Gripper for robot arm using stepper motor byj48 after converting it from unipolar to bipolar as bellow link:
   • Arduino Lesson 35: Convert 28BY48 To...  

Code for control stepper motor by CNC shield, A4988 driver & Joystick as below:
   • Arduino Lesson 37:Two Stepper Motors ...  

4 Axis Robot Arm intro:
   • 4 Axis Robot Arm Intro