TCP Orientation?

    Hey everyone,

    I've been programming industrial robots for some time now, but I've never had any formal training since I was a PLC / CNC programmer that transitioned into it. Typically, on most (if not all) industrial robots, the default tool Z+ vector is pointing directly out of the flange of the robot. When I create my new TCP to match a gripper, I typically rotate the frame so that Z+ aligns with the world Z+. So, If the gripper typically grips from the side on a part and is parallel to the world XY plane, then Z+ in the tool would be Z+ in the world. Similarly, if the gripper typically grips from the top of the part and is perpendicular to the world XY plane, Z+ in the tool would also be aligned with Z+ in the world. I find that myself and many others crash the robots much less and aren't sitting at the machine looking like a contortionist trying to bend our arm in the right hand rule while thinking about offset directions.

    Recently, a fellow programmer was saying that the the Z+ vector of the tool should always be in the direction of the part, more similar to how the default TCP is on a robot. I know there are a million different scenarios between applications and not all robots are doing work in the same orientation, but I wanted to get some feedback from the community and see if there are common standards or thoughts on this.

  • 95devils October 14, 2024 at 3:54 PM

    Approved the thread.

    In most circumstances, it doesn't matter to the robot. It's more important to establish a standard for your company and stick to it. GM's standard is detailed and enforced to an obsessive level of detail, for example.

    There are, however, a couple cases where it does matter to the robot. For example, certain option packages for arc welding assume that the Z axis will always have a specific relationship to the gun tip, and the X axis will have a specific relationship to the direction of the weld, and use that to generate weaving patterns, among other things.

    In my experience, Z+ "into the part" is one of the most typical, with X or Y aligned with some convenient flat plane on the tool. OTOH, if you're doing something like inserting pistons into cylinders, the TCP orientation should probably be determined by the piston (however the tool is holding it), rather than the tool itself.

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