Z Axis Research

Hello.

Will three lead screws mounted on an aluminum frame be suitable for a core xy z axis? They will be able to rotate freely and will all be driven by one stepper by a belt. Will this be wobbly or will it be strong enough? I am worried that when the bed goes up it will rotate as well if there is not some sort of linear rail on the bed as well. The screws will be mounted on the top and bottom, or would that be excessive as well?

Please help, Thanks in advance.

Without some sort of fixed rail or linear guide, I'd probably expect it to wobble.

Edited 1 time(s). Last edit at 08/08/2016 04:59PM by PDBeal.

Do you mean a cantilever bed? I think a 300mm need would be to big for that... idk

Purpose of bed on 3D printer
move up/down the Z Axis parallel to X-Y axis

Table must remain co-planar to X-Y plane by constraints of some type
allowing it to move +Z -Z without tilting.

Guides do this, Rods fixed on both ends with table utilizing linear bearings
to keep it level
Linear rails (MGN rails and trollies) or Vee-wheels in maker slide can also be used

The Bed must provide precise movement to allow layer upon layer
of extruded material to be layed down.
This accomplished by a stepper motor moving a belt or a leadscrew turning
moving bed in +Z -Z

I don't think using a leadscrew as a GUIDE and a mover is a good design idea.
But if you can get leadscrews to move bed up/down without tilting at all
you don't need the guides.

Why are the best designers / builders in this forum (digital Dentist, RodF)
using very tight and precise guides on their designs / builds

nuf said

In theory, you could use your form of motion as a guide as well, for example you could use large diameter screws bound at both the top and bottom to keep it straight.

The problem with this? If you take a brass nut for a lead screw, it has play In almost all directions and this means the bed will not be constrained to move in just the Z Axis, it will also move In the XY plane. Having a form of linear guide will mean your bed is constrained to only move in the Z Axis, and any backlash can easily be accounted for.

Look up the Core xy triple lead screw system on thingiverse. It's a proven well documented design that uses 3 lead screws driven by one belt and has 2 linear rails to keep it from moving from side to side. There are a lot of other similar designs out there once you know what to look for but start with that one. Dan Newman is a well known and trusted designer.

Just a heads up.fixing the top of the lead screw imparts wobble and z artifacts to your prints.