Cutting foam sheets... with a needle!

[RAGII]

Well in my quest to get my needle cutter working yesterday I managed to give myself a nice 2" cut on my hand. I went with Moebeast needle retainer on the bearing and was slowly ramping up the speed (while holding the cutter in my hand) when the needle must have bound up, bent and managed to come out of the guide. Now it was a nice weapon, caught my hand before I could cut the power. Not real bad, no stitches required, but did need gauze and tape to stop the bleeding.

In review (after reading Jason's article in fine detail) the washer I was using to space the bearing likely covered the outer raceway causing a bind which eventually led to the failure. I discovered that the extra shims that came with my Quad motors work perfectly for spacing. will make another attempt tonight, this time not holding it in my hand.

Jason,

Question for you if you are lurking. Do you have a design of you pre-guide bracket for the new MPCNC mount? The onshape file I found was for the quick change mount. My motor is different so the I need to modify the guide position which I did before I realized it was the quick change setup.

Thanks,

Rob

 

[dkj4linux]

Well in my quest to get my needle cutter working yesterday I managed to give myself a nice 2" cut on my hand. I went with Moebeast needle retainer on the bearing and was slowly ramping up the speed (while holding the cutter in my hand) when the needle must have bound up, bent and managed to come out of the guide. Now it was a nice weapon, caught my hand before I could cut the power. Not real bad, no stitches required, but did need gauze and tape to stop the bleeding.

In review (after reading Jason's article in fine detail) the washer I was using to space the bearing likely covered the outer raceway causing a bind which eventually led to the failure. I discovered that the extra shims that came with my Quad motors work perfectly for spacing. will make another attempt tonight, this time not holding it in my hand.

Jason,

Question for you if you are lurking. Do you have a design of you pre-guide bracket for the new MPCNC mount? The onshape file I found was for the quick change mount. My motor is different so the I need to modify the guide position which I did before I realized it was the quick change setup.

Thanks,

Rob

Ouch! Please be careful, Rob. This is intended to be a fun hobby... not dangerous work

Not sure even yet of which tool mount you are after but I think this one has the newest, standard MPCNC tool mount...

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

 

[RAGII]

David,

My dad always taught me no job is complete until a little blood is shed.

That is the tool mount I am looking for but I need the file I can manipulate as my motor to guide distance is different.

I got a lot closer to working today (this time running it attached to the tool mount ). I am currently using Moebeast's needle holder setup, but as soon as I got the RPM's where I think they needed to be the needle holder was thrown off. I noticed the needle was bent up pretty bad so I am not sure if the "flex" in the needle got too great that it pulled the needle out of the guide bending in and then getting thrown, or if it got bent after being thrown. It is a fair press fit on the bearing and I have not figured a good way to capture it to the wheel.

Rob

 

[jhitesma]

I'm here, just had what is probably the worst day of my life....but I'm here.

I do have a version of my file with the new style mount instead of the quick change, they're all in the same onshape document but there are multiple tabs and revisions. I think this should get you to it:

https://cad.onshape.com/documents/0...cb551c58564783c02f/e/0282404df574b68957c362e8

When I open it I see this version:

That's on the latest "Extra Length" branch and the "Cutter Body" part studio tab.


<personal tangent>

This is bad. I hope no one ever has to have a day like I just had. I'm not sure why I'm sharing but it seems to be helping me deal with it. If your'e not ready for some really deep personal pain please just stop reading now.

As for my day. I lost my wife this morning. She recently had surgery to remove a golf ball sized tumor on her thyroid that was found after a routine x-ray following a fairly minor car accident. The surgery was meant to be a 2 hour out patient procedure - and went perfect until they tried to wake her. At that point she stopped breathing and things got complicated. We spent a week in the ICU before they were able to get her off the ventilator, but once they did she started to recover quicker than expected. Last Monday they expected her to need 1-2 weeks of inpatient rehab - but by Tuesday she was passing all of her evaluations and cleared for release. She spent Wed near the hospital at her cousins house getting her strength up and had her follow up on Thursday where her surgeon said she was doing great. Wrote her a script for some speech therapy and PT to help her get back to 100% and she headed home (The surgery was at Mayo Clinic in Phoenix 3 hours from where we live in Yuma.) She got home and was doing amazing. She was happier than she had been in years and was overjoyed that she could swallow and breath freely again after years of having a lump the size of a golf ball lodged in her throat. I made her some of her favorite meals and we were getting excited about how much better life was going to be for her. She spent most of yesterday making cookies with our daughter. Then this morning she woke up at 2AM to go to the bathroom and collapsed at the foot of our bed. Still waiting on official word about what happened - but the doctor in the ER believes she had an embolism. Like that she was gone and it still doesn't feel real. Thankfully my parents are here since they came down from Ohio to help my wife with her recovery and they're being super supportive of me and my daughter. So things are pretty far from normal for me right now and I don't know when I'll be able to get back to any of my hobbies. But I'll probably still be lurking as I'd rather loose myself in building things than more destructive behavior when I need to escape from life for a bit.
</personal tangent>

 

[dkj4linux]

LOL! I must admit I shed blood with almost any worthwhile endeavor...

IIRC you have a Prusa I3 MK2S... what CAD are you most familiar with? Tinkercad and Onshape can both be used to manipulate STLs. Jason did an Onshape tutorial video -- using the needle cutter as the example -- that might be helpful...

 

[rockyboy]

So sorry for your loss Jason - heart breaking doesn't begin to cover it.

If there is any escape or silliness or comfort or listening shoulders or distraction we can provide (or anything else), your FT community of friends and I are here for you my friend.

 

[TEAJR66]

So sorry for your loss Jason - heart breaking doesn't begin to cover it.

If there is any escape or silliness or comfort or listening shoulders or distraction we can provide (or anything else), your FT community of friends and I are here for you my friend.

Same here Jason.
My condolences to you and your family.

 

[dkj4linux]

Oh, Jason... I am SO sorry for your loss.

My thoughts and prayers are with you and your daughter right now. May God's blessings be on you both.

 

[RAGII]

Jason, my thoughts and prayers are with you and your daughter. Please know that we are all here for you. Should you ever need a shoulder to lean, or just someone to listen let us know.

 

[randyrls]

Jason; I cannot image the pain that you feel. The death of a loved one is the most traumatic of life experiences. I pray for your healing and comfort. Try always to remember the good times.

 

[Michael9865]

Jason, I am so sorry for your loss. I will be praying for you all.

 

[jhitesma]

Thanks everyone. I didn't want to derail the thread - but just felt the need to share. My local RC friends have also been super supportive (as well as other friends) and it's blowing me away the number of people she touched who are reaching out to share their memories of her.

I really do hope to get back into some projects soon - but hard to say when I'll be able to do much actual cutting/building/flying.

 

[dkj4linux]

Not a derailment, Jason. I'm honored that you've chosen to share this deeply personal and incredibly difficult time with us. Obviously -- collectively -- our thoughts and prayers are with you in this incredibly difficult time. Please feel free to share, in this thread, whatever is on your heart, anytime, about anything, and know that our collective hearts are going out to you and your family. An extended family we are, here... and it is a privilege and a blessing to be able to voice our love and support for you and yours. Thank you.

 

[dkj4linux]

Watching some YT videos today, I was really attracted to a couple of pulse motors built from -- of all things -- fidget spinners. I really couldn't help thinking what potential an actual *flywheel* could have for a needle cutter.

And, as most of you know who keep up with this thread, Steve ("ironkane") has had great success using a large diameter (42mm?) 700KV motor and affixing the eccentric bearing directly to the motor bell. And it seems to work beautifully...

https://forum.flitetest.com/index.p...eets-with-a-needle.24251/page-104#post-416304.

My own early cutter used a CPU fan motor... and the plastic "bell" presented a flat surface that was perfect for mounting the eccentric bearing on a press-fit post... it worked like a champ and turned at about 4000 rpm but lacked the power/speed of more recent cutters

https://forum.flitetest.com/index.p...heets-with-a-needle.24251/page-98#post-395267

Then, we also have Shurakair's flywheel, which embeds the whole bearing in the flywheel and presents a simple. free-wheeling, post/crankpin on which to mount the needle... a far simpler and better needle-bearing connection

https://forum.flitetest.com/index.p...sheets-with-a-needle.24251/page-4#post-261510

So, with all these things in mind and not having the larger diameter motor that Steve has used, I decided to see if I could essentially replace the fidget spinner's central bearing with the bell of a little Blue Wonder brushless motor and create a "for real" flywheel that also embeds the cutter's eccentric bearing like Shur's... and uses pennies for the outer weights.

My thinking is the offset weight of the bearing and needle will be "swamped" by the momentum/inertia of the flywheel... and run smoothly without the need for balancing. I've not yet powered it up but I should be able to test it in the next day or two... if I can keep these pesky golf outings, that always seem to crop up at the most inopportune times, under control

I see a couple of things I want to change with the printed flywheel but this should allow me to test what I've got to see what else may be seen. I've got plenty of space for more pennies though I really want to stop short of any unmanageable gyroscopic effects that might show up. I suppose this idea, if it has merit, can be extended to almost any brushless motor (the cheaper the better) if you get the dimensions of the bell right. I'll also need to come up with a new cutter body/platform, as this flywheel is nearly 70mm in diameter, but that shouldn't present undue problems.

Any thoughts/comments/ideas? Am I all wet?

-- David

 

[quimney]

David,

I really like your new idea, it has a lot of merit. I used to work for a company that made equipment that could help you balance the rotors in large turbines used in power generation and petrochemical plants. We went to a lot of trouble to figure out where to put one extra bolt on a many ton chunk of steel to make it run perfectly.

I am afraid that imbalance is still imbalance no matter the size of the rotating mass but at the same time there is always a point of "good enough for what it's for". I anxiously await the results of your testing.

Here's a thought... since you know the weight of your bolt and bearing you could figure out what the radius should be for an extra penny or two 180 degrees away to offset the bearing/bolt weight to get back to balance. You could then simply resize the flywheel and place an extra penny in the hole opposite the bearing making it very close to balanced by design.

 

[TEAJR66]

Place another bearing in the opposite hole, you will only be off by the weight of the nut and bolt.

I like the radius offset idea of Quimney. With that technique in mind, you could make a series of overlapping holes radiating outward and test the position for the balance bearing.

 

[CMS_1961]

First of all, Jason I am so sorry for your loss. I have been reading and following this forum for a while and when I saw your post today it was truly sad. Prayers and thoughts to you and your daughter.

You guys (Jason and Thurmond) in the forum and videos inspired me to finally build a V1 - MPCNC machine. I built it 46 (X) by (33 (Y) and I have it just about done except for the electrical. I have a Mach3 setup from an old CNC engraver using a break out board and three microstepper drivers and 48V power supply I plan to use. From what I have been reading the 48 volts should be fine, I plan to limit the amps out of the microstepper drivers to about 2 amps or so. I will have three microstepper drivers; the X will drive two NEMA17 motors, the Y will drive two NEMA17 motors and of course the Z will drive one NEMA17. Just as a sanity check, I was wondering if this electrical setup sounds reasonable. I dont want to destroy the motors before I cut anything. Anyone recently build the MPCNC and use Mach3 with microstepper drivers and a break out board? Would you share your setup?? When I get this thing going I plan on using the needle cutter to cut DTFB.

 

[EDinCT]

Jason- So sorry for your loss. That is heartbreaking. I watched so many of your videos while building my MPCNC that I feel like I know you.

FT FOAM BOARD QUESTION-
I have my needle cutter dialed in using regular DTFB and its doing great. At one point I tried using ross FB but the needle cutter had a tough time with it and I was breaking a bunch of needles. Seemed like I couldn't do one sheet without breaking a needle.
I'd like to try a box of the Water resistant stuff from FT but I don't want to drop $50 just to find out my needle cutter can't handle it.
Anyone have any experience?

 

[ironkane]

Jason- So sorry for your loss. That is heartbreaking. I watched so many of your videos while building my MPCNC that I feel like I know you.

FT FOAM BOARD QUESTION-
I have my needle cutter dialed in using regular DTFB and its doing great. At one point I tried using ross FB but the needle cutter had a tough time with it and I was breaking a bunch of needles. Seemed like I couldn't do one sheet without breaking a needle.
I'd like to try a box of the Water resistant stuff from FT but I don't want to drop $50 just to find out my needle cutter can't handle it.
Anyone have any experience?

Jason, you and your family have my deepest condolences. That's one of the toughest things to bear.

I've burned through a 100 sheet case of the waterproof DTFB and it cuts best by far. Store it in the house. Too much time in the hot garage warped it all pretty bad. Vacuum table held it flat and the cut pieces were usable.

I love all the innovative designs. Seeing all the questions here about needle cutters, I took some close-ups of my K.I.S.S. design. Flite Test released the plans for the FT Edge. I've completed the Inkscape part of the process and hope to setup my cuts in Estlcam and cut up the last of my waterproof DTFB. Hoping to buy another case later. And I will find a place in the house to store it. Not bitter or anything

 

[EDinCT]

I cut the parts for the Edge the day after the plans were released. Fun build and it flies great. If I were to do it again I would re-enforce the motor box. after three flights mine is getting pretty spongy.... another reason why I'm looking at the water resistant stuff. I also added some sticks on the elevator.. one landing in tall grass and I wrinkled one side since the throws are so big and the leading edge hit the grass.