This is an improved ball and socket joint for giufini's excellent PCB Workstation with Articulated Arms.
The author used HIPS for his ball and socket joints but I only print with PLA and PETG. With both materials, I ran into a number of problems getting the articulated arms to work well. Here's a summary of the problems I had:
- The socket ball wears quickly and the articulated arm becomes very loose
- The ball easily pops out of the socket when the travel limit of the arm is reached
- The arms don't bend with a very tight radius so moving the arm around frequently causes the balls to pop out
I tried both versions of the alternative ball and socket design with heat shrink tubing but the heat shrink quickly breaks down and gums up the socket. Plus, the bend radius is also reduced with the heat shrink.
So I took a stab at designing an improved ball and socket joint. The biggest requirement is that the ball remain the same size so it fits all of the accessories in the original project. Here's the mods I made to the design.
- Raised the ball away from the socket by about 2 millimeters - this improves the arm bend radius significantly and also makes it much harder for the ball to pop out of the socket when the travel limit of the arm is reached.
- Made the socket wrap around the ball about 1 millimeter farther down - this makes the ball stay in the socket better and also improves the stiffness of the arm with the greater surface area in contact.
- Made the inside diameter of the socket slightly smaller to stiffen the joint and keep it from loosening as much
I'm quite happy with the final result. All of the probe holders and accessories I printed still attach fine but I no longer have the problems with loose arms and balls popping out.
Printed with a 5 outline brim offset by 0.3mm