[dkj4linux]

Having seen several mentions of foam cutting machines/methods in this forum, this might be of interest to some of you... especially RC folks. I have published a couple of versions my CNC sheet foam cutter attachment out on Thingiverse. There is a brushed DC motor version (MPCNC foam-cutter attachment by dkj4linux - Thingiverse) and a 2826/2822 brushless motor version (MPCNC 2826 Brushless RC Motor Foam Cutter by dkj4linux - Thingiverse). This is an add-on tool and mount for the incredibly flexible and economical Mostly-Printed CNC (MPCNC) by Ryan "allted" Zellars (Mostly Printed CNC / MultiTool by Allted - Thingiverse). It is simple/cheap and easily adapted to almost any CNC machine and is absolutely perfect for cutting sheet foams for RC aircraft parts.

The concept is simple. 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 a small flywheel. The flywheel is mounted on the shaft of a brushed/brushless DC motor and spun at 8000-10000 rpm, giving one stroke/perforation per revolution. A simple needle guide keeps the business-end of the needle "focused" to a point on the material being cut. A feed rate of 600-1000 mm/min yields 10-15 strokes/mm, which cleanly cuts DollarTree foam board (paper on), blue-cor fanfold foam, etc.

I originally built this attachment for a couple of BuildYourCNC machines I made and have most recently adapted it for the MPCNC. I've been using this method for several years now to machine-cut my planes out of fanfold foam insulation sheet and DollarTree foamboard and though it appears crude I have cleanly cut many sheets of foam using this method with minimal fuss.

I have a fairly lengthy build and development thread going on the RCPowers forum if you are interested (Mostly Printed CNC and cutting foam | RCPowers.com). It also includes a brief build log of one of three MPCNC's I have built for myself and a couple of buddies.

Please take a look. I'll offer information and support to help as best I can if you are interested and/or decide to give it a try.

[awerby]

That's a cool idea! Having tried cutting foam various different ways, this seems cleaner than rotary tools and less stinky than hot-wire. Are you offering these for sale as add-on items for CNC routers?

[dkj4linux]

That's a cool idea! Having tried cutting foam various different ways, this seems cleaner than rotary tools and less stinky than hot-wire. Are you offering these for sale as add-on items for CNC routers?

Thanks for your interest. No, I'm not selling anything... though I'm sold on the method and am frankly quite amazed there's no one else (to my knowledge) out there using it on a conventional 3-axis CNC machine. I'm a retired electrical engineer and don't want/need a job... I'm just a full-time hobbyist interested in CNC, RC, 3d printing, etc

This is DIY for anyone to build or use. I've been using this method and building these cutters for several years now. I was originally inspired by an engineer/artist Tom McGuire who AFAIK built several incarnations of his foam cutting machine.

https://www.youtube.com/watch?v=uxeFXGiankE)

I have recently engaged in further development/refinement/documentation of the process and machines out on the RCPowers forum thread. The Thingiverse links I referenced offer the 3d models (specific to the MPCNC) that can be downloaded and duplicated by anyone with a 3d printer... though it can also easily be built and adapted using conventional methods as well.

As far as the cutting method, it is indeed cleaner... there is little/no debris at all if the needle is properly dressed to a point; i.e. the relatively soft foam is simply pierced/displaced by the relatively sharp, stiff needle. It's also relatively quiet and neighbor-friendly. No heat, no abrasion, no stink... the kerf is narrow and the cut is clean if the feed rate and cutter rpms are selected to give sufficient perforations per unit length of tool travel; i.e. 10-15 perforations/mm in Dollartree foam board, etc. And the material holding/clamping requirements are minimal... the machine/tool forces are small and simple straight pins can be used to hold a foam sheet to a layer of styrofoam serving as waste board underneath.

The brushless motor version of the foam cutter is especially attractive to RC'ers because so many folks already have the components... a motor, ESC, and servo tester. These components are readily available and affordable and this simple setup gives variable speed, high rpms, and more power than needed for the job... everything runs cool because it's running well within its ratings. I hope you will follow all the referenced links to get more information/pictures/videos but here is the cutter in action.

[dkj4linux]

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:
Mostly Printed CNC and cutting foam | RCPowers.com

User build(s) and further needle guide development:
Brushless Motor Foam Cutter and cutting sheet foam | OpenBuilds

Universal MPCNC quick change/release system for assorted tools (including foam cutter) and user build(s):
New Universal Mounting System ? Vicious Circle CNC
Brushless foam cutter ? Vicious Circle CNC

All 3d-printed versions/parts --

Brushed motor versions:
MPCNC foam-cutter attachment by dkj4linux - Thingiverse

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")

[dkj4linux]

Shurakair over on the FT forum posted this great version of the needle cutter... very rigid and precise. -- David

https://youtu.be/MEkAsG_wmRs

[dkj4linux]

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 MPCNC 2826 Brushless RC Motor Foam Cutter by dkj4linux - Thingiverse. -- David

[dkj4linux]

Please check out the latest developments of the home RC hobbyist's version of my foam cutter at Cutting foam sheets... with a needle!.

This is a beefier, production-quality version of my foam cutter built by Bob Neitzke (Hoosier Cutout Service) cutting MPF at 0.75 IPS feedrate and 4000+ cutter rpm.



-- David

[aarggh]

Very nice work!

cheers, Ian

[harryn]

Thanks for posting this information and links. Do you think that this method would work if used with manual motion (I don't have cnc yet)

[dkj4linux]

Thanks for posting this information and links. Do you think that this method would work if used with manual motion (I don't have cnc yet)

Harryn, I really don't see why not. There has been mention of a handheld version numerous times but nobody's been ambitious enough yet to make one specifically for hand use. It has been *tested* that way, however, as guys have built it and are just guiding it through some foam by hand, just to see what it will do. It shouldn't be terribly different than an electric scissors... or a sabersaw... or a small router... and should probably have a base/foot that allows it to follow a straight-edge or guide. The cut edges won't as clean as when driven around with a CNC machine but I suspect they'd be perfectly usable. -- David

[dkj4linux]

Shurakair shared an updated video of his foam needle cutter with us in my thread over on the FT forum

Cutting foam sheets... with a needle! - Page 42

His foam cutter was built with the help of a machinist friend and features relatively heavy aluminum construction and custom-machined flywheel and Oilite (oil-impregnated bronze IIRC) needle guide. It's very much in its near-original condition, seems quite trouble-free, and he indicated he is extremely happy with it and the cutting method.

Here he is cutting DTFB at 900 mm/min and 9000 rpm on the cutter. He also indicated he feels he gets a cleaner cut when he does two passes on through-cuts. It's hard to argue with his results! -- David

https://www.youtube.com/watch?v=MLZi0NxGkOY

[dkj4linux]

All,

I'm posting this to the several relevant RC and CNC forums where I've started foam cutter threads, to acknowledge and express my appreciation for all the nice folks who've commented, encouraged, shared their ideas, and contributed in any way to the development of my foam cutter attachment... and to let you see an example of just how far we've come over the past year.

First, I want to apologize for being so inactive lately and basically taking the summer "off". I've actively kept up with all the great posts but contributed very little. Basically a lazy slob and living alone in my grandparents' old farm house with no a/c in the Texas summer heat (hey! my grandparents did it...), I've been pretty un-energetic and hunkered down most of the time under a fan. But, now, the heat is starting to subside, fall is in the air (sort of...), and I'm starting to feel a bit more energetic again. So I'm now trying to un-clutter my path back to my machines and hoping to start being more active and useful again with all this foam cutter stuff.

Of note, I promised one of my two 3d-printers to my son-in-law when he got settled in a bit more, so I have recently looked into getting another one. I've been rather spoiled having TWO printers to work with during all my MPCNC and foam cutter builds, so I really feel I NEED two printers going forward. I've been entirely pleased with the $300 FolgerTech 2020 All-aluminum Prusa I3 kit I ordered and built last year, so I looked there first... it's very well supported, there is a lengthy thread dealing with it on the FliteTest forum, and IIRC Jason (jhitesma) also has one and seems quite pleased with it. Anyway, it is indeed still available (google it... it's the ebay listing) so I ordered another one and now have it to build. It is another of my motivations for getting my workspace cleaned up and de-cluttered so I'll have the room to actively get back to building stuff.

Lastly, I can't begin to tell you how excited I am about all the foam cutter developments of the past year... and now -- cheap! -- VACUUM hold-down to boot! I think the magnitude of it all really hit me when Curtis (CartCurt), over on the FT forum, posted this picture of his very impressive, relatively inexpensive, and complete MPCNC-based foam cutter setup... that wouldn't exist today were it not for the collective contributions of all the nice folks in the several RC/CNC forums where all this development has taken place. What hobbyist RC'er in his right mind wouldn't love to have a setup like that? Thank you all! -- David

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