K40 Laser Beginner Insights draft document from FB K40 group

Here is a good link

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We can now host the floating wombat guide directly on makerforums.
K40-Alignment-Instructions.pdf (8.6 MB)

Ditto the smokeandmirrors PDF:
laseralignment.pdf (2.9 MB)


If you, as an experienced K40 user who has helped new users get started, had to choose exactly one of the existing alignment guides only for users completely new to K40, which one would you choose?

  • TimTheFloatingWombat
  • SmokeAndMirrors
  • Don’s blogs
  • Other (please comment!)

0 voters

Also, comment why your opinion.

Purpose: I’d like to link to the general preference from New to K40: Start Here and then have a new page on alignment in the Getting Started category to link to other guides.

Wombat was the first guide that I found that I could follow and get results from when I started my laser journey years ago with a K40. I had tried numerous others, and they seemed confusing to me.

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Same reasoning as Anthony, the wombatguide was the one that I found easiest to understand and that helped me in the very beginning.

I finished reading both Wombat and smokeandmirrors now, and they are certainly similar. However, Wombat says to disable interlocks and fire the laser with things open, wear safety glasses if you have them, and close your eyes. The smokeandmirrors / JustAddSharks guide says to close the machine up while firing, not to disable interlocks, and is clear about the need for potential tube alignment.

However, smokeandmirrors / JustAddSharks has pictures and assumptions (like moving Z) that don’t apply to K40.

Both have lots of pictures and specific instructions about how to turn the adjustment screws.

If we start with Wombat, I’d like to preface it with a suggestion to instead close the machine back up while firing the laser instead of taking your chances with disabled interlocks.


I have chopped the initial document into pieces. The cooling article is still longer than the default discourse length of 32000 characters (34837 characters right now) but the Start Here article is now down from 100K to10K characters. I think all the rest of the articles I pulled out are shorter.

@donkjr I linked to your modifications spreadsheet.

I realized that focus was already covered and linked to it directly.

I linked to Sam’s Laser FAQ instead of referencing it by name.

I updated the formatting in the cooling section to be easier to read.

I can’t remember everything else I did.

With the top-level article now a manageable length to read as a single document, I’m thinking of maybe dropping multiple links on alignment directly into it instead of having another complete document. I welcome thoughts.

I’m also thinking about changing the category of the Start Here document to the Getting Started category and pinning it. I think it makes more sense there in retrospect.

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What about this youtube video (for all the people like me, that don’t like to read as much):

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I hadn’t proposed it as the first resource for the same reason I worried about TimTheFloatingWombat — watering down the point of always, always using interlocks. But other than that, yeah…

Do it.
I added that early on when I was speculating more about getting mine running and less about teaching beginners. It’s a better fit in mods.

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OK, I tried to pull things apart and put them together well. I pulled the theory into a #k40:Discussion post Why water is the best place to dump the laser's heat which is linked from Cooling the K40 laser tube and then framed the idea from the end of the theory article into a #k40:Mods article Arduino-controlled secondary coil cooling?

In both cases, those are non-wiki articles of which you are the owner and should feel free to edit, because it’s your text with my light editing hand. Editing can include changing the title as well as any text, it’s yours! :slight_smile:

This has been a fun adventure so far. I’ve learned a lot!

Having slept on this a few times, my current plan is to write up my own first net new contribution to the category under my own name, a new article covering resources for mirror alignment. That will give me space to clarify that anything suggesting alignment without functioning interlocks is misguided (groan) in that respect. Do not look into laser with remaining eye!

I wonder if it would be more effective to say something like this:

It could be worse. The K40 will first burn away your cornea (which might be replaceable from a cadaver, though that’s never as good as the original), then your lens (cataract sufferers already know about the inflexible replacements, better than being blind), then the vitreous fluid (draining your eyeball), before it fries your retina. Some other lasers burn your retina in microseconds without causing immediate pain.

This to my thinking this is just TMI and dilutes the main point which is to make your K40 safe from accidents. (here is how).

Simply put: Moderate and high-power lasers are potentially hazardous because they can burn the retina of the eye, or even the skin.

If the reader wants to know how your eye gets damaged go here: https://en.wikipedia.org/wiki/Laser_safety

What’s particularly interesting here is that the typical multi-watt diode lasers that so many folks are buying without even an enclosure, let alone interlocks, will fry your retina first, probably painlessly; the CO2 lasers will burn your cornea first. But the TMI was intentional to try to gross people out into paying attention. :stuck_out_tongue:

I hear both sides of that. There is a fundamental disconnect here. We are expressing views of how to get people who are too new (or too ditzy and impatient) to read even a little about safety.
For us three, we have no issues with spending some time searching the net and reading, thinking, and then synthesizing an approach. We are, sadly, about 5-7 sigma outliers.
My approach is to give a small shot of information, then try to seduce them into reading more. I think Don’s approach is to tell them “do (or don’t do) this, and here’s a link to why”. You’re right, Don, they likely won’t read even a second sentence. I’m right that they surely won’t be able to concentrate for another five seconds. It’s truly dismal that people who are in this condition can buy burning-power lasers freely and think they need to, but that’s the condition we (the world) find ourselves in. It’s almost a corollary to the condition where many young people congregate when they can pass a deadly disease between them.

I don’t know the best way. But us several-sigmas seem to have decided that we ought to try to help.


Yes, you’re both right that it won’t suck people in. That’s why I didn’t actually put it into intro documentation.

Dunno whether 5-7 sigma outliers is precise, but I’ve certainly seen this in aviation as a private pilot. Some private pilots are cavalier, and some are careful. I think that population is skewed, because you have to convince an examiner that you’re going to at least try to be careful, so a lot of the “look ma no hands!” crowd never make the cut in the first place. But even of those who make the cut, a distressing number appear pretty sure nothing bad will ever happen to them, and even some extremely talented and experienced pilots are unwilling to consider the risks of assuming that not all pilots know what they are thinking. Another hobby that doesn’t reward carelessness or inattention.

@keen, I’m so glad you quoted Sam’s Laser FAQ — as far as I can tell, you were the first person to put a reference to that FAQ anywhere on this site! I certainly didn’t know about it. Now it clearly belongs in the list of valuable internet resources and we should probably consider another *Getting Started" post just for listing external resources in one place, even where they are also linked to from within other posts. For example, @donkjr’s blog would get a single top-level callout in that list, even though there are lots of links to it from within the text. But probably that’s after everything else…

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@keen My spare time has been absorbed in designing and making PPE for a while. I feel like I got the documents into reasonable shape from an editing standpoint, and others have appreciated them. Have you thought about filling out any of the missing bits, such as the rotary axis and moveable bed suggestions in K40 enhancements and modifications ?


I’m new to the K40, and do agree with the views on Facebook, seems to be online half hearted reply or people saying 5 different things,

I for one would love a read of your guides if you still have them… Nothing in the world is worth more than experience

Welcome to makerforums! @keen’s guide is now the basis of our K40 Laser: Getting Started category, which we are maintaining and updating as people have questions or comments.

Edit: oh, sorry, you were responding to @donkjr — I missed that on my phone the first time around.

Don’s guide for the K40 can be found at http://donsthings.blogspot.com/

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