I am currently interested in SCARA arm designs and I have few, beginner questions for which I didn't find answers yet.
1/ While comparing professional arms (made by epson, staubli...) I noticed that the actuator used for the translation on the Z axis is at the end of the arm. On "hobby" arms like the makerarm project on kickstarter they use a leadscrew with the actuator at the beginning of the arm. I thought it was smarter to put the actuator handling this DoF at the begining of the arm (because of its weight) and not at the end, but I assume that these companies have more experience than the company behind the makerarm. So I'm probably wrong, but I would like to understand why :)
2/ Also I would like to understand what kind of actuators are used in these arms. The flx.arm (also a kickstarter project) seems to be using stepper motors but they also say they are using closed loop control, so they added an encoder on the stepper motors right?
Wouldn't it be better to not use stepper and, for instance, use DC brushless motors or servos instead ?
3/ I also saw some of these arms using belts for the 2nd Z axis rotation, what is the advantage ? it only allows to put the actuator at the begining of the arm ?