New disk design for FED3

[Jordyn Czarny]

Hi all! I'm a grad student in the Kravitz lab and we have been testing a new disk design for FED3 that is easier to install and remove for cleaning. Importantly, there is no longer a melty step to install the brass insert! It takes ~2 minutes to update to the new disk, and it doesn't require disassembling FED3. Steps:

• Print the new disk (STL attached, TinkerCAD design here)
• Loosen the set screw and remove the old disk (requires a 1.5mm hex driver).
• Install a 5mm to 5mm Brass Shaft Coupler onto FED3 motor (secure with M3 set screw)
• Place the new disk on the brass coupler
• Secure the disk with an M3x6mm bolt

We've also recorded a short video documenting the process. Please post back if you try this, we'd love to get feedback from others on this new design!

[Alison Kreisler]

Is this new disk available for purchase? I'd love to replace ours but don't have easy 3D printing access. Thanks! 

[Lex Kravitz]

Hi Alison,

This part is not for sale, but you can print it at Shapeways.com (or any other commercial 3D printing site, Shapeways tends to be on the pricer side but in my experience has excellent quality control).  I'd recommend printing in Nylon PA12 on a MultiJet Fusion (MJF) printer - that usually produces great results.  I just uploaded it at Shapeways and they can do it for $10 plus shipping.

Also note that this part hasn't been extensively tested by many labs so please try it with a couple of your FEDs before you convert them all.  And if you do print and test it please write back here with your experience - it will help me tune things and make sure it's reliable.  Thanks!  -Lex

[David Mallet]

Hi Lex,

We have a few issues with some of the systems, and we are seeking out to you to hopefully find a solution. There is too much space between the disk and the rest of the device, creating a space where pellets can accumulate and block the system. This blocking happens also after thorough cleaning.

 

We have additionally tried replacing the disks. While this worked for some, for the others the problem continued. Do you think this new disk could be a solution for us? Or do you have any other recommendations?

Thank you for your help,

David

 

[Lex]

Hi David,

The new disk may help - I don't have a lot of testing data on it at the moment though (if anyone is using it please reply here!).

But it sounds like your disk is not seated correctly in the device - there should not be a gap between the disk and the housing.  When it's installed correctly you can push on the disk like the photo below and have no play at all. I recorded a video showing how to adjust the disk correctly.

If you follow the steps in the video and are still having trouble you may have an issue with the print itself - a small defect in the disk or housing can cause these issues.  Are you printing these parts yourself or buying the prints commercially?  Either way, you may want to try swapping to a new print for the pellet disk or housing and see if that fixes it.  Hope this helps, and if you try the new disk design please post back about your experience there as well!  

Best, -Lex

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[Alison Kreisler]

We have been trying the new disk design, too, in hopes of reducing jam frequency. The new disk, assuming it's printed well, is certainly easier to install well (with no space underneath), facilitating more regular, thorough cleaning out of pellet debris between sessions, which is necessary. However, it's VERY easy to install it imperfectly (with micro-space underneath), despite how easy it looks in the video, especially between researchers. I can confirm that this inconsistency is exacerbated by tiny differences between housings. We've been trying to print our own housing and, like Lex suggests, the quality is less consistent/more poor than the commercially available ones we got when we purchased FED3s fully assembled. We are trying one more housing batch printed in-house this/next week in hopes we can feel confident enough in the jamming rate to proceed. 

I'm fully prepared to have to consider ONLY buying commercially printed parts, despite it being rather unlikely that we can afford many :-/ 

Please continue to provide new tips for this, especially cheap ones!  

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[Joon Kim]

We use a slight variation of the new disk. The major difference is that the disc is mounted down onto the FED3 body, rather than from the side. This might help keep it flush against the housing to minimise gaps. 

See specific instructions on the coupler here: https://groups.google.com/g/fedforum/c/384D_mEeaPc

All our FEDs are now either using this disk variant or the mixer body (in link above). Overall I don't think this disk offers any improvements on the grinding issue, other than ease of use/installation and there is no need to buy the brass coupler. We still havent had any jamming with the mixer variant though. 

The lock-nut is crucial for the function of this disk and coupler variant. I've attached the STLs here for the disc part.