Hello everyone! This is my first build i have a mpselect mini but too small and lightweight still a wicked little entry. So i go big and rock solid and light as i can .Everything will be made of steel except moving parts will be aluminum or printed. I will be using 16mm chrome rods for z axis, carbon fibre x axis and im thinking on hiwinn hgr15 for y axis anyone have reviews on the hgr? using smoothieboard and titan aero extruder with bl touch bed sensor. 4 200x200 keenovo bead heaters with magnetic build plate. having issues with findind flexible light plate material? finding a 12mmX700mm leadscrew? second im thinking of using thrust bearing instead of mounted bearing on top of leadscrew so i could hang the buildplate therefore easier on leadscrews? using 2 motors for z axis as i dont think one will be enough? all aluminum bed except for bearings heater and plate and adjusting bolts. still more issues but those are the top. oh has anyone been using air pump instead of fans? Let me know what you think if you see any issues can take exact pics.
Thanks BBCBGGR
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I used belts and linear guides for UMMD's 700 mm Z axis, driven by 30:1 worm gear reducer (with two belts) that stops bed-drop when power shuts off. The bed is on a kinematic mount that is rock solid and stable.

I haven't used a conventional pump but did test using a centrifugal compressor/blower from a CPAP machine. As I type this I am printing the housing for a printed blower that copies the CPAP blower and uses a HDD motor. The CPAP blower is definitely capable of providing more than enough air to cool a print, and does so quietly.

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Ultra MegaMax Dominator 3D printer: [drmrehorst.blogspot.com]

I wouldn't use bearings on top of the lead screws at all. The smooth rods are there to constrain the bed, the screws are there to lift it.

Belt stretch is more of a maitenance design i will always be checking if the belt is getting worn just from constant strain i like the idea of three lifting points just much more stable in my eye. i do like your bed mount design as well as cam endstop profiles.

i understand the point of linear rods but if i can get a near perfect double fixed leadscrew assembly i can be faster and little to no z wobble. and is it not better to have the leadscrew holding the bed up instead of pushing so you get even less bending therefore less z wobble

How fast does your printer's Z axis need to go?

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Ultra MegaMax Dominator 3D printer: [drmrehorst.blogspot.com]

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bbcbggr54
i understand the point of linear rods but if i can get a near perfect double fixed leadscrew assembly i can be faster and little to no z wobble. and is it not better to have the leadscrew holding the bed up instead of pushing so you get even less bending therefore less z wobble

This is why i3 gantrys should have the motors at the top, so that the leadscrew is in tension rather than compression for less artifacting.

Z doesnt have to be a rocket but i do want it to be smooth and have no resrictions on speed

i would like te motors on top but my belts would get in th way of filament and air being fed to the extruder

Quote
bbcbggr54
i understand the point of linear rods but if i can get a near perfect double fixed leadscrew assembly i can be faster and little to no z wobble. and is it not better to have the leadscrew holding the bed up instead of pushing so you get even less bending therefore less z wobble

I agree with the benefit of a hanging leadscrew, but fixing the leadscrew at both ends is like keeping a dog from tail wagging:
You fix the tail and the whole dog begins to shake.

All the printed plastic parts will provide the required flexibility to compensate for all the misalignment as this set up is over over constrained.
Luckily linear rails can exert enough force to straighten things without binding.
Polymer bearings on the other hand would require at least NEMA23.

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"A comical prototype doesn't mean a dumb idea is possible" (Thunderf00t)

I don't understand two steppers on the bottom?
Two motors to drive 3 Z leadscrews?

Z motion three leadscrews and three guide rods --- over constraint?

Plastic parts shouldn't make up for over constraint.

Why linear rail and rod mix?

i was thinking three leadscrews for a more stable lift no twisting and 2 motors because i dont think one will have the power. and with seperate tensioning on the belt i might be able to eliminate the push pull effect. do you think one would do or just go to nema23 as i am running polymer bearings. would my rails keep it stable enough to just use 2 leadscrews.

i meant rod not rail in last statement and iwent for rails just to give me more stability. carbon fibre rods for light weight, steel rods for cost, strength and it is the z axis.

as for the happy dog if my leadscrews are straight and hanging where do i get the twist? or is it that to get perfect straight Lscrews and alignment is damn near impossible therfore you will always have at least a little wobble. i want to hang the leadscrews but i cant see how to drive them from the bottom and not have both sides fixed. as well as it is the most efficient way to run a Lscrew.

most of my parts will be made of aluminum once i have it running good

2 guide rails provide all the needed constraint. Trying to align two widely separated guide rails parallel to each other is tricky. Add a third and it becomes a much more difficult problem. Not impossible- the guys who make delta printers seem to manage, but not so easy.

The problem with bent screws causing lateral motion in the bed isn't just in the screws. End supported guide rails flex and allow the bent screw to have its way with the bed. If you use linear guides screwed to a solid frame, a bent screw will not be able to deflect the guide rail so it won't be able to deflect the bed. Or just use really big end supported rails (mounted on a solid frame).

Or use belts- they can't/don't produce any lateral forces that will deflect the guide rails...

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Ultra MegaMax Dominator 3D printer: [drmrehorst.blogspot.com]

when you end supported rails do you mean rods cause im using rods and can make them rock solid on the ends trust me thends should not flex

It's not the ends flexing - it's the rod/rail itself flexing. Always worst at the middle of the rail...

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Ultra MegaMax Dominator 3D printer: [drmrehorst.blogspot.com]

so you 3 16mm rods wouldnt be thick enough