Mini CNC Foam Cutter

This instructable explains how to make a mini CNC foamcutter from recycled e-waste.

Here are the core things you will need:

X1 Compact Photo Printer

X2 Desktop DVD-rom

X1 Hairdryer

X1 Arduino and USB connection to computer

X3 Easy Stepper Motor Drivers

X1 Grbl software

x1 Supply of Recycled Polystyrene

Smaller/optional things:

x2 torroidal magnets

x2 small springs

X1 set of jumpers and breadboard

x1 laptop power supply and female power supply jack

x1 4-wire ribbon cable

x1 heat shrink tubing

x2 jewelry crimps

x1 set of zip ties

x1 wire wrap

x1 extractor fan with carbon filter

The foam cutter has a comically small work area but once it's complete you can take photographs of scale foam sculptures :P!

Isolating the laser focusing mechanism has been documented in other instrutables very well already:

https://www.instructables.com/id/Mini-Arduino-CNC/

https://www.instructables.com/id/Poor-Mans-3D-Print...

The main challenge here is to find a CD/DVD drive with stepper motors instead of DC motors. I usually do this by trial and error though I do find that most DVD drives are stepper controlled.

For this machine you will need two CD/DVD stepper mechanisms. Ideally you would find two of the same make so that the worm gears are the same ratio.

You will need a compact photo printer which uses stepper motors to take apart. I lucked out and found an Canon Selphy CP720 Compact Photo Printer (http://www.amazon.ca/Canon-Compact-Photo-Printer-Selphy/dp/B000I9UT68) for $5 which has a sleek reeling mechanism and was stepper controlled. I have also had luck with Epson compact photo printers. I needed to remove a bunch of rollers and idlers in order to expose the stepper controlled roller (so that it could push the piece of foam through). Everyone's printer will be different so this will require a bit of improvisation.

I recommend finding a place which has lots of junk and will let you look around and take things apart before purchasing. If this is not possible, I would try and buy defective compact photo printers from ebay and trying your luck at finding one that is stepper controlled.

This machine works by squeezing a block of foam between the bottom rollers of the photo printer and a few idlers/bearings which rotate around two threaded rods between the tops of the CD drives.

I used some threaded rod I had lying around, cut two pieces of approximately 7" and used double nuts to attach them to other side. For the idlers I used plastic spacers from circuit board design.

I used zip ties to attach the CD/DVD mechanism to the compact photo printer reeling mechanism. I improvised and looked for good locations for the zip ties. The nice aspect about this solution is that the machine can be easily collapsed for storage or transport. There are also opportunities to screw things together if you get lucky.

I like to put the rubber vibration absorbers from the corners of the CD/DVD drives on the bottom of the compact photo printer mechanism as little feet.

To get nichrome wire, you can take apart a hairdryer and straighten out some of the coils. This is a good instructable to explain the process:

https://www.instructables.com/id/Hot-Wire-Foam-Cutt...

Using the harvested nichrome wire I also made a handheld mini foam cutter to cut down larger blocks of foam into the 18cm tall pieces needed for this machine. I used a 5V 1A adapter for this purpose and a workbench to get a straight cut.

You can use recycled polystyrene or you can buy insulation board from a home hardware type store as the cutting material.

Once you have extracted the nichrome wire from the hairdryer you can cut a piece about 7" long and prepare it for your machine.

The main challenge for me was soldering to the nichrome wire itself. I found that using jewelry crimps and crimping them around a loop of nichrome wire allowed for solid contact to a solderable material.

Attaching the nichrome to the CD mechanisms I used a pair of weak springs and found a hole to hook them into.

I use a separate adapter for the motors and for the nichrome wire. Also, be sure that the nichrome wire leads don't short (i.e. don't connect them to anything metal on the CD roms).

I use the nichrome wire with a 5V adapter, when I use a 12V adapter it goes red hot which is great for photographing but a little too hot for the speed of the motors.

I am using three easy stepper motor drivers and an arduino and using the Grbl pinout connections (which I will get to in the next step).

One thing to remember is that keeping everything here neat and tidy (i.e. short wires) will avoid making a machine that is extra sensitive to noise. Noise is very frustrating for CNC builds because it causes your machine to behave in strange unpredictable ways that are infuriating to debug. I use torroidal magnets (harvested from some old computer monitor wires) on each side of the set of motor wires and wirewrap with zipties to keep everything tidy.

Having a computer power supply is nice as it could take care of all of your isolating and power needs in one shot. These often supply two voltages: 5V and 12V at 2A. I power the DVD-roms and the nichrome with the 5V and the photo printers with the 12V. I find that DVD-roms can sometimes be destroyed by too much power so I like to keep them on a different power supply.

CamBam is a great piece of software for producing G-Code:

http://www.cambam.info/

You get 40 uses and if you keep the program open all the time you can stretch that to last quite a while. The main issue is that CamBam is for CNC milling. If you intend on just cutting out extrusions you can plug in your two CD-rom axis drivers together to the same arduino STEP and DIRECTION pins (making your machine a two-axis X and Y cutter) and use the "engrave" feature in G-code and ignore the Z (lift-off) commands. One issue, however, is the problem of tool paths cutting through your extrusions. I have found that manually connecting text, joining everything and then using engrave works to solve this problem. You can also experiment with free trails of software like these:

http://www.foamwork.net/

http://www.foamcuttingsoftware.com/eng/default.as...

There are various software options to read G-Code and send this to the arduino. Grbl is a hacker favorite:

https://github.com/grbl/grbl

Follow the instructions online to install onto your arduino depending on your operating system. I use grbl controller as the G-Code interpreter. This program is very user friendly.

I set my Y-axis DVD roms to: 50 steps / mm

and my X-axis compact photo printer to: 345 steps / mm

I use a feedrate of 400.

In order for this machine to be of any use, you probably need a way to easily cut blocks of foam into ones that will fit the dimensions of your machine. There is a little bit of play in that you can change the height of the threaded rods squeezing the foam at the top slightly by adjusting the nuts. However, what you really need to do is determine the perfect foam size and then cut a block with a foam cutter to get it nice and even.

Sometimes the plastic bearings can dig into the foam and create difficulties. This is one of the main flaws of this design: there are only active rollers on the bottom. The best solution I have so far is to put a surface of firm plastic between the top rollers and the foam.

You will also need to experiment with the speed of the motors depending on what density of foam you are using and the desired kerf.

Thank you for checking out the machine!

One idea to improve this design is to add another compact photo printer on the top of the machine. By doing this, the foam is now being squeezed between two active rollers (instead of an active roller below and bearings above). This requires, of course, a fourth motor driver which would take the same arduino instructions as the other compact photo printer stepper.

You can also use the small fan from the compact photo printer to divert some of the melted polystyrene away from your work space. Another option is to put a carbon filter on the other side of the fan so that it may filter some of the fumes.