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Dec 21, 2015, 11:24 PM
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Mostly Printed CNC and cutting foam


For you RC/CNC guys, I have published a couple of versions my CNC foam cutter attachment on Thingiverse. There is a brushed DC motor version (http://www.thingiverse.com/thing:1138627) and an RC brushless motor version (http://www.thingiverse.com/thing:1211039). This is an add-on tool and mount for the incredibly flexible and economical Mostly-Printed CNC by Ryan "allted" Zellars (http://www.thingiverse.com/thing:724999). It is absolutely perfect for cutting sheet foams for RC aircraft parts.

I originally built this attachment for a couple of BuildYourCNC machines I made and have most recently adapted it for the MPCNC. This is actually a resurrection and update of a short-lived thread I started in 2012 (https://www.rcgroups.com/forums/show....php?t=1663946). I've been using this method for several years now to machine-cut my planes out of fanfold foam insulation sheet and DollarTree foamboard. Though it appears a bit crude I have cleanly cut "miles" of foam using this method with minimal fuss.

WRT the tool chain I use, I most often convert PDF plans (or whatever) to DXF and import into SketchUp, scale/edit/arrange the parts into one or more sheets, and then use the SketchUCAM plugins to generate gcode. Throw a sheet of foamboard onto the bed of the CNC, set the origin, and let it rip. Twenty minutes or so later you have a sheet of parts that are accurately and cleanly cut, easily punched out, and hot-glued together.

Please take a look. I'll offer information and support to help as best I can if you decide to give it a try.
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Dec 23, 2015, 09:25 AM
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Foam cutter in action


MPCNC 2826 Brushless RC Motor Foam Cutter V2 (9 min 31 sec)
Dec 24, 2015, 11:17 AM
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Blue-cor, DollarTree foamboard, and the cardboard box it came in...
Dec 27, 2015, 04:50 PM
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Hi, nice work!

First time I have seen that style for foam cutting. I am curious tho about how the foam is cut, is that an abrasive wire oscillating/reciprocating or similar? Thanks.
Dec 27, 2015, 06:17 PM
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Quote:
Originally Posted by Datman
Hi, nice work!

First time I have seen that style for foam cutting. I am curious tho about how the foam is cut, is that an abrasive wire oscillating/reciprocating or similar? Thanks.
It's a very fast reciprocating needle... like a sewing machine. The needle is formed from a length of 0.025" music-wire and attached to a small ball-bearing mounted eccentrically on the flywheel. The flywheel is mounted on the shaft of a 2826 brushless motor (with ESC and servo tester) and spun at 8000-10000 rpm, resulting in a stroke/perforation per revolution. A feed rate of 600-1000 mm/min yields 10-15 strokes/mm and cleanly cuts DollarTree foam board (paper on), blue-cor fanfold foam, etc.

Pin a sheet of foam board onto the bed of the CNC, load the plane/figure gcode, set the origin, and let it rip. Twenty minutes or so later you have a sheet of parts that are accurately cut, easily punched out, and hot-glued together.
Jan 08, 2016, 10:41 AM
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All,

If you are interested in the active design/development of this foam cutter, Mostly Printed CNC, and/or building one (or all) for yourself, please check out the following:

Foam Cutter design/development --

A fairly lengthy thread featuring brushed-/brushless-motor versions of the foam cutter, a Mostly Printed CNC (MPCNC) build log, user build(s), and general DTF cutting thoughts:
http://www.rcpowers.com/community/th...ng-foam.18808/

User build(s) and further needle guide development:
http://openbuilds.com/threads/brushl...eet-foam.5862/

Universal MPCNC quick change/release system for assorted tools (including foam cutter) and user build(s):
http://www.vicious1.com/forum/topic/...unting-system/
http://www.vicious1.com/forum/topic/...s-foam-cutter/

All 3d-printed versions/parts --

Brushed motor versions:
http://www.thingiverse.com/thing:1138627

Brushless-motor versions:
http://www.thingiverse.com/thing:1211039

Universal MPCNC mounting system, including foam cutter head:
http://www.thingiverse.com/thing:1245848

Mostly Printed CNC:
http://www.thingiverse.com/thing:724999
http://www.vicious1.com/specifications/

etc...

Please feel free to join in the conversation and/or ask questions.

-- David Johnson (aka "dkj4linux")
Feb 03, 2016, 03:33 PM
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Shurakair over on the FT forum posted this great version of the needle cutter... very rigid and precise. -- David

CNC Foam Board Needle Cutter (8 min 21 sec)
Feb 22, 2016, 01:38 PM
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Here's my current MPCNC hard-mount foam cutter now outfitted with a "floating" guide tip holder with 0.035" copper welding-tip. The "floating" tip holder uses a short section of carbon arrow shaft for a spacer/insulator and a 3-point set-screw arrangement to effectively isolate the hot (in use) copper tip from the yellow PLA plastic. Check out http://www.thingiverse.com/thing:1211039. -- David

MPCNC cutting 2mm craft foam (7 min 25 sec)
Last edited by dkj4linux; Feb 22, 2016 at 09:53 PM.
Apr 12, 2016, 07:00 PM
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Wow, that's thinking out side the box !

Do you have any close ups of the resultant edge ?

Does it create ANY dust ? Or it THAT the main advantage.

Very nice development.

Are the "special" parts for sale someplace. I don't hav ea 3D printer.

Thanks

Bob
Apr 12, 2016, 11:44 PM
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Quote:
Originally Posted by birdofplay
Wow, that's thinking out side the box !

Do you have any close ups of the resultant edge ?

Does it create ANY dust ? Or it THAT the main advantage.

Very nice development.

Are the "special" parts for sale someplace. I don't hav ea 3D printer.

Thanks

Bob
Bob, I replied in your "laser woes" thread and posted a few pictures of typical cut edges and lack of dust/debris. And there really are no "special parts". It's quite economical and straight-forward to build -- even if you don't 3d print anything. My first foam cutters were not 3d printed... the first was actually a CPU fan and inflation needle guide clamped to the tool platform, then scrounged DC motors from inkjet printers...

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Description:

As you can see, in addition to a motor it requires only a small flywheel/eccentric, a small 3mm ball-bearing (out of junker RC motor is ideal), an sports-ball inflation needle (or mig-welding tip) guide, a 0.025" music-wire needle, and a right-angle bracket of some sort.

The brushless motor 3d printed version on Thingiverse uses a common RC motor, ESC, and servo tester -- which many folks on this forum may already have on hand -- and adds variable speed and more than adequate speed/power to breeze through foam. There are actually several more "advantages" to this foam cutting tool and method and you could realize most of them right away since you are already so "CAD/CAM/CNC-literate" and have the machines and experience...

1) It's simple/cheap and uses a very modest standard RC setup (motor,esc,servo tester) that many on this forum already have on hand and/or can easily obtain.
2) It's fairly easy to build -- requiring only a small flywheel of some sort, a small 3mm ball-bearing (out of junker RC motor is ideal), an inflation needle guide, a 0.025" music-wire needle, and a right-angle bracket of some sort... in addition to the RC motor, ESC, and servo tester.
3) It only lightly loads these RC components in this application so should last a long time. [Normal RC operation -- i.e. flying -- routinely needs 10's of amps... here we only need 2 amps!]
4) It's very compact and can easily be mounted/strapped on to virtually any CNC machine's tool holder/platform.
5) The servo tester variable speed control permits a wide range of feed rates to be used... 10-15 strokes/mm gives pretty clean cuts in DTF.
6) The power requirements are very modest (7.4-11.1 volts at 2-3 amps) and easily obtained with a common power brick or CNC power tap.
7) It's relatively quiet and neighbor-friendly.
8) It's relatively clean and requires little or no cleanup.
9) It requires no exotic clamps/fixturing on the CNC work surface... straight pins can do the job.
10) ???

I'd love to help you out if you want to build one of these. Now that it's being built by other folks (rather than just me) I'm confident in recommending you build one for yourself. I sure you'll find it very easy to build and use. -- David
Last edited by dkj4linux; Apr 13, 2016 at 12:29 AM.
Apr 14, 2016, 08:21 PM
When pigs fly rc
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Will it work on epp foam?
Apr 15, 2016, 01:54 AM
Registered User
Convert the Gizmo to a rotary cutter head and use the thing to cnc/rout an entire Airframe from Billet foam ??
Rather than cutting a thousand individual bits you then have to glue together poorly and then skin... if it's more than a flat foamy.
In which case a hand operated #11 blade is good proven method/ tool.
Apr 15, 2016, 07:50 AM
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Quote:
Originally Posted by rcrich
Will it work on epp foam?
Rich, though I have intended to try EPP I've never personally done so. I actually bought some to build the C&E but I'm the world's worst procrastinator (and pilot!) and have just never gotten around to it.

My guess is "yes" it will cut it fine... at some combo of cutter rpm and feedrate. Quite a few of these cutters have now been built by some pretty prolific RC builders and everybody seems pretty happy with its performance with the foams they use. -- David
Last edited by dkj4linux; Apr 15, 2016 at 08:04 AM.
Apr 16, 2016, 08:32 AM
Tony Audsley Retired Locksmith
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David, not quite sure how you have mounted the wire (cutter) to the bearing and flywheel ?

Lockeyt
Apr 16, 2016, 10:58 AM
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Quote:
Originally Posted by Lockey
David, not quite sure how you have mounted the wire (cutter) to the bearing and flywheel ?

Lockeyt
Lockey, the needle is simply a length of 0.025" (0.635mm) music-wire with a 1-1/4 to 1-1/2 turn loop formed in one end. It's sized to slightly under the OD of the bearing. I use a mandrel (a drill bit shank) with diameter equal to about 2/3 the OD of the bearing and leave a little tag-end handle to help open the loop and fit it over the bearing race. The small 3mm-bore bearing has a very shallow groove lightly ground into it (some folks use a flanged bearing) and the needle is held there by it's own spring-pressure... there are no significant side forces at work trying to pull the needle off the bearing race, Finally the needle is snipped off below the tip of the needle guide to the thickness of the material to be cut plus 2-3 mm. The needle point is then dressed to a short conical point by lightly holding it against the side of a grinder wheel or using a fish-hook sharpener to remove all barbs/burrs. -- David


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