Axial load on Rotary Stepper Motor?
Axial load on Rotary Stepper Motor?
(OP)
Hi,
I might have a dumb question. If a rotary stepper motor is connected to a lead screw system to lift something up, will the pushing axial load be transfered to motor itself? Will the load be supported by the motor partially?
Thanks.
I might have a dumb question. If a rotary stepper motor is connected to a lead screw system to lift something up, will the pushing axial load be transfered to motor itself? Will the load be supported by the motor partially?
Thanks.





RE: Axial load on Rotary Stepper Motor?
Benta.
RE: Axial load on Rotary Stepper Motor?
TygerDawg
Blue Technik LLC
Virtuoso Robotics Engineering
www.bluetechnik.com
RE: Axial load on Rotary Stepper Motor?
I was once involved with a product that used a stepping motor to move a couple of pistons using a leadscrew, and transferred the axial load to the motor using a Heli-Cal coupling. The load was mostly due to seal friction.
The motor bearings never gave trouble, but we discovered an unexpected side effect. Heli-Cals change their length as torque is applied, which caused the plastic structure coupling the cylinders and the motor to move, and buzz, loudly, in tune with the stepper.
Retrofitting a thrust bearing in the field population was fairly expensive.
Mike Halloran
Pembroke Pines, FL, USA
RE: Axial load on Rotary Stepper Motor?
Benta.
RE: Axial load on Rotary Stepper Motor?
Thanks for you guys' comments. A stepper motor has been chosen now. We are going to use a power-off brake to lock the lifting position when it is off. But also a manual override of the adjustment is also required once the motor turns off. Is there any clutch or system which can engage with the shaft once it is turning, disengage once it is off to perform the manual knob adjustment?
RE: Axial load on Rotary Stepper Motor?
When power is removed, other things happen:
The stepper takes half a step.
The stepper still locks the shaft, more weakly.
The stepper controller loses all knowledge of where it is, unless there's an absolute encoder or equivalent in the system.
Mike Halloran
Pembroke Pines, FL, USA
RE: Axial load on Rotary Stepper Motor?
As Mike said, there are a number of problems when power is removed from a stepper motor. It is best to maintain the power so that it doesn't lose steps, but limit the current to reduce the heating, but still provide enough "detent" holding force so that it doesnt slip down. A lot of stepper drive controls have this facility. I would also use the drive controller to "Jog" the position for manual adjustment, so that the controller doesn't lose track of where the load is, as would be the case if you turned the screw with a knob (unless you fit encoders).
I note that in your OP you said that the motor was going to LIFT something with a leadscrew, so the number of starts and hence the Lead of the thread will have considerable affect on how solidly the motor will hold the weight.