Build Your Own CNC Foam Cutter

by moebeast | July 29, 2017 | (10) Posted in Projects

After printing out, taping together and hand cutting about 20 Flite Test planes, I decided there had to be a better way.

I've had an interest in building my own CNC machine for many years, but the cost was always a barrier to entry. That all changed after I acquired a 3D printer. I found this really cool machine on Thingiverse called the Mostly Printed CNC (MPCNC). The designer Ryan, has come up with a rigid design that uses inexpensive components like electrical conduit, roller skate bearings, and 3D printer electronics. He has a version for 3/4" conduit, 25mm conduit, and 1" stainless steel tubing.

Print the Parts

If you do not have access to a 3D printer, Ryan sells these parts for $195.


Follow the instructions on https://www.vicious1.com/assembly/, and you end up with something like this.


Add Some Tools

This machine can use many different tool heads like Dremels, routers, spindles, vinyl cutters, drag knives, extruders, lasers, etc... Search Thingiverse for MPCNC and you will find mounts for them. But the best thing for foam board is the needle cutter that was shared with us by djk4linux in his forum thread Cutting-foam-sheets-with-a-needle! This long running thread has seen many versions of the cutter. My current version looks like this:


Assemble the Needle Cutter

The printed parts are the frame/mount, the flywheel, and the needle mount. They can be found at https://www.thingiverse.com/thing:2429886. My version is set up for a 2212 brushless motor. The flywheel mounts like a prop saver.  

The "needle" is a length of 0.032" music wire. It is inserted through the tip of the holder into the hub. There is a 90 degree bend on the end in the hub and it is pulled tight into the groove in the hub. The holder is then pressed onto a 10 mm O.D. bearing from an RC car. This bearing is screwed onto the flywheel in the first off center hole. Optionally, you can bend a loop in the wire and wrap it directly around the bearing. This is the way we have been doing it, but every time I've had a needle break, it was at the bend just below the bearing. I have not broken a needle since I started using the plastic holder.

Once the bearing/needle holder is mounted, you have to balance the flywheel using screws and nuts in the provided holes around the outside of the flywheel. djk4linux has provided a more detailed balancing procedure in the thread.

I am powering my ESC from the same ATX power supply that powers the Arduino/Ramps 1.4 driving the machine. I have a servo tester connected to the ESC to control the motor speed.


Guide the Needle

I have used athletic ball inflation needles for guides. They work well, but wear out after a few hours of use. I am currently using .035" MIG welding tips. You can find them in the welding supply section of your orange or blue store. The 3/4" block of wood has a 5/64" hole drilled all the way through. On the bottom, the hole is enlarged to 5/32" deep enough to thread in the MIG tip. I added some aluminium cooling fins to this one, but they are not really necessary unless you are going to try for higher speed cutting. 

Once the guide is mounted, cut the wire so that when the flywheel is in the full up position, the wire flush with the bottom of the guide. Use a file or stone to dress the tip into a conical point. A chisel point works, but the kerf will be wider in one direction than the other.


Hold Down the Foam Board

I used a piece of blue insulation foam for the bed/waste board of my machine. After it was secured, I mounted my small router and with a 1/2" bit, milled the bed level with the machine. Then you can place the foam board, crown side down on the bed and secure it around the edges with T-pins. This method works OK, but is time consuming and sometimes score cuts can be through cuts.

After FliteFest 2016, I added my vacuum hold down. I simply milled out 1/4" wide, 1/2" deep channels every 2" across the bed and spray glued down a sheet of foam board with 1/4" holes in a 2" grid. The hole in the lower right goes all the way through the base and is sized for my small shop vacuum.



Get the Files

The process for converting PDF plans to GCODE is not simple, but basically, convert the PDF to a .dxf file (most of us are using Inkscape), import the .dxf into a CAM program (Eslcam works great and is inexpensive) and define your cuts, then save to a SD card to load into the MPCNC.  Jason Hitesman has fully documented the process in a YouTube video.


Cut Your Planes

Set the needle speed to get 10 strokes per mm of travel. A good speed to start with is 600 mm/min travel and 6000 rpm on the cutter. Here is an example of a cut at these settings

You can see that it is a clean square cut.



Cost

PLA for parts ~ $30

3D printer electronics $35

Stepper motors $55

Gt2 timing belt $9

Bearings $40

Hardware $45

Power supply from scrap PC

Motor and ESC ~ $25

Conduit $8

Wire from scrap bin (speaker wire)

Total: $257

Alternately, if you do not want to source your own parts, Ryan sells a parts bundle from $252 plus $195 for the printed parts.

Conclusion

For a little money and a large investment in time, you can build your own CNC foam cutter. It takes about a half an hour to prepare a set of plans for cutting and about 15 minutes per sheet to cut them out. There is less fear in flying for me knowing that I can just cut another one. 

COMMENTS

blueangel6 on July 31, 2017
Nice job. I use inkscape for dxf. Sketchup with Mach 3 with my cnc foam cutter.
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moebeast on August 1, 2017
Thanks, I've used Sketchup with the Sketchucam plug-in. I want to play with Fusion360 next.
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ironmask on August 1, 2017
At FFE2017 I had the privilege of working in the build tent most of the day next to moebeast, his family and his CNC cutter. The machine is really amazing to watch. It does a great job. Its cuts are very clean, and precise. I assembled one of the planes he cut, and the fit was fantastic. The only thing cooler than the machine was moebeast. He spent hours answering questions, and giving demos, and cutting plane after plane, THE WHOLE EVENT. I saw dozens of kids get to build planes that may not have had the chance to otherwise.
moebeast, thanks for all you did, and thanks for the writeup. You are a Rockstar!

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moebeast on August 1, 2017
It was really my pleasure. Thanks for the compliment.
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OpenAir on August 24, 2017
Being completely NEW to RC, The articles and the forum it's really nice to hear people like you still exist in the world...it just gives you that warm fuzzy feeling inside...ok ok ok..."feelings aside" ...thank you for the write up and for the support to the community. To say I'm on a budget would be an understatement at the moment but if I ever hit the lotto or end up with decent work with my current search I hope to build a CNC like this or this one before the start of the next decade....maybe prices will fall and this will become old tech by then lol ....thanks again for all the info, time and your contributions to others.
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blueangel6 on August 1, 2017
I have a Phlat Printer MK1 . I use to have the MK3. Good luck with the fusion 360.
I have Auto Cad ,but hardly use it.
Have fun people.
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moebeast on August 2, 2017
The Phlat Printer MK1 uses a Dremel mounted under the foam right? A needle cutter may be tricky to set up on there, but probably possible.
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blueangel6 on August 2, 2017
Yes it is under the foam.
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blueangel6 on August 1, 2017
Hard to find 6mm Depron these days.
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phenompilot on August 1, 2017
Thanks for the awesome write up Moebeast!!! It was great talking to you at FF17. Since then I am about half way into the MPCNC build. Tomorrow I am building the table and cutting conduit. The last parts will have printed and hoping to have its maiden in just a few days!
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moebeast on August 2, 2017
Awesome, post a picture on the forum when you get it together!
I forgot to describe my table in the article. It is a scrap of OSB with a bed rail cut in half glued to the sides. It was free and portable, but not stiff. It normally sits on my table saw.

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Gravitysucks on August 2, 2017
Excellent write up. I'm in the middle of my mpcnc build and this gave me some good tips for the vaccum hold down. Thumbs up.
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moebeast on August 2, 2017
Most vacuum tables I've seen on YouTube are elabrate affairs. You don't actually need large chambers and paths since there is not much airflow if you have it sealed well enough.
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danallen82 on August 10, 2017
I love it, and I think you're contribution will be well appreciated. I really like how you found a way to improve the needle drive with bearings and a brushless motor. Bravo!
My only thought was, why not use a low cost IR laser? That's easy to say, since I have access to a 100w cutter. I know the reason is obvious. Cost, lens focusing, fumes, and danger to eyes.
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jhitesma on August 10, 2017
Depends on what you consider a "Low cost IR Laser" I run a 2.8w 445nm laser diode on my MPCNC along with my needle cutter. It's not IR (though it does have some emissions in the IR range) but it does fit my definition of "low cost" about $100. It's very useful and I cut balsa, thin ply, paper, black craft foam and other materials with it as well as engraving various things. But...not I specified "Black" craft foam. White craft foam and DTFB are much more difficult to cut because they diffuse the laser energy rather than absorb it. The black cuts like butter since the pigments in it absorb the laser light. But white...just kind of glows and sort of melts.

To actually cut white foam with a laser you need a much higher power and more expensive laser. Even then it doesn't give as clean of a cut as the needle. If you look at the FT kits you can see the undercutting of the foam due to the laser melting it more than cutting it. Some people like this (can put skewers in the edges for strength easier, and can cram more glue in there) but others don't like it (can cause paper to delaminate more easily, less clean, doesn't give as much surface to glue....)

And don't forget, a CNC can do more than just cut foam with a needle. It's quite easy to swap toolheads to do different things. Along with the laser diode I also have a small drag knife for cutting vinyl (make your own decals!), a pen holder (giant plotter for drawing designs on things), a router (cut wood and aluminum), and even a 3D print head so the machine can be used as a 3D printer as well. All for less than most of the low cost lasers that are powerful enough to cut foam.

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danallen82 on August 10, 2017
Great answer. I agree that this is a great solution for a simple and versatile tool. No need for a laser on foam core. Plus it would be easier to use Z height for half-way cuts.
I didn't realize you can even cut with 2.8w, that's impressive. Whenever I used the 100w laser, I typically ran it at 30w and 250mm/s. It would require 3 passes, but the result would be an unmelted foam cut. FT probably cuts with a single pass that results in the foam melting.
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allted on August 11, 2017
moebeast, Thank you so much . That is a great write up. I am so glad you like the machine and are sharing it with the community. I have also had a few emails telling me about your Flight Fest heroics. Sounds like you left a lasting impression on a ton of builders and pilots. I wish I could have been there, I went to Flight Fest West, about 15 minutes from my house.

Thank you so much, for all that you do, glad to have you as a MPCNC owner. I will be linking this article on the site so hopefully a few more people can see it.

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moebeast on August 11, 2017
Thanks Ryan,
Your design of the MPCNC is the coolest thing I've seen on Thingiverse. I tell everyone about it. A few guys at work are building them and Low Riders.
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Rocket on August 31, 2017
Hi Moebeast, Good article, I was at FF 17 and did see you cutting plane kitsssssssss, I was going to talk to you but you seem very busy at the time. I'm from Eastern Canada and would like to build a CNC that could take deferent cutting head. How would I contact Ryan and purchase a complete kit that I would just have to assemble. Moe
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moebeast on September 5, 2017
You can find them at https://shop.vicious1.com/collections/bundles .
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guitarbert on September 24, 2017
I am in the middle of printing the parts for MPCNC. I was wondering what your working dimensions are and what is your z travel. I was thinking of a 35"x35" and 8" in the z axes.

I was also wondering where you got your controller and stepper driver cause I have not able to find those prices.
Thank you
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moebeast on September 27, 2017
My rails are 41"x36". This gives me a cutting area of 30.5"x25". I have 6" of z travel. Depending on what you plan to use the machine for, you don't need a great deal of z travel. I use mine for cutting sheet material, and I have more travel than I need.
I bought my electronics on Amazon. It looks like the standard price for what I got is around $39, but here is one for $34. https://www.amazon.com/BIQU-Mega2560-Control-Controller-Stepstick/dp/B071YV3FCL/ref=sr_1_10?ie=UTF8&qid=1506525287&sr=8-10&keywords=ramps+1.4
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moebeast on September 27, 2017
I don't check these comments every day, so if you have a question, head on over to the forum.
http://forum.flitetest.com/showthread.php?24251-Cutting-foam-sheets-with-a-needle!/page167
Someone will help you within hours.
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jung on December 5, 2017

Hi from korea
I just wonder that machine can work with epp ?
in korea hard to get foamboard.

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Build Your Own CNC Foam Cutter