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Laser selection questions, electronics?

Posted by SupraGuy 
Laser selection questions, electronics?
January 04, 2018 03:22PM
In the process of working with my 3D printers, the first of which was crap, I have a large collection of spare parts and electronics, including several Arduino Mega, and RAMPS boards, a half dozen or so stepper motors, and many other goodies. Not quite enough to build another setup, but I shouldn't need too large a shopping list to do another simple robot.

I am rebuilding the first printer, in the process, I got a second one to do what the first couldn't, but I'm hitting limitations on the second, too. (It never ends, does it?)

So I started looking into using the stuff I have for a CNC milling machine, but I have no confidence in the ability of the parts that I have (~80-90 oz-in steppers, timing belt drives, etc) to handle any kind of cutting resistance. So naturally I thought I'd look at laser cutting. At least in terms of controlling the X/Y (Z?) movement of the laser itself, I ought to be able to do that with Marlin. It seems that there is at least something ready for laser control, too.

I was curious about cut feed rates, which of course depend on the focus and power of the laser, and that eventually brought me back here. Go figure.

I kind of want to just do a low power test solution, and I kind of want to be able to jump in and actually cut stuff. 6mm MDF at the very least. 12mm MDF would be great if doable. Also if possible, acrylic or polycarbonate would be extremely useful. (Black or coloured, great, clear, even better!) I found VDX's topic on using black paint and a low power laser for doing PCBs also extremely interesting, particularly since it required such a low power output.

I basically ignored any lasers that I found that didn't mention power, and any that didn't have some sort of controller. That narrowed the field quite a bit, but left me with 2 main options.

The first is lower power, 2.5W. (2.5W 450nM eBay laser) I was skeptical of the potential usefulness of this one, and almost dismissed it entirely. I can't see it cutting the thicker material at all, but if I can cut 2 identical pieces of 6mm MDF, a little glue and some clamps makes it 12mm easily enough, I figure. The issue will be cutting speed. Assuming it's possible at all, too slow a cutting speed greatly reduces the usefulness of a laser cutter to me.

The second option is of course more expensive, but at 15W of power, it seems to offer much more in the way of possibilities. (15W 450nM eBay laser) This looks to be quite promising, provided of course that it's not just horribly over driven and is going to die after a week. The 6X increase in power should offer something in the way of greater cutting potential, or at least possible cutting rates. It also says that it supports PWM control, presumably for power output. (Can the RAMPS/Marlin software output this?) I note that the listing shows 16mm for a focal length, but also states that it's adjustable. I know that focal length changes the depth of possible cuts, but I do not know what kind of cut depths are possible with what focal length. I also assume that there are additional safety concerns with a more powerful laser, but I'm a fairly careful person. I had thought that with the 450nM light, I could put everything under a red or orange polycarbonate cover, which would also do service as a fume hood. Rig a safety interlock so that the laser cannot operate if the hood is open. I'd do this with the lower power laser, too. I like my eyesight...

Edited 1 time(s). Last edit at 01/04/2018 03:27PM by SupraGuy.

Prusa i3 / Arduino Mega 2560 / RAMPS 1.4
Kit from a2aprinter
Beltless redesign in progress to move to T8 lead screw drive

MBot3D Printer
Kit from Amazon
Some teething pains, but a reasonably good printer, just missing a heated bed.
Re: Laser selection questions, electronics?
January 04, 2018 06:24PM
Video of 1.75 W 455nm laser
on Shapeoko 2 (arduino - GRBL)


I think it was 12 passes to get thru corrugated cardboard

Cutting takes lots of power and focused laser

confused smiley
Re: Laser selection questions, electronics?
January 04, 2018 10:53PM
... the "15W-diodelaser" is most likely an overdriven 6W-diode, if not a 3,5W-diode ... many of the chinese vendors count the electrical drawn power instead of the real output eye rolling smiley

6mm MDF is pretty hard even with a 6W diode -- better look into CO2 laser tubes, starting with 40W - this is also perfect for clear acrylic ...

Re: Laser selection questions, electronics?
January 05, 2018 11:00AM
Thanks, Viktor, that was exactly the kind of information that I was looking for. Well, I'd have rather heard that this would do what I want, but I'll take the truth when I can get it.

So it seems that I'm looking for a bit more complicated a system, but I can live with that.

With a tube laser, this isn't going to end up looking like an i3. Too bad, since I have tons of parts for that kind of platform. Probably more like my mBot3D printer, where the height of the X/Y head mechanism never changes relative to the box, and the bed travels up and down. Well, then again, since I don't plan on using this for thick materials, I may not need Z axis control at all, but I can think of some things that might want to be thicker. I was considering foam board, but that's apparently not a good thing to cut with a laser.

Well, my wants are to have some precision cutting. I was looking at laser to preclude the costs of more expensive motors. It looks like it's a race between the costs of a more powerful laser, which I can move with the motors and control electronics that I have, or more powerful motors, and the ability to control those to use the router that I have. The laser will limit what I can do with MDF/wood, the router will probably preclude cutting acrylic or polycarbonate, unless I use my full-size router at least, and deal with the clouded edges.

Clearly I need to do more research.

I still might end up doing a laser cutter with the stuff I have, even if I do decide to go with the router for the MDF projects. (I have never really been a fan of the burnt edge look on laser-cut wood.) There are still things that it can do that are difficult with the router, but that will probably mean that I go full-on with the CNC router project.
Re: Laser selection questions, electronics?
January 05, 2018 12:07PM
... good luck smileys with beer

Re: Laser selection questions, electronics?
January 08, 2018 08:45AM
So looking around and reading more, a few things are becoming clear.

Few laser cut projects are done with MDF. Most are done in thin poplar plywood because it's a much less dense material, with fewer nasty fumes when burnt, and less likely to catch fire. Okay, I can let go of the idea of cutting MDF, it's not like I can't get a hold of the poplar plywood. I'd still like to be able to cut acrylic, even if I stick to black, or at least absorbing colours.

I think I have a pretty good handle on the control electronics, at least, using the arduino/RAMPS controls, provided that I can obtain a useful laser. Aside from assembly, this is probably the only thing that I'm missing.

I still need to look at the software control, but I'm fairly confident that a solution exists for the hardware that I have.

I don't have a lot of faith in most eBay vendors, which is why I was asking about the selections I had above.

It would seem that somewhere from 2W to 3.5W, it is possible to use a laser cutter for some useful projects, up to cutting thin balsa or poplar. Laser engraving also has many intriguing possibilities, and should be possible with a lower power laser as well.

I think that I'll keep looking at the 40-80W CO2 lasers as well, though that route no longer looks anything at all like a cost-saving measure. grinning smiley
Re: Laser selection questions, electronics?
January 09, 2018 11:01AM
Big difference in diode laser
CO2 laser

Diode laser can be moved around on print head
CO2 laser tube fixed and optical system points the cut point.

Many passes to cut things with 2 -3W laser

confused smiley
Re: Laser selection questions, electronics?
January 11, 2018 11:51AM
Thanks, Cozmicray, I am aware of those issues.

I was initially looking at a diode laser in order to do exactly as you said, and move the laser around as a simpler system, if it could do as I wanted. As you say, it would take many passes with a 2-3W laser, which is okay, so I was looking at something purported to be a 15W device. If it had been so, I'd have been quite happy, but it seems likely that it's kind of like the power ratings on cheap audio amplifiers, I'm sure that there's 15W somewhere in the system for some instant in time, but it's probably not in the actual sustained laser output, unless the lifespan of the diode device is severely shortened.

I still want something that cuts, which is why I'll still look out for CO2 lasers. I am not expecting at all that I'd be using the same configuration or even hardware for the CO2 laser as I would be for a diode laser. I'll be looking at that as something to build an entirely different machine to use.

So at present, with the information that I have as of my prior post in this thread, I'll be building a CNC router for cutting. My initial interest in the lasers was to see if it could be a potential cost saver, as opposed to buying all new motors and controllers since I have enough of the smaller ones to build 3 or 4 3D printers, or laser cutters (Of either design). I'll still be looking at that 2.5W laser device as an engraver, with which I can probably cut foam, maybe balsa, and have as a neat toy. In the meantime, I'll keep an eye out for stuff for a CO2 laser system which I could set up as a laser cutter for acrylic or thin wood stock.
Re: Laser selection questions, electronics?
January 12, 2018 01:06AM
It's even worse: The high power diodes usually have a bigger spot, which requires additional lenses to focus. Without these lenses, your power/mm^2 is not better than the 2-3W diodes.
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