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Old Jun 07, 2012, 03:12 AM
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DIY CNC Foam Cutter version 2

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

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

- Michael Hammer
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Old Jun 07, 2012, 06:19 AM
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That's great Michael! Thanks for posting the details. One question: the metal bar that's attached to the hot wire.... it seems to be just free to rotate... can you post a photo/description of how the bow is anchored?

Thanks!!
J
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Old Jun 07, 2012, 06:38 AM
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Hi J, No problem.

The bow is normally held by a piece of string from the bow to the top of one of the towers. The string has several loops. I just place a loop over the screw head at the top of the tower. If needed I can adjust the length by picking another loop.

The reason why the bow in some of the photos is leaning up aganst the towers, is that I needed all the "free space" to clear the rather large chunk of foam. I need to make a bigger bow...

- Michael Hammer
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Old Jul 29, 2013, 08:05 PM
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CNC Plan?

Hi Micheal,

Is it possible to have the plan for your CNC version 2 machine?

Thanks!
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Old Aug 01, 2013, 01:34 AM
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Hi

Sorry, but I don´t have any plans for the foam cutter. But it shouldn´t be to hard to build one if you use the photos of my machine.

Michael Hammer
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Old Oct 06, 2013, 10:42 PM
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what software do you use?

Hi,

I am in the process of finishing off my JGRO CNC mill. its cutting its own parts now, great feeling and this week i am going to try and cut some wing ribs! very exciting.

I use Mach3 and Vertic aspire to do the work for that, What software do you use to run this?

I hope you dont mind if i shamelessly copy your design????
the pictures are pretty good and i am guess the are sizes in the previous version.

Fodder.
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Old Oct 07, 2013, 07:27 AM
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Hi Fodder

Congrats on your JGRO CNC mill. Nothing like watching a CNC built by yourself work it´s magic.

I use Rhino, RhinoCAM, Profili2 Pro and Mach3 for my CNC Mill. And for the CNC foam cutter I use DevFusFoam, Profili2 Pro (wonderful programs) and Mach3.

Feel free to copy my design and post your progress in this thread.

Cheers, Michael Hammer
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Old Oct 07, 2013, 07:42 PM
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Hi Michael,

thanks for that information. I an still a couple of months away from starting, the CNC mill still need to be "fine tuned" by i am really excited to be able to make foam cored wings!

the main thing is i will need to save up for a controller solution. My CNC uses a Hobby CNC board 4AUPC(old version) & new 4 axis version is around US$100. I am happy with it as i had it sitting around, but there are several new options available since i brought it back in 2004. One on KickStarter looks interesting as does the arduino solution i have seen (only in passing) so lots of research is needed on the electronics side as well.

thanks for posting your machine and if i need any details i will post some more questions.

Chris.
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Old Oct 08, 2013, 06:55 AM
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Hi Chris

I wouldn´t waste time saving up for a Hobby CNC stepper driver. Just buy a cheap chinese 4 axis stepper driver on E-bay.

When cutting foam you want to cut really slow (100mm/minute) with a wire temp juuuuuuuuuuuuuuust hot enough to melt the foam. If you see or smell smoke your wire is too hot.

So you don´t really need much performance from the stepper driver. I use a Gecko 540 for my CNC mill and like it very much, but I would never use one for my foam cutter unless I had one lying in a drawer doing nothing.

So get cracking! You could have the machine up and running by the end of this weekend if you collect the parts now and start putting things together ;o)

Cheers, Michael
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Old Nov 11, 2013, 10:56 PM
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Hi Michael,

sorry i missed this message. I have been doing a lot of reading on this and (sorry) everything you said above is what everyone else said.... (man that would have saved me some reading)

Anyway. I brought some plans for a 88" A-10 thunderbolt the other day and fully intend to use my CNC mill to cut everything. then the brain started to catch up and "allowed" me to remember all those bits i have been hording in the garage and this post.

Now the project has been moved up in the queue and the a-10 is going to have a foam core wing!

I will have a look for the controller on Evilbay!
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Old Nov 11, 2013, 10:58 PM
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Hi Michael,

sorry i missed this message. I have been doing a lot of reading on this and (sorry) everything you said above is what everyone else said.... (man that would have saved me some reading)

Anyway. I brought some plans for a 88" A-10 thunderbolt the other day and fully intend to use my CNC mill to cut everything. then the brain started to catch up and "allowed" me to remember all those bits i have been hording in the garage and this post.

Now the project has been moved up in the queue and the a-10 is going to have a foam core wing!

I will have a look for the controller on Evilbay!
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