Hello, I am new to the forum and would like to ask for advice on an ambitious project for me. I would like to build a gripper arm that should consist of Nema 17 motors and a Nema 23 motor. The arm should be able to reliably lift 500 g with a total length of 50 cm at a good speed. The arm itself will be 3D printed from PETG. Now to my question. For the main axis, on which the entire gripper arm hangs, I chose this motor with 20 Nm torque: https://www.oyostepper.de/goods-308...Grad-28A-125Nm-26V-Getriebe-Schrittmotor.html

I need advice on whether the motor has enough power and whether the gearbox is too slow. I have concerns about Nema 17 motors (59Ncm), which also have some mass. I hope you can help me.

 

Just convert mN to something you understand like Kg or ft/lbs.

 

10N is near enough 1Kg. So to lift 500g at a distance of 50cm you need a torque of 2.5Nm. This does not take account of the weight of the arm (at an average of 25cm from the axis) and the gripper weight. The curve shows you how the torque reduces with speed but you must ramp up and ramp down to this speed to avoid slipping. Best to assume only half the stated speed is achievable. Remember that the maximum torque is only necessary when the arm is horizontal - optimizing the drive control for the angle of the arm is a bit more complicated

 

sll replies are spot on. but if you need more help, you need to provide more info. it is not clear what the mechanical arrangement is and what forces/torques are present, what the weight of the Nema17 motor is or what exactly is "good speed" or "too slow" or how much you need to lift. all design choices can have significant performance impact. for example one can use SCARA-like construction (turned on side) so that gripper motor (Nema17) is not at the end of the arm. that would reduce weight and inertia.

many steppers are 200 steps per revolution (1.8deg per step). gearbox reduces speed and travel but increases torque.
1.8deg/46.656 = 0.03858 deg per step.

so to lift 250mm the main arm would need to turn 30deg. 500mm*sin(30)=250mm
to make 30deg, your motor would need to make 777 steps. (30deg/0.03858deg=777)
if load is within motor specs this should be doable in about 1sec.

 

Another option would be to purchase a robot arm system. they are able to be programmed to do a whole lot of motions and repeat them to within 0.01mm repeatedly "Motoman" division of Yaskowa made the one that I programmed , it took about an hour to get it perfect.