This article shows how I built a CNC hot wire foam cutter.
Firstly if you’re not sure what a CNC hot wire foam cutter is, then let me explain. Most foams can be cut with a hot wire and if you can control the wire very accurately then you can make wings and fuselages for RC airplanes. It can be done without a CNC (Computer Numerical Control) machine just by guiding a hot wire over templates.
Why build one? a few reasons
- In the build of the Vickers Super VC10 airliner I’ve had to make many templates for various parts. The first couple aren’t so bad but after a while it gets a bit tedious. A CNC cutter would eliminate this
- I visited Mike Black of Green Air Designs to see his VC10 and had a very pleasant time. Mike showed me his laser cutter working and showed me his other machines. That inspired me to build a hot wire CNC
- It’s really quite feasible to do and a quick search on the net show many DIY CNC machines, most tend to be routers
- I’m always been fascinated by CNC but never thought it would be possible until now.
After a lot of research and some real good advice from CNC forums ( http://www.mycncuk.com/ and http://www.cnczone.com/) I decided on building this version. Full details on this page http://www.rckeith.co.uk/cnc-detailed-build-and-plans/
I’ve decided to use threaded rod for the lead screws, because I believe the accuracy required in foam cutting is not that critical. These came from http://www.screwfix.com/prods/98942/Fixings/Injection-Fixing/BZP-Threaded-Rod-M12-Pack-of-5
I used 2 PC Power supply in series 2 ATX PSU wired in series to give 24 Volts. This can be a little dangerous if you not careful to isolate the second PSU, so I’d recommend you putchase on specially designed to give 24 Volts. These are now quite cheap and take up up less space
The X-axis use a captive T-nut the one with spikes on that bites into the wood. The Y-axis uses a small aluminium block which I drilled and tapped the threads into. I’ve turned the ends of the threaded rod to match the size of the stepper motor spindles and used rubber hose with two hose clips. Seems surprising solid and give a little bit of flex.
Build finished with some pictures below. Tested and it works. I used RJ45 cables and sockets to connect motors to controller. This allows easy dismantle when not in use, my space is limited . It’s been wired so each motor wire uses 1 pair of the RG45 cable to allow for higher current.
I’ve used a old Dell computer running XP and no other unnecessary software installed. You need a PC with a parallel printer port usually known as LPT1.
To control the CNC machine you need some software and after much research I decided to go with Mach3 from ArtSoft http://www.machsupport.com/ its very well supported and there are several videos on YouTube that describe how to install and configure. There is a free version that allows 500 lines of g-code to run.
G-code is the instruction sent to the machine that tells it how far and what direction to move he stepper motors. You don’t need to learn g-code as there is software to convert drawings into the code. I’ve tried a couple FoamWorks and Profili2 and have settled on Profili2 which does a lot more than generate g-code for wing profiles.
The wire between the 2 towers is tensioned by a spring so they can move interdependently for tapered wings. The wire is usually ni-chrome but several other can be used including guitar strings. I’ve powered my wire with the iCharger 206 which has a foam cut program but I have used a car battery charger connected to a house dimmer switch for manual cutting. This allows control of the heat and works very well.
Its quite exciting when you get it all powered up and move the cursors keys and see motors spinning. The video show a small test aerofoil which was about the 5th attempt. The hot wire cuts my radiance so its basically melting the foam in front of it. My first pieces were not very good as the feed was too slow but as you can see it didn’t come out too bad when I cut the feed right
Below is the flying wing which was the first model plane I made with the CNC machine. This was just a quick test as a proof of concept and its proved to be the model I fly most now. Its flies really well and is fast. Profili2 Pro http://www.profili2.com/ is very good for generating the code and has a massive database of aerofoils.
Here is a free g-code generator that will generate the code for you http://swarfer.co.za/rc/wire/index.php I’ve not actually used it on my machine but should be enough to get you going for simple wings.
Another free one is JediCut which I haven’t tried yet seem to have good support https://www.jedicut.com/en/
This one cost a few dollars but I haven’t used it. NCGen http://www.foamcasualty.com/products/ncgen-2 Its a plugin for Sketchup http://www.sketchup.com/ . Skeckup is very good and the plans I’ve detailed on the build page were all produced with Sketchup
Hope you found this of interest and if you need any advice or help then you can contact me through this website.
I’ve included the configuration for Mach3 with the TB6560 controller board on this page Mach3 TB6560 configuration
This is the flying wing I made first with this CNC machine and its a little gem. I now fly this most weekends. It goes really fast with a 2200 KV motor and a 6×4 prop. Its a blast. If you want to build it then check http://www.rckeith.co.uk/hot-wire-cnc-ymf-38-flying-wing/ I’ve included the gcode for each wing as well.
I’ve now made a Hawker Hurricane with the CNC machine both wing and fuselage, you can see it here http://www.rckeith.co.uk/cnc-hot-wire-hawker-hurricane/
I’ve also made a much bigger wing for FPV(First Person View) with it as well details here http://www.rckeith.co.uk/fpvfw/
The CNC machine is now starting to pay for itself as I don’t buy many ARTF models now, nothing against them but I just enjoy researching and making my own RC Models much more
After making several models and getting through a lot of foam if I were to build this again what would I do now.
The actual machine the only change I’ve made has been the couplers to the stepper motors. The rubber hoses occasionally came off which ruined some foam so I purchased some proper couplers and these have been very reliable. Details on the build page.
I would now probably use a usb controller like the ones I’ve listed on the build page as alternatives and a purpose built power supply. This would allow me to use a laptop as well. My machine takes a lot of space when running. The TB6560 has been very reliable and never missed a step.