How to Build a $200 USB Hot Wire CNC Foam Cutter – Free eBook

posted in: CNC, Hot Wire | 13

Would you like to build your own CNC hot wire foam cutter using 3d printer electronics for around $200/£160/€170? The pictures below are just a few of the RC models I’ve built with my CNC foam cutter.

So why do I use a Hot Wire CNC foam cutter to make RC planes?

Surely it’s cheaper to buy foam models than building with a Hot Wire CNC foam cutter.   

  • Yes, it can be to start with but some of the big EDF foam jets can be quite expensive. I’ve seen a few crashes beyond repair at my flying club.  The first flying wing I built with the machine flew fantastic until I crashed it. Well, I crashed it a few times but the last one was it’s final. So power up the machine cut some new wing cores and I was back in the air in a few days. 
  • Another reason is to build models that you can’t buy or if you could they would be very expensive.  I really enjoy researching and designing my own and there’s some great software you can use now. 
  • Learning CNC has been great fun and the bug soon bit me. I now have a CNC router and 3d printer as well. These are great for those other parts that you can’t easily find.

How much will it cost to build

Probably not as much as you think. Building the USB version in 2020 is going to cost approximately $200/£160/€170. If you would prefer to build the Parallel port version then that’s going to be around 30% more.

There is free software you can use as well to generate the G-code which works well and maybe all you need. More details later in this article.

Plans and eBook

The new eBook and plans contain full details with a step by step instructions, there is a small charge for the plans but the eBook is free. The full-size plans can be printed on any printer except for two parts. These are then used as templates to get exact hole locations.

The plans also include G-code for a Clark-Y airfoil to test the machine once built and also the G-code to make a 38″/960mm flying wing. Full setup of the fly wing is included in the ebook.

hot wire cnc fly wing
Another Wing

I’ve had some great feedback and one question that pops up quite often is Can I use the USB interface on my computer for the CNC Hot Wire Foam Cutter? Yes, you can but I decided it was time to make a new version of my original CNC foam cutter.

So why a new design?

My old design, see below, used an old computer with a parallel port to run the CNC controller. This has been fantastically reliable and never failed me. But these older computers may become more difficult to find. Since 3d printers are so popular and the hardware is relatively cheap I’ve decided to use these in my new version. This also helps to reduce the cost by about 30%.

The eBook also includes details on how to build the old parallel port interface if you still want to use that option with bigger NEMA23 stepper motors.

USB CNC Foam Cutter
New Design
4 axis cnc hotwire foam cutter with airfoil
Old Design

My original plan was just to convert the old design that I built with 18mm HDF(high-density fibreboard) which I over-engineered. But when I started to investigate the options using 3d printer stepper motors it soon became apparent the smaller steppers would struggle. It was a heavy machine and using smaller steppers could cause steps pulses to be lost. So a lighter machine would be required to use 3d printer NEMA 17 stepper motors.

The main goals of the new CNC Hot Wire Foam Cutter

  • To run from modern computers with USB connectivity
  • Lighter Design using 12mm MDF
  • Utilise 3d printer stepper motors and controllers
  • Comprehensive Plans, full size for key parts and detailed instruction,
  • Easy to build.
  • Still, be able to use the old parallel port interface with Mach3 and LinuxCNC if that’s your preferred option.
  • 4 part video series showing how to build the new version.
usb cnc foam cutter


We will start with the electronics first because we can get this tested and working before we install it in our machine. It’s good to know it all working if you just purchased the parts. If we did the mechanical first it could be a while before we notice a problem with the electronics

I’ve spent a considerable amount of time researching and testing the electronic components and have used the same stepper motors as my Anet A8 3d printer. This helps to keep the cost down.

This new build uses the same type of controller found in many 3d printers. We will be using the Arduino Mega 2560 with a RAMPS 1.4 board attached.

I highly recommend buying a geniune Arduino Mega if you can. Because I have seen it myself that the USB can sometimes be problematic on connecting. The Chinese boards use cheaper compoents and the build quality is not always the best. One off my boards the sockets where the RAMPS board plugs in was not straight. I did manage to staighten them and luckily it worked OK.

The stepper motors will be NEMA 17 size and a 12 Volt Power Supply. Here’s the link to the Full parts list with a PDF download.


This is can be the most challenging part of the build but once you’ve had some practice it gets a lot easier. I have several videos on YouTube that will help you.

There are two parts to this, first, we have to get some g-code for our new wing or fuselage design and then we need software to translate the g-code into machine movements.

To generate g-code check my article here which you can use both free and paid options For the second part, the software is free and needs to be uploaded into our Arduino Mega.

You may have heard of Mach3 or LinuxCNC which are very popular in the CNC world but these can’t be used with the Arduino controller. The ebook has full details and this website has tutorials with links to videos if you want to use either of these.

I originally used the firmware and software modified by a user on RC groups called Rasciodc. It’s based on the GRBL 0.8c2firmware. The article he’s made is excellent and provides some great software and firmware.
I modified the parameters to suit this machine and you can use the Windows software to control the hot wire temperature via a slider

Full details in the eBook and Part 2 of the video series.

Updated firmware and software

This new firmware and software based on the original but using later GRBL Mega 5X firmware with a few configuration changes to suit foam cutting with a 4 axis machine. Please read the post linked below for full details. You can now also upload precompiled firmware which is much easier if you are new to this.
The updated software has bee reworked to better suit foam cutting and the later firmware,

Alternative Firmware and Software – DevCNC Foam

DevCNC Foam

DevCNC Foam is purpose-built for 4 axis foam cutting and will run on several hardware configurations.  It can even be used to make an old parallel port controller compatible with USB using an Arduino. DevCNC Foam cost €60 in 2020.

One benefit as well is very easy to install and doesn’t require the Arduino IDE to load the firmware.  It checks the controller board and will upload the correct version. You can try it for free for up to 400mm of total movement. Just enough to confirm your hardware works OK before you purchase a license.  DevCNC Foam is very good and the wire path display is in 3d. It will also run in simulation mode so you can check how the foam would be cut. Very good for spotting errors. It’s saved wasting foam a few times for me.

What tools do I need? 

To ensure the holes are drilled straight a pillar drill is very useful. I used M6 cross dowels with socket/Allen key heads to join the major parts, which are available at most DIY stores.   These are great because you can take the machine apart very easily if you need too, without having to wonder which size screw did I use on this part.  

For the mechanical part of the build, you need anything fancy just screwdrivers, pliers, measuring tools and a few clamps.

Building the mechanical side

Full instructions are included in the eBook together with a cutting list along with the plans. The plans are full-size plans with hole centre marks, except for 2 larger parts. The design uses metric dimensions which are a little easier to work within my opinion.
I’ve used 6mm cross dowels and barrel nuts to join the main parts together with a few screws

To save yourself time and some expense take the cutting list to your local DIY store and get them to cut all the parts. My local store does this and you only pay for what you need and you’ll get them cut to the correct size with nice square cuts.

Affiliate Disclaimer

Some of the links on this website are affiliate links so if you use them to purchase from thank you very much.  You don’t pay any more but I earn a little commission which helps the cost of running the website.

Parts List

The parts list can be found here which includes the USB and Parallel Port versions.

Software to generate g-code

Once you’ve built your CNC foam cutter you’ll need some software to generate g-code to cut the foam wings or fuselage sections.

The software can be the most challenging part of CNC foam cutting. I would suggest starting out with the free versions first and upgrade as your skills and knowledge grow. I’ve used all the options listed below which will produce G-code for your designs. The paid options are excellent and worth the money in my opinion.

Free options

Here is a free g-code generator that will generate the code for a wing. I’ve used it on my machine and it’s easy to use and may be all you need   Start with this first. The G-code generated uses the axis letters XYUV but this build uses XYUZ but this isn’t a problem. All we need to do is use a text editor like NotePad++ and use the search and replace function replacing the V with Z.

David has released an update here on GitHub which will generate the correct axes letters. You will need to have Python on your machine to run the code.

Another free option is JediCut my video here is a tutorial on how to use Jedicut. Not the most intuitive thing to use but very good for free software. If you install Jedicut it won’t work with the Hot Wire Controller. Here’s my post on how to modify its settings so it works.

WingWire is another option as yet I haven’t used it. Very impressive. Here’s the link on Thingiverse

Paid options

The following software options need to be purchased which are a lot more comprehensive. You can use the demo versions which are full versions but the only restriction is you can’t save the g-code.

The software comes from the DevCAD team who are based in Italy. DevWing Foam2 one costs €125 and DevFus Foam 2 €95 in (2020). I think this is quite reasonable when you consider how many models you can make. Most foam models will cost more than that and once you’ve built a few the investment pays for itself.

Profili2 Pro was the software I started with and it was very good for generating the code for wings and has a massive database of airfoils. I used it for several years and it’s now been replaced by DevWing Foam 2 which I’ve just recently upgraded to. I have a new video tutorial series on DevWing Foam 2

DevFus Foam will generate the g-code to produce the fuselage sections. My Hawker Hurricane and T45 Goshawk fuselages were built using this software. Once I could make wings the next logical step was fuselages. I have a full video series on my channel showing how to use DevFus Foam


The response to this project has been amazing and I do get quite a few questions from builders. So I’ve made a video covering the most common issues and questions. It’s a long video so I’ve included time codes below

Time Codes
00:50 Troubleshooting
01:29 Axis Not working
09:36 All axes not working
20:22 Axis direction needs reversing
30:21 Buttons Missing from GRBL HotWire Controller
34:59 Jedicut display looks weird
40:03 Arduino Line Numbers

41:35 What size wing can I make with the foam cutter?
47:46 How to power the Hot Wire
52:10 Tensioning the Wire
53:24 What type of wire do I use?
54:07 Wing size incorrect – Calibration and Foam Placement
54:29 Saving GRBL Settings
1:00:43 Can I use these Stepper Motors?
1:08:10 What types of Foam do I use?
1:10:35 Can I use the Arduino Uno?
1:12:19 Can I use leadscrews instead of threaded rods?
1:13:38 Can I use Limit/End Stops switches?
1:21:17 Looking at using some updated firmware – just a heads up.


I’ve been making foam aeroplanes for several years with my machine and it’s a real buzz to fly something you’ve made yourself. You’ll soon have people saying can you make me one.

If you have any questions first check the FAQ page and if that doesn’t answer them then please drop me a line from the contact page. Good luck with your build, it’s a real sense of achievement when you see it it all working.

Check the builder’s gallery showing some of the guys that have built the machine. Some have put there own interpretation on the design. Please send me pictures of your build and any models you’ve made and I’ll add them to the page.

If I can do it then so can you.

13 Responses

  1. Fernand Robert Oppliger

    hello, i bilt the foam cutter using GRBL controller. every thing ok , but… I need to have 24v on D8 . I made the following modifications on Ramps 1.4. (Components are ok for 35v.)
    1. removed D1 and Arduino is supplied by its 12v jack.
    2. removed the 11A fuse and made a bridge.
    3. green connector (right) the on for D8 is supplied with 24v
    4. other green connector is still 12v for the steppers
    ISSUE: I dont get more than 12.5v on D8 !!!!!! even if I ask M3 S24000 . GRBL Controller displays 23.8v 99,8% but D8 is still 12.5.
    In the INO file ,I changed max Spindle RPM from 12000 to 24000 but nothing .
    Thanks for HELP

    • Keith

      Hi Fernand
      Not sure why you need 24v on D8 I’ve never needed that much to heat the wire. Foam cutters work best with a constant current I run at 2.2a the voltage varies to maintain the current but rarely goes above 7-8v. That’s on a 750mm wire 0.4mm diameter.

      The option to heat the wire via the controller works but not very well after trying it several times. A few builders have found this to be the case as well. Check my video here and I explain how I power the wire.

      I didn’t write the Controller Program software so I don’t know why it still supplying 12.5 volts. If you really need 24v then I would consider powering the wire separately. DevCNC Foam software and firmware have the option to control D8 so it may be worth contacting them to see if 24v would work. But this costs 60 Euros.


  2. Fernand Robert Oppliger

    Thanks Keith,
    I have a 1,5m long hot wire cutting 34kg/m3 extruded polistiren. ( I’m building a 6m span sailplane ).
    Now using gauge 26 wire. Gone try with 32 , but I think it will e too thin for such a length.
    Greetings from Italy, ciao

    • Keith

      Hi Fernand
      The wire doesn’t need much tension when the current is correct. So it may be OK. Could you make the wing in two sections?
      Hope things are getting back to normal in Italy after the virus. I haven’t been flying for several weeks now and will not be back for a while. But better to be safe.
      Good luck with your build.


  3. irwan

    Hi Keith,
    I made CNC fot wire from the instruction you gave a few years ago, everything was okay but I have too much flexing when the gantry move up, and I alsawys have difficulty setting everything to zero this year I decided to make more rigid frame (rectangular using v-slot) and wanted to use contact cut instead of radiance. The frame build has no issue, I also printed some tools to hold the block in place on the frame, and have a refference to set it to zero quickly.
    Long story short, being just hobbyist and not coming from engineering background :), little did I know that the wire (stainless steel) stretch like no tomorrow and I cant get it tensioned properly if I do a taper cut. The spring just doesn’t work.
    After seeing one of your post about using lead weight with pulley, I decided to go that way, cutting by radiance (again), even tho the result is not as smooth as the contact one (our foam quality issues), at least I can start building again for now.
    I am using similar wire size 0.4mm I have both stainless and nichrome.
    Can you please share the settings such as the wattage used for cutting various lengths you have experienced? Also the kerf value for that wire and wattage for taper cut ?
    That would save tons of foam from being wasted 🙂
    Thanks in advance !

    • Keith

      Hi Irwan
      I’ve just made a video showing the settings I use. Its a troubleshooting and questions video that’s quite long It you have a look around 47 minutes in I discuss powering the wire and settings.
      I never need to use very much tension on the wire, I only used the pulley system when I made fuselage sections because the carriages where close together. The spring just got in the way.
      I use around 2.2 amps on a 750mm wire 0.4 diameter and a cutting speed of 2mm/sec or 120mm/min. The foam cutter works best with a constant current power supply. I wonder if you are supplying too much power to the wire and cutting too fast. I’ve never had any issues with the wire stretching. I always leave the cutting speed at 2mm/sec and vary the current to get a good cut. My Kerf is set a 2mm but I use the Smart kerf option in DevWing Foam 2 which help with tapered cuts.

      Hope that helps

  4. irwan

    Thank you Keith, I watched the video, very informative.
    I am now having issues with the lead weight (1.5kg) not pulling the wire enough for tension on return cut for tapered wing at the wider chord. Is it possible heavier lead caused the wire to actually grip the pulley more.
    I learned a few things or two with the frame the rigid boxy frame, the smaller cut requires longer travel when placed at middle 🙁 Luckily Devwing has option to tilt the cut, however, it doesnt make the wire to start at home, unless we enforced it to get to home position before cut right ?

    • Keith

      Hi Irwan
      You might want to try using a bow on the machine have a look at this video from Nathan who just built a new machine using a bow.
      This doesn’t apply any tension on the machine which may work better for you.
      I use the option to align the trailing edge to the wire and it always works OK, not sure I understand question maybe you could send a picture.

  5. irwan

    Hi Keith,
    The video you sent me, its awsome setup with the bow,
    Its do able with my setup, I will need to print afew mounting, may be I will try that if I cant get current one to get a good cut.
    I need to see fiddle around with devwing to find that align the trailing edge to wire, I dont recall of that option. I only remember setting the LE as home. In the simulation cut, instead of starting from home, when I cut the wing at an angle , the wire starts at the trailing edge at an angle.

    • Keith

      Hi Irwan
      The option is in the cutting project. Here’s a link to a picture showing the option Align Trailing Edge

  6. irwan

    Noted. Will try that one. Thanks a bunch

  7. irwan

    Hi keith I dont know how to post picture here.
    I just want to let you know the cnc works now, after trying several wires, I ended up with awg 28 nichrome wire, right now cutting at 160mm/s with 1.6kerf and 35 watt (1.6A) . The result is good. Finished cutting a few turtledecks. I will be trying 900mm length tomorrow for the wing, it should be fun trying to get good kerf 🙂
    I also changed my controller to Novusun NVCM, changed the motor wire to shielded ones, it has been running reliably now. In the past I keep burning driver, and get electrical noise which made the motor running erratically at random times.
    If I know I would stuck with radiance cut again, i would use belt system instead, it would be cheaper.
    The frame I am using is v-slot and i made it to a box frame. its quite rigid, the only downside is with the length I got at 1179 between X and A, I am space limited in cutting shorter length part and need to offset the parts, something i learned after the frame was done. The good side i can easily zero the gantry with some measuring shims I made.
    to pull the hot wire I put 2kg at one end, tension is good.
    Since I am using v-slot, I also made a few 3dprinted foam holder which makes things alot easier too.

Leave a Reply

Your email address will not be published. Required fields are marked *

This site uses Akismet to reduce spam. Learn how your comment data is processed.