Current recommendations for laser alignment

[Simon Gornall]

So I've got a new laser, and although it does indeed mark/cut wood, doing the linearity tests (pulse at the beginning of travel, pulse at the end of travel) shows that it's clearly not aligned correctly.

So, I wanted to figure out what the best options are - Russ has several videos about aligning the laser, and it's not entirely clear to me what the best combination is at this point in time,

• The most-recent head option seems to be #175 which isn't yet available, but might soon be from cloudray. I can wait, I guess
• The most-recent laser-tube alignment seems to be the ( #118/#119) but I'm not sure files for those parts have been released ? The comments on the page asking for them don't seem to have replies. It was a year ago, and there were a couple of gotchas in the videos, so perhaps this has been, for lack of a better word, discontinued ?
• There's a beam-alignment video for the lightblade machine (#90)
• There are various beam-setting videos for the ebay-style machines (#51a, #51b, #79a, #79b, #44a, #44b)
• The adjustable tube-clamp (#37). It's not *entirely* clear from the video, but it seems that these are the clamps that help align the tube forwards/backwards to aid in the Y axis alignment. I think all the above beam-setting videos depend on having these adjustable clamps in place.

So, I'm thinking my best option is:

a) Make myself some adjustable clamps
b) Wait for the adjustable head from cloudray
c) Run through the instructions in #175 (and any other beam-setting videos that apply)

Is there any point in just doing (a) and (c) - or am I better off waiting (I'm not good at waiting [grin]). I'm assuming that people did successfully align their system before Russ came up with the adjustable head...

I'm also assuming that getting the laser aligned correctly is the first step, then onto the characterisation shown in #95 and then finally onto playing with the machine

Any help gratefully appreciated. I realise there's a lot of questions in this post

Cheers
Simon

[sebastien laforet]

I'm also assuming that getting the laser aligned correctly is the first step, then onto the characterisation shown in #95 and then finally onto playing with the machine

that's definitely the first step. chances are that once done, you can stop here. adjustable clamps, new head, ... are probably the icing on the cake, but most of us have totally working machines without all the bells and whistles..

you definitely have to check :
- the perpendicularity of axes
- the table is flat and aligned (same focal height on every part of the table is especially important)
- all mirrors are clean, correctly setup and fixed (beware of vibrations)
- lens is clean and not prone to move in the tube (vibrations again)

[Pete Cyr]

1. a picture or two of what you are calling a problem would be helpful to understand what you are describing.
2. Run a test pattern of 10 horizontal lines about 1" long each aligned vertically (each start and stop for a line should be in perfect alignment with the other lines)- @15% pwr 300mm/s
3. Without knowing which software you use to operate the laser it may be difficult to evaluate some issues.
4.If you have not I strongly recommend backing up you vendor settings. - The following steps assumes you have a Rudia Controller and are using RDWORKS

-follow this link to perform a back-up of vendor settings viewtopic.php?f=104&t=3459

5. execute the process in this file to validate the precision of laser head movement in the X/Y axis

Adjust Cut Length to be = to design length.pdf

(and if you don't have a digital verier that reads in MM - I recommend getting one $30.00-$50.00 range is plenty good

After perfomring the stuff above post a picture of step 2. above and the values you measured for X and Y in step 5. above.

[Simon Gornall]

Okay, here goes

So last night I took a few pictures while fiddling around trying to fix the issue. The problem I was trying to solve was the misalignment on the third mirror. Here's an image of a pulse when the third mirror (on top of the head) is very close to the second mirror...



and this next photo is after moving the carriage to the end of the rail (100cm away) and pulsing the laser again.



It's a lot closer to center now than it was the first time I posted. It's still not perfect and I could do with getting that better aligned I think. It's not *very* easy to play with the mirrors - the machine is rather large and there's only one place it can go which happens to be up against a wall. I do have access to both sides of the machine, but I can't just walk around it like Russ can

The Z axis is still significantly off though...



The small dot is at the focus point, the large hole is when you wind the bed down by a few inches. It doesn't help that my bed definitely "wobbles" as it goes up and down though - not to the extent that the above burn positions show, but visibly you can see it oscillating from side to side and back again.

I also did your lines test - 10 horizontal lines of 10mm each, and I got:



Should I be worried about the "waviness" of those lines or is a certain amount of judder along a straight line normal ? Is there something I can do to make them straighter ? - I'll have to do some reading on that.

On the plus side, it looks as though my head is already adjustable to a certain extent, it's not as nice as Russ' version, or *as* adjustable, but there is certainly both vertical and horizontal adjustment possible



Cheers
Simon

[Jeffrey Aley]

The small dot is at the focus point, the large hole is when you wind the bed down by a few inches. It doesn't help that my bed definitely "wobbles" as it goes up and down though - not to the extent that the above burn positions show, but visibly you can see it oscillating from side to side and back again.

I also did your lines test - 10 horizontal lines of 10mm each, and I got:



Should I be worried about the "waviness" of those lines or is a certain amount of judder along a straight line normal ? Is there something I can do to make them straighter ? - I'll have to do some reading on that.

You should be worried about the waviness of those lines.

Given, however, that your bed wobbles, I'd try adding a temporary wedge to keep the bed from moving and re-checking to see if the lines are wavy.

If the waviness is caused by the bed moving - fix the bed. If it is not, then you need to find the source of the waviness (probably a loose mirror or loose lens). I suppose there's a possibility that the tube is not secured well and is vibrating, but I've never heard of anyone actually having that problem.

[Simon Gornall]

As far as I can see, the bed only wobbles (oscillates would be a better term) as it's moving up and down the Z axis. It's very periodic and predictable, and the mass of the thing would prevent it from wobbling unless it was being moved, I would have thought.

It's entirely possible I left a mirror untightened when doing the alignments. I'll check those, thanks

[Pete Cyr]

1. Picture 4 shows that you don't have a backlash issue
2. Picture 5 shows your rail is dirty and it is not obvious it is greased

Lithium-Thickened Grease
These multipurpose lubricants offer good heat and moisture resistance.
Mobilux EP 1 and EP 2—This brown multipurpose grease offers rust and corrosion resistance for use in moist or wet conditions.
Mobilux EP 1 (-4° to 266° F) Cartridge for Grease Gun (14 oz.)
Product Detail Mobil Lithium-Thickened Grease, Mobilux EP 1, Cartridge for Grease Gun (14-oz)

I am a fan of Mobilux EP 1 or any equivalent for use on the rails in a laser. This particular grease does not dry, is the correct weight for this application (as recommended by HIWIN -one of the better bearing manufacturers)
But you must grease the rails AND clean them on occasions

3. Beam alingment - this is one of the better videos to align you mirrors viewtopic.php?f=141&t=4036

viewtopic.php?f=141&t=3466

4. Wavy lines - that is hosed. I am not sure what the issue may be - several things can cause it and all of the reasons deal with something being loose or and earthquake. check all the securing screw you have manipulated.

[Simon Gornall]

1. Good

2. I'll get the grease. It doesn't surprise me that it didn't come greased... Since the machine is in the garage, in a relatively dirty environment, the grease is probably a good idea ...

3. I'm fairly happy with the beam alignment now:



The top right image is with X=0cm, the bottom right image is with X=100cm, both with Y=60cm. The left hand image shows the lines now... much better

4. It turned out that I'd not tightened the lock-screws back up against the mirror-holder back, so although the alignment screws were pointing the mirror in the right direction, they weren't properly secured, and I guess the vibrations were causing the beam to wobble. They've been suitably tightened now.

I still need to check the Z axis, and I'm a little concerned that the spot is too low on the head mirror, Russ seems to have his center-of-spot higher up. The power meter isn't due for a week or so though, so I'll figure all that out when it arrives.

[Gene Uselman]

Russ pointed out that on his laser head the center of the mirror in the head is not aligned with the center of the aperture in front of the head- it actually is up a bit from the apparent center. I have found that to be the case with mine as well. These parts are mfgd by many different companies of widely differing capabilities.

[Richard Norris]

Hi, I have noticed that in several of Russ videos when aligning the tube or checking the power levels, he places tape or acrylic near the first mirror when performing a mode burn. This is quite near the end of the tube output mirror as well. I noticed on the reci website that for any co2 laser one of the general warranty statements is "Put the acryl(ic) 300mm far away from output mirror, when testing its laser spot". This sounds like a mode burn test, and specifies a large separation distance, I assume to guarantee that fumes are not going to damage the mirror.

Not having done this before, I would like to ask for guidance on this, as I hope to be carrying out some tube alignment soon Should I be concerned about performing a mode burn near the tube?

Cheers Robert.