buildlog.net

So ... I've been itching to get either a laser cutter or a 3d printer, and I decided to settle on building a 2.x laser cutter -- mostly because I'd be able to build almost all of a 3d printer on one, but very little of a laser cutter on a 3d printer. I'll be building it over the next few months, and I'll probably pull the trigger on the first order of parts shortly. Each month I'll make another order as cash flow allows. Mostly I plan on using it to do precision cuts in light wood or plywood for various hobby projects -- electronics enclosures, robot limbs, some artsy crap, and I really want to play around with building my own remote-control airplanes. Most of the time I'll be cutting 3mm or less thicknesses of wood, but I want to be able to do 1/4" acrylic and plywood, too. From what I've seen, that shouldn't be a problem if I get a longer-focus lens and go slow and don't mind charring on the wood, right?

I've got enough experience with electronics that I don't anticipate any problems on that side, and enough experience with tools and such that I don't expect major problems from that side, though I have very minimal machining equipment. (Read: hand-tools and a radial miter saw.) That's part of what drew me to the Buildlog 2.x laser build -- it requires almost no precision cutting/drilling/machining, meaning fewer opportunities for me to screw up in a way that ruins materials and costs me money.

One thing I'm still trying to decide on is how big I want to make it. On the one hand, the standard 2.x profile is well-tested. On the other hand, I think the cutting area's a little dinky, particularly if I'm making airframe or wing parts, and the added cost to increase it is minimal. I'm thinking a 3'x2' laserable area -- do you folks think that'll be too large to align, or encounter other problems? Maybe I should just avoid buying trouble and go with the standard dimensions first, then upgrade later.

I plan on acquiring the parts in stages:

- Frame & Fittings -- basically, all the Misumi parts and the McMaster-Carr parts.
- Inventibles.com (mostly) order -- the makerslide and all the other bits needed to get the XY gantry going, along with the pulleys and belts and such.
- Motors, Drivers, and Controller -- FWIW, I want one of the Lightobject DSP controllers, but it'll probably be among the last parts I buy, since it's the single largest investment. I'll probably try to use an Arduino Mega or an Arduino Due to control it, mostly for testing, until then, unless I DIY a Mach 3 controller.
- Laser Fittings and Optics and Tube -- I think I'm going to go the HD-platter mirror route to save some money. I may split this into two orders, tube last.
- DSP controller -- as soon as I could afford it.

I figure I can do this in about 6 months and $1300-1600. Of course, that means it'll probably take a year and half and nearer to two and a half grand.

Does the "NY" in your post title refer to New York state?

I'm sure that you'll have a good time building your laser. I recently finished a 2' x 4' laser and it is awesome. It's mostly my own creation and not based on the 2.x, but I did use makerslide for the linear rails. I think that you will find that the cost of building a laser is in the >$2k range. I would recommend using a laser head with adjustable optics instead of having a Z axis that moves the bed. That makes focusing over the whole bed a lot easier if you are doing a large laser.

If you enlarge the 2.x, you'll be on your own for skins. That, I think, is the hardest part if you don't have fabrication facilities.

There is even a calculator on Thingiverse to generate your oversize BOM.
http://www.thingiverse.com/thing:12864

Indeed it does, timogiles. I hadn't considered a head with adjustable optics; this sounds like it's probably hideously expensive. Got any links?

kbob, I found that thinkgiverse model -- been playing with it for the last couple of days. I realize that the skins will be a problem, but if worse comes to worst, I can contract out with someone who does, or use Pokono, or something. I think that shouldn't be beyond me, though -- it's not like imprecision cutting the skins will affect the printer output, which is the thing I'm most paranoid about, and I could always cut certain parts of it on the printer itself. I can practically guarantee you that it's going to spend some time skinned in cardboard (with some aluminum foil to prevent burn-though towards the operator) until I get everything together.

Is your 2x4 laser 40W? Does it have any problems with attenuation on the furthest side from the beam origin?

I posted about my 2'x4' laser here: viewtopic.php?f=16&t=909&p=17576#p16828. A couple posts after that I linked to the laser head i'm using. It's $70 from lightobject.com and I'm very happy with it.

I started with a 40W Chinese model (DC-KIII) and I built a new chassis with the 2'x4' work area. The tube, tube power supply and mirrors are all from the DC-KIII. I'm doing my buildlog out of order. I completely built the thing and now I'm going back and writing about what I did.

I don't have any attenuation problems at the farthest point, but focus is a little trickier. Since the beam has diverged a bit at the farthest end it is wider when it hits the focusing optics. This makes the depth of field smaller so your focus needs to be more accurate. For my machine holding that accuracy is no big deal, but the flatness of the material that is being cut is not usually flat enough. That is the real challenge.

Nice. The sad thing is, I Read that build log a couple of days ago. Somehow I missed the bit about the adjustable head. That's rather neat, and unusually reasonably priced -- I'm assuming the lens is kept in the bottom part that you move up and down? I may just go with that and eschew the z-axis movements initially, and save a few bucks. On the other hand, I have a few ideas about using an autofocus-type feature in combination with the automated Z axis to map the surface of the workpiece and compensate for height differences.

It's good to know that at 2x4 & 40W I shouldn't have too many problems -- and I think that for my first build I'm going to stick to 2x3' (mostly 'cause 2x4 is a bit more machine than I have convenient places to put it,) so it should be less of a problem. If I stick with the laser cutter thing and start using it a lot, I'll probably wind up rebuilding the cutter at some point anyway to stick a bigger tube and a bigger laserable surface in there.

Have you seen anyone integrate fire suppression into their builds? I haven't but it's something I'm considering doing; I figure I can rig a big paintball CO2 canister to a soldenoid, which would dump the contents of the canister into the enclosure if I either hit a scram button (which would also activate the e-stop) or the temperature inside the cabinet hits 'it's on fire' levels. A 20 oz CO2 bottle holds about 11 cubic feet of CO2, which should be plenty to flood any enclosure without presenting any danger of asphyxiation (and only costs a couple of bucks to refill.)

If you go the CO2 route you might need to rate limit the CO2 dump. I'm just guessing but I could see you blowing the sides off the macine with an uncontrolled discharge.

I've had a CO2 paintball tank valve jam full open before. It does take some time to dump the entire contents of the tank, and would be about perfect for keeping the space flooded with CO2. Good idea there. I may have to look into doing something similar. Very cheap alternative to actual fire extinguishers.

steves wrote:If you go the CO2 route you might need to rate limit the CO2 dump. I'm just guessing but I could see you blowing the sides off the macine with an uncontrolled discharge.

Naw, that wouldn't be a problem. The flow-rate isn't -that- high, not unless you literally break the neck off the tank or otherwise mechanically compromise it, which takes some doing. I've seen tanks blow pressure lines and it takes about 30 secs or so for the whole tank to discharge. If the cutter were well sealed it might lift the lid a bit, but if you've got any kinda vent / intake holes, that should be sufficient to allow expansion without causing problems. Also, because of the nature of expanding gases, it's inherently rate limiting -- the cooling from the rapid expansion starts inhibiting the rate of expansion almost as soon as you let it out.

TLHarrell wrote:I've had a CO2 paintball tank valve jam full open before. It does take some time to dump the entire contents of the tank, and would be about perfect for keeping the space flooded with CO2. Good idea there. I may have to look into doing something similar. Very cheap alternative to actual fire extinguishers.

That was my thinking -- it's not cheap to fill up fire extinguishers, they tend to be messy and ruin your electronics unless -- and even if -- you do get the CO2 ones, and it's something you need multiple actions, including raising the lid of the laser cutter, to engage. I want to be able to just slap a panic button. Of course, I'll still have a higher-volume fire extinguisher handy, I just want to never have to use it.

I've been trying to think of a way to set it up that would be able to be engaged either electronically, or, in the case of a power loss, manually. I could run a tube from the tank to the solenoid valve, and then make it possible to cut the tube with a lever actuation, but I think that I'd probably slowly lose pressure that way while the system was on standby -- when I had a paintball gun, the tank would lose pressure slowly over a couple of months if I left it attached. On the other hand, I could have a valve with a manually-engaged lever mounted outside, but then I'd need some kludge to get it to work with the electronics...hrm. Maybe some sort of 'firing pin' mechanism would work, that could be either engaged by a lever or by the solenoid ramming the mechanism in and engaging the nipple on the CO2 bottle.