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Thread: Universal Hub

  1. #51
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    Time for this thread to make it back to the top.

    Today I went in and made a small improvement to the universal hub.

    These cartridges were redesigned to simplify universal access with many filament feed solutions. Original spool, external spool, or mini-spool are all supported with the universal hub efforts.

    One mode, the internal spool, requires removal of the spool itself from the cartridge to refill it. That one mode of operation requires the removal of the tube coming from the filament driver mechanism. If the barrel nut was in place, then the tube could not be removed... and as you know, I can't stand that barrel nut to begin with. So the solution is to have a snug fit of the tube in the bulkhead. This means the tube is just held in the driver and can easily be removed without removing the driver mechanism itself. This is doable without too much issue but you will find that these tubes will be drawn back onto the gears from time to time and gets some chew marks on them. This has not affected the performance but replacing the tube when you put a new spool in can slow you down a bit. Just to review, the tube wants to be really close to the gears so that feeding new filament doesn't just collapse the tube. It is inevitable that the ends will wear but the feed has always worked flawlessly.

    Another thing you will notice with stock tubing in any configuration, including the B2B universal hub, it squirms! Meaning that under pressure, it will deform changing pre-loading the filament. Not so bad considering this is what the printer was finally dialed to manage. The entire stock bowden tube stretches significantly during operation. We got in the way of that!

    Now to go to overdrive on the design side... a quick review of what could be done if you have the tools to do so.

    I really wanted to protect that feed functionality. However, a rigid tube from the driver's gears to the appropriate depth in the bulkhead won't let you assembly the cartridge. The two ingresses are simply too deep to deform the case making the connection. So I considered another solution:

    Driver mechanism with solid feed guide.

    21719_d.PNG

    The aluminum tube is a K&S aluminum tube #83060 often available at hobby shops and hardware stores. It is .1875" OD and a .049" wall thickness. This leaves a nice over-sized center ID of just over 2mm which matches the stock Teflon tubing. As a matter of fact, it easily passes the bicycle spoke test... and the threads on the end of the spokes can be used to ream and descale the center. This will help ensure that the ID doesn't collapse when you make the bends and smooths the ID. Making this a permanent member makes the ingress of the remaining tube more manageable by shortening the reach.

    The second part of the tube that is machined to 2.9mm to fit in the bulkhead. The depth into the bulkhead is .57". The mechanism side OD reduction is only about .18" long. Depending on the mechanism you use; machined V. cast, the ID may varies. I like the cast mechanism for this because their opening is nearly 1/8" where the machined version is only 2.9mm. Either will work, but the remaining wall thickness will be further reduced. Bends in the tube were accomplished with a small hobby vice. If the whole thing can be put in place and relaxed as shown below, you got everything lined up correctly. As a note; the thick part of the tube is 2.75" long. Add it up; .18+2.75+.57=3.5" total length before bending operations.

    Relaxed fit test:

    21719_e.PNG

    Just for fun I ran the lathe across the entire length. Obviously not required but it gives you options to thin things up if you prefer.

    Again, remember, we are trying to remove the tube to remove and replace the internal spool without removing the mechanism from the case. And... we are making sure that when we do remove the spool, we don't collapse the stock tubing because there simply is no way to remove the spool without risking damage to the PTFE feed tube.

    Closeup of "the system";

    21719_c.PNG

    Once you are ready to button up the system, you will deforming the case to plug the end of the tube into the mechanism's receiving hole. This is quite a bit easier than making sure the PTFE tubing is fully seated before putting the thicker tube over it and pushing on the snug bulkhead. in this case, the bulkhead doesn't need to be snug. This is a foolproof solution.

    Case deformation will let you plug this into the driver mechanism;

    21719_b.PNG

    There is the other benefit in the fact that you've just saved yourself 99mm of original PTFE tubing for B2B nozzle solutions.
    And the larger Teflon OD tubing can be used for many more circlips for the grooved bowden tube.

    More options is a good thing

    21719_a.PNG

    This is certainly not the only means to accomplish this. Bottom line, this is just another fiddly bit that can be accomplished with these cartridges. I've made something similar with brass tubing. With this 2-piece solution, the spool removal will be even easier. You can make the short tube by soldering some wire around the tube to keep it where you want it instead of machining something. The second, longer tube will be trapped and has no place to go once the cartridge is re-assembled. I suggest finding 3mm OD brass tubing since the 1/8" tubing has a larger ID meaning a much thinner wall to make it work. And of course, the small segment could be machined from solid stock without too much additional more effort.

    If you want to hybridize this solution, it is certainly possible. Consider the short piece for your mechanism in metal but the remaining tube to be the stock PTFE tubing with the heavier PTFE sleeve. In this case, the short intrusion on the mechanism side could pop the tubing out during printing and get stuck in a compromising condition. Instead, make the short insert with a counterbore on the exit end to receive the PTFE tubing (Dia 2.9mm). You can get another .20" of ingress this way.
    This longer PTFE tubing being flexible and the additional ingress depth is not a problem with assembly. The point of doing this is to prevent manage to the end of the tube so it doesn't get chewed up in the driver mech.

    Let me know if anything requires clarification. Every upgrade is meant to make the Cube3 even more usable. Happy Printing!

    - - - - - - - - - -

    Cartridge "POP" tool.

    If you've been taking apart Cube 3 cartridges, you know there is a little difficulty in releasing the latches near the filament driver.
    I've stated in the past I've sharpened an unknown tool to get into the rectangular slots to release the two tabs at the "bottom" of the filament driver.

    Well, I got a few gifts with the Arduino Nano's I've been ordering.
    Decided to see if I could re-purpose one of them...

    041419_screwdriver1.PNG

    Sure enough, a simple and sufficient mod to a small blade screwdriver is all it takes.
    Use this when you have most of the perimeter latches unhooked then popping these two center latches will finish the job.

    041419_screwdriver2.PNG

    A quick grind or filing off to get a semi-sharp edge will let you get behind the little tab to release it.

    ...and it doubles for a filament trimmer by pushing the edge into the filament where you want to cut the filament and it also helps wind the filament through the bowden tube.

    One tool is doing it all now
    Last edited by TommyDee; 04-14-2019 at 08:28 PM.

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  3. #52
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    I built the grooving kit so that I could switch filaments a bit easier, but I didn't have the larger tube available, so I opted for o-rings. The closest size I could find was one with an ID of 5/32" and an OD of 9/32". This works out fairly good.

    I cleared the interior channels of the B2B parts using an 11/64" drill bit and on the B2B parts that normally seated the circlip, I used a 9/32" bit to enlarge the area so that the o-ring will fit. Here are the results:


    https://drive.google.com/open?id=1-5...A4KUBeejF00JIl

    https://drive.google.com/open?id=1-8...Pyxt4yACKojWgP

  4. #53
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    Looks to be a most excellent solution! Happy printing.

  5. #54
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    I am thinking about coming up with a rounded groove rather than the flat groove, but I need to find the right tool first. Any thoughts?

  6. #55
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    Grinder and jewel's screwdriver.

    - - - - - - - - - -

    Printed Circlips!

    This seems to work even without file modifications...
    I made it 1.6mm tall. Let the seam fall on the closed side.
    PLA

    circlip.PNG

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  8. #56
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    Do you have a CUBE3 file? I wanna try.

  9. #57
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    Sure... it comes with an optional larger ring

    - - - - - - - - - -

    As small as this clip is it could easily be made into a longer segment and trimmed, maybe without retractions (continuous print). Maybe up the pressure a little to get wall-2-wall adhesion. Maybe remove a layer and see what happens

    - - - - - - - - - -

    ...And we're getting closer to securing a lot of cartridges for B2B conversion.

    This is the latest version of the external spool access and the mini-spool post holder hole.

    This makes it practical to sell as well as functional access to the filament driver.

    spoolcovers.PNG

    - - - - - - - - - -

    ...and we secured 20 cartridges Blew a big hole in the wallet though! B2B carts coming soon to your favorite 3D Printing Forum and eBay.

    - - - - - - - - - -

    bittle_spool_protocol.PNG

    B2B BSP <Brittle Spool Protocol>

    All B2B cartridges will include the external spool post with an ABS hex-nut already present inside the cartridge for deployment.
    The spool adapter is the winder on Thingiverse.

    BTW, this is quite solid from an external spool perspective. Only a 1/3rd Kg so things are quite stable using this option.
    The pattern in the spool adapter helps keep things from 'un-spooling' too.
    First time I tried this solution. Normally prefer the mini-spool for the posts.

    - - - - - - - - - -

    BTW, if you have particularly brittle 3DS filament, don't toss it. As long as it remains 'relaxed' it will survive. Basically, plastics break down over time by shortening the molecular chains that make plastics strong. These can be thought of as long microscopic filaments that bind the whole lot together. Over time, these long 'filaments' break down to shorter ones. That is where plastic filaments become vulnerable to micro-fractures. Basically, your filament is bent straight and the inside of the original radius is stressed. This leads to failure because the shorter filament strands no longer take up the stress and it micro-fractures. Left in this state, it will break as the stress risers (area where stress fracture propagate) accelerates the molecular chain breakdown. That is why a filament that runs nicely all day long ends up breaking in the bowden tube overnight. This black filament came with the latest printer, already open, and failed. I can leave the filament under minor stress and it breaks within an hour. However, the prints are still strong and fundamentally sound. They look as good as new plastic prints look. So maybe the filament isn't getting "old' or 'dry' as much as it is simply reverting back to its native state. That simply means that handling it becomes more of a challenge. This B2B BSP is a means to facilitate this 'condition'.

    - - - - - - - - - -

    We're getting there...

    The B2B nozzle is live on Thingiverse...
    https://www.thingiverse.com/thing:3804561

    Need to complete the Bowden tube and the groove cutter and we can have a consolidated Thingiverse post pulling all the bits for Cube3 together.

    Don't forget the Cartridge saver, spool post, and minispool... as well as the spool winder. Oh yea... 'overbrim' needs to go there too.

    - - - - - - - - - -

    ...and the TubeNuts are up.

    https://www.thingiverse.com/thing:3806898

    - - - - - - - - - -

    ...and I haven't forgotten. Still working on the printed circlip. Having to make a very custom print for this. Stay tuned.

    - - - - - - - - - -

    ...and the circlips have been added to Thingiverse. Turns out that the 70 micron prints work just fine as long as you adjust out all "elephant foot" from the gap. Also be sure the seam is in the middle of the "C". I still recommend the larger stock tube but this will work. Just be sure they easily plug into their respective mating parts.

    circlip_pair.PNGbulkhead_fit.PNG

    - - - - - - - - - -

    ... t h e y ' r e h e.e.e..e.e r e

    - - - - - - - - - -

    Now we're making progress. Two Beta B2B cartridges are out and about in the post. And I am waiting a replacement nozzle and spring that was inadvertently 'overlooked' in the choices of sending me new <smirks>unused </smirks> lot of 20 cartridges. Well, 16 are unopened and I knew 4 were opened but not failed cartridges. They did run long but definitely not new on 3 or 4 open ones. Good news is that 3 are ABS and that tolerates exposure better than PLA and of reasonable vintage. One is even GITD green ABS! Even the black PLA may be viable as it is not that old. And there is no telling when each was opened. But the box matches the labels.

    Anyway, today I did a de-trash on 5 cartridges. Take them apart; mark the guide tube position; secure the 2 metal moon pieces; align the mech and reinstall; strip the tubes most of which is damaged by aggressive over-molding; and finally - mod the covers.

    All 20 units will be old style covers. Here is a comparison including the last minute mod I decided they needed for the 'pop-cart' cartridge saver option:

    b2bnews_final_covers.PNG

    I ended up making a template and a fixture to mark all the holes. That worked nicely today. Mod'd 7 covers including cleanup in a couple of hours.

    One thing on order is Teflon tubing. I only have enough to complete a couple of cartridges on-hand. Not that bothers this me in the least as I can do 20 tubes in a hour when they finally arrive.

    And that still leaves me with 16 sealed cartridges with red and brown ABS that are lot-coded around 2014.

    I'm considering -not- re-spooling them and selling them with either an empty internal spool or with the stock filament older filament. 2014 ABS will print... but the print may be brittle on the first layer. It will also stick like mad to Lokbuild w/ CubeGlue!

    So the 5 colors will be;
    PLA Black
    ABS Neon Green
    ABS Red
    ABS Blue
    ABS GITD Green

    And the only way to ship these is Priority. They fit nicely in medium flat rate mailers. I need to check the weight without filament to see if I can get anything better in first class.

    - - - - - - - - - -

    Someone needs to put a pause in here for me please. My attachments are lagging.

    Anyway, since I am putting an external spool post on the cartridges, maybe you guys would like the spool adapter with all the bits.

    click image for download from -google drive-
    spool_adapter.PNG

    I put the post and nuts in for posterity. Just the flanges are needed. This design comes from the Winder and just adapted it to the post. The outer flange is the same with new art.
    Attached Files Attached Files
    Last edited by TommyDee; 08-19-2019 at 06:36 AM.

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  11. #58
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    Can't wait for mine!

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  13. #59
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    Nor can I. According to TD, it should be arriving today. Just like the Pointer Sisters song, "I'm so excited and I just can't hide it!"

  14. #60
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    LOL! According to the post office, yes, today. And we all trust the post office.

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