K40 Laser Beginner Insights draft document from FB K40 group

Given that HP Perrson has been reported to accept payment and not deliver product by multiple people on this forum, I’m hesitant to drive additional new forum members to his site where he offers product for sale, where they might encounter the same problem.

Also, one of the other links on that topic is dead, and the wayback machine has recorded only dead content, no live content with anything useful, even as of the date of posting the link, which is confusing to me.

For editing existing content, and for things where theoretical knowledge is enough, I’ve been (I think) competent to expand slightly while editing @keen’s work. But for these specific tasks, I don’t think I’d be the best person to orient them to the resources.

This is a case where I’d love to help edit someone else’s work because my knowledge of the mechanics is theoretical and if I wrote total-new-user-focused introduction to the topic my lack of experience would show terribly. @donkjr’s guides look interesting, but we’re also telling people they should do this alignment before using their K40, so there’s a bit of a chicken and egg problem for the first alignment to use the guides that they will later cut, after alignment. But for many of the other guides out there, on the other hand, we’re trying to encourage people to install interlocks before they ever fire their K40, and a lot of other guides tell people to blip the laser with the lid up while wearing laser safety glasses, so I’m not sure I want to point the K40 newbie (like me) at guides that assume that you blip the laser with the lid up, which I rather think I’ve seen. There was a video linked to recently as part of a "make your own laser cutter* series that showed the alignment process without any case in place; great for actually being to show all angles of the process and understand what is going on, but doesn’t quite send the message we’d like on interlocks. :roll_eyes:

It would be great if we could have “how to do your first alignment” — then we could recommend do your initial alignment, cut @donkjr’s guides, use them for subsequent alignment. Does that even make sense?

Also, not every page in the Getting Started category has to be originally written by @keen. If one of you want to write a draft of one of those topics as a comment in this topic, and then we like it, I can promote it to the relevant topic in the category and make sure it’s a wiki that we can all edit together to keep improving it over time.

Was it the floating wombat link? If so that’s a link to my dropbox.

Yeah I agree about the HP Pearson link.

No, it was the smokeandmirrors link from @HalfNormal

Here is a good link

1 Like

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.

1 Like

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.

1 Like

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

1 Like

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.

1 Like

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…

1 Like

@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 ?