Printrbot-Based Laser Cutter

[Pieliker96]

I figured that trying to troubleshoot my old Printrbot simple was too much of a hassle, so I'm starting new, and repurposing it. I'll be reusing the bearings, steppers, endstop switches, and controller board, and building an entirely new frame.



I've got all of the parts I need either at my house or on the way, and they should all get here within the next month.

I would use lead screws, but the carriage and gantry will be light enough for belts, especially with 2 motors on the x axis. The bearings will be attached with a little indentation into the MDF and some zip ties (Sounds sketchy but works great with low loading)

All rods are 8mm diameter. The X axis runs on 1000mm rods, the y-axis on 600mm. I doubled up the X-axis rods to reduce sagging at long lengths, and this was cheaper than buying new bearings and a thicker rod.

The Laser I am using is this. It should have more than enough power to get through the paper layer, although I am not sure about cutting through foam. Either way, It's still better than tracing everything out myself! It will be plugged into the fan port on my controller, which provides the required 12v.

The base and all of the rest of the machine is cut from a sheet of 2'x4' 1/2" MDF.

The cutting area is exactly one sheet of DTFB (20"x30")

Total cost was just shy of $150, including shipping and stuff like eye protection

That's all for this post, feel free to critique my design, as I haven't designed a CNC machine before. I think this should work fine, but let me know if there are any obvious flaws.

 

[jhitesma]

500mw you'll probably have a tough time getting through the paper. I run a 2.8w module on my CNC and can cut posterboard and thin balsa no problem...but DTFB...not a chance.

The problem is the foam dissipates the light energy too much since it's basically just a big diffuser.

I'd suggest looking into a higher power laser, or if you want to cut foam adding a needle cutter (even a lightweight machine should be able to handle the needle just fine.)

 

[Pieliker96]

Assembly of the pieces went smoothly - I used CA to tack them into place while I drilled out the holes for the screws. The bearings are attached by zip-ties and kept in place by a small groove that I filed into the pieces. The assembly is very rigid and I did not observe any sagging of the rods during operation - I'm starting to think that I may have gone a bit overkill. The cable chains provide excellent shielding for the cables, as well as keeping them out of the way, and the endstop switches allow the carriage to home itself automagically.

Due to some firmware limitations of my board (from the factory, designed for my specific printer), I was not able to move the axes more than 150mm in each direction. 10 hours of faffing around with compiling my own firmware solved that, and the machine can now use the whole build area without compromise.


Fully Assembled, with a sheet of DTFB for reference


The cable chains just clear my bed for storage



Mounting of the linear rods, bearings, and the laser

It may not cut foam that well, but it engraves/cuts wood with ease. I used inkscape and some specific laser tools to outline and raster some images.


First test engraving, an SR-71.


The laser in action rastering the dark areas of the XB-70.


And the finished product.

I'm impressed with the accuracy of this machine for the $150 over the cost of the 3D printer, and the parts that were rather jaggedly cut with a coping saw. The level of detail is absolutely incredible: see the US Air Force text and logo in the above image. I can even read the tail number!

Further testing and optimization is required (getting the raster spacing and power correct), but I'm already starting to find uses for this where I didn't expect to. This will be great for engraving some "Arrow of Light" plaques (my Dad's a Cubmaster), as well as the plywood gear mounts, control horns, and painting templates for my B-70 build. It still sort of works for foam, cutting through the paper and a little into the foam (effectively a weak score cut) and provides much better accuracy than I could trace by hand or stitch together with paper. I may end up building a needle cutting attachment in the future, but with my one large project progressing slowly, I don't have any current need at the moment.

 

[rockyboy]

Excellent work! Don't forget to buy a pair of safety glasses so reflected light damage doesn't make us call you 'Odin' some day

 

[fofopadilla]

Hello

Sorry for bringing to life such an old thread.

But I would like to ask OP: How was the laser wired to your Printrboard?

I intend to do the same with my own printrbot metal with a 2.5w laser head.

 

[Pieliker96]

Hello

Sorry for bringing to life such an old thread.

But I would like to ask OP: How was the laser wired to your Printrboard?

I intend to do the same with my own printrbot metal with a 2.5w laser head.

Sorry for being a bit late to reply!

I wired it directly to the fan header of the printrboard. I used JTech Photonic's laser tool in Inkscape with the fan start/stop Gcode (M106 & M107, for my board at least).

For your case (a higher powered laser), I'd recommend finding the voltage regulator / MOSFET doing the PWM switching for the fan control and find out how much current it can take. That, and if it supplies the right voltage. If not, your best bet is to use a relay and a separate power supply (for simple on/off control). It may also be possible to get duty cycle control back if the laser uses a driver board by somehow adapting the fan output to the input for the driver board.

Best of luck on your project!