Nope that didn't work either -- the problem is that the angled screw pulls the gear teeth out of alignment. Using a 90 degree screw plus a locating pin seems to be the winner.
0 Boosts
0 Likes
1.5kg of filament and 36 hours of printing time for the scaled up orrery with a one meter outer diameter for the zodiac ring
While sleeping on the design a bit, I realized that it would be easier to fine-tune the gear mesh if the extrusion arms didn't need to be drilled. So I modified the hub to have them offset and then sliding brackets that restore the offset to the centerline.
these new test gears are 4mm modulus and are very satisfying to spin on their 608 bearings
I should have realized that flex clamping action aligned with the layers would result in fractures, but it was fairly easy to make the more conservative split clamp design instead.
2 media files
I'm having trouble with gears sections lifting, so I thought maybe there are some cold spots on the print bed. Looks fairly uniform, however, and close to what the controller is reporting.
I don't think that gear is going to mesh very well.
What's the bambu equivalent to prusa's first layer calibration? Because this looks terrible.
The 12mm circular tubing on the arms were making it a challenge to maintain alignment, and for the herringbone gears to run smoothly they need the idlers to be very close to parallel, so I'm redoing that part with aluminum extrusion instead.
Family portrait of my orrery designs and the current large work in progress. Not shown: the giant pile of 3D printed gears and brackets along the way as the design has been worked on.
To route wires through the gears for the eventual suns and stars I've made some customs axles on the lathes. Are they consistent? No. Are the threads straight? Also no. Will they work? Too soon to tell.
Another work in progress pic as I wait for more brackets to be 3D printed. Enough of the mechanism is working that it has been running while I'm assembling it. Even at 10x speed, the motion is just barely perceptible.
I'm impressed by FreeCAD's constraint solver's ability to help with this sort of design: "I want these two parts to have a 60 degree angle and also these pieces to have 20mm separation and this piece must be 900mm long and ..." (for another 160 constraints!)
Math is amazing! Those brackets worked on the first try and the 900mm cross braces make the geocentric orrery look like clockwork alchemy diagram.
The larger multi-piece ring gears are more sqooshy than the single piece versions and this is making the mechanism jump rather than rotate smoothly. With a 2kg weight, the moon ring deflects from 66 to 61cm, about 92%. Going to try making a version that is more resistant.
Doing a science to try to quantify how much flex different ring gear sections flex.
That's better! Added some decorative webbing and now the deflection is about 1/8th what it was with the old ring gear design.
Since I'll need to reprint the big ring gears to make them more rigid, I can also apply some lessons learned and redesign the gear train to eliminate the enormous 85 tooth zodiac gear.
I do wish FreeCAD had a way to add text labels, other than on dimensions. It would be very useful to be able to annotate complex sketches to explain why things are laid out in certain ways.
The printer skipped a step or something on a middle layer, leading to seven thousandths* of runout on this gear.
*: Of a meter.
The additional structure and webbing on the ring gear really improves rigidity and makes the entire mechanism turn so much more smoothly than before. I'm still experimenting with how to display the moon phase on the ring, which is why each one is a little different (and the colors are random)
I walk away from the printer for ten minutes and look what it does. "Printing completed" no it's not.
FreeCAD's constraint solver helped me find the angles for this complex bracket and it worked on the first try (once the printer successfully produced one). Those aren't nice 30 degrees; they are 34.9 and 25.1 because of the 20mm offset in the axle spacing and the need to meet up with a T bracket on top.
It has not been a good day for our printer.
The one that worked fits quite nicely however!
Maybe it's just bad filament or K factor settings? This gold pla seems to work fine.
@th One METER!? Holy moly.
:o
I look forward to pictures of this new scaled-up beast if you're willing to share.
An orrery scaled to 1:1?
As the orrery project scales up to a ceiling mounted size, the central hub is being redesigned to use aluminum extrusion for the arms. I really like the x-ray view to see how all of the bolts will just clear each other.