Robot ballbar testing
The following screen can be seen in the ballbar test parameters menu. It can be accessed by double clicking the item Ballbar accuracy validation in the station (see previous step).
It could be that the ballbar test is not feasible by default. The feasibility of the test depends on all these parameters plus the robot joints of the center toolcup and the position of the TCP.
If the test is not feasible in the first place, we can select “Preview test” and we will probably see an incomplete sequence. In this case, we can decrease the “Angle turn (deg)”) so that the program is feasible. If this is not the case, we can reduce the radius of the circle (“Target distance”). With the Renishaw QC20-W ballbar, we can test distances of 100 mm, 150 mm and 300 mm with an error of +/-1 mm. With the Renishaw RCS L-90, the range of the ballbar is 240 mm to 330 mm. The “Approach distance (mm)” and the pause (“Pause (seconds)”) can be left as default. These parameters allow detecting the start and the end of the test.
The test plane is oriented with respect to the robot base reference frame (“Reference” in the “Align” section), this means that the XY plane of the robot reference frame is used to create the circle. We can choose to make the test with respect to the tool reference frame. In this case, the XY plane of the tool is used (when the center was taught). We can add additional rotations with respect to X, Y and/or Z axis of the reference frame in both cases.
If we change certain parameters (such as adding the tool in the validation), the message “Important: The TCP must be accurate” will appear. This means that the movements are calculated with respect to the tool center. Otherwise, we can have TCP errors and the test will be feasible anyway.
If we select the option “Include TCP” the tool orientation changes with the movement along the circle. This option allows evaluating the error of the robot plus the tool as one system. Otherwise, we are checking the error of the robot only (“Ignore TCP”).