How to build a Hot Wire CNC Foam Cutter – Parallel Port Version

posted in: CNC, Hot Wire | 2

This post details my original build which I’ve now updated with a new version. Here’s the link if you prefer to build the USB version

The parallel port has long since been discontinued but in 2020 it’s still a viable option. If you check on Amazon or eBay there are still many CNC controllers being sold that still use it. If you have and old PC kicking around it’s an ideal candidate, or you can buy a parallel port add-on card for a more modern PC.

Why build a Hot Wire CNC Foam Cutter?

For me, it was a way to build wings and fuselages for RC aeroplanes that weren’t readily available. Doing it yourself (DIY) is not as hard as you may think.

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

I built my first machine in 2012 and here a few of the projects I’ve made with it

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 aeroplanes 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 a 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.

After a lot of research and some really good advice from CNC forums, I designed this version. Full details on this page

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 China which included the stepper motors, controller board and a few cables. These vary in price so check the parts list for the 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 2020  if you had to purchase everything except the PC, then I would budget for around $280 (US) £220 (UK), but you may be able to do it for less if you have some suitable materials already.   The USB version is a little cheaper around $200 because it’s based on 3d printer components. Which are so popular now it keeps the costs down. But do check the parts list for the latest prices.

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 it’s 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 a 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 nichrome 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.

Lead screws are a lot cheaper now compared to when I first built the machine but still more expensive than the threaded rods. If you prefer I would use T8 lead screws link here

If you decide to use threaded rods I suggest you get them locally if you can so that you can check they are straight. It the UK I get mine from Screwfix come as a pack of 5 for around £12.

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 off so I replaced them with couplers. See the details page

4 axis cnc hotwire foam cutter with airfoil

The build was finished see pictures above and video below. Tested and it works. I used RJ45 cables and sockets to connect motors to the 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. The unlicensed version allows 500 lines of g-code but you’ll be surprised how many lines it can take to make a wing. The licensed version costs $175.

What Computer can I use?

The computer needs a parallel port the one that printers use to connect to. These are obsolete now but you can still find them quite easily. Mach3 or LinuxCNC will run perfectly well on very modest hardware.

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. There are other options now for USB and Ethernet(LAN) connections check my post here

Software to generate G-code

G-codes are the instructions sent to the machine that tells it how far and what direction to move the stepper motors. You don’t need to learn g-code as software converts drawings into the code. I’ve originally used Profili 2 Pro and have now upgraded to DevWing Foam 2 which does a lot more than generate g-code for wing profiles. Here’s video tutorial series for DevWing Foam which on my YouTube channel link here

DevWing Foam 2 is the next generation of software replacing Profili  2 Pro. If you’re just starting out I wouldn’t recommend this just yet as it can look a bit daunting. My advice would start with the free options below and then as your skills and needs progress then get DevWing Foam 2. It’s the best software for generating the g-code and is well supported.

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 fuselages the wire can get some very steep angles which puts to much tension on the towers. Using a pulley with a weight keeps constant tension on the wire whatever angle it’s at.  I’ve used a 20-pound fishing line with a wheel on an axle to route the fishing line with a 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 others 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.  An RC battery charger set to NiCad of NiMH also works.

I get best results from very thin wire about 0.4mm 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 mostly use the default settings in the software I and sometimes adjust the kerf value for swept wings.

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. It flies really well and is fast. Profili2 Pro was very good for generating the code and has a massive database of aerofoils. It’s been replaced by

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

The first aeroplane made with the Hot Wire CNC foam cutter

This is the first flying wing I made with the CNC machine and it was a little gem. I did fly it most weekends. It super fast with a 2200KV motor and a 6×4 prop. It’s a blast. If you want to build it then check I’ve included the g-code 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 ARTF models anymore, nothing against them but I just enjoy researching and making my own RC aeroplanes.

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 an effort to get LinuxCNC working in 2018  and it’s now my prefered software for the parallel port version of the foam cutter  My video below shows how to make wings using Free software with LinuxCNC

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

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 parallel port machine.  It’s free and under constant development. Development of Mach3 has stopped, they have moved on to Mach4 which requires additional hardware. 

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

The new USB foam cutter can also be built to use the Parallel Port full details are in the eBook.

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

This kit is good value on Amazon and has everything you need for a parallel port build.

TB6560 separate drivers

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.