Hot Wire CNC foam cutter

This article shows how I built a hot wire CNC (Computer Numerical Control) foam cutter.

and this is the Hawker Hurricane finally finished

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.

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.

After a lot of research and some real good advice from CNC forums ( http://www.mycncuk.com/ and http://www.cnczone.com/) 

Here's my plans and full detailed build page on my website http://www.rckeith.co.uk/cnc-detailed-build-plans/

All the wood material came from an office clearout, old desks

The electronics can seem quite daunting but if you can build a electric airplanes and wire up motors and speed controllers then you should be OK

I purchased the electronics from Ebay and built my own power supply.  But I noticed several ads now including the power supply.  Just do a search on Ebay for "4-axis CNC"

For the power supply I used two old computer PSU from the same make and model of PC. Nice atricle here on how to do ithttp://www.procooling.com/index.php?func=articles&disp=52&pg=1

The lead screws are threaded rods mine being M8 thread.  Because foam cutting doesn't have to be as accurate as other materials e.g. wood and aluminium these are OK.  You can get proper Lead screws but these tend to be expensive. If I were to build a cnc router I would probably use lead screws as they eliminate any backlash.

The towers run on drawer slides which you can get from most DIY stores.

The X-axis use a captive nut the one with spikes on that bites into the wood.  The Y -uses a small aluminium block which I drilled and tapped the threads into.  I’ve tuned the ends of the threaded  to match the size of the stepper motor spindles and used rubber hose with two hose clips.  Seems surprising solid and gives a little bit of flex

I've used a old Dell computer running XP and no other unessecary 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-codes are the instruction for 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 tension 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 208 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 airfoil 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

My next cut will be a flying wing just to see if I can do it.  Profili2 Pro http://www.profili2.com/ is very good for generating the code and has a massive database of airfoils.

Update

Here are some of my first tests.

Hope you found this of interest and if you need any advice or help leave me a comment or check my website out www.rckeith.co.uk

The only difference between men and boys is the price of their toys!!

Keith