Explanation of Normal Limits

Several Yaskawa robots can be tilt or wall mounted, with some limitations to S-Axis rotation. This limitation exists because the S-Axis now needs to account for gravity of the robot arm and payload, so not all postures are permissible if the motor torque is to stay within acceptable values.

The typical S-Axis limit is +/- 30° from the S-Axis home position when fully mounted to a wall. The robot can be facing directly up or down when mounted this way (shown below).

When tilted, this range limit can expand depending on how much the tilt angle is from horizontal (see image below). Each robot’s specific manual must be checked to confirm exact values, found in the Installation chapter of the standard specification manual. (This article will continue to assume a robot is wall mounted and using 30° as the standard S-Axis limit.)

However, applications may require S-Axis rotation beyond the published limits. The +/- 30° S-Axis limit is set so that the robot can still have unrestricted max reach and payload. So, if rotation beyond +/- 30° S-Axis rotation is required, then the robot reach and/or payload need limits instead.

Robot Reach Restriction

The robot can have its full S-Axis rotation if the overall reach is limited instead of the S-Axis rotation. This limits the robot’s working range in-between two planes in the Y-Direction. These planes typically exist where the P-Point of the robot would be if the robot fully extended and rotated +/- 30° in the S-Axis. These planes can be either setup by interference planes, FSU, or hard set by specific parameters.

Please contact PSG for specific value for these Y-Direction planes and any requests to hard set this with parameters. For general estimates though, use the following formula to provide an approximate value.

Payload Restriction

If the above reach restrictions are still not enough for a certain application, the only other option is to limit the payload of the robot. Lower payloads will allow slight increases to the Y-Direction planes shown above. Contact PSG engineering about the specific application. Please provide the total mass and CG location information of the payload so they can analyze the potential increase in reach.