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3 Z axis Assembly which one

Posted by bbcbggr54 
3 Z axis Assembly which one
May 07, 2018 05:17PM
So i have these 3 Z designs to choose from unless someone else has something better. No cantilever designs as this is going to be 400X400 heavy bed assembly. I have had reviews that the 3 leads and 3 rods is over constrained but not on the 2 leads and 4 rods which i dont understand as i have 6 points of contact with each. The rods will be have solid steel mounts. We can talk about lead mounts. I want to hang the leads as it seems s much better to hang the bed then push it. With the 3X3 bed assembly i cant hang the bed as the belts would inhibit the ease of filament to the X carriage so i put the leads on the bottom, or i threw up a few more pulleys and longer bed to make it a square. I feel i need to motors as the weight of the bed would be to much for one. the only problem im having with 2 seperate motors is keeping them sinked, but will this be much of and issue? i do plan on running the through a belt to drive each lead as seen in the 2X4 setup. I wnt to hear what you think of the designs spacing, mounting driving etc. i want to start building but am having an issue getting this Z thing figured out. i would like to go linear guides but dont see the funds to do so unless i go cheap shitty china.
Attachments:
open | download - 2X4 Bed ASS v4.png (288.8 KB)
open | download - 3D 3X3 Bed Ass v7.jpg (25.4 KB)
open | download - 3X3 Bed C v4 v2.png (80.1 KB)
Re: 3 Z axis Assembly which one
May 08, 2018 03:15AM
I use the second design on my coreXY printer and it works well...
Re: 3 Z axis Assembly which one
May 08, 2018 03:05PM
None.
No excuse to come with such non sense when you have good designs presented here.

Edited 1 time(s). Last edit at 05/08/2018 03:07PM by MKSA.


"A comical prototype doesn't mean a dumb idea is possible" (Thunderf00t)
Re: 3 Z axis Assembly which one
May 08, 2018 10:32PM
do you have yours mounted on top and what are your leadscrew mounts
Re: 3 Z axis Assembly which one
May 08, 2018 10:35PM
no excuses is right they are the best i can think of or seen. which designs are better i havnt seen them? this build is up for discussion not just negatuve remarks i am a rookie.
Re: 3 Z axis Assembly which one
May 09, 2018 01:30AM
Quote
bbcbggr54
no excuses is right they are the best i can think of or seen. which designs are better i havnt seen them? this build is up for discussion not just negatuve remarks i am a rookie.

See here, in a thread you initiated: [forums.reprap.org]


"A comical prototype doesn't mean a dumb idea is possible" (Thunderf00t)
Re: 3 Z axis Assembly which one
May 09, 2018 10:19PM
i dont understand whats wrong with it could you explain how im overconstrained
Re: 3 Z axis Assembly which one
May 09, 2018 11:13PM
You're trying to constrain (prevent) lateral motion while allowing vertical motion. One round guide rail prevents linear lateral motion, but allows rotation as well as vertical motion. A second round guide rail stops rotation around the first and allows the desired vertical motion. That is fully constrained. Adding more rails doesn't add any stability but can cause problems if the rails aren't parallel.

As far as lifting goes, you can make a cantilevered bed, lifted with one screw, but the free end will tend to bounce. Lifting with two screws at the middle of opposite sides of the bed reduces the bounce problem, but it is still cantilevered- just half the length. Lifting with 3 screws provides a stable platform for lifting, like a 3 legged table or stool- it won't wobble like a 4 legged table/stool.

Two screws alongside guide rails (rails and screws should be kept close together) on the right and left sides near the front of the printer (providing easy access to the print from the front of the printer), with a third screw (with no third guide rail), which keeps that cantilevered end of the bed from bouncing, at the center of the back of the printer is just about ideal.

If the frame is built solidly, the bed plate is on a stable support and leveling structure, and the Z axis screws are driven by a single motor, you will level the bed once and will not have to relevel it.

You'll see a lot of variations. It isn't impossible to get a system with 6 guide rails and 5 screws to work, but the more you do beyond basic constraint the harder it is to make it work (and the cost goes up).


Son of MegaMax 3D printer: [www.instructables.com]
Ultra MegaMax Dominator 3D printer: [drmrehorst.blogspot.com]
Re: 3 Z axis Assembly which one
August 09, 2018 08:32AM
Do a cantilever. The hgr15 rail will take 100 N-m of moment in that direction. In real units thats like 45 pounds at the far edge of your build plate. You step up to the hgr30 rail and you could use your build plate as a seat.
Re: 3 Z axis Assembly which one
August 09, 2018 09:15AM
Quote
Leafy1
Do a cantilever. The hgr15 rail will take 100 N-m of moment in that direction. In real units thats like 45 pounds at the far edge of your build plate. You step up to the hgr30 rail and you could use your build plate as a seat.


Real units ??? Amusing. We are in the 21° century you know. In fact 9 Aug 2018 so how about working in REAL TIME, you answer to discussions that have been dead for months and where even stillborn smiling smiley

[www.youtube.com]


"A comical prototype doesn't mean a dumb idea is possible" (Thunderf00t)
Re: 3 Z axis Assembly which one
August 09, 2018 09:40AM
I assumed it was relevant since it was on the first page. I guess I should have liked for the date. And yes, real units, it's what we use when we make real parts in actual industry. And I'd like you to tell me how much you weigh in Newtons without having to calculate it.
Re: 3 Z axis Assembly which one
August 09, 2018 11:36AM
Quote
Leafy1
I assumed it was relevant since it was on the first page. I guess I should have liked for the date. And yes, real units, it's what we use when we make real parts in actual industry. And I'd like you to tell me how much you weigh in Newtons without having to calculate it.

Real units like here: ?
[www.youtube.com]


"A comical prototype doesn't mean a dumb idea is possible" (Thunderf00t)
Re: 3 Z axis Assembly which one
August 12, 2018 02:36AM
Quote
bbcbggr54
So i have these 3 Z designs to choose from unless someone else has something better.
I believe that the simplest design you may choose will be 3 motors Z. Belts look nice but they add an additional constraint to the design - belt length. Since it is closed loop belt redesigning your printer for a different size will be challenging. In 2 years your belt will wear out and boom nobody makes belts of that length anymore (kidding). Or just look how complicated your design already is, and how much it will be simplified if 3 motors will replace all that structure around the belt. You also adding vertical height to your printer when using the belt, cause the belt needs to run under the bed in the lowest bed position. It is not a lot but still something you add.
But I know that you are already convinced that belt design is the best. So for picking the design you like first find the belt of appropriate length - because this is what you will design around.
Re: 3 Z axis Assembly which one
August 31, 2018 01:29PM
Not much to add to the DD excellent description on why you only need two vertical supports but still three lead-screws, unless you have very stiff vertical supports with long/dual bearing assemblies, in which case two lead screws could work but you would give up some Z-travel.

So your option 2 is the likely most efficient. You can run all three lead screws off one motor, just make sure it is a decent size Nema 17. The lead screws act as gear reduction, so even with 4-turn lead screws and a heavy bead (I have basalt tile on mine), one motor can work. If your bed is really heavy or the motor is struggling, you could switch to 1-turn lead screws for 4x more torque.
Re: 3 Z axis Assembly which one
August 31, 2018 01:30PM
Quote
MKSA
Real units like here: ?
[www.youtube.com]

That video is gold. Standard was OK for building my house, but anything small and mechanical design greatly benefits from millimeters, like printer parts!
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