frank26080115 9 Apr 2019, 18:32
What is your strategy for getting the nozzle at least 0.2mm from the dead center of your bed (or else all your prints will have a hole in the middle of it)? Using shims/springs/screws/slots on your extruder mount is an OK solution, definitely don't simply reprint the entire bottom of your printer simply for calibrating that position.
Probably Shims for getting dead centre.
There's noooo way those two angle braces are enough to keep your Z axis perfectly vertical. Add some sort of horizontal stabilizers. Mount the Z stepper up on top if you have to (I know this is counter intuitive) I would personally want the bottom of the printer to look like a "H" or at least a "T" and not a "I". Mounting the stepper on top would ruin your center of gravity but it gives you less headaches when arranging parts.
I guess if I go for a T shape, with an extra bit of 2020 laying flat and perpendicular to the main bottom extrusion, I can use a t joining plate at the back, with some angled brackets on top, and I'd only have to move the Z motor up 10 or so mm. May need to tweak the motor mount slightly too.
I'm not sure how you are making that bottom lazy susan bearing, or where you are buying it from, but it looks like it's meant for radial loads and not thrust loads. I would use something that has a tapered race at least, which is a easier geometry to machine anyways (as opposed to an internal groove). I get that the load is probably not very high but it just looks weird to me to see balls like that.
I have it left over from building a Ciclop 3D scanner, it's a 16014ZZ. So yeah, for radial loads, but I'm probably not even going to put a metal bed on it (definitely not heated), so there'll be minimal axial load, aside from any heavy handedness on my part. If you can recommend anything specific, I can take a look.
I didn't however mention that I'm attempting to only use parts I already have, so I'll likely stick with that bearing, at least until I've got a physical, working proof of concept (which, knowing my track record, I may never reach).
Or forget about a lazy susan bearing and put three ordinary cheap skateboard bearings near the outer rim of the build plate, if your plate is stiff enough. I see you have bars on the bottom that make this not practical though
This is just a few hours work on a first draft design - so open to changes, even major to it. The bars are a 3 point bed attachment, to allow screws and springs at the end for some manual levelling - so that the bed itself would be attached at these points. So that would be trivial enough to redesign, and just have the bed run on rollers, with a centrally attached shaft. Would have to make the mounts for the bearings vertically adjustable somehow to allow for some levelling.
With a 3 point system though, it'd only require 2 of those bearing to be adjustable, so less complex.
