Cutting foam sheets... with a needle!

[moebeast]

That's right!!!! Moebeast... you took your MPCNC foam cutter system to FliteFest again??? And offered cutting services to a plethora of interested RC folks??? Goodness, it's been a year already??? I/we would love to hear of your experiences and get a report on how things went.

Without doubt, you've got to be one of the bravest and most prolific needle cutter users out there... and I see you're still using the needle cutter in its most basic configuration! How did it hold up? Were you as busy as last year?

Nice remix on the cutter BTW... thanks for doing it. -- David

It worked great for the most part. My needle I used since last year finally broke at midnight Friday. It was running practically non-stop for 8 hrs Thursday and 14 hrs Friday. On Saturday, I broke three times between 9 am and 2 am. There was one break on Sunday. I must have had last year's wire bent perfectly. Every break was at the bearing.

The only other issue was my control box was acting a little glitchy at times. When I turned the knob to scroll through the files, the list would disappear.

I was not having to re-zero between cuts as long as the machine stayed on. The vacuum made the set up very quick and easy.

I was much busier this year probably since I was the only one there cutting and I had more files ready. I was letting people write their name and what they wanted on the foam they provided and leave it with me. I ended up with more than I could cut. Also, since Adam's didn't sponsor this year, there was a very limited supply of free foam. This led to kids coming by and grabbing foam out of my to be cut pile. Someone even took a Simple Cub (4 sheets) that had "Rogers Family" written on each sheet.

If I do it again, I think I'll go back to a limited selection of single sheet designs and give them out as they are cut. Or, add some enhancement so it can be self service (with a credit card reader ;-) ). I will also add tabs so people can carry away without a trail of parts behind them.

I also should have made up cards or fliers with links to this thread, Jason's Instructible, and Ryan's site. It would have saved some writing, and many others that just watched for a few minutes may have gotten the information.

Several guys had seen this thread and said they were definitely going forward after seeing it in person.

 

[dkj4linux]

It worked great for the most part. My needle I used since last year finally broke at midnight Friday. It was running practically non-stop for 8 hrs Thursday and 14 hrs Friday. On Saturday, I broke three times between 9 am and 2 am. There was one break on Sunday. I must have had last year's wire bent perfectly. Every break was at the bearing.

The only other issue was my control box was acting a little glitchy at times. When I turned the knob to scroll through the files, the list would disappear.

I was not having to re-zero between cuts as long as the machine stayed on. The vacuum made the set up very quick and easy.

I was much busier this year probably since I was the only one there cutting and I had more files ready. I was letting people write their name and what they wanted on the foam they provided and leave it with me. I ended up with more than I could cut. Also, since Adam's didn't sponsor this year, there was a very limited supply of free foam. This led to kids coming by and grabbing foam out of my to be cut pile. Someone even took a Simple Cub (4 sheets) that had "Rogers Family" written on each sheet.

If I do it again, I think I'll go back to a limited selection of single sheet designs and give them out as they are cut. Or, add some enhancement so it can be self service (with a credit card reader ;-) ). I will also add tabs so people can carry away without a trail of parts behind them.

I also should have made up cards or fliers with links to this thread, Jason's Instructible, and Ryan's site. It would have saved some writing, and many others that just watched for a few minutes may have gotten the information.

Several guys had seen this thread and said they were definitely going forward after seeing it in person.

Thank you, Mark, for the report from FliteFest. Sounds like you've lacked practice making needles though... a unique disadvantage with having your "original" needle last so long If you're not already, I'd suggest using jeweler's round-nose pliers to form those bends in your music-wire. It's too easy IMHO for the sharp edges on common needle nose pliers to nick/stress the high-quality steel of the needle, especially in a sharp bend.

And... WOW! That's a lot of cutting... even with all the needle breaks. I wonder what happened to those guys from last year that brought their rotary-bit machines and cut planes for folks? And it's a shame about the foam "shortage" and pilfering that was going on.

That was pretty generous/ambitious of you to do all the custom orders and multi-sheet designs. I know you want to do it for folks but, as you saw, that can really turn into a lot of pressure/work... especially if you start fighting balky equipment. I think your plan for a limited number of single-sheet designs and having a bunch of pre-printed cards/flyers for the future is a good one.

Secretly, I hope you are able to do it again next year. It's been such a great test of the MPCNC and needle cutter... and a truly remarkable display of perseverance, generosity, and talent on your part! I know people have to be impressed [I know I am!] to see a guy drag a relatively lightweight and inexpensive home-built machine out of his car/truck, quickly set it up, and then do such nice work almost non-stop for three or four days straight. Hopefully, over the next year, we can demonstrate that the near-straight line motion of the newer versions of the needle cutter results in longer needle life and improved cut quality... and get you set up for an even more successful trip next year!

Again... THANKS, MARK!

-- David

 

[jhitesma]

Dang, these little bearings are TOUGH. Trying to put a groove in one so I can attach a needle...mounted it up like David shows, took my dremel to it. And...pretty much just managed to take the chrome off and not much more.

Still spun it fast/hard enough to get hot enough that the screw got warm enough to start melting the flywheel. But after 5 minutes of going at it with the dremel I can't really feel a groove yet - just a slightly rough spot.

These cheap chinese motors may have had weak shafts, but apparently they did NOT skimp on the bearings!

 

[dkj4linux]

Dang, these little servos are TOUGH. Trying to put a groove in one so I can attach a needle...mounted it up like David shows, took my dremel to it. And...pretty much just managed to take the chrome off and not much more.

Still spun it fast/hard enough to get hot enough that the screw got warm enough to start melting the flywheel. But after 5 minutes of going at it with the dremel I can't really feel a groove yet - just a slightly rough spot.

These cheap chinese motors may have had weak shafts, but apparently they did NOT skimp on the bearings!

Jason,

It really doesn't take too much of the groove to do the job. But you shouldn't let the bearing spin up to full speed of the dremel... you'll overheat it and destroy it. I hold the cutting wheel at a slight angle to the bearing race and lightly touch it for just a moment, right in the center of the race, and then back off... never letting the bearing spin up too fast. Repeat touching, releasing, touching, releasing, etc... until a light scuff/groove appears in the center of the race. It really doesn't take too long and the bearing should never spin too fast or heat up significantly.

The cutting disc needs to be one suitable for cutting steel and hard materials... not just a little grinding wheel. Also, one fellow (I don't remember who...) lightly held a rubber band to the backside of the bearing race to provide a little resistance while grooving it... allowing it to just slowly rotate when touching the cutting disc.

I'm sorry I wasn't as clear on these steps as I should have been...

 

[Michael9865]

I use engraving for all cuts.

If you are getting multiple passes to get full depth, check the settings on your tool in the tool list. There is a depth of cut setting. I set mine to 10mm.

I still haven't got the rapids to work straight out of Estlcam. I am using notepad find and replace to bump the G00 speed to 3500. It looks like it could go faster.

Moebeast,
I do engraving also.

I am cutting to full depth in one pass. It just does one pass per full and then another pass for half cut. On the Baby Baron it will cut the score cuts for the fuselage then got cut something else, then come back to cut one of the tabs, go cut something else, come back for another tab. That is what is driving me bonkers. Sorry that I was not clearer before.

I will get to editing if version 10 doesn't help, I will try Jhitesma's suggestion of upgrading first.

Jhitesma & David,
Thank you! I will look into version 10. I will try the "seesaw" method. LOL

all,
I am so thankful for this community. You guys are so helpful. Thank you all!

 

[jhitesma]

I started out going gentle and easy on the bearing as suggested...but it just didn't seem to be leaving much of a mark even...so I started using more pressure and more time. Eventually did get a scuffed surface but not a groove like in David's photos.

Anyway...I have to do it again. Yesterday was one of those days when I apparently should not have even attempted anything

I started prepping my new flywheel. It did not go well. Even though the support material came out easily The M2 screws didn't want to go in...so I had to drill them out a little...and then it turned out that they weren't quite long enough. Then all my 1.5mm allen wrenches started spinning in them with almost no pressure - those tiny screws are finicky. Finally go the M2 screws in and playing nice and then it didn't want to seat all the way on the motor. I didn't modify that part of the print so no clue why it didn't want to fit this time. Bit of work with a blade and got it to go on eventually but never fit quite as well as the previous flywheel. Then tried to mount up the bearings and the new snugger holes are just a bit too snug. Grrr. So...I went back to the flywheel I had mocked up previously but felt the bearing holes were just a hair too loose on. Figured it would be ok at least for a quick test.



I need to find some non-allen head m2 screws....looks like Amazon has a nice set https://www.amazon.com/dp/B01FTI8TM8/ref=cm_sw_r_cp_dp_T2_TxICzbH15V8YW But the heads look kind of big....hmm...those are IBM notebook screws...I think I have an old thinkpad stashed away somehwere...if not I know I've got an old Dell and HP that aren't usable as computers anymore...maybe I can scrounge some suitable screws off them tonight...

Whipped up a quick guide mount and all was looking pretty good:



Closer inspection shows that my bumps for the guide bearings are indeed just a hair too tall. I had assumed the needle would come off the center of the flywheel bearing...but it actually sits somewhat off due to the coils wrapped around the bearing - so removing the washers from behind the lower bearings would help...but then it wouldn't line up with the guide as well. So I think a second washer behind the flywheel bearing or making the flywheel just a tiny bit thicker would be a better way to go:



But turning it by hand action felt and looked great! I was getting hyped!

So...bit of work to balance the flywheel. I don't have a grains scale...so I just went for the prop balancer style method. Grabbed an M3 screw that was a bit shorter than the one that holds the bearing and put it in the furthest hole on the basis of "That looks about right" - put the flywheel on a shaft and gave it a few spins...and it sure seems to be pretty well balanced - though without the actual needle so maybe a hair more on the counterweight in practice will be needed.

Put power to it (without the needle) to see how it felt...and...motor just juddered Crud. Apparently in all my messing around the tonight one of the motor wires got damaged. It will run if I hold the wires "just right" though and I have a couple more of these motors just have to dig one out. For now got it to spin up...and yeah that feels pretty darn smooth.

So mounted it in the machine and tried to get it going. These motors have a nice shiny chrome bell so I had just put some black electrical tape around most of it leaving one patch of shiny - which I figured would make the optical tach happy. Nope. Got all kinds of crazy nonsensical readings. I know this thing is doing more than 22RPM and highly doubt it's doing 10k at less than 1/4 "throttle" Ok, piece of the reflective tape that came with the tach on the shiny spot...and...we're getting readings that seem ok again.

Oddly enough...much like my old one it runs really quiet and smooth at around 5k, and at about 8k. But at 6k where I usually run it there's some kind of harmonic vibration that isn't great. 5k doesn't make a good cut though, and the old one would blow the crank out and cause the needle to come off at 8k. I'm hoping this one will be happier at those higher RPM's mostly so it will run smoother but also because I'm hoping it will let me run a slightly faster feedrate on cuts.

Anyway...got a feel for where my speed needs to be...things seem good...let's put the needle back on and fire it up!

Ok...so far so good...all looks good to my eyeballs. Sounds pretty good. Let's try cutting a bit of foam! I didn't actually do any cuts, just grabbed a scrap of foam and held it under the guide and moved the foam instead of moving the tool. It was working...then...the needle came off. Grrr. And before I could reach the servo tester to turn it off...is that...is that PLA I smell? BOOM! Crud.



Apparently even at about 6k somehow the flywheel bearing was running fast enough to build up enough heat to heat up the mounting screw enough to melt the PLA. No clue where the screw, washer or my bearing are - I looked for them but they're MIA so can't fully post-mortem the bearing. I'm guessing my attempt to groove the bearing resulted in some damage to it that caused it to run hot. Either that or when the needle came off it got stuck behind the bearing and was rubbing creating heat...but it sure looks like it was the screw that got hot.

I'm half tempted to order up one of these - it's 10mm OD instead of 8 but is pre-grooved:
http://www.vxb.com/623VV-V-Groove-Guide-Miniature-V-Bearing-p/623vv.htm

Just don't want to spend $5 on one silly little bearing...and they only offer UPS shipping so no way I'm spending $14 to ship a $5 bearing They are on Amazon for $6.55 with free shipping though: https://www.amazon.com/dp/B00TKYW7MG/ref=cm_sw_r_cp_dp_T2_0tICzbNEBBS80 Kind of tempting.....

4x13x6 v-groove bearings are apparently very common and cheap (I can get 10 for $3 with free shipping from China) but seem a bit big for this. (that's 4mm ID, 13mm OD, 6mm deep) though as deep as the groove on them is the od at the bottom of the groove is probably pretty close to 6mm. (apparently it's 9.6mm at the base of the groove according to one spec sheet I found.)

I was actually looking for flanged 3x8x4 bearings but found those grooved ones instead...a 8mm version of the 623vv would be perfect...but doesn't seem to exist. And VXB's photo of the 623vv is somewhat different than the others I'm seeing - VXB's is grooved - other are a more pronounced V shape....hmm.

Looks like F693-ZZ is a 3mm ID 8mm OD 4mm thick flanged bearing...two of those together could make a nice needle retainer that doesnt' need manual grooving....but that's two bearings so more weight. They are available 10 for <$5 on ebay though....I have a few spare flanged bearings from my 3d printer upgrades...I need to check what size they are....


But the big question is...why did that bearing run so hot that it melted the flywheel. It was only running for a minute maybe two at most. And shouldn't have been running too fast or anything, even if the tach wasn't quite right the motor kv and voltage I was at should have had me very conservative on speed at the "throttle" setting I was at - About a 2 on my servo tester... 850kv motor on 13.8v power supply should = 11,730RPM at full throttle. And without the flywheel I was seeing about 11k at full throttle and 6k at the 2 setting I was using. (note this was just hooked to my cheap radio shack supply for testing - eventually I plan on powering it off the same 12v PC supply I use to power the MPCNC so will actually be running on 12v not 13.8 so theoretical max RPM will be 10,200 and I'll hopefully move the sweet spot closer to mid-throttle.)

 

[dkj4linux]

I don't know what to tell you, Jason... can't tell from the pictures enough to say for sure.

Here's what an overheated bearing looks like. I think this one (from one of my early brushed motor cutters) was maybe overheated while grooving and then run at relatively high cutting speeds until it finally came apart... no clue where the balls went (burnt up?). The mounting screw and washer also heated up to the point that the washer pretty well embedded in the plastic...





It's quite important that the washer (or raised area supporting the inner race) not drag on the outer race as well. I can't tell from the pictures much about those raised areas... are they really contacting the inner race only and is the bearing really turning freely? Those bearings are so small I haven't even tried to print support for them... but instead used a M3 washer/lockwasher combo to space them from the flywheel face.

Obviously everything must turn freely and the bearing needs to be in good shape. And apparently not all bearings are created equal. I've had some groove a bit better than others... but even the hardest ones have accepted at least a shallow groove and been perfectly fine in use. -- David

 

[jhitesma]

Yeah all the bearings spin freely, I have m3 washers behind them and they just barely clear the outer race. At least they seem to spin freely and don't seem to be dragging.

The guide bearings seem fine, and were still spinning freely even after the failure.

The flywheel bearing definitely came loose due to heat. Just not sure why that bearing generated so much heat so quickly. I mean the motors they came out of were 2300kv motors running on 3S and never got warm. So they should have handled MUCH higher RPM's than what it was subjected to on the cutter. And the bearing seemed free turning.

It's hard to tell in the photo but looking at the flywheel in person it's pretty obvious that the screw holding the bearing got hot and melted the threads out of the flywheel. I had printed the flywheel with 4 perimeters and 25% infill - the 4 perimiters should give almost 2mm of solid plastic around each hole. (.48mm extrusion width X 4 - 1.92mm) I thought about bumping it up to 5 perimeters but that seemed like overkill.

The only way I can see that screw getting hot is from the bearing getting hot. Maybe the bearing was spinning on the screw...I'm just not sure.

I may try printing the flywheel in ABS or PETG just to give it a bit more temperature resilience...but really it shouldn't be getting that hot.

I'll try with a new bearing and a new flywheel tonight.

I'm also playing in Onshape trying to do the "final" cutter body I've been picturing in my mind...but...trying to make it happen is exposing the limits of my Onshape knowledge!



I can picture what I want in my head...just can't seem to figure out how to get all the compound angles right in onshape

That's getting close...but ends of the tops of the support arms should be parallel with the bottom of the base...and figuring out how to extrude the bearing support is proving VERY difficult.

Pretty sure I need to use some lofts instead of extrudes to pull of what I have in mind...just not sure how to draw the sketches I need for the lofts I have in mind.

File is here if anyone wants to take a look at it:
https://cad.onshape.com/documents/c...3741c3e356a0e4fafa/e/0fb4e335198df1edfc9dffd7

 

[jhitesma]

It's alive! Only ran it for a few minutes but no meltdowns or booms so far.



Started the night with a few minutes in onshape to modify the flywheel. Opened up the m2 holes a tiny bit, made their countersinks a bit deeper (they're now 4mm deep, half the depth of the flywheel itself,) made the opening that goes over the "nose" of the motor a hair wider, and adjusted the spacing of the bearing/counterweight holes. I moved the inner most holes out a little bit so they didn't interfere with the nose of the motor anymore - then adjusted the distance between them to 4mm so they fit better. This gives a bit more stroke on the shortest position than David's (his is 6mm out so 12mm of stroke, mine is 7mm so 14mm stroke) which I don't really need...but had to do to get hole away from the nose hole.

While that was printing I went out to my shop and took a look at the motor. Found out that the problem was cold solder joints between the wires and the windings - not broken windings as I had feared. So rather than dig out another motor I fired up the soldering iron and re-attached the wires:



Once I had those on I noticed my FT allen driver that came with the B power pack I bought at Flite Fest 2015....hey...that looks like..it is...1.5mm! And it's a much nicer fit in these m2 screws than any of my allen keys! So once my flywheel was done printing I brought it out...and with the FT driver was able to install the m2 screws MUCH easier. The fit on the nose of the motor was still a bit tight...but now I was able to use the screws to pull the flywheel on so it didn't matter as much. Sweet!

Did a bit of looking for the bearing that went flying yesterday....but no sign of it. Did find the screw though. And I have two more bearings. Though one is really iffy looking - only shielded on one side and doesn't appear to have a ball retainer so most of the balls are on one side...don't think I'll be using that one. (IIRC it came out of a friends sunnysky 2204 on his warp quad back when those things first came out a few years ago.) I had one more bearing on hand...it's missing a shield on one side...but still has a ball retainer and looked good - the shield just got damaged as I was extracting it from a motor.

I took a closer look at the failed flywheel from last night...and...hmmm. It does appear to be melted the entire 8mm of a bearing. I wonder.....put a new M3 washer against the new bearing...it does come pretty close to the outer race. Good thing I also picked up some M2.5 washers while I was at the store on Wednesday! Had to drill out the center a little bit to get it over a M3 screw...but clears the outer race just fine now for sure.

I decided to throw caution to the wind and forgo grooving my bearing. Instead I gave the coil on the needle a bit tighter of a twist and crossed my fingers. Installed it on the cutter...and...

It worked. It's not balanced perfectly yet...I need to do some fine tuning...but it's already way smoother and quieter than my old cutter. The main reason it's noisy right now is the slightly loose fit in the hicwic mount (I never did adjust my design...my design matches the hicwic stl's perfectly so I'm not sure why it comes out a little loose...but I'm hesitant to change it. I suspect once I put the screws in to attach it to the mount it will be nice and solid again.)

Video of it in action is uploading - but won't be done before I go to sleep.

So here's a little shot of my desk which was almost clean on Monday:



I'm rather surprised that the considerably more complex cutter body only took me 2 prints to get a usable version - while the simpler looking flywheel has taken me at least 4 revisions. At least it's a lot quicker to print!

Oh...and so far doesn't look like I can eliminate the piece of wood Even after just a few short minutes and with the guide bearings the mig tip was warmer to the touch than the inflation needles usually are. The bearings are all cool to the touch (wish I had one of those FLIR cams to see how cool/warm!) but once again the MIG tip is getting warm. However - that was a test without oiled cotton...I added oiled cotton for a second test which lasted longer (so I could record the video) and that time the tip stayed quite a bit cooler....but if I eliminate the wood there's less room for cotton/oil so doesn't look like I'll be eliminating the wood anytime too soon.

Can't wait to give it a go on a sheet of foam tomorrow!

 

[jhitesma]

Well, late night posting got messed up apparently...here's the actual desk photo:


Guess I can't tell thumbnails apart when I'm tired anymore

And here's the test video:

Little more balancing on the flywheel (I haven't even put it on a balancer rig yet - just eyeballed it), put in the screws to lock in the QC mount...and should be ready to cut some foam!

Think I'm going to make a few adjustments on my gcode as well. I'm running my rapids way slower than the machine can handle and speeding those up will save some time. Also going to speed up my Z moves since this thing can plunge as quick as the machine can move.

But...I also want to get Marlin upgraded on the machine before I go too far because the goofiness in RC6 when re-setting the home position is a major bummer right now. And I want to change it so the steppers don't time out - and add a menu option to enable steppers (there's currently a disable option but no enable.) That way I can square the gantry and power up the steppers to lock the machine square easier.

But...have to do some family chores first

 

[dkj4linux]

That really looks nice, Jason.

A couple of observations...

You may find the needle flex to one side a bit greater than the other with the needle shaft coming off the bearing at a tangent as you've shown. Use a jeweler's round-tip pliers to bend the shaft to align with the center of the bearing... may not be essential to operation in the short term but probably would help for needle longevity.

I think you're using a slightly larger diameter needle than I do... I use 0.025" wire. I'm wondering if the MIG-tip heating you are seeing is from a tighter fit, needle in guide. While the inflation needle is maybe a bit too sloppy for absolute best cut accuracy, you may want to adjust the MIG-tip bore and needle diameter ratio for just a bit of more slop. Hopefully the friction will be reduced enough to eventually do away with the wooden platform and still result in improved cut accuracy over the inflation needle.

Neither of these things are show-stoppers of course but anything that might improve needle life and result in smoother operation is, at this point in the cutter's development, important. I'd love to see Mark (Moebeast) go to FliteFest next year and be able to cut continuously for 3-4 days without any needle issues at all. I'm so impressed he's done so well with the original cutter, I can't help but believe one of the newer versions would be even better

-- David

 

[jhitesma]

That really looks nice, Jason.

A couple of observations...

Thanks, I'm super hyped with it so far. In fact I'm shirking a few responsibilities (Should be cleaning the pool right now) and giving it a quick test...even though my better judgement says to do a bit of fine tuning first I had to see how it would do on a full sheet. And it did GREAT! But more on that after I reply to your feedback

You may find the needle flex to one side a bit greater than the other with the needle shaft coming off the bearing at a tangent as you've shown. Use a jeweler's round-tip pliers to bend the shaft to align with the center of the bearing... may not be essential to operation in the short term but probably would help for needle longevity.

Yeah, In fact I just did a short video at 60fps so I can slow it down and take a close look at how things are doing. I was debating whether it would be better to try and put a bend in like that to equalize the deflection - or if putting in a bend (even with round tip pliers) would create more stress in the needle and weaken it more than the offset deflection. I'm also debating which side of the bearing the needle should come off of vs. which way the flywheel turns and which way the wrap of the needle coils are....but the coffee is just starting to kick in so I'm not quite ready to think too deeply on those issues just yet

I think you're using a slightly larger diameter needle than I do... I use 0.025" wire. I'm wondering if the MIG-tip heating you are seeing is from a tighter fit, needle in guide. While the inflation needle is maybe a bit too sloppy for absolute best cut accuracy, you may want to adjust the MIG-tip bore and needle diameter ratio for just a bit of more slop. Hopefully the friction will be reduced enough to eventually do away with the wooden platform and still result in improved cut accuracy over the inflation needle.

I actually switched to thinner wire on this one. My old one was ~0.8mm and the new one is ~0.6mm...in fact let me check...the label on the new wire bundle is .025"/0.64mm so same as you're using - the old wire doesn't have it's label anymore but was the next size up in the K&S rack so according to their website 0.032" (metric not specified but a conversion say 0.812mm)

I'm using a 0.30" MIG tip currently, but could try a 0.35" as well as I have both. I also have some .015"/.38mm wire I could try - it seems way too flimsy to work but I bought it because a few hundred pages ago for so someone posted that they were using that size successfully and I thought it might be worth trying (lighter/thinner).

I just ran a full sheet..and at the end of cutting the mig tip was warm but not hot. Not sure I'd trust it in PLA...PETG or ABS it would probably be ok though. Apparently remembering to add the cotton/oil makes a big difference since it was noticeably cooler after 20 minutes of actual cutting than it was after 2 minutes of dry running without the oiler.

Neither of these things are show-stoppers of course but anything that might improve needle life and result in smoother operation is, at this point in the cutter's development, important. I'd love to see Mark (Moebeast) go to FliteFest next year and be able to cut continuously for 3-4 days without any needle issues at all. I'm so impressed he's done so well with the original cutter, I can't help but believe one of the newer versions would be even better

I'm REALLY happy with the improvements so far. And I already know I've got quite a bit of room for improvement. Like I said I haven't even checked the balance yet so I'm sure I can smooth it out quite a bit. But already the noise reduction is remarkable. I don't NEED my hearing protectors in there with it anymore - the needle puncturing the foam is markably louder than the cutter itself for the first time finally

I tried re-cutting one of the failures from last weekend - tossed on the sheet of foam where the guide came loose and let it cut with the new cutter. I didn't try to line it up to the same starting point but somehow got very close just by luck:



It's hard to tell from the photo...but the left cut is with the new cutter and thinner wire....and is MUCH cleaner and less kerf than with the old setup! I had my Z a bit off on this test (too high so I didn't get quite enough depth) since it was just a quick test...but the cuts came out great. One thing I need to adjust still is that the needle itself is too long...it retracts almost all the way into the guide but there's still a tiny tiny bit sticking out...and it's just way longer than I need, I can trim 3-4mm off it easily which will leave less of it sticking out of the guide and more accuracy.

After a few cuts I turned the feedrate up to 120%. It sped up noticeably and cuts still seemed just as good. So I got braver still and turned it up to 150%...I could see the needle bending below the guide just a bit at this speed...(I was running at about 7500rpm) but like I just said the needle still needs to be trimmed to length...and once I final balance the flywheel I believe this will easily handle 10k RPM which should smooth things out a bit more at the higher speed. Even without those improvements though the cuts look a lot better than what I was getting with the old setup already...and the same cut that took 33 minutes last week only took 20 just now.

So i'm REALLY happy and excited even though I still have a decent list of little adjustments that should give some more improvements. Oh...and I also picked up some white LED's that I plan on mounting to the bottom of the cutter so I can see it cut easier now That's the other reason I wanted to switch to a motor that will run on 12v instead of 7.4v...with this translucent PLA I"m also half tempted to put a strip of LED's inside the cutter to make it glow...but that might be overkill

Ok...now I really do have to go clean the pool before my daughter gets back and wants to go for a swim!

 

[moebeast]

I also could not resist playing today. I made a little needle holder to try out. Every needle break I've had was at the bend under the bearing. This piece holds the wire perpendicular to the bearing with no fancy bending. Just one small 90 degree bend which is captured by the bearing. This one is for a 10mm bearing and .030" wire. It may be beefier than necessary. I used a counter balance screw .5" longer than my original and it is fairly well balanced. I had to press it on the bearing, so it is not making it easy to change, unless I decide the bearings are disposable. I also switched back to a .035" MIG tip.



I added the holder .stl to my mount thing.
https://www.thingiverse.com/thing:2429886

 

[jhitesma]

Neat idea moebeast! Curious to see how it works out. Was also curious what size wire/mig tip you were using. Do you know what RPM's you're running yours at? I'm wondering how warm your mig gets and why mine seems to run warmer than others

Also, was wondering what kind of speeds you're using in your gcode files. With all the cutting you do at FF I'm kind of assuming you run faster than I do since I doubt 30 minutes per sheet is very tolerable at an event like that.

 

[moebeast]

Neat idea moebeast! Curious to see how it works out. Was also curious what size wire/mig tip you were using. Do you know what RPM's you're running yours at? I'm wondering how warm your mig gets and why mine seems to run warmer than others

Also, was wondering what kind of speeds you're using in your gcode files. With all the cutting you do at FF I'm kind of assuming you run faster than I do since I doubt 30 minutes per sheet is very tolerable at an event like that.

Jason,
I don't have a tachometer, so I usually run on sound. It is a 1000 kV motor, running off the computer power supply at nominal 12 V and servo tester set at 4. I am guessing it is around 6k rpm.
I drilled out the tip at the entrance to try and reduce friction. After adding the oiled cotton, it seems to run cooler than before, but I haven't run a cut yet.

I've been cutting at 800 mm/s and rapids at 3500 mm/s. Both could be bumped up. Most cuts take 13-18 minutes.

I'll go cut a new perf board for my bed and see how it works.

 

[jhitesma]

I'm LOVING the new cutter! Going to have to put together the files and get them up on thingiverse later this weekend. Still a few little things I wouldn't mind tweaking...but they're minor enough I may not get to them

First thing I did was try David's suggestion of putting a small bend in the needle right under the bearing:



As predicted it evened up the deflection:



What I didn't expect was that it also eliminated quite a bit of the remaining vibrations! Big difference in how smoothly it runs which I was not expecting - super happy I gave it the bend.

I also trimmed a few mm off the end of the needle and re-sharpened it. It's still a bit longer than I need but I didn't have a ruler handy so I'm sneaking up on the length.

I also gave the flywheel a better balance. I took it off the motor and attached the needle - then put the whole thing on a shaft...and sure enough the bearing/needle always hung at the bottom. Swapped my balance screw for a slightly longer one and added 2 washers under it:




With that little adjustment the flywheel now balances very evenly. I can put it in any position and it will stay there with no one spot falling to the bottom.

Spun it up...and it's super smooth. There's still a bit of vibration at the "nose" of the cutter but overall it's way more stable than my old one. I kind of wonder if putting the solid sides/bottom back on the cutter would stiffen it up and stop even more of the vibration at the guide...but I'm in no big rush to print a new one to find out...maybe I will at some point but I'd rather do more cutting than revising at this point

Before I put it back on I did one more little upgrade. As I threatened I added a small strip of 3 LED's:



I ran the wires up the side/back of the cutter using a few drops of hot glue to hold it in position:


I soldered it right to the power connections on the ESC - so as long as the cutter has power it's lit:


I want to add 3 more LED's up front to light the actual point being cut better and eliminate some shadows...but that will be trickier since I can't just stick a pre-made strip on there - I'll have to mount individual LED's with drops of super glue and solder them together to pull that off. Project for an evening I'm feeling like dealing with something fiddly.

This is the other change I made...I added a second set of these: https://www.thingiverse.com/thing:1755510 so I can position the machine at my desired home without having to re-position it and reset the home:


Now I just push it against those to find "home" and position my work accordingly. Then make sure it's pressed against them before I start the program. Eventually I'll upgrade the firmware and go with my plan to keep the steppers powered more often...but this is a good temporary solution that helps make sure it's square.

So how's it cut? GREAT! I upped my rapids to 2500mm/min and my feed rate to 20mm/s I cut a full baby bugatti in 27 minutes:



The parts aren't falling out on their own...but do pop-out fairly easily. I saw the needle dragging just a bit so I need to try either upping the RPM of the cutter or slow the feed rate back down. I think I'm going to try upping the RPM's a bit since I like the faster speed and suspect this new cutter can handle the higher speed.

I recorded that cut with the same camera setup I used to record the last full cut video so hopefully it will show the sound and speed difference. It's rendering now, then has to upload so I'll link it in later tonight when it's ready.

Thanks again to everyone who's contributed to this project. I can't get over how much better this keeps getting and love the way so many are contributing such great input to what David started!

 

[jhitesma]

Jason,
I've been cutting at 800 mm/s and rapids at 3500 mm/s. Both could be bumped up. Most cuts take 13-18 minutes.

Oh wow! That's a lot faster than I've been going! I was using 15mm/s for cuts and 1200mm/min for rapids. I just bumped it up to 20mm/s for cuts and 2500mm/min for rapids (at least I think that's what I'm using...it seems that estlcam is using mm/min on the setup page but mm/sec in the tool list.)

I'll have to try those speeds and see how it does. I noticed I'm not quite getting a full cut on the bottom paper at these higher speeds so was going to speed up my cutter head a bit more...but if you're only running 6k and cutting at 800mm/s I'm wondering if maybe I should use a bit more depth instead.

If I could get it down to ~15 per sheet I'd be SUPER hyped!

 

[dkj4linux]

Wow! You guys are making great progress with the cutter. I really like the idea of the printed needle/bearing fastener-thingie, Moebeast... and not having to do any fancy bending of the needle or grooving of the bearing. The minute amount of plastic it takes can't possible weigh much... maybe even less than the couple of turns of wire it "replaces"?

And I really like the LED lighting, Jason... my lighting is so bad I often times feel I'm working "blind". That would help immensely

I'm not set up to do any full-sheet DTFB cutting at this time... but you guys have really piqued my interest in building a cutter incorporating some/all of the ideas you've all come up with. I've got a couple of 2'x2' machines I could mount it on for testing and cutting smaller items... and one at least already has the Hicwic mount.

Hopefully you guys will apply a few more tweaks and have this really dialed in before I try building my own. In addition to improved reliability, I'm real excited about the possibility of trying (once again!) to up the feeds/speeds and reduce the time it takes to cut full sheets of plane parts. I doubt I'll personally be building too many planes in the future but I do love building/developing tools that allow others to do so. I would love to see some of you more prolific builders building/flying/showing off your needle-cut creations... and sharing your work, and generating interest, with an even broader audience than we do now.

Well done, guys! :applause::applause::applause:

-- David

 

[moebeast]

So the needle holder was too big and the wire snapped where it enters the plastic. I made one much smaller that seems to be working. I updated the Thingiverse file with the smaller one.



Here is the rendering of the back side so you can see where the wire comes out and the 90 degree bend is held by the bearing.

 

[moebeast]

Jason,
...
I've been cutting at 800 mm/s and rapids at 3500 mm/s. Both could be bumped up. Most cuts take 13-18 minutes.

Whoa! I meant to say 800 mm/min! Which is slower than your 15 mm/s.