Cutting foam sheets... with a needle!

iGull

New member
I tried moebeast's latest needle holder and I'm still breaking needles. If I keep the rpm at 5000 or less then it's fine. As soon as I go above that though, the needle snaps. Has anyone tried designing something like this? View attachment 95435

LOL, creepy, did you see my 'I have a cunning plan' comment above :)
The 'cunning plan' uses a 'scotch yoke' arrangement like your pic - perhaps not quite as complex 'tho - it's in hand as I type :)

On your head, I'm assuming that you are using piano wire as the needle (/music wire USA) ? If not, then use it, otherwise regular steel 'wire' doesn't have sufficient tensile strength to withstand the harsh treatment we give it :) If you are, then try increasing the distance between the head and the top of the nozzle (to reduce the side deflection of the needle).
If that still doesn't help, reduce your horizontal feedrate - I use 1000mm/min and 4500 RPM on depron with no issues and I've put a pile of it through my machine in the past few days. Also ensure that the backing you are using is sufficiently soft.
And finally, you only need enough stroke length to cut through the material - and keep the nozzle as close to the material as possible - 1 to 2mm max (unless you are using something like my foot design in which case it's on the material).
Hope that helps.

Cheers

Neil
 

Nactan

New member
LOL, creepy, did you see my 'I have a cunning plan' comment above :)
The 'cunning plan' uses a 'scotch yoke' arrangement like your pic - perhaps not quite as complex 'tho - it's in hand as I type :)

On your head, I'm assuming that you are using piano wire as the needle (/music wire USA) ? If not, then use it, otherwise regular steel 'wire' doesn't have sufficient tensile strength to withstand the harsh treatment we give it :) If you are, then try increasing the distance between the head and the top of the nozzle (to reduce the side deflection of the needle).
If that still doesn't help, reduce your horizontal feedrate - I use 1000mm/min and 4500 RPM on depron with no issues and I've put a pile of it through my machine in the past few days. Also ensure that the backing you are using is sufficiently soft.
And finally, you only need enough stroke length to cut through the material - and keep the nozzle as close to the material as possible - 1 to 2mm max (unless you are using something like my foot design in which case it's on the material).
Hope that helps.

Cheers

Neil

I'm using 0.025" piano wire. The distance from the center of the motor shaft to the center line of the top bearing is 60mm. I haven't put the needle under load yet. Just free spinning.
 

iGull

New member
I'm using 0.025" piano wire. The distance from the center of the motor shaft to the center line of the top bearing is 60mm. I haven't put the needle under load yet. Just free spinning.

Hi

As you are using a mount design that others have built and don't have an issue with, maybe the batch of piano wire you have is bad ? Have you tried using wire from a separate supplier ?
BTW, how much stroke are you using on the disc ?

Cheers

Neil
 

Nactan

New member
Hi

As you are using a mount design that others have built and don't have an issue with, maybe the batch of piano wire you have is bad ? Have you tried using wire from a separate supplier ?
BTW, how much stroke are you using on the disc ?

Cheers

Neil

I reduced the initial 12mm stroke to 10mm. I haven't tried a different supplier yet. I might go up to 0.03" wire or just design a scotch yoke like you.
 

Michael9865

Elite member
My Emax 2822 Powered Improved Needle Cutter by Jason is alive! 8309 RPM, now to make some cooling fins and install it onto the new Z axis on my MPCNC. Not sure how soon that will be, the rest of my month is already pretty busy.

My update
https://www.thingiverse.com/thing:2545595

Jason's original
https://www.thingiverse.com/thing:2450613

Emax 2822 Powered Improved Needle Cutter 8309 RPM Test.jpg

Video of it running
https://youtu.be/g2lbigAp83E
 

jhitesma

Some guy in the desert
Mentor
My Emax 2822 Powered Improved Needle Cutter by Jason is alive! 8309 RPM, now to make some cooling fins and install it onto the new Z axis on my MPCNC. Not sure how soon that will be, the rest of my month is already pretty busy.

With the pre-guides you probably don't even need any cooling fins. I don't have any on mine and haven't had any heat issues with this setup. I do have a cotton ball oiler in the plastic base...but it dries out and I forget to re-oil it so it's probably not making a big difference.

The biggest files I've cut have been about 20-30 minutes and at the end of that time the mig tip is still not overly hot. It's not comfortable to hold for more than a few seconds - but it doesn't give me burns or leave my fingers red. (It's too small for my IR thermometer to get a reading off of so I can't say exactly how warm it is.)

I've actually been considering eliminating the wooden insulator since it stays so cool now. But it's good insurance and doesn't hurt anything so I leave it in there :)
 

dkj4linux

Elite member
My Emax 2822 Powered Improved Needle Cutter by Jason is alive! 8309 RPM, now to make some cooling fins and install it onto the new Z axis on my MPCNC. Not sure how soon that will be, the rest of my month is already pretty busy.

My update
https://www.thingiverse.com/thing:2545595

Jason's original
https://www.thingiverse.com/thing:2450613

View attachment 95469

Video of it running
https://youtu.be/g2lbigAp83E
... the
Outstanding, Michael! I really doubt you'll need cooling fins... should be fine with straight-line motion of needle in guide.
 

iGull

New member
If it ain't broke ...

Hi All

Just a quick update again. :)
I received the sewing machine needles for a different version of the head that I was thinking about, but before stripping mine down (I have a few things I want to cut first :) I thought I'd do a quick couple of tests using a 'scotch yoke' arrangement at the top of the needle.
I've attached the pix of the mod I made - nearly a complete failure :) The idea 'works' - in that the side to side movement of the needle is reduced to nearly zero (you are bound to get some resonance), but as I suspected, it also requires linear support above the top of the yoke to ensure the needle and yoke don't fly off and poke you in the eye (don't ask :)
This is more engineering when it's unnecessary really, so I'm leaving it alone for now - it all works just fine. I did try a quick fix by attaching a larger washer on the bearings to hold the yoke in place, but the vibration was way out of course due to the weight.

One thing that I did do was to make a new needle (0.7mm/22swg again) and I spent a bit of time sharpening it properly (lazily in a drill on my belt sander :). Once I got a nice long point like a 'proper' needle, I used a fine oilstone (still in drill) to get a good polish on the wire end. Did another quick test and the quality is again slightly better than previous - even though my needle was sharp before, the tip was rounded after a couple of mishaps with some balsa that was lying on the bed :))

So, the moral is, if it ain't broke ...

Cheers

Neil
 

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  • DepronCNC Yoke Head.jpg
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dkj4linux

Elite member
Hi All

Just a quick update again. :)
I received the sewing machine needles for a different version of the head that I was thinking about, but before stripping mine down (I have a few things I want to cut first :) I thought I'd do a quick couple of tests using a 'scotch yoke' arrangement at the top of the needle.
I've attached the pix of the mod I made - nearly a complete failure :) The idea 'works' - in that the side to side movement of the needle is reduced to nearly zero (you are bound to get some resonance), but as I suspected, it also requires linear support above the top of the yoke to ensure the needle and yoke don't fly off and poke you in the eye (don't ask :)
This is more engineering when it's unnecessary really, so I'm leaving it alone for now - it all works just fine. I did try a quick fix by attaching a larger washer on the bearings to hold the yoke in place, but the vibration was way out of course due to the weight.

One thing that I did do was to make a new needle (0.7mm/22swg again) and I spent a bit of time sharpening it properly (lazily in a drill on my belt sander :). Once I got a nice long point like a 'proper' needle, I used a fine oilstone (still in drill) to get a good polish on the wire end. Did another quick test and the quality is again slightly better than previous - even though my needle was sharp before, the tip was rounded after a couple of mishaps with some balsa that was lying on the bed :))

So, the moral is, if it ain't broke ...

Cheers

Neil


Very nice work, Neil! And you stated your conclusion well... "..[t]his is more engineering when it's unnecessary really... it all works just fine."

Ultimately, this is the same conclusion Jaochim ("x33"/Germany), Dave ("GremlinRC"/Ireland), and I all reached when we attempted to harden/improve the needle cutter... KISS is king! If you haven't already, check the numerous pages around page 100 of this thread to get an idea of some of the several things we tried...

As you saw, "the idea 'works'" but the addition of moving parts just complicates the design, adds resonances galore, and creates that many more points of failure. It was all good fun, however... and we learned a lot making the attempt. Eventually we were able to reach the goal (straight-line motion of needle in guide) -- without adding any moving parts at all! Hence, the various "pre-guides" (bearings, sideboards, stacks, etc) employed on most of the newer cutters!

A fairly entertaining "blast from the past" -- an idea which worked beautifully but just wouldn't hold together for long...


-- David
 
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iGull

New member
V
A fairly entertaining "blast from the past" -- an idea which worked beautifully but just wouldn't hold together for long...
-- David

Ha ha, I like that, I'm always on the lookout for the 'lowest common denominator' when making things - this pretty much beats anything I've done LOL :) :)

Anyway, enough of machine building, I have a 1500mm Carbon Cub design that I'm working on - all depron with a 3d printed cowl and 3d printed urethane tyres (I've yet to try flexi TPU in my machine yet :) That was the whole reason for building this machine - that and the fact that I detest spending my day sticking down paper templates and cutting depron :)

Thanks to all for getting me on this track !

BTW, the heatsink/foot design on the bottom of my cutter now has an official engineering term, the 'Bell-End' :rolleyes:

Cheers

Neil
 

jhitesma

Some guy in the desert
Mentor
With a few mentions of feedrate and needle RPM lately...I thought it might be nice to have a quick easy way to figure them out (not that the math is hard)

So...

https://jscalc.io/calc/46UNa6KQoeqDptKR

Basically put in your feedrate (currently accepts mm/min and mm/sec - not sure if I want to bother with imperial options) and your desired holes per mm and it will give you the RPM your cutter needs to be running at to get that many holes.
 

RAGII

Member
Wow! You guys are really taking these needle cutters to the next level.

I got my needle cutter printed. When you balance your flywheel, do you leave the needle keeper on and what position do you place it in? I have mine balancing with the pointed end of the tear drop pointing towards the center of the wheel.

View attachment 95401


Can someone point me to the files for the flywheel and needle keeper. We got a 3D printer here at work so I can finally print some smaller parts while at work (sits idle most of the time so I need to do something to keep it in shape :D).

I have the original MPCNC mount so the other mounts won't currently work for me, just need the flywheel and keeper.

I have been running the mouse trap version for awhile with success but just looking for something a little better.

Thanks,

Rob
 

moebeast

Member
Can someone point me to the files for the flywheel and needle keeper. We got a 3D printer here at work so I can finally print some smaller parts while at work (sits idle most of the time so I need to do something to keep it in shape :D).

I have the original MPCNC mount so the other mounts won't currently work for me, just need the flywheel and keeper.

I have been running the mouse trap version for awhile with success but just looking for something a little better.

Thanks,

Rob

The keeper and a copy of David's flywheel is on my version of the 525 mount. https://www.thingiverse.com/thing:2429886
I have 3 versions of the needle keeper. The original for 10mm bearing, and a slimmed down version for 8mm and 10mm.

Mark
 

rockyboy

Skill Collector
Mentor
This is the one I pulled the needle keeper from:

https://www.thingiverse.com/thing:2429886

There are several different flywheels - sort of depends on your mount / motor length which one you need. I'm using the one @jhisteman made for the 611 mount, but you might need to just grab a flywheel from somewhere and adjust scaling to meet the spacing you have on the mount.
 

ironkane

Member
Nice job, it sounds smooth. I just wanted to make a small comment on the Emax CF2822. It's a nice motor, but I've trashed two of them so far. It's the pedestal mounting. It doesn't stand up well to the abuse and ends up starting to wobble.
Fortunately they're very reasonable priced and I bought a 4 pack after the 1st one went bad. I don't remember the cause, but the 2nd motor got trashed when my DTFB lost vacuum causing it to lift and then then dragging the DTFB instead of cutting.

Looking around my garage, I spotted a H-Quad I had built a while back that I'm not flying with some nice 650Kv motors
http://www.buddyrc.com/sunnysky-v2216-15-650kv-ii-brushless-motor.html which will give me a max of 7,800 RPM @ 12v. Best of all, no pedestal mount. Of course I'll have to print out a new cutter mount, but it should be worth it. And make a new flywheel to accommodate the threaded shaft vs the smooth. I'm using an aluminum flywheel btw. Very happy with it.

I intend to try to fabricate a needle keeper out of aluminum as well. I haven't tried a 3D printed one, but I can't help but think that it's too fragile for the load. Anyone have any feedback or comments on that?

My Emax 2822 Powered Improved Needle Cutter by Jason is alive! 8309 RPM, now to make some cooling fins and install it onto the new Z axis on my MPCNC. Not sure how soon that will be, the rest of my month is already pretty busy.

My update
https://www.thingiverse.com/thing:2545595

Jason's original
https://www.thingiverse.com/thing:2450613

View attachment 95469

Video of it running
https://youtu.be/g2lbigAp83E
 

dkj4linux

Elite member
Nice job, it sounds smooth. I just wanted to make a small comment on the Emax CF2822. It's a nice motor, but I've trashed two of them so far. It's the pedestal mounting. It doesn't stand up well to the abuse and ends up starting to wobble.
Fortunately they're very reasonable priced and I bought a 4 pack after the 1st one went bad. I don't remember the cause, but the 2nd motor got trashed when my DTFB lost vacuum causing it to lift and then then dragging the DTFB instead of cutting.

Looking around my garage, I spotted a H-Quad I had built a while back that I'm not flying with some nice 650Kv motors
http://www.buddyrc.com/sunnysky-v2216-15-650kv-ii-brushless-motor.html which will give me a max of 7,800 RPM @ 12v. Best of all, no pedestal mount. Of course I'll have to print out a new cutter mount, but it should be worth it. And make a new flywheel to accommodate the threaded shaft vs the smooth. I'm using an aluminum flywheel btw. Very happy with it.

I intend to try to fabricate a needle keeper out of aluminum as well. I haven't tried a 3D printed one, but I can't help but think that it's too fragile for the load. Anyone have any feedback or comments on that?

Well, since nobody has chimed in, I'll tell you of my experiences...

The pedestal mount on the CF2822 has never caused me significant problems -- except stripping of the grub screws -- so I always replace the grub screws with real M3x6mm/8mm machine screws. I've cut numerous sheets of DTFB without issue with that motor though, to be honest, I don't cut nearly as much and as often as the more avid plane builders here. Jason has had the same issues you describe however, so you're probably best following in his footsteps.

Those motors sound like they should work fine. You mention printing a new cutter body to accommodate them but you also mention using an aluminum flywheel. Sounds like you have both 3d printer and machinist experience so you're good going either way. If you should want to try the printed needle keeper... they've worked fine for me. And I think Mark (moebeast) has had only good experience using his... and he cuts a lot of foam. The point is... if it fits properly over the bearing, the printed keeper is strong enough and shouldn't go anywhere. In my experience there are no significant side forces trying to pull the keeper or needle off the bearing (IIRC Jason didn't even bother to groove the bearing on his previous cutters... :eek:)... all the significant forces are in the plane of bearing rotation.

As always... YMMV ;)

-- David
 

jhitesma

Some guy in the desert
Mentor
(IIRC Jason didn't even bother to groove the bearing on his previous cutters... :eek:)... all the significant forces are in the plane of bearing rotation.

Close...I tried grooving my first one, and burned out the bearing without ever really putting a noticeable groove in it. So I skipped it on my second.

Haven't had any issues with it cutting DTFB. Cutting cardboard....it did come off a few times, but a carefully placed drop of super glue solved that and I haven't had any issues since without the groove.
 

iGull

New member
Close...I tried grooving my first one, and burned out the bearing without ever really putting a noticeable groove in it. So I skipped it on my second.

Haven't had any issues with it cutting DTFB. Cutting cardboard....it did come off a few times, but a carefully placed drop of super glue solved that and I haven't had any issues since without the groove.

Rather than attempt trying to cut case hardened bearing stock with a dremel, just add another bearing with a washer in between them that is slightly thinner than the needle - you form a 'groove' that holds the wire in - haven't had mine pop out at all - loctite on the main screw of course.

Cheers

Neil
 

jhitesma

Some guy in the desert
Mentor
My very first comment on this thread (back on like page 7 or so) I chimed in to ask if anyone had considered using the servo outputs on the RAMPS board to control the needle cutter:

Have you looked at using one of the servo outputs on the RAMPS to control the motor? Seems silly to tie up a servo tester when the RAMPS board has several servo outputs.

I'm getting ready to start printing a set of MPCNC parts (was hoping to do ABS but I can't take the smell of printing that big of a project in ABS.) I'll have to order more PETG though. I need it to be usable outside and PLA melts in the shade here in summer :D While I'm working on that I may have to look into if it's possible to use a bit of G code to trigger a Servo output...can't be too hard.

Oh wait...quick google: http://3digitalcooks.com/2013/12/setup-servo-with-marlin/

Yeah. Just enable the servo pins and then use M280 PX SX (P=which servo S=angle or miliseconds)

Should be able to control the speed for different types of cuts if necessary then too...but that would take some manual g-code tweaking or a smarter slicer or some kind of g-code post-processor.

Or is there something I'm missing that makes this not a usable method?

Well, I now know that there really isn't a need to use different speeds for different cuts. So I was a bit off on that bit of speculation.

And shortly after I got my needle built I confirmed that the RAMPS could be used to control it as I suspected. But my original cutter was so finicky about RPM that I found it wasn't my favorite to deal with. I had setup some shortcuts in my RAMPS LCD controller to turn the needle on at 3 pre-set speeds...but none of them were quite right and with no computer hooked to my ramps it was kind of a pain to experiment to find different speeds. I put a bit of effort into adding a way to choose an arbitrary speed from the menus...but couldn't figure out how to pull that off in the Marlin source.

So I've lived with a servo tester. Which has always kind of bugged me.

Then two days ago I mentioned all of this again in RockyBoy's low rider thread since things have been reliable enough for me lately I've been meaning to try controlling the needle automatically again.

But didn't have time until tonight.

Now that I've tried it...I'm wishing I had done it earlier! Wow, this rocks!

As I speculated in RB's thread it is possible to set start/stop gcode in estlcam - so I did a tiny bit of testing with my tach and took the code I speculated in that thread and tried it:

image.png

image (1).png

My setting of "85" gives me right about 10k unloaded on the cutter. Which is a littler higher than I've been running...so I may drop it down to 80 and see how it goes - but the new cutter can handle 10k no problem so I'm cutting an X-29 for a friend with it right now at "85".

My cutter is plugged in like so:
20170929_221416 (1).jpg

Now - I no longer need to mess with the servo tester. I position the cutter over zero and zero the z - then hit print from the menu. It does the rest for me.

I could probably shorten the pauses a little, it doesn't really need that long to stabilize, but I also don't really need to save 2-4 seconds per sheet so...<shrug> I'll probably tweak it at some point but it's pretty low priority right now. Also, the M400 probably isn't really needed...since estlcam moves it up to the clearance pane after the last cut before zeroing at the end it should be safe to just turn off the needle when done without waiting for movement to finish.

It's probably also possible to use estlcam's s variable to set the speed using the spindle speed field in the tool list...but I don't mind going in here to change the speed since once you find a speed you shouldn't have to change it again.

It's a little thing...but not having to power the needle up manually makes it so much nicer to use. I HIGHLY recommend giving this a try!