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Old Jun 12, 2012, 07:37 AM
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Denmark
Joined Dec 2004
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Build Log
DIY CNC Foam Cutter

Hi All

After the succes with my CNC Router build I started thinking about building a 4 axis CNC Foam Cutter. The CNC Router originally started as a low budget build with small second hand stepper motors, threaded rods and rods from old printers. But I ended up buying big Nema 23 steppers, ballscrews, linear bearings and Gecko 540 stepper driver etc. I don´t regret spending a lot of money on the CNC Router. It works great and will last for the rest of my life. BUT the idea of making a CNC machine with free second hand parts was still there. So I decided to build a quick and dirty Proff of Concept CNC Foam Cutter " without spending a single $ (well "kroner" in my case, as I live in Denmark).

Parts list:
4 Nema 23 steppers salvaged from old thermo label printers.
8 drawer slides. Surplus from server racks
2 8mm threaded rods + nuts
2 6mm threaded rods + nuts
Flexible fuel line as connectors
Wood. Planks and plywood I had lying around.
Screws for wood

The whole thing came together rather quickly as the photos reveal. I opted to mount the vertical axis stepper motor at the bottom of the axis in order to avoid having too much weight at the top of the tower and risking toppling over. The wire was mounted in a bow and rested in a groove as shown in the photo.

In spite of the crude design I was pleasantly surprised by how well the machine performed and the precision of the cuts. Of course the threaded rods with the ends flapping freely didn´t make things move fast - on the contrary But a Foam Cutter should only use cut feeds of 100 - 200mm/min. So all in all the machine cost me nothing and cuts with sufficient precision.

More to follow on my version 2 of the CNC Foam Cutter

- Michael Hammer
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Last edited by michaelghammer; Jun 12, 2012 at 07:43 AM.
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Old Jun 12, 2012, 01:25 PM
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United States, PA, Beaver
Joined Sep 2001
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COOL!!! I've always wanted one, and after I built my CNC router thought it would be easy enough to make a foam cutter, but my home brew gravity one works so well with templates I cut with the router that I kind of abandoned that idea.

Question... I see this on a lot of 4 axis foam cutters, why go so high on the up/down (z?) axis? At the most a model wing is about 4" and that is stretching it.
Just curious...
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Old Jun 13, 2012, 12:47 AM
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Thanks

If you only need to cut wing foam cores, you don´t need much vertical axis movement. But, as you will see in my following post, I want to cut fuselage sections too. I plan to produce rather large sections and hence need the tall towers. Also if you want to cut tapered parts, you need a lot of movement.

And as you probably already know from working with your CNC Router: the workspace can never be too big

- Michael Hammer
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Old Jun 13, 2012, 01:01 AM
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Denmark
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559 Posts
Hi All

The version 1 CNC Foam Cutter showed me that it was possible to build a low budget machine and still make parts with acceptable precision. But the machine was a bit of an eyesore and several issues needed to be adressed in order to improve performance and ease of use. So I decided to spend some money on improvements, and basically ended up redesigning the whole machine.

List of things I wanted to improve:

Looks!!! 6.5mm birch plywood all over.
8mm threaded rods on all axis´
Ball bearing supports on all threaded rod ends
Replace flexible fuel line connectors with new solid ones
Rotate horizontal axis drawer slides
Remove half of the vertical drawer slides
Move vertical axis stepper motor closer to tower center of gravity
Make some kind of lock for wire to keep it fixed
Removable towers
Work area box for electronics with a "manual 5 axis" More on that in a future Blog entry
Faster and easier setup

This time I used my CNC to cut the parts. You could easily cut the parts (except the connectors and the nut fixture parts) with "analog" tools.

I ended up with an open box like structure for the horizontal axis with a ball bearing at the end. This time the drawer slides were mounted on the side because they are designed to work that way and hence work much better than on the version 1. Connectors were cut from bamboo plywood. I had a sample of bamboo lying around and it worked great for the connectors. Fantastic wood or maybe I should say grass which it actually more correct. Connectors were glued to the stepper motor axles and threaded rods with epoxy. Holes for the 8 mm nuts were routed into plywood parts and nuts were sandwiched between.

The vertical axis´ or towers were reduced to just one drawer slide because two were overkill and made the towers way too heavy. The stepper motors were moved to a position just beneath the CG of the tower. On version 1 the stepper motor position on the side would cause the towers to lean to the side like a couple of Pisa towers. Little rotating "hooks" were CNC cut and mounted on the wire rests. The wire slides into narrow slots and the hooks lock it in place. Towers are secured to the horizontal axis´ with four screws each. Remove the eight screws and the towers can be stored along side the vertical axis´.

At each end of the horizontal axis´ base plate I have put little rods of bamboo skewers. Two pieces of flat metal with matching holes help align the machine during the setup. In the photos I´ve placed the XY axis right at the end of the kitchen table (I don´t have a real workshop at the moment). The flat metal pieces align the AB axis making it parallel to the XY axis.

The new Foam Cutter works better than version 1. It doesn´t cut more precisely, but it just works much better. And it´s MUCH faster to set up. I can set the machine up and align it in the time the computer boots up (old PC with XP )
And it looks much better than version 1

Check out my Blog for more images.

More to come about the box and the "manual 5th axis"

- Michael Hammer
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Old Jun 13, 2012, 06:18 AM
EDF rules... :)
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Hi Micheal,

Nice work mate.

Eric B.
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Old Jun 13, 2012, 06:23 AM
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Thanks Eric

How´s your big transport (C-5 Galaxy???) coming along? Any progress?

- Michael Hammer
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Old Jun 13, 2012, 10:18 AM
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Quote:
Originally Posted by michaelghammer View Post
Thanks

If you only need to cut wing foam cores, you don´t need much vertical axis movement. But, as you will see in my following post, I want to cut fuselage sections too. I plan to produce rather large sections and hence need the tall towers. Also if you want to cut tapered parts, you need a lot of movement.

And as you probably already know from working with your CNC Router: the workspace can never be too big

- Michael Hammer
Ahhh more than wings... Makes perfect sense now And yes, no matter how big the work surface, you always find yourself needing more (same with number of electrical outlets) ; although I have unlimited X travel (Piece moves, and not the gantry), and 26" of Y with 2+" of Z.....so for now I'm OK ;-)
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Old Jun 13, 2012, 12:08 PM
EDF rules... :)
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Quote:
Originally Posted by michaelghammer View Post
Thanks Eric

How´s your big transport (C-5 Galaxy???) coming along? Any progress?

- Michael Hammer
Hi Michael,
The templates are done for the fuselage, wanted to ues the cnc but cant get the computer repaied till next month.
The model will be an AN124.
Hopefully will get everything working on the cnc going again soon.
Eric B.
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Old Jun 14, 2012, 02:11 AM
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Eric,

Ahh, Antonov An-124. I saw one 6 years ago. I was in the garden when I heard an airplane above and looked up. what a surprise. A huge An-124 was doing a landing approach at the local airport 30 km away and it passed my house at maybe 500 meters with all motors at iddle speed. It was very quiet and just filled the sky. Very impressive plane!!!

I hope you get the computer problem sorted out soon at get started cutting the beast. I look forward to the build thread

- Michael Hammer
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Old Jun 14, 2012, 02:15 AM
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United States, CA, Lancaster
Joined Jan 2009
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Devfus Foam

Are you going to use Devfus Foam with this machine?
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Old Jun 14, 2012, 02:18 AM
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michaelghammer's Avatar
Denmark
Joined Dec 2004
559 Posts
Hi All

The nature of the CNC Foam Cutter design dictates a raised work area. So I made a plywood box with the help of my CNC Router. The box contains the stepper driver board (cheap TB6560 type from Ebay), stepper motors powersupply (second hand from old thermo label printer) and hot wire power supply (home made). All wires exit two rather large holes and can be tucked back in when not in use. Holes also act as carrying handles.

When cutting foam fuselages you most likely need sections of different length. So you end up cutting foam blocks to the correct length, rotating, aligning and then cutting shape. A lot of time is "wasted" rotating and aligning. Not a big deal if your fuselage consists of 4 segments, but if you´re making a complex scale fuse you might have 20 segments or more...

So I made a removable 90 degree rotating top for the box. Built in plastic rollers (plastic beads from my daughters stash) reduce the friction of the top. A grid pattern of holes and matching pins help align the foam block. Works like a charm

- Michael Hammer
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Old Jun 14, 2012, 02:19 AM
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Yes I´m using DevFusFoam. More on that later...

- Michael Hammer
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Old Jun 14, 2012, 02:24 AM
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Been using Devfus and been looking at building a CNC foam cutting machine myself. Will follow this thread.
Thanks
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Old Jun 14, 2012, 05:42 AM
EDF rules... :)
AirX's Avatar
Joined Nov 1999
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Quote:
Originally Posted by michaelghammer View Post
Eric,

Ahh, Antonov An-124. I saw one 6 years ago. I was in the garden when I heard an airplane above and looked up. what a surprise. A huge An-124 was doing a landing approach at the local airport 30 km away and it passed my house at maybe 500 meters with all motors at iddle speed. It was very quiet and just filled the sky. Very impressive plane!!!

I hope you get the computer problem sorted out soon at get started cutting the beast. I look forward to the build thread

- Michael Hammer
Thanks Michael,

I will have a blog post to keep track of the little monster when it starts till it is complete.
Speeking of the AN124, Volga Dnepr had one at Houston Bush recently. Wish I could have gone down to see it.
I like your idea for the 5th axis table, would make it easy to cut a wing cutout on a section after cutting the parts or before cutting the parts and still keep everything in the same orientation without relocating the part.

Cheers,
Eric B.
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Old Jun 16, 2012, 03:30 PM
skumgummi dave
Gresham, OR.
Joined Mar 2004
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Lurking and learning...

Dave-
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