New laser build underway. K40 converted to the extreme. Bed is 36" x 56" with an 18" Z. More pictures to come.
#K40ReBuild
That thing will be Huge… Share progress! Damn Exciting 
By the way; I would take lots of care to make the gantry and optical mounts as stiff and square as possible. Considering the x optical distance it won’t take much to get a wiggle in the beam at the surface.
Yeah, I’m worried about the x axis. I planned on 10mm duel shafts but there’s too much flex over the distance it runs. I’m going to try to bump that to 20mm shafts and see if I get the rigidity I need.
Looking good. Are you using a profile linear rail for the x axis too?
Mine will be a bit smaller at about 30x45. This is a mock up before I cut the extrusion down. Iko linear rails for the Y and THK HSR for the X. The extrusion is 80/20 1"x2".
I was going to use servo motors but all the Copley servo drivers died in a lightning strike that hit my house a few months ago. Probably just use steppers now.
@Jim_Fong , thanks. No I am not using profile for the x at the moment. It seems too big. It also drives me nuts that it of sets the laser head to one side (Just looks bad too me). I might end up back with it bit the current plan is to go to a heavier round rail. I think at a 20mm diameter I should be ok. I cut my 10mm shafts to length as a test fit and they’re better than I though so upping to 20 should work.
Servos would be nice! I am using steppers though. I have a tendency to build around parts I already own to keep the costs down. Here’s my progress as of this morning.
I’m very interested in this…please keep up the feedback!
I’d be interested to know what kind of power fall off you get at the far corner. That’s a lot of air the laser us travelling though. I’d love to go this big but thought I’d have to upgrade the tube too.
That issue is something that occurred to me as well but I’ve seen bigger beds and they don’t seem to have a problem. I will keep you posted though as things turn out. I’m currently waiting on the new thicker x rails to arrive so it’ll be a bit before I can test.
#K40LaserOptics
…if I recall correctly, is that its not so much attenuation from air (at this length) you have to worry about rather its the change in waist diameter. I.E. the beam will be larger the further you get away from the source.
The laser beam is Gaussian in shape and diverges as it leaves the laser tube. [Lots of math behind predicting this].
To retain full power the larger beam must be collected on the mirror and collected by the objective lens.
Note: I think the bigger problem will be alignment and stability at the extremes using this length
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You can calculate the change in waist diameter … have fun with that :).
Here is a calculator that may work (I did not check it) to estimate the waist at this distance.
Another calculator is here: fxSolver - Equation Library.Graphing Calculator.Math Solver
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Theory and math
This is the simplest math explanation and form
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