How to build a Hot Wire CNC Foam Cutter – DIY

posted in: CNC, Hot Wire | 2

Why would you want to build a hot wire CNC foam cutter machine?  For me it was a way to build wings and fuselages for RC airplanes that weren’t readily available. Doing it yourself (DIY) is not as hard as you may think.

Traditional building methods for RC airplanes involves lots of Balsa wood cutting and gluing many parts together.  I can cut a foam wing core in about 15 minutes and usually I cut several at time.  Building your own models is very rewarding and when they fly well its a real buzz.

My machine has been running since 2012 here a a few of the projects I’ve made 

Here are the main sections

How does it work ?

If you’re not sure what a Hot Wire CNC foam cutter is, then let me explain. Most types of foam can be cut with a hot wire and if you can control the wire accurately then you can make wings and fuselages for RC airplanes and many other things e.g. signs. It’s possible to do without a CNC (Computer Numerical Control) machine just by guiding a hot wire over templates. This method is less expensive and is a good place to start on the hot wire cnc foam cutter journey. You’ll get good experience of working with a hot wire. My Super VC10 wings were made this way before I had my machine.

Is it difficult to build ?

No. If you are reasonably practical then you have all the skills you need. Don’t be put off by the electronics. It can look a little daunting but if you follow my articles on the website or sign up for the eBook you have all the information you need. If you do need help reach out to me via the contact page and I’ll get back to you with some answers. I get quite a lot of questions from all over the world asking for advice and recommendations on parts to buy. I’ve provided links to all the parts I’ve used and recommendations.

Why did I build one?

  • When I built my Vickers Super VC10 airliner I had to make many templates for wings and tail plane. 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 easy to do and a quick search on the internet shows up many DIY CNC machines, most tend to be routers and 3D printers (I’ve got them as well, the CNC bug bit me)
  • CNC has always fascinated me but I never thought it would be possible on a small budget  to have my own machine.  Thanks to the Chinese and the affordable CNC kits its quite easy.

After a lot of research and some real good advice from CNC forums I decided on building this version. Full details on this page

4 axis hot wire cnc foam cutter

How much does it cost to build a Hot Wire CNC Foam Cutter

Probably not as much as you think. My 4 axis CNC kit came from eBay which included the stepper motors, controller board and a few cables. These vary in price so check the parts list for latest  I check them regularly to make sure they are still the best in my opinion. 

The power supply I made from two old computer PSU and the rest came from Local DIY stores. See the build page for a full list with links. I’ve spent more money on software than the rest of the build, but there are now some very good free alternatives, check the build page

The majority of the cost, if you use the free software options will be the CNC controller, stepper motors and power supply. If you have an old desktop PC with a parallel port then this will keep the cost down. Working on average prices in 2018 if you had to purchase everything except the PC, then I would budget for around $320 (US) £220 (UK), but you may be able to do it for less, if you have some suitable materials already.  

It’s a bit of an investment but it won’t take you long to recover the cost. I’ve built several wings and a couple of fuselages and its a real buzz when that wing core reveals itself from the foam block.  Foam models can be quite expensive now, guys at my flying club often pay £200 to £400 for a jet with a big EDF. I’ve seen a couple of these destroyed beyond repair.

Parts required to build a Hot Wire CNC Foam Cutter

  • Stepper Motors – these drive the towers where the hot wire is attached
  • Control Board 4 axis – sends signals to the stepper motors to move a certain amount and in which direction. Receives inputs from limit switches and pendants
  • Computer – drives the control board. It receives g-code and turns that into signals for the control board.
  • Lead Screw – connected to the stepper motors and then the towers to move them in the desired direction,
  • Software – I use LinuxCNC now but started with Mach3 which turns the g-code into signal that the controls board and stepper motors can use. I then use Profili2 Pro and DevFus Foam to generate the g-code from the design. You can use LinuxCNC and free software to generate g-code for wings and fuselages. Check my article Free CNC Software
  • Drawer Slides – used to provide vertical and horizontal movements for the two towers
  • Power Supply 24V – this powers the control board and the stepper motors
  • Hot Wire – usually ni-chrome wire.

Foam Cutter Accuracy

I’ve decided to use threaded rods for the lead screws, because the accuracy required for hot wire foam cutting is not as critical as a CNC router.  But I still get very good results when I compare the cut parts with the scale drawings. 

Power Supply

I used 2 PC ATX Power supply in series to give 24 Volts. This can be a little dangerous if you’re not careful to isolate the second PSU, so I’d recommend purchasing one specially designed to give 24 Volts. These are now quite cheap and take 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. Update – worked OK for a while but dropped of so I replaced them with couplers. See the details page

Arduino CNC Foam Cutter coming soon

I’m working on an Arduino Mega 2650 version of the CNC foam cutter which I hope to have completed soon.  I’ve purchased all the parts and will have two options.  One will be to convert a parallel CNC controller and the other will use and some TB6560 driver modules.TB6560 driver modules.  Using these option a laptop or a PC with USB can be used.

4 axis cnc hotwire foam cutter with airfoil
All made with this

Build was finished see pictures and video below. Tested and it works. I used RJ45 cables and sockets to connect motors to controller. This allows for easy dismantling 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.

Hot Wire CNC Foam Cutter Software

To control the CNC machine you need some software and after much research I originally decided to go with Mach3 from ArtSoft it’s 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.

Update 2018. I now use LinuxCNC on my foam cutter and on my CNC router.  Its free and updated regularly.

I’ve used an old Dell GX620 computer running XP and no other unnecessary software installed for Mach3. For LinuxCNC I use the same machine and just swap the disk over.  You need a PC with a parallel printer port usually known as LPT1. There are other options now for USB and Ethernet(LAN) connections check my post here

G-code is the instructions 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 Pro and have settled on Profili2 Pro which does a lot more than generate g-code for wing profiles.

DevWing Foam is the next generation of software replacing Profilii Pro 2. If you’re just starting out I wouldn’t recommend this as it’s quite complicated. I have the demo but for my needs it’s not worth the cost to upgrade from Profili.  Start with the free options below and then as you progress then get Dev Wing Foam.

Here is a free wing g-code generator that will generate the code for you I’ve used it on my machine and it works well and is fairly easy to use.  Check my post here

Another free one is JediCut which I’ve made a video on How to cut a tapered using Jedicut and this CNC foam cutter  You can download Jedicut from here /

The Hot Wire

The wire between the 2 towers was tensioned by a spring so the towers can move independently for tapered wings. I’ve now converted it to a pulley with a weight attached.  The springs are OK for wings but I’ve found when making fueslages the wire can get some very steep angles which puts to much tension on the towers. Using a pulley with a weight keeps a constant tension on the wire whatever angle its at.  I’ve used 20 pound fising line with a wheel on a axle to take the fishing line to 1.5 lb or about .7kg lead weight. The pictures below should help explain it.  Ran a few tests and it seems to work well.

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.  I get best results from very thin wire about 0.6mm in diameter.  Doesn’t require as much current to heat. The kerf value, the amount of foam melted away is very small.  This helps in the design process.  I use all the default settings in the software I use.

It works

It’s quite exciting when you get it all powered up and move the cursors keys and see stepper motors spinning. The video show a small test aerofoil which was about the 5th attempt. The hot wire cuts my radiance so it’s 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 got the cut the feed right

Below is the flying wing which was the first model plane I made with the 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 is very good for generating the code and has a massive database of aerofoil.

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 For LinuxCNC check my article here on how to configure it

First airplane made with the Hot Wire CNC foam cutter

This is the first flying wing I made with the CNC machine and its was little gem. I did fly it most weekends. It super fast with a 2200 KV motor and a 6×4 prop. It’s a blast. If you want to build it then check I’ve included the gcode for each wing as well. 

Crashed her in 2017, pilot error, doh!.  So I made another here’s the full playlist 

Hot Wire CNC flying wing
First flying wing made with the foam cutter

I’ve now made a Hawker Hurricane with the CNC machine both wing and fuselage, you can see it here

I’ve also made a much bigger wing for FPV(First Person View) with it as well details here

The CNC machine is now starting to pay for itself as I don’t buy many ARTF models very much now, nothing against them but I just enjoy researching and making my own RC airplanes much more.

Updates I’ve made to the Hot Wire CNC foam cutter

The biggest change I’ve made is that I now use LinuxCNC instead of Mach3.  I decided to make and effort to get LinuxCNC working this year(2018) and its now my prefered software.  My video below shows how makes wings using Free software with LinuxCNC

After making several models and getting through a lot of foam I’ve only changed the coupler 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.

If I were to build a new machine then I would probably use an ethernet controller like the ones I’ve listed Here as alternatives and a purpose-built power supply. This would allow me to use a laptop as well. LinuxCNC can also use an ethernet connection with a Mesa card.

I’ve now stopped using Mach3 in favour of LinuxCNC it better suited to a hot wire CNC foam cutter machine in my opinion.

The TB6560 kit has been very reliable and never missed a step and I use it on my CNC router as well.


Is now my preferred option to control the machine.  Its free and under constant developement. Development of Mach3 has stopped, they have moved on to Mach4 which requires additional hardware.  My video below show how to get LinuxCNC up and running

Plans, Parts and Instructions to build  a Hot Wire CNC Foam Cutter

The plans and parts list with instruction can be found here along with some videos.

If you need any help or advice them don’t hesitate to contact me.  I get question from all over the world and I love to hear from fellow enthusiasts.

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