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  1. #1341

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    Quote Originally Posted by dkj4linux View Post
    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.

  2. #1342
    dkj4linux's Avatar
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    Quote Originally Posted by moebeast View Post
    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

  3. #1343
    Posted a thousand or more times jhitesma's Avatar
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    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!
    Last edited by jhitesma; Today at 04:27 PM.
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  4. #1344
    dkj4linux's Avatar
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    Quote Originally Posted by jhitesma View Post
    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...

  5. #1345

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    Quote Originally Posted by moebeast View Post
    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!
    Enjoy a blessed day!

  6. #1346
    Posted a thousand or more times jhitesma's Avatar
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    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 :P

    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.

    Click image for larger version. 

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    I need to find some non-allen head m2 screws....looks like Amazon has a nice set https://www.amazon.com/dp/B01FTI8TM8..._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:

    Click image for larger version. 

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    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:

    Click image for larger version. 

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    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.

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    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-Gu...ng-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 :P They are on Amazon for $6.55 with free shipping though: https://www.amazon.com/dp/B00TKYW7MG..._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.)
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