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Sheet Metal Brake and 3d Printer.
WeldingRod:
:bugeye: You've been busy!
Do the different types of wheel/rail interactions make more sense now? You can imagine what happens if the two back Z rails move toward or away from the front ones; a few mm either way doesn't affect the operation at all!
I essentially treated my Cobblebot kit as a box of parts to build from, some of which kind of sucked. The Arduino was a junky clone and the wheels were terrible.
Yeah, that stuff adds up quickly!
Oh, I should mention: I have a new design for the Z plates that has a much longer arm along the Y rails to reduce the sag. If you re-style it to 20x40 the deflection will drop by 57% anyway. Probably still worth having the new plate design.
I agree, Sketchup has some really cool stuff and some really terrible stuff. Its all about the visual! Tricky to get it to produce good STL files, but that's what I work in... I actually worked with some folks who designed a complete cement plant in Sketchup! OMG a big model!
Can I get that SKP model to add to the Thingiverse file?
kayzed1:
--- Quote from: S. Heslop on September 16, 2018, 09:39:44 PM ---
--- Quote from: WeldingRod on September 16, 2018, 09:06:09 PM ---20x40 will definitely pay off on the main Z verticals and the two y rails. Everywhere else it won't help much, just get in the way. Going to less length on the y rails will help drop too.
I can easily make you dxf files for the plates corrected for those rail dimensions, if you want them.
Sent from my SAMSUNG-SM-G891A using Tapatalk
--- End quote ---
I've downloaded the dxf files from your thingiverse page and gonna try import them into sketchup at some point. I figure i'll start with the thing as close to yours as possible and then start shifting the dimensions about from there. I also feel other people might make some use from a CAD drawing, even if it's sketchup.
--- End quote ---
PM me your details again and i will search out that box O bits i have.
Lyn.
nrml:
If you moved the leadscrews to the middle of the Z gantry on either side, wouldn't you have a much better chance of the wheels running without binding?
Is there a reason for having the Z axis moving the hot end up rather than the build plate down? Wouldn't having the hot end moving in all three axis make it more vulnerable to vibration errors? I would think that a cast aluminium tooling plate bed dropping down with gravity and held in place by a couple of big beefy NEMA 17 motors with astrosyn damper clones and trinamic stepper drivers would make for a Z axis with minimal vibration issues. With a strong non moving top frame to float the XY gantry on, you can focus on making the gantry as light and vibration resistant as possible.
There was an interesting thread on the reprap forum a few years back on someone designing a z axis with 3 leadscrews and no slides driven by one stepper motor and pulley/ belt arrangement.
WeldingRod:
I've worked with moving part printers, and Z is certainly the right axis to choose! I agree that three axis motion on the extruder leaves you more open to vibration that 2 axis. I was happy with that tradeoff, though.
With my design, the optimum location for the Z force is on the front two columns, as those are the ones that control rotation around the X axis. If you put the Z drives in the center of the Y rails you have the additional problem of reversed loading; it wants to move like a see-saw, and your backlash adjustment is really critical. With my layout the loading direction on the bearings is always the same.
S. Heslop:
--- Quote from: nrml on September 18, 2018, 02:48:27 PM ---If you moved the leadscrews to the middle of the Z gantry on either side, wouldn't you have a much better chance of the wheels running without binding?
Is there a reason for having the Z axis moving the hot end up rather than the build plate down? Wouldn't having the hot end moving in all three axis make it more vulnerable to vibration errors? I would think that a cast aluminium tooling plate bed dropping down with gravity and held in place by a couple of big beefy NEMA 17 motors with astrosyn damper clones and trinamic stepper drivers would make for a Z axis with minimal vibration issues. With a strong non moving top frame to float the XY gantry on, you can focus on making the gantry as light and vibration resistant as possible.
There was an interesting thread on the reprap forum a few years back on someone designing a z axis with 3 leadscrews and no slides driven by one stepper motor and pulley/ belt arrangement.
--- End quote ---
I mentioned it earlier but my thought is that you'd want to keep the forces in a constant direction so you're only dealing with flexing. Where if it was in the middle then any time the gantry crossed over the pivot of the screw, any play in the bearings/ rollers would let it abruptly tip over.
I think i've seen that leadscrew only Z axis thread. It is pretty cool but I think it'd be dependant on fairly decent ballscrews.
--- Quote from: WeldingRod on September 18, 2018, 02:00:13 PM --- :bugeye: You've been busy!
Do the different types of wheel/rail interactions make more sense now? You can imagine what happens if the two back Z rails move toward or away from the front ones; a few mm either way doesn't affect the operation at all!
I essentially treated my Cobblebot kit as a box of parts to build from, some of which kind of sucked. The Arduino was a junky clone and the wheels were terrible.
Yeah, that stuff adds up quickly!
Oh, I should mention: I have a new design for the Z plates that has a much longer arm along the Y rails to reduce the sag. If you re-style it to 20x40 the deflection will drop by 57% anyway. Probably still worth having the new plate design.
I agree, Sketchup has some really cool stuff and some really terrible stuff. Its all about the visual! Tricky to get it to produce good STL files, but that's what I work in... I actually worked with some folks who designed a complete cement plant in Sketchup! OMG a big model!
Can I get that SKP model to add to the Thingiverse file?
--- End quote ---
Yeah they make more sense now, assuming I made the model right! From photos I was thinking there was a weird combination of rollers on flats and in grooves but it's alot simpler than it seemed.
https://drive.google.com/open?id=1dQQLoEQGdezWYBSKnv0mcwOitJjoQ6Yb Hopefully this link works. Tell me if I got it totally wrong.
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