Re: Location of FED3 New Disk stl file

[Lex]

Thanks for noticing that the STL wasn't on the FED3 Github!  I'm attaching the STL to this reply, it's also now available here. 

Please see the original post for instructions on how to do the mod, including a video!

Best, -Lex

On Tue, Sep 23, 2025 at 6:31 PM Umika Vutukuri <umikav...@gmail.com> wrote:

Hello all,

I would like to update the FED3 disks with the new coupling disk released in May 2024. Where can I find the stl file to 3D print?

Thanks! 

Umika Vutukuri

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[Umika Vutukuri]

Hello all,

We are in the process of updating the FED3s with the new disk, but we have run into some issues. It appears the motor is not able to move the disk and complete the turns (maybe due to the weight). I have attempted to solve the issue to by supergluing the pieces together, this appears to work better but when I put in the pellets it stops working again. If anyone has any suggestions to fix the problem. Please let me know. Thank you.

[Lex]

If you can provide photos/videos of what you're experiencing that might help!  But I would say to be careful you don't push down too hard on the disk while securing it - that can increase the friction between the disk and the hopper bottom which can make it hard for the motor to turn.  Try gently placing the disk on before securing and see if that helps?

On Tue, Feb 10, 2026 at 5:36 PM Umika Vutukuri <umikav...@gmail.com> wrote:

Hello all,

We are in the process of updating the FED3s with the new disk, but we have run into some issues. It appears the motor is not able to move the disk and complete the turns (maybe due to the weight). I have attempted to solve the issue to by supergluing the pieces together, this appears to work better but when I put in the pellets it stops working again. If anyone has any suggestions to fix the problem. Please let me know. Thank you.

On Wednesday, September 24, 2025 at 9:24:40 AM UTC-5 lex.k...@gmail.com wrote:

Thanks for noticing that the STL wasn't on the FED3 Github!  I'm attaching the STL to this reply, it's also now available here. 

Please see the original post for instructions on how to do the mod, including a video!

Best, -Lex

On Tue, Sep 23, 2025 at 6:31 PM Umika Vutukuri <umikav...@gmail.com> wrote:

Hello all,

I would like to update the FED3 disks with the new coupling disk released in May 2024. Where can I find the stl file to 3D print?

Thanks! 

Umika Vutukuri

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[Umika Vutukuri]

Hello,

I have a link to the video for reference. We have also tried to gently place the disk, but that doesn't seem to work. Hopefully, you are able to view the video (for some reason, I am not able to directly attach videos to the forum). Ask suggestions would be appreciated. 

Link: https://files.fm/u/qk9vfkdu2j

Respectfully,

Umika Vutukuri

[Lex]

Thanks for the video Umika - from what I can see it sounds like the disk is touching the hopper housing somewhere and this is stopping it from turning. Here are some troubleshooting ideas:

- If you remove the disk, does the axle of the stepper motor rotate correctly?  

- If you take your disk off, can you see any evidence of where it might be rubbing on the housing?  You can often see where 3d parts are rubbing because the area that touches will look whiter and have signs of abrasion.  If you identify this, you can try manually filing down the disk in those areas to see if that fixes it.  Or you can re-print the disk scaled to 95% in your slicing software and see if that helps.

- If you print and install the original FED3 disk does it move correctly?

One challenge with 3D printed devices is that the tolerances of different printers can be quite different - we've experienced variances of >1mm when printing FED3 parts on different machines.  This is not a problem for 3D printed dragons, but it can be if you have moving parts that need to work together.  Once you track down what's causing the issue you can tweak the parts to get them dialed in for your printer. 

Have fun! -Lex

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[Umika Vutukuri]

Hello Dr. Kravitz,

Thanks for those tips, they've been helpful. But now, a new issue we are running into is that the disk pops off periodically, and we keep having jams. I'm not sure what exactly causes the disk to pop off, but when I look into the hopper, I see that there is a bunch of pellets and pellet powder under the disk, and the disk is completely detached from the motor. Any tips to keep the new disk from popping off? We've tried tightening the screw touching the motor, but that just keeps the disk from rotating.

Thanks,

Umika

[Matt Gaidica]

We are looking into tapping those motor shafts for similar reasons: https://neurotechhub.wustl.edu/threading-a-28-byj48-stepper-motor-shaft/

[Lex]

Thanks Matt!  Tapping the motor shaft would be ideal, but it's not the easiest thing to DIY unless you have the right tools.

Umika, you shouldn't need to tap the motor shaft though - we are literally running dozens of FED3s over months and the disk popping off hasn't been a big issue.  A few additional ideas:

1) If you put the pellet disk on a table, does it sit flat?  If it's warped like in the photo below it can allow pellets to slip underneath, where they will dislodge the disk over time.  It needs to sit perfectly flat.  You can either try bending the print until it's flat or just try a new disk.  

2) Are you printing them in house or are these professionally printed by OEPS?  If you are printing them yourself they need to be high quality.  If you provide photos of the prints I can advise on this.

3) Lastly, Have you viewed this video on how to clean and position the disk?   At ~3:00 I show how to make sure there's no space under the pellet disk that can allow pellets to get under it and cause it to dislodge over time.

I hope this helps, and sorry I can't give a definite fix, we just don't see this happening very often!

-Lex

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[Umika Vutukuri]

Hello Dr. Kravitz,

Thank you for the tips. I have a few photos of a recent jam that I'd like to share and get your input on. This time the disk was still very firmly secured but all the pellets had somehow been grinded to powder. You can see in the photos all the dust that got stuck under the disk. There was a lot more dust on top of the disk but I cleared it out. This is a very common issue for us, happens at least once a week unfortunately. I've removed the disk and it lays very flat on the table, no warping. We do print the parts in house. We use the Bambu X1-Carbon printer and PLA basic to print them. I've also attached a photo of how the disk sits in the hopper. We've made sure the disks are really secure and we don't feel any pull when we tug on the disk either. 

Any tips or ideas of what could be causing the jams? Thanks so much for your support. 

[Umika Vutukuri]

Since there's a cap in message size I'm attaching the remaining photos here: 

[Umika Vutukuri]

[Lex]

Ohhhhhhhhhh - you're using the new disk.  Have you tried with the original disk and set screw mount?  The original disk has been tested much more extensively than the new disk design.  I made the new design to get away from the set screw but to be honest we haven't used it as much, everyone in my lab just stuck using the old design because it works fine.

Also what kind of pellets are they? Are they crumbly?

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[James McCutcheon]

Also, probably not the main problem, but humidity can cause the pellets to turn to powder very quickly. We fix a small sachet of silica gel to the underside of the lid to prevent this

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