CNC foam cutting, the cheap and easy way
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In the X-mas hollidays of 2014 I spend some time discovering the possibillities with foam cutting. So I could make a simple sign without having to waste lot's of time. This because my machine isn't the fastest CNC machine around. So cutting wood takes a lot of time, cutting foam can be done a lot quicker. I noticed that EPS insulation foam (Expanded PolyStyrene) can be bought very cheaply at the local hardware store, so this opens up a whole new world. The fun is that you can make a large sign very cheap, quickly and light. A good and fun example is also the project you see at the end of this page.

Cutting foam isn't done with the router I use to cut wood, nope, I really don't like routers as the make a mess and lot's of noise. And since I don't have a decend method of cobering the machine, the entire workplace is covered in dust within minutes after starting the machine. Fortunately foam cutting can be done much easier. Hot wire cutting is a great example of doing this. But the problem with a hot wire is that is must go through your objects. So instead I go for a hot rod, something that can easily replace my router. And after lot's of thinking how I could make this, it suddenly struck my mind that I'm using such a device already almost every day. My trusty old soldering iron. This has a method of controling the temperature very accurately and it only requires me to make a special tip. Fortunately I have such a tip, which requires only a slight modification in order to use it. I modified the oldest and worst soldering tip I had (no problem since it was time to be replaced anyway) and by doing so giving it a new purpose, cutting foam. Modifying the tip was very easy, using my drillpress and a file to file it to the desired width. You could say that I used my drillpress as a lathe, always be careful if you want to do this yourself. This is only possible because soldering tips are made of very soft material (copper) and because my file was a very sharp one.
First test used lot's of tie-raps to hold the iron to the machine. I wasn't sure if the soldering iron was to heavy for this task, I experimented with the temperature and settled for a point where the foam was molten only slightly. I didn't wan't to burn it. So a temperature of 225 degrees Celcius on my modified tip causes a stable hole in the foam of 6mm. Allmost twice the size of the tip, which is great because the foam melts before it touches the tip. But only when the speed of the machine is set to move slow enough, since my machine is slow by default (it just can't go that fast), this is no problem at all. the lable on the machine says "CC1" which stands for Cheese Cutter 1, the design of the machine was for very simple tasks. Although in practice it can cut more dense materials then cheese, it still is a simple and low cost MDF and ball bearing based machine. The Z-axis coupling is a rubber hose on the photo, but has been replaced by a aluminum coupler I bought from an internet shop for just a few euro's. This was a huge design improvement because the hose coupler simply wasn't up to the task of moving a router up/down for long periods of time. This because the stepper motor becomes hot, resulting in the hose becoming hot. Making it less rigid and harder to fix Z-axis to the axle of the stepper motor.
So now with the principle proven to work, it was time to make a simple holder for my soldering iron. Very important, because I need my soldering iron for soldering also, so it must be easy to place/remove from the CNC machine. So now you see, whith just a few simple actions, my CNC machine is converted (you could say downgraded) into a foam cutting machine. Fortunatley I can easily replace the soldering iron for the router and cut the designs into wood if I need to.
I then cut my first "serious" object. Drawn in QCAD, prepared using CAMBAM and machined using MACH3, a little pacman figure, followed by a set of ghosts. When all the figures were cut, it was time to paint them and when the paint was dry (enough) I put the figures onto the fence. In case you want to do this also I have a small tip: do not use spray paint. The solvents in the spray paint may attack the foam, which simply melts, destroying your creation. There are some tricks or special paints which bypass this problem, but in case you do use spraypain, always testit on a piece of foam that you are going to trow away anyway.

The IKEA lights now have reached their full potential. I like it, the simple old fence is now a lot less boring.