Hello,
This post is building from the post that was skillfully modified by justcheckinm8 found here. I just needed one more modification to the sketchy physics file. Currently, the red arm of the robot goes into the orange arm. With the given specifications of the pistons (movements from -0.5m to 0), how can I prevent the arms from going into each other? Does the size of the circle that drives the effector have to be changed? Also, the orange arm on the hinge cannot go beyond 90 degrees. It has to stay within 90 to 0 degrees. Attached is the file that I need help with. Thanks.test13update.skp (178.8 KB)
Beat me to it…was going to suggest you colour the parts to make it easier to describe 
You can’t make a circle with the end effector if nothing else is allowed to move in anything but an arc. At best, you can only draw an arc. Put your index fingers, one on each end of a stick (like a ruler) . Now try and draw a circle with one finger whilst keeping the other finger still. Same problem…unless the stick is allowed to change length, it is not possible to create the circle. You would be able to get away with removing one of the pistons and making the objects it was connected to a single object.
You can get the motor to spin with the whole assembly upright (achieving your requirement to stay in the 0-90 deg range) if you boost the power of the motor. Set the maxAccel to 20, and it will spin up right from the play button. If you slow the motor down, it will reach stall point.