OpenBeam Kossel Q&A

Discussion in 'OpenBeam Kossel Reprap and OpenBeam Kossel Pro' started by Chris Gilroy, Jul 22, 2014.

  1. ChopOMatic

    ChopOMatic Active Member

    I didn't get an oopsie bag, unfortunately. And had parts missing.
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  2. grainiac

    grainiac Active Member

    I was lucky buying and receiving a spare end effector PCB and a set of shoulder bolts. The bolts are another annoying thing that's totally proprietary and we should think about how to replace them with standard parts. If you want to replace the controller I encourage you to try a SmoothieWare powered one. Especially the Azteeg X5 Mini fits very nicely into the KP. You can reuse nearly all the connectors as well, it is really a no brainer.
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  3. protoserge

    protoserge Member

    What proprietary bolts are you talking about? All the supplied bolts appeared to be standard issue to me.

    I agree on swapping out hot ends to a more supported one as well as moving away from a Marlin-based board.
  4. William Siers

    William Siers Member

    Shoulder bolts that go thru the bearings in the swing arms. If you know a source let me know. McMaster Carr doesn't have. Part Numbers???
  5. protoserge

    protoserge Member

    Do you have the dimensions offhand? My calipers are in my shop (different location). Amazon has some shoulder bolts as well.
  6. Jackal

    Jackal Member

    Shoulder diameter: 4mm
    Shoulder length: 11mm
    Thread: m3
    Thread length: ~6mm
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  7. samspade4321

    samspade4321 Member

    12mm shoulder bolts seem common - maybe we could add a ~1mm washer to shorten the shoulder?
    William Siers likes this.
  8. grainiac

    grainiac Active Member

    You need to be careful with washers. I was experimenting with them while I tried early versions of my E3D end effector, where the arm mounts were using M3 nuts. The washers will easily block the bearings when you screw them to tight. When you have them a little bit to loose the effector will wobble and the bolts will loosen themselfes during a print. Of course some Loctide 242 screw lock will help.
  9. Chopomatic and William Siers: what parts are you guys waiting for? Shoulder bolts?

    You can have my oopsies if you want; I already selected the 6 that actually fit out of my set, and long term I'm not even going to be using those anyways. I suspect you can get the oopsies to just fit with very light sanding.
  10. ChopOMatic

    ChopOMatic Active Member

  11. I've got 12 extra, so I can send you 6, and I'll send the other guy 6 if he wants; PM me your contact info or something. Again these were the ones that didn't fit for me, so you'll probably have to work them a little to fit.

    Wait I just remembered a KP takes 12 since it's 6 on the carriages as well.

    What a design nightmare. If you've got another printer, just print up a replacement carriage that maybe doesn't use shoulder bolts. Like, two 4mm rods, and a rubber band that pulls the rods together or something. Screw this shoulder bolt business.

    Let me know how many you guys want, again I only have the 12 spares.
    Last edited: Sep 10, 2015
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  12. William Siers

    William Siers Member

    Thank you, very generous. Posted address to your profile page. Question is why don't they fit? Still doesn't solve root problem of why so many don't fit and why mfg has not responded. I just need one, I hope.
    Last edited: Sep 10, 2015
  13. grainiac

    grainiac Active Member

    My next KP tuning project is adding magnetic ball joints. The stuff needed is already ordered and on it's way! I will modify my E3Dv6 end effector and add mounts for the magnets and design a new carriage with magnet mounts as well. When I have success I can also donate 12 bolts.
  14. protoserge

    protoserge Member

    The shoulder bolt issue is likely a rough edge. Try filing the shoulder leading edge down to add a little bit of chamfer. I found this to be the case with mine. A slight raised spot will cause interference and the bearing will not fit on.
  15. William Siers

    William Siers Member

    The bolt I had problem with was not threaded completly, just a shallow thread. No spares. When I had a machine shop thread it, it was loose. I suspect they had a bunch of these.
  16. David Boyd

    David Boyd Active Member

    Way way back @Terence Tam posted that they were having quality issues with these custom sholder bolts which is why they provided a bunch in the OOPSIE bag. But apparently not everyone got the bag.

    I have have non-threaded bolts, and several with the shoulders too large, and one with a rounded out hex head.

    I like @grainiac idea about going to magnetic ball connectors. I am waiting to see success. I have seen a couple of other delta designs that use them. My only concern is how well they will hold up under speed and vibration. That said, they would also provide some safety in the event of a hard head crash.
  17. William Siers

    William Siers Member

    No oopsie bag. :(
    Yes magnets seem nice.
  18. I don't think it was a "quality" issue (that's not to say that there probably weren't some messed up parts anyways). The part was not properly spec'd with the plating/coating. I think it's supposed to be just under 4mm (3.96mm?), but the plating pushed it out of spec. It might be that just the shoulder needs to be taken down, but maybe not.

    5/32" happens to be very close; I found some 5/32" rod at the local hobby shop but haven't checked it for fit just yet. My KP's been on the backburner.

    First option is to take 5/32" or 4mm rod, forget the cap, and just thread it (or find an existing normal part) for M3 and pull the effector rods together.

    Second option would be to ditch the threaded stuff and just use straight rods to begin with. This would be easiest to test with the carriages first if you don't want to do it on the effector.

    That's the lowest hanging fruit and will probably yield the most gains for everyone involved if it actually works because who the Hell wants to deal with this crap in the long term?

    I've seen the magnetic joints but I have my doubts about them. It's a great idea, but I haven't seen any implementations that I'm super comfortable with at this time.


    I haven't kept up with SeeMeCNC's stuff in a long time, but they have now pretty much implemented what I was saying on their Rostock V2 carriage:


    No shoulder bolts, no o-rings, no threaded aluminum standoffs, no sniffing superglue.
    Last edited: Sep 30, 2015
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  19. Taylor

    Taylor Moderator Staff Member


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