Laser (actually hot knife) sled design

I’m going to use my maslow to cut full sheets of foam to make full-scale aircraft fiberglass molds. Foam is super simple to cut, so I thought I’d try using the simplest method, Lasers! The laser beam itself is tiny compared to the frame of a router. I was thinking of making a simple “single-point” attachment sled with the laser beam running just above the attachment point. Does anyone have a sled design like that that I can steal from?.


I don’t think anyone has mounted a laser on the Maslow yet (at least I haven’t seen it there) super interested in seen this work for you. Also interested in your project (I’m a pilot and have restored several old airplanes with my dad while growing up).


It was never tested with the bit in the sheet because it is known to fail. It would drag the bit behind and cause an error. A laser would not cause that drag and therefore it might work.

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I’ve been flying/building for 20+ years; built an Alisport Silent-IN and an RV-4. This will be my first “self-design”, it’s a Part 103 legal, folding wing, “road-able” electric glider. I haven’t given it a name yet, but here are my cad renderings.

The plan is to use the maslow for all the molds. First; slice the fuselage (down-the-middle & nose-to-tip) into 1" cross-sections. I’ll long-board to final shape and glass to matched left/right mold pair. For the wing, I’ll create one non-tapered 8’ wing section mold using foam cross-sections, this will mold 90% of the wing skins. And finally I’ll make a left/right wingtip molds. The spar will be box center section (inner 8’) I’ll use the maslow to cut the foam core of the spar so it contours around the fuselage. Outer wing will be a simple box to C-beam spar. The molds will be done in cheap e-glass, but the final skins will be s-glass because it’s just as strong as carbon, but much easier to wet and a bit cheaper.

I’m probably going to create a project github when there’s more to see than a maslow.


Only one image per post :frowning:


Perfect thanks! I’m stealing it.

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Nice looking project! :sunglasses:

Note that depending on the type/thickness of foam you want to use, lasers may not be appropriate. Polystyrene foam (ie Styrofoam™) is famous for its hotwire cutting ability BUT when cut with a laser in thin sheets the edges sort of melt and in thick sheets you get a bit of an hourglass edge from the beam divergence. Basically the cutting temperature of the laser is much higher than a hot wire, so the foam tends to deform more.

For those reasons, you may want to consider using the Maslow for its intended purpose first and test machining some nice square edges on your foam of choice. :slight_smile:

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Wow… that’s awesome info. It sucks that I bought a 500mw laser already. Oh well, I will definately try it no-matter. I still have three other options…

  • Use a router, like you all do
  • Use a water jet made from a pressure washer (it doesn’t take much to cut foam)
  • Use a hot wire cutter

I think I’m going to try #3 first after the laser, it’s the obvious simple/light way. I have a massive amount of foam to cut and I want something really really fast.

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Nose-to-tip is 20’, I won’t need to cut every single cross-section and I may go up to 4" in some sections, but that’s 240 cross-sections x2 (left/right) just for the fuselage. I’ll also cut support “stringers” that will run the length to align and hold the mold together.

I’m open to suggestions if anyone has any ideas.

One of my crazier ideas was to use 2-axis mirrors (remember… laser) to angle the cut and use much thicker foam… up to 12" even.

Totally understand that!
Won’t you be limited by the 48 inch per minute max speed of the Maslow itself though? Or are you planning on using the Maslow to make templates?

Is the Mega 2560 capable of driving it at the hardware limit consistently and reliably? If so, then this is all moot and I can worry about other problems.

You can’t steal what is free :slight_smile:
By shifting the opening on both, to the side you can keep the chains aligned at same hight.

It depends to some extent on the gcode you send it. With simple curves and straight cuts folks see 700-800mm per minute as workable. Some gcode generators create a tremendous number of tiny steps for curves, though, and then the time it takes to send an process each gcode line enters as a factor. You may find that tuning some parameters in the CAM processor you use will make a difference.

you don’t want a single point attachment sled, use the normal sled design (you
will have to experiment with weight and frame angle to see how light you can
make it)

don’t forget eye protection

If the sled is enough lighter (very possible with a laser) you should be able to
go to 25 tooth gears and increase the speed by 2.5x.

The limit isn’t the arduino, it’s the motors keeping up.

testing will be needed, but there is a good chance that tuning the machine
dmensions will make it work.

you probably will need to change the height of the triangulation kit (ring or
arms) and the top beam position to make everything balance properly.

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@Bruce_Meacham Welcome to our group. I’m a little late joining in. I think seeing the results of routing here, you will be better off with that or a hot knife/ drag knife type of device. I have lasered foam and it is very inconsistent , the out gassing is toxic. You can’t control the amount of melt/shrinking around the kerf of the laser. Also if it catches fire it will burn up quickly. If you do decide to use a laser you will need a active filtering system. Be safe.

Sanding and carving of foam is it’s strength.

Thank you


But mind the dust! Very fine filter respirator is a must (foam does not degrade once inside the lungs).


True that, but the dust falls!

Thank you

Also, please don’t leave your maslow for a second if you try this, i have very little faith that it won’t catch fire sooner or later.

Maybe install something like this above the maslow


This is going to sound like full-circle… But maybe I started this wrong and a stock router sled is best… If I use a long round nose I can taper or “engrave” the mold side on thicker foam using the full plunge depth of the z-axis the trim the edges. Then when I assemble the mold, I’ll have no carving and just finish smoothing with bondo.

What is the full plunge depth? From the pictures of the R22002 it looks like maybe 2".