[peter] send in a reprappable laser cutter that he’s been working on. Even though he’s still having some problems with the accuracy of the beam over the entire square meter bed, it’s still an amazing build.
The build started off with a bunch of t-slot aluminum extrusions. After taking delivery of an absurdly large package containing a CO2 laser tube, [peter] started working on attaching motors to the axes. The optics travel the solid rods on pillow block bearings driven by the age-old stepper motor & timing belt drive.
The 1-square-meter of cut area on this machine is enormous for a homebrew laser cutter. [peter] discovered that once the necessary components are in place, it’s really how much aluminum you’d like to buy that becomes the limiting factor for the cut area. [peter] put the files for the 3D-printed carriages, brackets and mounts up on Thingiverse in the hopes his design can be improved by others.
I bet if you got some of Barts upcoming makerslide rails it would solve your sagging problem.
http://makerslide.com/
Or use industry standard supported rails.
80/20 is rigid but there is a reason no commercial machines use it. Most people don’t understand how much flex otherwise highly rigid metal has over long spans. It is considerable!
So then what’s the preffered system to use?
Some cross-bracing or thicker members would certainly help a lot. If the outer bars were supported more rigidly it would help a lot…it wouldn’t fix everything, but a few thin supports on the outer bars would make a big difference I think.
BTW…considering that is uses all of about $5 worth of 3D printed parts, it is hard to consider it 3D printed…more like store bought with a couple of 3D printed adapter pieces.
The “E” (modulus of elasticity) of aluminum is 1/3rd that of steel so considering two equivalent pieces the aluminum even if as strong will the 3 times more deflection so you loose rigidity.
Backlash in the system maybe causing the accuracy problems. You could mostly eliminate the backlash from the system if you only “cut” after travel in only one of the directions per axis use the opposite directions only for travel.
I have been doing calculations on my laser cutter. On a 20mm 1.8mm long solid steel support rail i am expecintg up to 2mm of center sag with only a half kg load! This is expected considering it is completely unsupported.
wen you consider the 15mm shafted sagged almost 4mm in calculations that is enough to throw off mirror allignment and shift the focus of the laser completely
I’m really looking forward to makerslide as well. Want to make a CNC.
I love how the laser stays still and it uses mirrors along the axises (:
Would love to see one of these but instead of a laser a loop of nichrome wire. heated by a PC’s PSU (high current and cheap) so you could put in a polystyrene block and have it cut out a plane :D
Hmm similar concept maybe with a plasma arc and send the power inductively by resonant coils. (Tesla :D)
Or maybe a gigantic football pitch sized plotter that uses quadcopters carrying spray paint? :D
That’s how it works on every commercial laser engraver/cutter I’ve ever seen. Well, that’s not entirely true. I’ve seen systems that engrave polymer printing plates that use a UV laser and fiber optics, but that’s the only one to not use mirrors.
Lasers like this are called ‘flying optics’.
The other method is where the single mirrors is just angled about instead, called ‘galvo’. Galvo’s are much faster, and much harder to build & control.
you may be interested in machines called “Electric discharge machines”, EDMs can use that same priciple but with steel as well. Interesting to see.
Where can I buy a cheap power supply that will work with a laser tube? I can find neon sign transformers that are appropriate voltages but too high of a current. Anyway a link would be appreciated.
LightObject is a reputable source for laser power supplies and optics. They also have tubes but they are expensive compared to e-bay.
http://www.lightobject.com/40W-PWM-CO2-Laser-Power-Supply-P71.aspx
Scaling up a laser cutter actually creates more problems than one might expect because alignment problems get worse over large distances.
Top that off by using cheap optics and printing the load bearing parts out of plastic and I suspect that this laser will always have accuracy problems.
Plastic deformation may be an issue here too. It creeps over time. See: the AK-47 printed magazine. Some plastics are worse than others but pretty much all experience it to some degree. Since errors multiply over distance…. this may not be accurate enough just yet to be truly useful.
Several comments here –
1: “rigid” materials are all elastic- that means they deflect according to the force applied to them. The amount of deflection is determined by the material, the size and shape of it, and the force applied. (and where it’s applied)
Sending a laser beam through a series of mirrors is non-trivial- it must be very accurately parallel with each axis of motion, or it will move around in the focus lens when the machine moves.
Any vibration of the structure will cause the mirrors to vibrate, and the reflection from them will wiggle.
Strength counts, smoothness counts, squareness of axes (one to another) counts.
Oh, yes- don’t forget that Aluminum has more thermal expansion than steel per degree. So it will change size as the temperature around it changes.
Someone should make a PCB etching machine using a plasma arc setup to burn through the slightly conductive paint.
Combine with spin coater using old power supply fans and voila.
Hey Ryan.. Thanks for that link.. That rocks! Aside from all the cool HP laser stuff, I love this dead-man switch!
http://www.lightobject.com/Emergency-Push-Button-Switch-with-lock-P534.aspx
Been looking for one of those for years!
Tweeks
Ah! The good old BRB! Every project needs one of those.
Yeah very impressive link! I can see myself spending som money there. If your looking for contactors and switchs like that then IMO have some good ones, as does phoenix connectors.