You are correct. Beam goes in curved side, goes out flat side. If it is the other way around the focal point gets spread out more along the beam direction. My diagram shows just a generic lens, but in the machine I do have the lens put in correctly like you point out.

at 6:34, you reference the flat side, then state "curved down," hence my comment. Thank you for the video, as I've learned a few new things for laser alignment and will soon perform those checks.

Yeah I did say that wrong... Thanks for pointing it out, I'll add a caption or something.

video diagram shows diagonal not end view

you are incorrect. beam enters flat end is spot focused on curved. both need study optical physics. join the Boy Scouts for life experience

Put it in the correct way, and you get a smaller spot for finer engraving and higher power density for things like marking metals and hard woods. Put it in the 'wrong' way and aberration will stretch the working depth out just a little more at the cost of lower power density. Helps cut a bit deeper in acrylic which doesn't require such a high power density to melt through.

Thank for your reply. By the way, really good videos and well explained.

funny thing is even though it shakes a lot, it always would fall back to the same place. Ive since tightened up those joints so it is not so sloppy, but it was never really a problem I needed to urgently fix.

Yes. I said it wrong and didn't realise until well after i put the video together. But even if you put it in the wrong way, for a narrow single wavelength beam like this it doesn't make a very big difference

Yeah I meant to say curve up. That's how it is normal placed. Really though with the characteristics of the laser and what you are trying to achieve it makes very little difference how it goes in. Just be aware though that the way you put it in will affect the distance to the focal point by a few millimetres so either be consistent or make a separate focal point measurement for either orientation.

1) Just a 3mm aluminium plate cut to shape. I wrote how I made it here goo.gl/6vYxW3 2) A bigger tube is longer and wont physically fit. But if you did manage to modify the case to fit it all the control stuff will work fine, the only thing you need to check is to make sure your laser power supply puts out enough current. I would just buy a new power supply along with the laser tube.

My laser is 50W. That is just good enough to start cutting up to 8mm deep in softer hardwoods provided everything is aligned and set up well. 60W will make things much easier, 80W even better. Just depends if you have the money and the space to put the larger machine.

I like that idea! I think a bulky carousel might get in the way and bump into things, but some system with magnets and guide pins so you can quick-change different lens tubes would be great. I really like it. If I get around to making it up myself I will be sure to credit you with the inspiration :)

@@makestuffnow I'd really be interested to see how it turns out with magnets! Guide pins might certainly help resist them shifting under the accelerations used in engraving. Clearance issues are certainly something to look out for as well as not adding too much mass to the head. It might be that it'd only work well with a smoothieboard brain swap or similar where you can tweak the acceleration rates. But most of the large Chinese cutters I've been looking at seem to have plenty of mechanical clearance. Thinking of something like how you change magnification on a microscope. I'm also thinking of this for a community makerspace laser though, so don't know if I'd trust people to be able to physically remove the lens assemblies to swap them!

Things are only shaking sideways mostly due to play in the screws holding the table bed. The up/down distance isn't changed once it settles back so it won't have any affect on trying to test the focal length.

those little solid state lasers have the lens attached directly to the laser unit. You can adjust the focus a bit by twisting the screw mount holding the laser, or by lifting or lowering the work piece. In principle it all works the same.

Ive cut acoustic foam for making inserts for cases mostly, but also tried a few other foams which would be similar to costuming. You need to test materials first. Some foams and plastic types will just burn black instead of cutting nicely (very bad). As a quick test you can try bringing a lighter up to the material. If it just melts away it will probably cut nicely, if it burns brown/black it is not suitable to put in the laser cutter.

Im going to film a few things while I install a bigger laser tube this weekend. I may do some tips on cutting various materials as well.

Very good explanation and useful information, thank you

It came already fitted. Like the rest of the stock fitted air flow system, it doesn't work very well.

You should be having no trouble cutting 3mm MDF with any lens. Set the distance from the nozzle to the workpiece exactly where the focal point is. If this distance is set correct you should be cutting through 3mm easily. Make sure the airflow from the nozzle is working ok.

You're trying to engrave a bmp/png image file. When the laser scans left to right it needs a bit of space to accelerate up to speed first. So if you have your image too close to either the left or right of the table, the laser has no room to get it's run up, and gives the 'not enough extended space' error. Move your image about 1cm away from edge and it should then work ok. At least that's how the chinese ruida brand controllers work.

Some Old Guy Coding the

Fancy seeing you here!

That is strange because plexiglass should be one of the easiest materials to cut. I would need to see how the laser is marking the plexiglass. Feel free to email me. Email address in 'about' tab on my channel page

I just drew the lines and numbers in the control software RDWorks. I made each line/number a separate colour/layer so I could quickly choose which individual ones to sends to the laser.

The drawing is correct for a gaussian shaped beam. The intensity profile does curve like shown in the diagram. Look up information on 'TEM00 mode' if you want all the technical mathematics behind it.

makestuffnow! Never heard about. Will take a look .👍

You need to compensate the backlash, had to adjust mine to -0.3

www.instructables.com/id/How-to-Improve-Engraving-Quality-of-Laser-Machine/

Very likely it is a mirror alignment problem. Another possibility is the cutting surface isn't level, but has a slight slope to it which you need to fix.

Thanks a lot for your time, well, from what I've seen and analyzed it should be a mirror alignment problem.

email address is in the about section on my channel page. Happy to help you out.

@@makestuffnow thanks brother. when i click the about section of your channel it shows empty. anyways shoot me an email and ill respond to it please. kingsman.arms@gmail.com

check the 'about' tab on my channel page. email address there. I'm happy to help