Hello,

I'm tasked with retrofitting a simple, custom made, press brake. Press is currently manually operated and consists of trapezoidal screw with a flywheel on top, screws' nut is stationary while screw itself changes it's position axially (20mm of travel at most) while rotating, what will be best and cheap solution to transfer torque from gearbox / motor to screw?

there are some requirements:
- torque - I haven't measured required torque but Im was told it's at least 120Nm, I have decide to target 200Nm - just in case.
- motor - we have one stepper motor with 8.5Nm holding torque
- gearbox - I can use anything, but it is strongly suggested to use belts and pulleys (for reasons unknown to me), I was thinking about worm gearbox.
- screw - TR36x6, machined to square on top

I see a few solutions:
1. mounting motor and gearbox on rails so these travel with screw - this is most popular idea as of now since we already have some heavy duty HIWIN rails, although that would work I don't like idea of using expensive rails and carriages for just 20mm of movement
2. using universal coupling (double Cardan) with telescopic shaft - we can quite easily get these with ends machined for square ended screw, the problem I see here is that since our press was custom made long time ago it has some problems with screw alignement - it moves radialy while rotating (about 2mm of movement!) so some additional radial compensation is required (Oldham coupling maybe...)
3. using splined shaft and splined hub - seems like good solution to me, some axial compensation still required though. In my imagination it would work like this: Motor -> gearbox -> some stiff coupling -> splined shaft (With bearings) | splined hub with flange -> Oldham -> Square Converter -> Screw, a bit complicated...
4. Transfering torque using toothed belts - these should not be at angle, but maybe shaft's pulley could be mounted on some kind of hub that would allow it to change it's angular position and align to the belt mounted on the other side on the not moving gearbox?


My question is - do you think any of these solutions is good? Maybe there are some other solutions, I didn't think of, that are significantly better?

Any help will be appreciated!

Best Regards