3 x Z-Axis - Idea vs Engineering reality
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I'm hoping this can be a 'rarely used' feature.
The intent - drive the bed to the bottom of the frame (end stop on each axis) to get a 'basic' level done (should be pretty level at this point), I set all this up using a DTI supported from the X axis ( I make sure axes are perpendicular using a laser level on a bench that I know to be level).
From there do the final trimming on the Z steppers. I prefer the steppers with built in leadscrews as I've had problems with the 'flexible' joints historically.
Once trimmed unless the bed or Z axis is manually disturbed / dismantled / otherwise molested it shouldn't need doing again - unless the cat decides to adjust something which has happened a couple of times on the other printer. I have had a couple of head crashes (Pinda issues) that have caused one Z stepper to get out of synch with the other on the Prusa, one of the reasons I don't want to use the Pinda as an endstop as Prusa does - in my build it is strictly for mesh levelling and first layer height adjustment.
I did think about connecting them all but then it only takes .1mm variation corner to corner to screw up a first layer
@mrehorstdmd - read your blog on CoreXY and end stops numerous times - hats off to you sir ....
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If you use common 2mm lead lead screws, the screw has to rotate by 1/20 of a rotation to move the bed 0.1 mm. That's 18 degrees. A GT2 belt could never stretch enough to allow an 18 degree rotation relative to the other screws driven by the same belt. It just can't happen. A pulley set screw coming loose is much more likely, but easily prevented with a drop of locktite.
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@Garfield I use fusion. Thingiverse only accepts stl.
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I'll stick to 3 independent Z screws and leave all the belts up top - at some point I may explore ball screws on the X and Y but that's way off in the future. I want to explore using my CoreXY or light PCB engraving / production, even laser at some point but I may just build a CNC - not decided.
The only time I expect to run a mesh bed level is during initial commissoning or recomissioning after disassembly and even then only really for information. If my bed is so bad that it is needed every time I'll replace the bed.
Currently have two separate build plates one using PEX and the other PEI (Wham Bam) that so far are pretty flat.
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@Garfield the kinematic theory about pinned connections and tolerance take up are outlined in a link I provided in the project. I can link them if you wish. A simpler example is a bridge - typically one end is pinned (think three point) that’s highly constrained and prevents the end from slipping off the mount, and the other end is a slip connection that allows for remap explanation, flexing dimensional change, etc. from a purely geometrical proof, as the angle of the bed changes in any of the three axis, the triangulation naturally lends to a change in vector lengths. That’s why you don’t want the equivalent of all connections being rigidly bound and therefore an over constrained assembly. You force the stresses to be resolved in the rails and therefore bind up everything.
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@Nuramori I didn't know that - that will explain why I rarely find the source files on there.
I've got balls, springs and some hardened dowels ordered now (bought the balls from Duet).
I'll seek out the link and study some more ...
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@Garfield I’m slowly consolidating my blv cube work into one file; I haven’t gotten to putting the bed itself into the file yet, but should be able to by the weekend. Here’s the link if you want to track and see later on. It should be in there soon enough.
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That's darn good of you - much appreciated.
Not seeing the link on Thingiverse - links to parts etc but all in the US - sourced all mine in the UK.
The Fusion workflow can be challenging - I've been hacking away for two years and my prototyping in fusion always results in the components and bodies being a mess as you go back and adjust stuff. Would be so cool if they provided a little more assistance to fix missing faces / references - OK the reference is lost - show me what it looked like - give me a clue here.
I've modded a RatRig linear to accomodate a Hemera which has involved modding quite a lot to avoid Z axis collisions and maintain 300mm sq build area (mines actually slightly larger) and I have 320mm currently in Z.
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@Garfield here’s a decent, not overly nerdy “white paper”
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Many thanks - all this fun stuff you get to learn just because you got into 3d printing, I find it almost as much fun as building the models that I got into printing for, it has become an interest for me in its own right.
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@Nuramori said in 3 x Z-Axis - Idea vs Engineering reality:
I use fusion. Thingiverse only accepts stl.
What? You can upload fusion archives. STEP, IGES, whatever you like.
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@Phaedrux said in 3 x Z-Axis - Idea vs Engineering reality:
You can upload fusion archives. STEP, IGES, whatever you like.
As of december 2019 you can no longer use whatever you like. The formats you mentioned are okay, but solidworks and any other format in their cloud translation thing is not accessible to the personal accounts after the update.
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can you look at this
https://www.youtube.com/watch?v=a9irK9rOUHY&t=36s -
@Garfield You mentioned in one post above that the bed levelling with 3 independent lead screws will be a rarely used feature. Be aware that whenever you cycle power, the steppers will jump to the nearest full step (actually it's worse than that), which could be either forwards or backwards. So you'll need to run bed levelling whenever you cycle power.
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All things good to know.
I kind of wish I was aware when I started designing the printer last year - and I'm a fan of E3D - was going to buy a toolchanger machine until it got 'terminated' so you'd think I'd have known about this joint.
I've never uploaded to Thingiverse, I'm rarely a consumer, I am a Fusion subscriber though ( yes I pay for it ).
I've not experienced the Z axis thing on the Prusa but I have seen steppers 'twitch' on startup.
I'm working on something, I'll let the group klnow how (if) it works out.
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@Garfield what do you mean about the E3D tool changer being 'terminated'?
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They decided not to go to market - cost constraints or something - I read it in one of their blogs but I'm struggling to find it now.
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@Garfield they definitely sell it.
It's still closed to people on the original interest list but I think in the next month or so they should have all the back orders complete -
Looks like I may be wrong on this one - found the blog post and it relates to the 'Big Box' ...
But I still don't see anywhere to buy the toolchanger on their site. All that I can find is an opportunity to join the queue, the last update where it was indicated to be 'going into production' was April last year.
Whilst I was interested I never joined the queue and I'm glad that I didn't. I may reconsider if it ever finally appears.
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@Garfield said in 3 x Z-Axis - Idea vs Engineering reality:
Looks like I may be wrong on this one - found the blog post and it relates to the 'Big Box' ...
But I still don't see anywhere to buy the toolchanger on their site. All that I can find is an opportunity to join the queue, the last update where it was indicated to be 'going into production' was April last year.
Whilst I was interested I never joined the queue and I'm glad that I didn't. I may reconsider if it ever finally appears.
They are getting close to the end of the queue now, so I expect the kit will go on general sale soon. Bear in mind that it is not intended to be a complete printer, more a platform for experimenting with tools.
