2 stepper Y axis vs 1 stepper with driveshaft

Im trying to decide if I should design my Y axis using two nema17 (which I already have) or 1 larger stepper to drive both sides.
I plan to have linear slide mech on each side of my printer each with two 10mm shafts and linear bearing sliders.
The slides are timing belt driven.

I could drive the right and left sides independently with two linked nema17 steppers, or use nema23 with a drive shaft going to the right and left side of the printer to move both Y axis sliders with one servo.

Is one setup considered better than the other???

or will linking two steppers make it prone to error???

my current printer has two linked nema 17 steppers driving the Z axis from either side and I haven't had issue yet...

Any opinions on the matter???

I am not sure if I fully understand your setup, but it sounds like you intend to use 2 drive belts on the Y-axis?.. Is the reason because your linear slides have the belts integrated?... or maybe you are building a gantry style machine?..

If building a moving bed platform, I would try to use one motor and one belt if possible, and position that belt so it pulls on the middle of the bed (in X direction) and between the centerline of the slides and the center of mass of the axis (in Z direction)...

Two stepper motors linked together on the same mechanism will tend to fight each other, so I would avoid it if possible.

For the Z-axis it is fine to have them paralleled because there is relatively little load on the motors, they are turning slowly, and they stop on a full step (if you have it set up right) where the detent torque holds it in place.. also, the motors aren't really linked together as each side of the z axis will move quite a bit independently from the other side on your typical printer.. so unless you got some serious alignment issues, the motors won't fight each other..

My bed is 12"X by 8"Y
The plan was to have two 10mm shafts on either end of the X axis with each end set about 3 to 4 inches apart vertically.
The plan was also to have a belt drive on each end of the X axis so that I could keep the belt away from center and make the whole thing lower profile. my X axis shafts would be set p the same bay but mounted to slide on the Y axis (Y axis shafts fixed to the chasis).

I was afraid the long drive shafts coming from a single mototr might cause torque error but It sounds like the dual motor will be much more problematic so Ill take your advice and scrap that idea.

The dual belt drive is something I stole from a high end ABS printer we have here at the studio.

Its works great but that printer is built with a much higher budget so that might be why it does...

Actually, the way you describe it, I think the dual motor might be fine in that application.. Let me reiterate, to make sure I am visualizing it correctly....

So you are using 4 10mm shafts for the y-axis that will be fixed to the frame.. the x-axis carriage slides on the y-axis.. and the bed is mounted on the z-axis?.. so basically the same design as a makerbot replicator.

The reason dual motors should work for you is for much the same reason why they work on the z-axis of a mendel.. the slide rods are pretty far apart (in x-direction), while the bearings are more than likely fairly close together (in y-direction in your case).. Because of this, the whole x-carriage can't resist rotational movement (about z-axis) very well.. ie, you push forward (in y-direction) on the right side of the x-axis while pulling on the left side, you should see quite a bit of play with very little force.. It definitely exceeds the tolerance level of the stepper motors to where they won't be fighting each other if you have one on each side.. If you zoom in on the system in, you would probably notice that one side doesn't track exactly with the other side, but this wouldn't be noticeable in the practical sense..

As far as driving the y-axis, you would probably want to look into having a separate driver for each motor.. I don't have a lot of personal experience paralleling two stepper motors on one driver (aside from z-axis on my printers), but from what I understand, it doesn't work too great at higher loads and speeds..

I didn't understand the last post too well because I wasn't sure if you were talking of my build or the replicator... not sure if they match....

Here is a quick sketch of what I plan to do...

I guess I was referring to both.. your build appears to be the same layout as a replicator.. I was just pointing out that given the geometry, the y-carriage assembly can rotate about the z-axis relatively easily assuming no belts are hooked up.. in reference to your picture, the right and left sides of the green lines can move forwards and backwards independently from one another alone the pink lines.. in other words, you could move the right side of the green lines one way while moving the left side of the green lines the opposite way at the same time, thus rotating the whole y-carriage.. it doesn't take much deflection in the pink lines to allow the green lines to rotate...

It would be the same thing as lifting the x-carriage on a Prusa Mendel along the z-axis from one side.. it wouldn't slide straight up.. the side you were lifting would be higher than the side you weren't lifting..

It was the long way of me saying that the motors wouldn't fight each other and one motor on each side should work fine..

Awesome... thank you that helps a lot.

You are very welcome.. keep us posted with the progress..

Will do. I just got my extruders in so as soon as work slows down next week I'll design my cnc parts and start the assembly process.
I'm new to the forum. Where is the best place to post progress of something like this?

I am new to the forum as well, so I may not be the best person to ask.. I put my project in the "New RepStraps and Post Mendel" section.. but I may not have put it in the right category..