Z-Axis Follower Prototype
by blarbles, published
Description
The goal was to make it fit inside the regular z-axis constraints and require minimal modification to the z-axis (4 screw holes currently).
There are obviously no bearings on one side due to space constraints, but I was hoping having two of these would essentially force the z-axis to push against the inside bearings.
If this works it would probably wise to add screw holes to secure it to the z-axis side pieces to improve rigidity.
The design is ugly and boring but it is somewhat easy to modify. I used Sketchup which I know is disappointing to many, but I am a visual person and struggle with OpenSCAD.
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I created version 2 which printed out and seems to work here: http://www.thingiverse.com/thi...
Don't forget that radial ball bearings will present less friction under similar cantilevered loads when compared to bronze bushings. Yes spacing the bearings further apart would be better, but this still might be better than the original.
Personally I'd be looking to have bearings both within the Z platform as well as below it, to decrease the leverage that the Z platform can exert.
Well, the other part of the problem is leverage meaning the contact points with the rod need to be further apart than stock-hence my tube mod. Going inside the space is even smaller than stock so this gets a definite no-go vote from me, but that's just my opinion and it may work fine.
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Instructions
This uses 693 bearings. I ordered 693ZZ (3X8X4) bearings off eBay.
I will first print out just the bottom 4mm with the rod hole to make sure it all matches up then print the whole thing. When I print it out I'll update this.
In the end you probably want to try these more polished options instead:
thingiverse.com/thing:8823
thingiverse.com/thing:6184
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Its a good idea, but have you looked into just getting something like this:
http://www.vxb.com/page/bearin...
you can probably find them cheaper, or just switch to 8mm shafts and bearings (which seem to be much cheaper). Real linear ball bearings are far and away the best option.
If I understand how this fits into the Z stage, you remove the two bronze bushings from one rod and install this in their place.
However, the bearings on +X and -X just duplicate the over-constraint problem: one rod-with-bushings already keeps the Z stage from moving sideways in X and Y, so you don't need those bearings.
The two ball bearings on the front of the rod prevent the stage from rotating around the other rod. It
would be nice to have bearings on the back side, but assuming the plastic slides freely on the rod and doesn't wear too fast, this should work.
Perhaps you could angle two bearings in back, so they're almost aligned against the front ones?
I like it!
Actually you do need those bearings.
Look at this: http://www.thingiverse.com/thi...
My final version for bearings would be considered 'over-constrained'.
However, you need to either have the guide rods as close together as physically possible, or you need to include bearings to support both sides of the Z platform in both the
X AND Y planes.
Otherwise you are supporting most of the weight on one rod, and if thats still a bronze bushing, things will bind.
So long as you design things correctly, over-constraint is not an issue. The Z axis I linked to works extremely well. The issue with the ToM is not that its over-constr
ained, its that theres too much friction. Supporting cantilevers with bronze bushings is just not very effective. Believe me, I've designed and build quite a few Z axies!
I created version 2 which printed out and seems to work here: http://www.thingiverse.com/thi...