I am toying with the idea of building a robot arm which can change the tools on my CNC milling machine. I am aware that a robot arm will never be as fast or efficient as a dedicated tool changer, however, it is way more fun to build and may just find many more uses than changing tools. For instance, it can help with flood cooling, air blasts and who knows maybe even part changes. I will be posting more details here as the project progresses... Any comments/feedback is greatly appreciated.
SCARA Robot Arm Type
SCARA Selective Compliance Articulated Robot Arm is my choice for this project because apparently, they are good for inserting pins into holes which is what a tool changer needs to do. They are rigid on the Z axis which should allow for smaller motors since they do not need to fight gravity.
I would love to use ClearPath servo motors, however, I think to keep things simple I will start with stepper motors...
I will start with TinyG CNC Controller. It has 4 motor outputs for a reasonable price. Its stepper drivers handle 2.5 amps per winding which will handle most motors up thru NEMA23.
This will probably be an Arduino. You will manually jog the arm to teach the locations of the tools. Coordinates can be recorded and assembled into G code which is sent to the TinyG.
Interface Teach Pendant to Tormach Controller
This worries me the most. How to interface the Arduino to Tormach PathPilot. If there is anyone out there that know how to extract a tool number from PathPilot, I would love some help here. In the meantime, I will be using the USB IO interface to test a couple tools. It will mean hand coding G code but it is a start...
I will be using Aluminum T-slot struts to make the arm as flexible as possible. I have yet to figure out how to calculate the flex of these struts.
The tool holder will be a modular bracket holding 3 tools at a time. Multiple of these brackets will be fastened at various points around the inside of the machine using Aluminum T-Slot struts. This holder will hold the majority of the Tormach tools. The Tormach tool changer uses a nylon clip to retain the tool. I am thinking this will require too much force so it may be better to use an actuator to hold the tool.
The joints are the most important aspect of a robot arm. It is where it all comes together, the motor, the gearbox, angular feedback, strength, and rigidity. Each component is affected by the other. This is where I expect to spend a lot of time and many iterations. It may take a couple months...