It has been suggested to me that the RC'ers here on Openbuilds might be interested in my Brushed/Brushless Motor Foam Cutter. The method is "novel/unique" but not new... I've been using it for several years now to cut all kinds of planes and figures out of various sheet foams (bluecor, DTF, etc). I actually introduced this back on the Phlatforum (http://www.phlatforum.com/xenforo/threads/perforator-style-foam-cutting-head.2836/) in the summer of 2012 as a possible attachment for the Phlatprinter Mk3 -- Mark even thought it was neat! -- but sadly it never gained tracion or much notice. But recently it has undergone further development/refinement on my thread over on the RCPowers forum (Mostly Printed CNC and cutting foam) and been adapted to Ryan "allted" Zellars' Mostly Printed CNC (Mostly Printed CNC / MultiTool by Allted). This is a very flexible and affordable CNC machine in its own right... I've built 3 of then over the past 2 months for myself and a couple of friends. The foam cutter attachment itself however is simple/cheap, relatively easy to build (3d printed parts are NOT necessary), and easily adapted to virtually any CNC machine. I have published a couple of versions the CNC foam cutter attachment on Thingiverse. There is a brushed DC motor version (MPCNC foam-cutter attachment by dkj4linux) and an 2826/2822 brushless motor version (MPCNC 2826 Brushless RC Motor Foam Cutter by dkj4linux). It is absolutely perfect for cutting sheet foams for RC aircraft parts. 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. Basically, 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. 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. Straight-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/pressed 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.
VERY cool!! Only place I've seen this type of cutting was at a place that cuts custom gaskets. Never really thought about it as a good foam cutter. Fantastic share! Plane looks good too, pretty sure I bought one of those as one of my first foamies. Here is a pic of my last version.
Thanks! My inspiration came from engineer/artist Tom McGuire who made AFAICT several dedicated foam cutting machines... I simply took his idea and adapted it to a conventional 3-axis CNC machine... first, for a couple of BuildYourCNC machines I built several years ago and, most recently, the Allted's Mostly Printed CNC. The plane in the pictures and video is an RCPowers F117 v3. I've always loved his score and fold build method -- the first nearly-five minutes of the video in my first post are all the 50% depth score cuts, the rest is the full-depth outline cut for the central fuselage. I've bought/built most of his V3 and V4 plane packages and they are not only impressive to look at but also perfect for cutting with this foam cutter. That's also why my thread is over on the RCPowers forum. I'm still astounded that so many accomplished RC builders are still hand-cutting their planes... but then again relatively few have a CNC machine. I doubt that's the case here on the Openbuilds forum...
Thanks! I'd encourage to build it... and judging from your website and bio, it'll be a piece of cake for you. Trickiest part is getting the flywheel balanced well enough to turn 8000-10000 rpm or so. But regardless the cutter speed you can get, if you can adjust the feed rate to it to get 10-15 perforations/mm you can cleanly cut DollarTree foam board with the paper still on. -- David
Guess I'm old, before Steve (if I remember the name right) really got going or had any Vs is when I had mine. Great little plane, lost it in a full on dog fight with some birds that nest in my trees and ditches. Got below the hard deck you could say.. Moved on to 3D foam, but get the park jet urge now and again. The F117 I did a few years ago was drawn using solidworks sheet metal tools as a training exercise. Fit together perfectly, and was bent by compressing the depron as much as I could with aluminum angle. Then bend to the correct angle with a small amount of hot glue on the inside of the bends. Gonna have to build another park jet soon, they are a lot of fun to do. I've got a laser, but I've been finding more and more reasons I want to be able to cut either partial depths or chamfers. So I've been working on a router that is large enough for full sheets of depron and can later have the laser added to it as well. After looking at this approach I might dump adding the laser to the new machine. Should be easy enough to do some test rig piercing heads on the router once it's up. Have you used this machine on any EPP?
This is such a cool idea @dkj4linux thank you for sharing it. I see a lot of these being adapted to future machines
Hi, I suggested David post this GREAT idea over here because I know, like me, several would find it a much better alternative to a small laser in cutting out foam for flight. I was just about to sink several thousand in a large Chinese CO2 laser in the 100 watt range. Now I can hold off till I have a real need for that much power if ever! Thurmond
Not sure how old you are, but I'm going on 70 years now. By "Steve" -- do you mean Dave Powers? RCPowers has become pretty big over the past several years, has a nice civil forum, and I have "met"/interacted with several nice folks over there since starting my thread. It's been a bit frustrating though finding people willing to talk... the interest level is very high but most of the folks simply don't have CNC's, 3d printers, etc and really don't feel they have anything to add to the conversation. Hopefully that's not the case here on Openbuilds. I've actually pretty well resigned myself to the fact that I'll never fly worth a flip -- in truth, I'd rather build/develop anyhow -- as my old spastic/shaky thumbs appear un-trainable. My fishing/flying buddy is several years younger and does a much better job flying them... in fact, most of the parkjets I've built I give to him to fly. I just get a big kick out of building them and then seeing them in the air. In a near-final attempt to fly *something*, however, I did buy some 9mm EPP... was gonna shoot for a Cheap-N-Easy? Will probably still do it but I've been busy for the last couple of months building 3 MPCNC's and developing the foam cutter to where it is today so haven't tried machine cutting it yet? You got any suspicions or gotchas to share about how well it should cut with the foam cutter? -- David
Thanks, Mark. Do you remember my Phlatforum posts? You said then that it would be a great addition to the Phlatprinter Mk3... you're not putting the "kiss of death" on it now, are you?
I see you made it over here... welcome, Thurmond. Speaking of power... I'm turning 8000 rpm or so (enough for nice cuts at 600 mm/min) on the 2826 brushless motor, drawing just 1.25-1.3 amp at 7.4 volts. Rather than the 10's of amps these components often see while flying they're loafing along at only 10 watts or so. I'd bet a BW 1300kv would do the job nicely as well. -- David
Link to the phlatforum Post: http://www.phlatforum.com/xenforo/threads/perforator-style-foam-cutting-head.2836/ It has evolved significantly since then. By the way David a poster over at FliteTest lead me to your RCPowers Forum post so this idea is now making the rounds! Just got the wheel printed. Motor mount tomorrow after Church Service! Thurmond
Ahh, Dave sounds more like it. At 70 you've got me soundly beaten. I was going to volunteer some EPP if you didn't already have some. I'm uncertain as to how it would behave. Recently I've been doing things like using a smooth stone rather than an HSS bit to cut hinges and cannot believe how well it is working. Makes me wonder if a 1/32 dowel at 50k rpm wouldn't cut nicer than the laser. Trying to think of what is happening inside the foam... What comes to mind is a shaper machine. You're basically shaving off little scrapes with every punch. This requires the material to be somewhat rigid. But at the speeds it's happening you will benefit from the inertial forces incurred. The material, even being flexible, is getting hit awfully fast. It won't have much time to move out of the way. I would suspect that more pinning will be needed to keep from pushing the material around. Possibly avoidable with some attention paid to the order of cutting. Try inside to out, so as to keep the pins effectiveness as long as possible. A vacuum bed would be outstanding for this process. I suffer the same lack of interaction with the RC guys I know. Very few will even post a "that's cool". And I also enjoy the design and production process development as much as flying. Lucky and thankful to have one friend I can share ideas with. Thanks for the posting load info and motor specifics. I was wondering about that. How long do bearings last in the motor? Good to have bumped into you here! Sam
For those that don't have a login on the Phlatforum... a walk down memory lane. The original foam cutter was an Intel CPU fan from a PC... with all the fan blades broken out of it, the inflation needle screwed into a hole drilled in the side frame, and simply C-clamped to the tool platform. It was amazing how well it did and how long it lasted... I nearly cried when it finally gave up the ghost. The HP printer DC motor version replaced it... I still have it mounted on my BuildYourCNC machine. I measured the RPMs on it just recently to see what it was turning... about 4000 rpm at 12 volts... enough for pretty clean cuts at 24 inches/minute feed rate (it is a leadscrew-driven machine) and got decent cuts in blue-cor FFF. DTF not so clean as now, I'd cut it with the paper on, strip the paper, and then punch out the parts. The dinosaur in the picture with my grandson was cut that way a couple of Christmas'es ago. -- David
Well I am very happy with the flywheel. I enlarged the center hole to 4mm to match up with the 3DR closeout Iris+ motor shaft (unbranded T-Motors for $3 each) and the two flywheel holes just outside center were drilled out to 3mm. They were the perfect distance apart for direct mounting to the motor's existing flush mount prop holes with 3mm X 20mm long button head screws. Now off to look for a bearing and other parts. Thurmond
lol I do remember this post on the Phlatforum! Super cool then and now even more super cool Thanks for bringing this idea back to life here on OpenBuilds David and Thurmond!
Looking good, Thurmond. It'll be interesting to see how you balance it... and how/where you mount the bearing. A good source of small bearings is a junker motor you may have... or the replacements you may have purchased for motor repairs. The holes you used are 6 mm either side of center, the next are at 11 mm and the outer ring holes are 15 mm. Once you find the bearing and mounting hardware, weigh it all together with an electronic scale and multiply by the distance you mount it from center; i.e. my bearing/mounting screw/washer weighs 26 grains and using the 6 mm hole, the torque due to the bearing is 26 x 6 = 156 gr-mm. Now it's the "seesaw" problem... find counter-weight hardware and hole(s) combo on the other side that yields the same torque... i.e. big kid in close counter-balances the smaller kid further out on the opposite side of the seesaw. Rig up a prop-balancer setup to check it. When static balance is close, mount it in your Dremel and, starting with slowest speed, start spinning it up and note where it gets uncomfortable to hold, add/remove washers to adjust the balance, and try again. Eventually you should be able to get it dynamically balanced to get to 8-10K rpm and you're good to go. You gonna counter-sink/bore for those button-head screws? I start spinning it when it gets this close...
I did run it up to full speed as is with a 3S LIPO and I was able to hold it with 3 fingernails clamped to the base so the flywheel balance is pretty good till I add the bearing. Yes I plan to countersink and I have a very high speed bearing from a hard drive I will try. If it doesn't work out since I may be one of the worlds largest pack rats (18 years in Semiconductor fabrication has blessed me with many technical cast off items) I have lots of bearings. I will use a prop balancer for static balance and a laser for dynamic (if necessary). I did not get a chance to print the mount yet. I have some nice titanium tig filler wire for a needle. More to come. Thurmond
Sam, I'm not sure about the scraping action you mention... there is virtually no debris generated if the needle is pointed properly. That's certainly the case in all the foams I've tried... blue-cor FFF, styrofoam, and DTF. I try to get a short, conical point on the needle... much like a sharpened pencil... and symmetrical so that the cutting action is the same regardless of direction of travel. I plan to give the 9mm EPP a try but I'll need to take care to get the needle length right... there's only 12 mm of total needle travel with the current flywheel. I'd like it to barely retract into the body of the guide, leaving only 10-11 mm exposed. I'm thinking the rounded head of my carriage bolt needle guide might actually be something that makes the hold-downs simpler... much like the needle foot on a sewing machine (flexible material lightly pressed down under the foot). I've never had bearing issues in the motors... I did have a bearing go out on the flywheel though. I replaced it with a bearing out of a junker motor. The outer race needs to be lightly grooved to help retain the needle loop. -- David
David, If you have no dust then you are compacting the foam or melting it. I think either would be good with EPP, if it will stay still enough. Looking at your project, as well as following the links you've shared, pushed me over the edge. I ordered a 3D printer last night, a prusa i3 (not the best, but I'll make a better one later. Will be using it to help with the router parts, as well as testing what I can do with this method of foam cutting you've brought to light. Thinking about a pair of cutters at 45 degrees, for cutting hinges partial depth results. Just fun stuff to think about! Can you share how the version that needed to stop at top of stoke assured that it had? I remember running across it while following links. Thurmond, can you share some details about that motor? I'd like to know how long the threads are on the prop adapter, and if they are right handed on the black motor. I'm also curious if they come with an X-mount.
Sam, I know you said you ordered one but one of the best deals going on 3d printers IMHO is this Folger Tech 2020 (all-aluminum frame) Prusa I3 out on Ebay (Folger Tech 2020 Aluminum 2020 Prusa i3 RepRap 3D Printer 1.75mm). I bought and built one 4-5 months ago to go along with my older NWReprap Prusa I2 and am totally pleased with it... there's also quite a bit of buzz about it out on various forums, etc. It's sturdier than the acrylic-framed models, ships in/from the US, free expedited shipping, and arrives at your door in just a few days. And it runs less than $300 for everything... and that includes the optional LCD controller module with SD card reader. No melting (unless you go too slow feed and/or too high cutter rate) of the foam, the needle does "compress" the foam to a degree... but not much. It's much like (I shudder to think about it!) the thin, sharp-pointed, rapier blade being run through soft belly flesh; i.e. innards offer little resistance and get pierced and/or pushed aside very rapidly/easily. Yuck! Last time I'll use that analogy... Tom McGuire's machine IIRC was a dedicated foam cutter that didn't implement a real Z-axis... so it had to stop the needle at the top of its travel before moving to the next cut. He used HPGL (no gcode) and somehow reversed the polarity of the motor voltage when he needed to pick up the needle... that then engaged a solenoid-operated catch-arm that swung over and caught the head of the set-screw as the flywheel backed up to the upper-most position. It was quite clever and obviously worked well but I think he said it was very fiddly to initially get set up and aligned. It's far simpler when you have a fully-implemented Z-axis like we have... just let it run all the time and then pick up the whole mechanism when it's time to move to the next location. I love the idea of angle cutters though I'm not sure how the Z-axis movement and plunging to depth would work... I had thought of side-by-side and/or gradually-deepening passes "chewing" the foam to make a chamfer/channel but never pursued it. -- David
No X-Mount as they were for the Iris+ which did not use them. The Black prop adapter uses the standard right hand thread nut. The package contains the motor, the prop adapter (total length of adapter shaft is just under 12mm and too short for most prop hubs and a locking nut) and two 3mm cap head Allan bolts to hold on the adapter. No prop nut is included because the Iris used spin on props. 16" motor leads and the leads are glued where they enter the motor housing. The motor is perfect for the 3 hole direct mount hubless CF props if desired for flight. Thurmond
Thurmond, I was looking at them for flight. If they just needed X mounts they would make decent private labels. Could just laser something on them and what not. They happen to be a perfect fit for my 9mm outdoor size kits. David, That looks like about the same specs as what I got. Major difference is mine will be acrylic. But I did get a heated build table and the table leveling prox. Also got it with the MK8 head, not sure which the one you shared comes with. I assume that as soon as the router is working I'll be building a 3D printer to replace the new 3D printer... The aluminum structure would have been a better way to go.
Well mounting a bearing was as simple as removing one of the button heads and replacing it with one 5mm longer. Two 3mm washers were placed under the bearing. I still have to groove the bearing a bit deeper. This puts my bearing in the same place as David illustrated above but without any of the hardware to tighten it to the shaft since it is bolted directly to the motor bell. More to come. @gotswrv I had the same idea about private label on the motors. I got enough to build a whole lot of AP Multicopters! Thurmond
Sounds great, Thurmond. I always love it when things just "fall into place" like that. Looks like all you'll have to counter-balance is the bearing and 2 washers... maybe a short-ish 3 mm screw on the backside at the 11 mm 0r 15 mm position is about all that you'll need. I'm anxious to hear how it goes.
OK sorry I was not around yesterday. Here is a modification I made pictured below. I used some .030 mig wire I had around for Skew Planar Antennas and since it is MIG wire I did the logical thing and used a MIG gun tip for the needle guide. It was a Tweco® Model 14T-30 .030. Balance was achieved with one 3mm X 6mm black cap head socket screw from the back side of the flywheel and 1 small slug of copper wire in the next hole in from the perimeter (see pictures). I plan to do a better mount for the needle guide. The threads are 1/4"-28 UNF-2A. My needle guide is glued in for now since I was improvising when I came up with it. The needle guide needs to be lower in my next iteration. Thurmond
Outstanding, Thurmond. I actually used 0.025" MIG-wire for my first versions. I'm not a welder so really didn't know about the tips that are available. They look PERFECT for what we are doing... and far easier than boring out a carriage bolt! I'm anxious to see it running. I wonder if Lowes carries the tips... that's where I got the spool of wire. I'm gonna go check as soon as I finish this post. You may know this already... but did you know that you can straighten and work-harden/stiffen MIG wire by twisting it? I use my Dewalt hand drill and a drill-press vice... take a couple of feet of wire, pinch/hold one end in the vice, attach the other end to the drill chuck, stand on the chuck while gently stretching the wire and start twisting it with the drill motor. You've gone far enough when it breaks. The wire is then perfectly straight/stiff and almost perfect for forming needles for the foam cutter... or push-rods for your RC aircraft. Also, too cool... Karl Tinsley has published an assortment of quick-change tool adapters -- including the foam cutter -- for MPCNC. Take a look - Assorted Mounts for MPCNC Universal Mounting System by karltinsly David
Oh, happy day! Lowes had MIG tips... 0.035" (0.9mm) card of 10 tips for less than $7! They ought to be perfect. I've got to print Karl's quick-change version of my foam cutter yet so I think I'll build it up using one of these tips. What a great tip (pun intended!), Thurmond! -- David
I was wondering if the .035 tip would work well with .032 wire (can be had at most local hobby stores). You will have it thoughly tested very soon. Been wondering if a hardened nozzle for a 3D printer would do well, and last longer. I've also been wondering what RPMs you've tested? I was thinking I'll likely have excess 24v and 63V available. Both would require a pretty low kV motor if 10000rpm is the "right" speed. Got a few 12v supplies, but would like to keep the controls components space down if possible. Another option I have is to use one of my digisparks to control RPM and run whatever voltage is handy. As you are not pulling many amps I could put a little DC-DC voltage buck on it too. Got a couple of those off ebay for cheap a while back. Looks like you guys will have a few well refined systems under your belts before I can get around to trying this out. Thanks a bunch for sharing as you are!! sam
