror 3, see directions below.

1. Wear nitrile gloves or finger cots to protect the lens and your fingers.
2. There is a tool in the laser cleaning kit that is a round piece if aluminum that is made to remove the retaining ring in the focusing tube. It's design makes it more difficult, but not impossible, to scratch the lens with it so use care.
3. Under the retaining ring is a rubber o-ring that keeps the lens in place. use a pair of the plastic tweezers to remove the o-ring. Once the o-ring is removed the lens will be free from the focusing tube.

At Protohaven in the laser cleaning kit we have a pink cleaning solvent for optics. The directions say that denatured alcohol or acetone can be used but stick with the pink stuff unless told otherwise.

The lens surface should be somewhat difficult to see. Look at a reflection in the lens to help see dirt on the surface. Make sure to clean the lens and not leave water marks or dirt smears.

⚠️ The focal lens should be replaced if the lens is Cracked, the coating is scratched or pitted, the core material is darkened, the coating is delaminating, or any other significant damage is found.

Some minor blemishes are acceptable, but these problems waste power and will result in reduced laser power at the target material. Any dirt, contaminate, or damage to the lens will cause the lens to become damaged faster.

• Use the puffer to blow any dust or loose debris off the lens.
• Use a lens tissue or cotton tipped swabs (Q-tips) to apply the solvent.
• Do not scrape the lens. Use the solvent to dissolve the dirt from the lens surface.
• Only use a soft swirling motion when applying the solvent.
• Use a dry swab in soft swirling motion while evaporating the solvent.
• Use as many swabs as needed to result in a clean lens surface.

1. When putting the lens back into the focal tube make sure you put it in the correct direction. the flat side is the side facing the retaining retaining ring.
2. Replace the o-ring
3. Replace the retaining ring and use the tool to tightening it with a medium light pressure.

Reverse the removing the focal tube steps to re-install the tube. once it's in but still loose use the following steps to set the focus length on the tube.

1. Raise the bed as far as it will go.
2. Set a focusing block on the bed and adjust the length of the focal tube so that it's just a hair lower than the focusing block. i.e. even paper will need to move the bed down from it's highest position.
3. Tighten the ring to lock the focal tube in place.

At Protohaven in the laser cleaning kit we have a pink cleaning solvent for optics. The directions say that denatured alcohol or acetone can be used but stick with the pink stuff unless told otherwise.

For the weekly asana task to clean mirror 3, do it with it mounted in it's holder. Clean it while the focal tube is out so you're not dropping anything down onto the lens.

This mirror is located directly above the focal lens. This mirror should be cleaned at least every one month. If there is any incident of fire or large issue of smoke/fumes, then it is advised to check the mirror and clean it.

It is possible to clean the mirror in its' mounting bracket, but highly advised to remove the mirror from position and thoroughly clean it. The laser beam alignment should be checked after cleaning is completed.

• Use the puffer to blow any dust or loose debris off the lens.
• Use a lens tissue or cotton tipped swabs (Q-tips) to apply the solvent.
• Do not scrape the mirror. Use the solvent to dissolve the dirt from the mirror surface.
• Only use a soft swirling motion when applying the solvent.
• Use a dry swab in soft swirling motion while evaporating the solvent.
• Use as many swabs as needed to result in a clean mirror surface.

The mirror surface should be difficult to see. Look at a reflection in the mirror to help see dirt on the surface. Make sure to clean the lens and not leave water marks or dirt smears.

The mirror should be replaced if it is pitted/scratched, rusted, discolored from heat damage, or any other significant damage is found. Some minor blemishes are acceptable, but these problems waste laser power and will result in reduced laser power at the target material. Any dirt, contaminate, or damage on the mirror will cause the mirror to become damaged faster.

This mirror is located directly at the end of the gantry rail. This mirror should be cleaned at least every two months. Use the same directions as found for mirror#3

This mirror is located directly in front of the laser tube. This mirror should be cleaned at least every three months. Use the same directions as found for mirror#3

This lens is located at the output end of the laser tube. This lens should be cleaned at least every three months. You must be very careful when cleaning this lens. This lens cannot be removed from the laser tube. You can use the puffer, a Q-tip for applying acetone or alcohol. The ideal situation is that you are only removing dust, film contaminate from humidity, or smoke fumes. Do not scratch this lens. This lens is not replaceable in the laser tube.

The linear rails are the guiding rails along the left and right sides, and across the gantry. these rails should be clean, without rust, and have a slight glaze coating of some oil. The linear rails should be given some attention about every month. The surfaces of the metal should always have oil on it such that it is wet to the touch. The best way to see that you need to do some cleaning is to check the end of the rail near where the home switch is located. If you see a dirt line, then clean the rails off and apply fresh oil.

The linear bearings are found under the gantry(to mount the gantry to the side rails) and under the focal head(to mount the focal head to the gantry). These bearings have grease fittings for pushing lubricant into the ball bearing areas. You might not have a special grease pump to lubricate the bearings. Try the cheap and easy approach. 1) Remove the grease fitting, 2) Apply the grease to your finger, 3) Push the grease into the little hole, 4) push more grease into the little hole, 5) go to step #2 ….. 6) Put the grease fitting back on.

The rubber belts should be checked for appropriate tension at least every six months. You should expect the two side belts to be the same tension and should be tensioned at the same maintenance schedule. These side belts work together to move the gantry from front to rear. If one belt is tensioned more often than another, then that belt could become stretched more than the other. It is difficult to describe how tight the belts should be, but there should not be a slack, sagging, or flapping. If the belt appears to be worn on one side, check the bearing alignment or damage to the matching bearings. There are many laser machine designs, but the method of changing the belt tension should not be too complex. It is normally a method of tightening a screw and then applying a lock nut to keep the screw in place.

The cooling fans are used to force air over the electrical parts of the laser machine control system. If the fan blades get dirty, then that fan cannot move air as quickly. We can check the fans to see if our laser environment is not so clean as we hoped. If the fan blades are dirty, then we can clean the blades with a spray bottle of alcohol, q-tips, and some paper towels. It is best to clean fans with the power turned off…. Not spinning.

Many people forget about the screens in the exhaust system. Your exhaust system could have a few screens. 1) Bottom of the vacuum funnel under the worktable, 2) at the intake of the vac/blower fan, 3) at the building exhaust flange. We don't want the chunks of scrap materials to get sucked into the blower fan blades. Some screens are there to protect the exhaust system from animals wanting a warm place to build a home (until the off-gas of PVC kills them). There are often screens located at the wall exiting the building, prior to entering a filter device, at the exit of the laser machine. The biggest issue of forgetfulness is regarding the small chunks of wood, styrofoam, or other materials. These pieces clog up the screens and greatly reduce the air flow. The reduced air flow means that the smell of cut acrylic, ABS, or whatever stays in the laser machine. The exhaust system just can't do the job any more. If you notice that the exhaust system suddenly isn't working as we'll as it used to, then you might want to check the screens. A shop vacuum can work nicely, but it is best to take the screens apart and really clean them. Don't be tempted to permanently remove the screens. They are there for a reason.

The jack screws are like threaded rods that are used to elevate the work surface. Most all laser machines have a work table that is motorized. The jack screws should be greased when assembled at the factory. Additional grease can be applied if desired, but is not likely to be needed more than every few years. Chains: A chain is sometimes used to synchronize the turning of the jack screws. The chain will be woven from the Zaxis motor shaft around the sprockets at each of the jack screws. The chain was greased when the machine was assembled at the factory. Additional grease should be applied as needed each year.

If concerned about these items rusting, then you should apply a thin coating of silicone-base grease. One application per year should be enough.

The best coolant is de-ionized water. In the absence of de-ionized water, distilled water can be used. Tap water should be a much later resort. The coolant should always be clean and clear.

It is a common problem for the coolant to become infested with mold. This often looks like murky-green water with snot building up on the inner walls of the hoses. The solution is a multi-step process.

1. Flush out the bad water
2. Add fresh water with 20 percent bleach. Cycle the bleach-water for 30 minutes. Flush this water out also.
3. Switch the inlet and outlet hoses. Flush with water. This should dislodge mold from inside the laser tube.
4. The flow safety sensor could also be full of mold. The best solution is to take it apart and clean with a soft brush or pipe cleaners. Make sure to re-assemble the sensor correctly and without leaks. It is possible that harsh cleaners could creep into the sensor electronics and cause permanent damage.

Check the water level on a regular basis. Make sure the water is not low. It is a good idea to change the water after the first 3 months of usage and checked every 6 months thereafter.

Some chillers have a water filter. The water filter should be cleaned out if dirty from bugs, mold, or other dirt.

Some chillers have been known to use silicone glue to seal the fittings. It is possible for small clumps of silicone glue to release from the hoses and fittings. The filter should catch these clumps.

The bed can get pretty gross and it should be cleaned regularly. twice a year in spring and fall I'd recommend.

1. Move the gantry to the back and lift the bed out of the laser.
2. take it back to the shop and use one of the manicure tools to free all the debris stuck in the honey comb.
3. Take outside, put the bed into a large bag and coat well with easy off oven cleaner. Let reset for 30-60 minutes.
4. Hook up hose to hose barb on outside of building and rinse bed till water is flowing clean
5. Let bed stand to dry.
6. Blow out moisture with air hose outside.

For now, we'll be using a masking tape method of aiming. We're looking into either reverse aiming or adding attachments that can use plain paper targets and will update the guide if so.

See also this guide: https://drive.google.com/file/d/1HqF4v4dy58CxrLZ7Xn5FZhOe5hOBJph7/view

One source recommended Harbor Freight masking tape as a high paper, low adhesive tape. Make sure the tape is adhered flat around the mirror but not to the mirror itself. Make many ~2×2 inch pieces of tape for test targets. One source recommended using multiple layers of tape for the main target to minimize burn through and then adding other pieces on top to see new marks. Have a water sprayer ready in case of the tape catching fire.

It's also likely good practice to have two people for this job so that the openings can be closed while the laser is being pulsed to minimize radiation. Make sure there aren't bystanders, as well.

In the machine menu, set the power of the Pulse button to about 15%. More seems to burn the tape right away, less barely registers.

First open the red panel in the rear left of the machine, closest to where the laser comes out of the tube.

Arrange the target on mirror 1. Pulse the laser. Adjust the mirror until the beam hits the center of the mirror. If this is really problematic, the tube itself may need an adjustment, but it shouldn't be necessary.

Screw turning may be very minor to get a good adjustment. It's better to leave the diagonal screw alone and focus on the other two adjustments individually.

Now open the side door. Bring mirror 2 as close as possible to mirror 1 and affix a new target.

1. Alignment is the laser beam running parallel to the gantry across the full length. Adjust this first by using the mirror screws.

2. Accuracy is the laser beam hitting the center of the mirror. Adjust this by adjusting the mirror mounts on the gantry.

Alignment

Pulse the laser at the closest point and at the furthest point between the two mirrors. Mark the first mark if you have trouble remembering. This should give you an idea of the line the laser is traveling. Adjust mirror 1 until the beam hits the same spot up and down the length of the gantry. (Alternate technique - use a red hash mark over the first close mark, add a new piece of tape over the mark but still so you can see the pen marks. move to the end of the gantry and fire again. Adjust the mirror until the beam lands inside the pen marks. Test again.)

Accuracy

Now see how you will have to move the mirror mount to center the laser. You can adjust either the sending or receiving mirror side to side, but the receiving mirror might be easier, since you risk losing your first alignment if you move mirror 1. Height should only be adjusted on the receiving mirror. Check again to make sure it's still aligned the length of the gantry.

Close the side door and open the lid. Use the same process between mirror 2 and mirror 3. An important distinction is that mirror 3, since it's at an angle, doesn't have a good way to adjust for height.

To test the alignment of the mirror in the tube, remove the lens attachment. Use a flat target and pulse the laser at the top and bottom of the bed height. Change the angle of the beam with the mirror 3 screws, and the accuracy by moving mirror 2 mount side to side.

Now return the lens tube to position. Pulse the beam in all four corners of the bed. It should make a nice round dot - if not, the beam is hitting the nozzle somewhere.

Make sure to clean any smoke or adhesive off the mirrors after testing.

YouTube example