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Cutting foam sheets... with a needle!

I have a MPCNC build with a Eric TimSav needle cutter converted by David. I cannot seem to get more than one sheet cut without breaking the needle or melting the mounting screw out of the flywheel. I think I have fixed my issue with the flywheel melting by fabricating my own small washers that set on the inner bearing race. I will probably have to break down and buy those M3x5mmx0.3mm thick washers. The needle breaks about one inch from the mounting screw in the flywheel. I believe the stress is happening at the needle guide bearings slapping against them. The needle is sharp (dremel style). I have tried different needle holders out there (teardrop style) in hopes to solve the needle issues.

The main issue I have with the teardrop style needle holder is that I cannot get the .025" wire through the hole. I have tried heating up a pin to enlarge hole. How does one get the wire through on the needle type holder?

Can I remove the top set of bearing for the needle guide to eliminate the stress on the sire? Last, How can I eliminate the bearing mounting screw from melting out of the flywheel?

cutter settings:
6000-8000 rpm
600-800 mm/min feed rate
do yourself a favour and change the bearing of the needle holder...i tried different needle holders and messed around with the same problems...until i replaced the bearing with a 450size helicopter bearing from the tail...same size, but 0.5mm wider. i never had a problem again since then...and then it doesn´t matter, which needle holder you use.
 

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I have a MPCNC build with a Eric TimSav needle cutter converted by David. I cannot seem to get more than one sheet cut without breaking the needle or melting the mounting screw out of the flywheel. I think I have fixed my issue with the flywheel melting by fabricating my own small washers that set on the inner bearing race. I will probably have to break down and buy those M3x5mmx0.3mm thick washers. The needle breaks about one inch from the mounting screw in the flywheel. I believe the stress is happening at the needle guide bearings slapping against them. The needle is sharp (dremel style). I have tried different needle holders out there (teardrop style) in hopes to solve the needle issues.

The main issue I have with the teardrop style needle holder is that I cannot get the .025" wire through the hole. I have tried heating up a pin to enlarge hole. How does one get the wire through on the needle type holder?

Can I remove the top set of bearing for the needle guide to eliminate the stress on the sire? Last, How can I eliminate the bearing mounting screw from melting out of the flywheel?

cutter settings:
6000-8000 rpm
600-800 mm/min feed rate
A couple of things. - lubricating the needle will reduce friction, and thus reduce heat. WD40, grease, anything is going to be better than nothing. I use the mig welder tips.. they seem to work the best. Look at my EZ-Flywheel in my signature, as you will be able to see my setup in those photos that I have setup on my mpcnc. I don't use the flywheel with the special washers, as too difficult to locate in my neck of the woods, along with I didn't like bending piano wire. Anyway, look at the write up for the EZ-Flywheel.

Since you have a mpcnc, I have had great success with my setup atm, and would recommend it for you as well. I had the same issues you are experiencing.
I haven't broke a needle since I've gone to my setup over 20 sheets ago and still going.. .. if you decide to go with the setup I have, use these retention linkage stoppers. They have an allen wrench grup screw that holds the piano-wire/push-rod better, (not that I have had issues with the flitetest version of linkage stoppers, just like the tightening method better.)

Aslo, I use the hobby lobby piano wire, as it's cheaper, but a little thicker than the size you are using .. 0.032" with the mig welder tip.

Hope this helps.
 
I really dived in eventually and built a sleeve style with guide bears and all, spent the time designed it to match my motor, tested, reprinted, rebuilt, tested reprinted rebuild, changed bearings, made mistakes and eventually got to a point it was worth spending the 2hrs tweaking balance. Was a lot of work, cuts are cleaner, unit runs faster then old one. But I spent maybe 30+ hrs on the project. It has cut a lot of sheets.

Vs

I spent maybe 2hrs building a plywood clothes pin spring unit originally, dab of super glue and a few bends to keep the needle on, and it cut many hundreds of sheets no issues. Was loud and unbalanced but worked, and I still have it in a drawer if I wanted to mount it again. After the first few sheets I threw a needle made one adjustment and never had an issue again. Something to be said for simple.
 
I really dived in eventually and built a sleeve style with guide bears and all, spent the time designed it to match my motor, tested, reprinted, rebuilt, tested reprinted rebuild, changed bearings, made mistakes and eventually got to a point it was worth spending the 2hrs tweaking balance. Was a lot of work, cuts are cleaner, unit runs faster then old one. But I spent maybe 30+ hrs on the project. It has cut a lot of sheets.

Vs

I spent maybe 2hrs building a plywood clothes pin spring unit originally, dab of super glue and a few bends to keep the needle on, and it cut many hundreds of sheets no issues. Was loud and unbalanced but worked, and I still have it in a drawer if I wanted to mount it again. After the first few sheets I threw a needle made one adjustment and never had an issue again. Something to be said for simple.
what do you want to tell us ?
 
what do you want to tell us ?
Just saying as time has gone there are new ideas, they improve on the designs before them, but they are not simple or easy to implement properly and will take lots of time, trial and error. Pick what works for you. My original one was chosen due to lack of 3d printer. Had no bearings or anything. Still worked well. And don't be discouraged by failure!
 
Just saying as time has gone there are new ideas, they improve on the designs before them, but they are not simple or easy to implement properly and will take lots of time, trial and error. Pick what works for you. My original one was chosen due to lack of 3d printer. Had no bearings or anything. Still worked well. And don't be discouraged by failure!
you´re absolutely right...finding and solving problems is also the funny part of our hobby...ihave tried many things, but it was an easy solution...of course using a good needle and everything....but a higher quality bearing changed everything. no heat any more...donßt even need to lubricate...
 
do yourself a favour and change the bearing of the needle holder...i tried different needle holders and messed around with the same problems...until i replaced the bearing with a 450size helicopter bearing from the tail...same size, but 0.5mm wider. i never had a problem again since then...and then it doesn´t matter, which needle holder you use.
Is it a flanged bearing? Do you have a part number?
 
I finished my CNC machine - Moebeast's Foam Ripper. I have a pen zip-tied to the mount right now, and it draws pretty well. Just gotta get the motor for the needle cutter and I'll be cutting out some planes. :) First up will be a Tiny Trainer, then a MS P-38. :D
View attachment 189649
Awesome to hear !! Glad you were able to get it completed.

Personally, after having built 3 Tiny Trainers, because I crash often, destroying 1 motor, and countless 6x3 props, teaching myself to fly, I've come to the conclusion that I should have started with the FT Explorer, with the training wing, and several nose setups, as the in-field repairs doesn't take very long to get back into the air. When crashing with the explorer, it doesn't destroy the prop like it does on the TinyTrainer, but I've been destroying only the nose. and the nose slides off easily, and a new one can be installed easy. Quite honestly, I'm still learning the controls, and by using the explorer, I've saved at least a dozen props. I can tell you, the first several attemps, 1 prop lasted 10 seconds on the TinyTrainer. Aggravatingly I built 3 Tiny Trainers, as I don't want to have to perform in-field repairs, and found by using the explorer, I was able to get more 'air time' than the TinyTrainer, and the Explorer quite honestly is easier to fly. Just my $0.02 . I love the whole journey, I just wish I could fly better.. but that will come with time and rebuilds. :)
 

2jujube7

Well-known member
Awesome to hear !! Glad you were able to get it completed.

Personally, after having built 3 Tiny Trainers, because I crash often, destroying 1 motor, and countless 6x3 props, teaching myself to fly, I've come to the conclusion that I should have started with the FT Explorer, with the training wing, and several nose setups, as the in-field repairs doesn't take very long to get back into the air. When crashing with the explorer, it doesn't destroy the prop like it does on the TinyTrainer, but I've been destroying only the nose. and the nose slides off easily, and a new one can be installed easy. Quite honestly, I'm still learning the controls, and by using the explorer, I've saved at least a dozen props. I can tell you, the first several attemps, 1 prop lasted 10 seconds on the TinyTrainer. Aggravatingly I built 3 Tiny Trainers, as I don't want to have to perform in-field repairs, and found by using the explorer, I was able to get more 'air time' than the TinyTrainer, and the Explorer quite honestly is easier to fly. Just my $0.02 . I love the whole journey, I just wish I could fly better.. but that will come with time and rebuilds. :)
I completely agree with that. I was having the same problem with 70% scale FT A-10 (and my original TT), until I installed landing gear. It really absorbs the shock of landing and I've saved many props with the addition of gear.
 
Awesome to hear !! Glad you were able to get it completed.

Personally, after having built 3 Tiny Trainers, because I crash often, destroying 1 motor, and countless 6x3 props, teaching myself to fly, I've come to the conclusion that I should have started with the FT Explorer, with the training wing, and several nose setups, as the in-field repairs doesn't take very long to get back into the air. When crashing with the explorer, it doesn't destroy the prop like it does on the TinyTrainer, but I've been destroying only the nose. and the nose slides off easily, and a new one can be installed easy. Quite honestly, I'm still learning the controls, and by using the explorer, I've saved at least a dozen props. I can tell you, the first several attemps, 1 prop lasted 10 seconds on the TinyTrainer. Aggravatingly I built 3 Tiny Trainers, as I don't want to have to perform in-field repairs, and found by using the explorer, I was able to get more 'air time' than the TinyTrainer, and the Explorer quite honestly is easier to fly. Just my $0.02 . I love the whole journey, I just wish I could fly better.. but that will come with time and rebuilds. :)
And with a good concept and needle cutter you get to cut them in bulk. Lost count how many explirers I have cut for ppl.
 

2jujube7

Well-known member
Tonight I finished the needle cutter part of my Foam Ripper, and I was able to cut out a few basic shapes that I found online in the .dxf format. Next, I tried to convert the TT plans to be .dxf using Inkscape, but it isn't quite working out. I know what I have to do, but the drawing just doesn't seem to be cooperating. Parts of it will randomly white out and just not exist anymore. (Without me deleting anything ;)) Here's a screenshot of the closest I've gotten. Has anyone had this problem before? Am I just doing something wrong?
1611278400319.png
 

Wildthing

Legendary member
Tonight I finished the needle cutter part of my Foam Ripper, and I was able to cut out a few basic shapes that I found online in the .dxf format. Next, I tried to convert the TT plans to be .dxf using Inkscape, but it isn't quite working out. I know what I have to do, but the drawing just doesn't seem to be cooperating. Parts of it will randomly white out and just not exist anymore. (Without me deleting anything ;)) Here's a screenshot of the closest I've gotten. Has anyone had this problem before? Am I just doing something wrong?
View attachment 189920
I have no idea having never done it but I would try increasing the thickness of the lines before converting them and see what happens.
 

2jujube7

Well-known member
Alright, I figured it out. I had to place it on the 20x30 page the first time and not move any parts around. Now I'm stuck on another part: saving. It gives me this message when I try to save the dxf. I was able to save an svg, but still not a dxf. I tried different directories, to no avail. I have no idea why it's saying this, and I've tried lots of things. Sorry for bringing my noobie questions to the forum. :)
1611281307920.png
 
Tonight I finished the needle cutter part of my Foam Ripper, and I was able to cut out a few basic shapes that I found online in the .dxf format. Next, I tried to convert the TT plans to be .dxf using Inkscape, but it isn't quite working out. I know what I have to do, but the drawing just doesn't seem to be cooperating. Parts of it will randomly white out and just not exist anymore. (Without me deleting anything ;)) Here's a screenshot of the closest I've gotten. Has anyone had this problem before? Am I just doing something wrong?
View attachment 189920
Inkscape can be a bit evil on some computers, good chance the info is still there, just not being displayed. Zooming in and out can help, saving in svg and reopening can help. Ungrouping helps sometimes, but ungrouping can sometimes feel like things are locked up, wait it out.
 
Alright, I figured it out. I had to place it on the 20x30 page the first time and not move any parts around. Now I'm stuck on another part: saving. It gives me this message when I try to save the dxf. I was able to save an svg, but still not a dxf. I tried different directories, to no avail. I have no idea why it's saying this, and I've tried lots of things. Sorry for bringing my noobie questions to the forum. :)
View attachment 189932
May need to ungroup, be sure no graphics are left, just vector drawings. May be the settings when you are saving it. Also try the other dxf format that you have an option of.
 
Alright, I figured it out. I had to place it on the 20x30 page the first time and not move any parts around. Now I'm stuck on another part: saving. It gives me this message when I try to save the dxf. I was able to save an svg, but still not a dxf. I tried different directories, to no avail. I have no idea why it's saying this, and I've tried lots of things. Sorry for bringing my noobie questions to the forum. :)
What operating system are you using? I use Windows and have found that I have had issues with dxf files in Inscape 1.0.x. I now only use Inscape 0.92.x and have no issues saving dxf files. They import with the correct scale when I create gcode.
 

2jujube7

Well-known member
What operating system are you using? I use Windows and have found that I have had issues with dxf files in Inscape 1.0.x. I now only use Inscape 0.92.x and have no issues saving dxf files. They import with the correct scale when I create gcode.
Yeah, I use windows also. I'll try 0.92.x, thanks!
 

TEAJR66

Flite is good
Mentor
Alright, I figured it out. I had to place it on the 20x30 page the first time and not move any parts around. Now I'm stuck on another part: saving. It gives me this message when I try to save the dxf. I was able to save an svg, but still not a dxf. I tried different directories, to no avail. I have no idea why it's saying this, and I've tried lots of things. Sorry for bringing my noobie questions to the forum. :)
View attachment 189932
Download Doublecad.
In InkScape, save the svg file.
Open DoubleCad and open the svg., save as a DXF.
Save the file with the name that doublecad assigns. Usually, FILENAMEuntitled. In file explorer you can change the name to whatever you want.