top mounted ballscrew, would it work properly ?

[Rory13]

I suspect what Rory meant, was only having a single central ballscrew on the long axis, instead of twin ballscrews with one either side, not an entire machine that runs on a single ballscrew.

Yeap thats what i meant. Reason i m looking for friction coefficients for linear rails is that i d like to compare to alternative methods like some rolling bearings on the steel frame. I suppose the more diy methods would require a bigger motor to overcome the additional friction. Waggon type rails are great but their price is out of the question at the moment. Another question, is configuring different motor for each axis a harder task ? I was thinking about a nema34 for the long axis on a single ballscrew and nema23 for the rest, perhaps movement by belt on Z axis.

[m_c]

The more DIY methods might not require a bigger motor, however they're not recommended unless you want to be constantly having to adjust things to try and get consistent and accurate performance.
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Different size motors on each axis are not a problem. Whatever controller you end up using, is only interested in the number of steps it takes to move the axis a set distance. The controller is only responsible for sending the correct number of steps to the motor drivers, and has no interest in what the motor driver is actually powering.

[Boyan Silyavski]

The more DIY methods might not require a bigger motor, however they're not recommended unless you want to be constantly having to adjust things to try and get consistent and accurate performance.
.
Different size motors on each axis are not a problem. Whatever controller you end up using, is only interested in the number of steps it takes to move the axis a set distance. The controller is only responsible for sending the correct number of steps to the motor drivers, and has no interest in what the motor driver is actually powering.

In fact if a top notch machine is the final aim, there could be a problem with PSU choice. I was going to buy some stuff these days and almost for a moment missed that point.
Was looking to buy 2x 3Nm Nema 23 closed loop kits for x and z , plus 1x 8Nm nema 34 for the both long screws connected by belt. then i woke up and saw that the different sized drives need different voltage. This could be cured buying the intended motors but only with the bigger drives, which could drive the small motors. So feed all with same voltage.
For normal motors just consulted with Dean yesterday, and he confirmed me that to keep all same /speed, torque, acceleration/ and exchange 2 motors with 1, you need higher voltage for the nema 34motor. Basically in this case- 2 different power supplies. Which is not a big deal, just to have in mind