3D Printed CNC Hot Wire Foam Cutter

[Brent Williams]

I have been following the progress of the development of this neat
3D printed CNC hot wire foam cutter from Flightory.  A clever young aeronautical engineer in Poland offers the files and manual for a cnc setup you can build yourself.  I purchased the print files and instruction manual for my future use.  Very nicely thought out system.  Any builders out there have thoughts on this offering?

https://flightory.com/2023/03/10/cnc-hotwire-cutter-design/

Demo video (in Polish with English subtitles):

[Paul Wescott]

Thoughts:

I don’t like how the 4 L-brackets have to be mounted on scrap-wood spacers to keep the two carriages from rubbing on the tabletop.  That could have been done better.  He could have taken 1/8” or 1/4” off the bottom of the carriages, which would have reduced the material usage and the print time (and the cost).

I don’t like how the cutting wire is 6” above the tabletop at it’s lowest point.  That’s going to make for some strange maybe Rube-Goldberg clamping situations for the foam being cut.  If the carriages holding the wire were designed to hold the wire lower you could use a couple pieces of plywood flat on the tabletop as edge clamps to hold the foam, they could each be held down with 2 screws w/washers, or simply weighted down.  But it would be easier than trying to stack material under the foam to lift it 6” off the tabletop PLUS hold it still while cutting.

I don’t like that the parts are 3D printed.  Most days I am 90% anti-3D-printing.  I have seen many items that CAN be 3D printed but I haven’t seen many that SHOULD be*.  The 10% where I approve of 3D printing is I have a buddy who 3D prints miniatures on a resin printer (prints upside down in a tank of liquid resin using a laser and has incredible laser-like resolution) and then paints them by hand.  This is a MUCH better solution than buying pre-made miniatures for $8 each and up.  But I have not yet seen anything STRUCTURAL worth a hill of beans come off of a standard 3D filament type printer, and the parts for this foam cutter require structural integrity.  They’re simple enough that I would make them out of wood.

* I did see one interesting print at a Thunderbugs Free Flight meeting in Torrance Calif a couple of years ago.  Brian Furutani printed some 6” diameter wheels/tires for an RC piper cub for Show-&-Tell.  The wheels (hubs) were a non-yielding material but the tires were a different rubbery flexible material.  The tires were printed with diagonal voids for some built in shock absorption.  Seemed like a nice solution.  But still buying some commercial lightweight foam wheels would have been easier and cheaper.

Maybe the XYZ system is good, the software, the stepper driver hardware, etc.  but then again maybe it’s just some guy who did a poor job designing some 3D files, and packages them with someone else’s off-the-shelf XYZ system to make a few bucks.

I’d like to hear an actual review from someone after assembly and use.

Just a few thoughts.

Paul W.

[Tim Wescott]

I've done just enough foam cutting to know that even with a CNC machine to help me with the "steady hands and a helper" part, there's still a huge amount of hands-on knowledge I'd have to learn to do it right.

So when you start getting decent output, let me know and maybe I'll put you on my list of folks who might take my cut files and make me stuff.  If I quibble about prices it'll be on the lines of "dude, you need to charge more".

[Chuck Matheny]

For most of us who aren't running a foam cutting business the CNC Machine is like shooting rabbits with a bazooka.
The guy who taught me his way of cutting foam ran a metal fab business right out of his garage.
He used a $4 dimmer switch hooked up to 115 VAC and he used  formica templates that he fine sanded to a near polished edge.
This is all I've ever used along with about 7 or 8  feet of .020" stainless "aircraft fastener safety wire" in the circuit.
Make sure you are controlling THE HOT and not the neutral [0 volt] conductor.
Don't cut in your bare feet on a concrete garage floor.... wear shoes and do not go out of your way to come into contact with anything that is at "ground potential" while cutting.
Sure...you can do mighty fine work with a DC power supply..but I'm here to say you don't have to if you obsever the basic safeguards I've spelling out.
The actual cutting voltage out of the dimmer is less than  half of the incoming 115V

[Brett Buck]

For most of us who aren't running a foam cutting business the CNC Machine is like shooting rabbits with a bazooka.
The guy who taught me his way of cutting foam ran a metal fab business right out of his garage.
He used a $4 dimmer switch hooked up to 115 VAC and he used  formica templates that he fine sanded to a near polished edge.
This is all I've ever used along with about 7 or 8  feet of .020" stainless "aircraft fastener safety wire" in the circuit.
Make sure you are controlling THE HOT and not the neutral [0 volt] conductor.
Don't cut in your bare feet on a concrete garage floor.... wear shoes and do not go out of your way to come into contact with anything that is at "ground potential" while cutting.
Sure...you can do mighty fine work with a DC power supply..but I'm here to say you don't have to if you obsever the basic safeguards I've spelling out.
The actual cutting voltage out of the dimmer is less than  half of the incoming 115V

      Please use an isolation transformer!

   Brett

[Chuck Matheny]

      Please use an isolation transformer!

   Brett

Brett...I've been doing it this way since I first got into C/L Combat back around 1985 or 86 and the guy who "lined me out" on how he does it dated back to the days of when foam first became "a thing" in C/L Combat.
If I averaged 6 new C/L combat models per year plus who knows how many RC Combat foamies I have built over the years...we're talking 100s without feeling even a slight tingle [except for THE ONE TIME I WAS BARE FOOT ON A CONCRETE SLAB FLOOR and too lazy to insulate the cutting wire at the handle end.....and all I felt was a slight 60 cycle tingle].
I suppose if a person wanted to stand in a steel wash tub full of salt water that has a ground wire tied to a ground stake....
As I took a seat in the class room of my   3rd year of the Electrical apprenticeship I noticed a fish tank full of water on the "professor's" desk with a lamp cord dipped into the water and the other end plugged into a wall outlet.
At the tank end the hot and neutral had about a foot of distance between them.
There was bare copper showing at both ends.
The teacher asked for volunteers to come up and dip their hands into the water.
None of us budged..so  the teacher plunged his hand into the water  with no ill effects.
Of course he was well insulated from ground potential via his shoes and the carpet he was standing on....but his hand was SEEMINGLY still at risk.
The water acts like a voltage divider and no matter where you place your hand the low voltage gradient that is created by the water  is constant.
Same goes for the auto-transformer/ dimmer..the only way you will get injured is if you go out of your way to touch the cutting wire while you are well grounded.
If I was really paranoid I'd wear nitrile gloves.

[Brett Buck]

Brett...I've been doing it this way since I first got into C/L Combat back around 1985 or 86 and the guy who "lined me out" on how he does it dated back to the days of when foam first became "a thing" in C/L Combat.
If I averaged 6 new C/L combat models per year plus who knows how many RC Combat foamies I have built over the years...we're talking 100s without feeling even a slight tingle [except for THE ONE TIME I WAS BARE FOOT ON A CONCRETE SLAB FLOOR and too lazy to insulate the cutting wire at the handle end.....and all I felt was a slight 60 cycle tingle].

  Please use an isolation transformer.

   Brett

[Istvan Travnik]

Yes, the isolation transformer is a minimum level of safety.
But, the most neat method is to use laboratory supply unit: that approx. 80 or 100 bucks for a 10A x 30V   1,5 kilograms heavy digital unit is an affordable investition.
Some hours ago I helped my good old friend in his very first foamwork: I noticed the parameters: 1,2 A  with 12,5 V limit, .015  Sullivan 7-strand control line (!!), for middle density bluefoam...
Istvan

[CircuitFlyer]

I really like the DIY 3D printed CNC router I built.  It works far better and more precise than I ever expected.  This machine looks like it should do the job.  How much load on a hot wire going through foam?  Simple enough and not a huge total parts count.  Making your own mods is the nice part about open source projects.

From what I have seen with the DIY machines, the trouble a lot of people have is with the electronics and programming.  Is the machine well supported via an online forum to help with any troubleshooting you may encounter?  Maybe just start with the stepper motors and the electronics and make sure you can get everything working first, then build the rest of the machine.

Some might find it overkill but for others the challenge of building the machine is all part of the journey.

[Brent Williams]

The Flightory 3D printed CNC hotwire setup is an evolution from the popular MDF/Plywood DIY system supported by RC Keith.  https://rckeith.co.uk/how-to-build-a-usb-cnc-hot-wire-foam-cutter/

Nothing is really plug and play in my experience.  Plenty of trial and error is involved before a useful wing is produced, which also happens to be true of any method for cutting foam.  I have made full garbage bins full of terrible foam wings as I have experimented with manual bows.

The world of CNC hotwire cutting of foam is a lot bigger and more diverse in application than just model airplane wings, which is fortunate for all of us.  From what I have seen, there is a pretty decent community to draw upon for support while a person is getting started with the learning and building process. 

[Howard Rush]

I have seen many items that CAN be 3D printed but I haven’t seen many that SHOULD be*. 

I am renowned for printing items that shouldn’t be printed.

[dave siegler]

there are many cutters out there that you can either make out of metal or 3d print

https://www.thingiverse.com/thing:3676825

the problem isn't going to be the 3d printed material, all the hot wire cutters have a problem with calibration. 

[Tim Wescott]

I don’t like that the parts are 3D printed.  Most days I am 90% anti-3D-printing.  I have seen many items that CAN be 3D printed but I haven’t seen many that SHOULD be*.

As long as the part is designed with the material and fabrication process in mind, and as long as it does what it should, why not?  Designing a part as if it were aluminum and printing it out of plastic would be bad; designing it as if it were machined 2024 aluminum and printing it out of sintered aluminum is also at least kind of bad.  But designing it to be printed and then printing it -- that's fine.  If it doesn't work it's not a 3D printing problem, it's because it was designed incorrectly for the material and manufacturing process.

(Note that designing something that cannot be suitably fabricated is different -- you won't see me flying any 3D printed airplanes anytime soon.)