Robtargets do not change on their own. Something else changes, such as the mounting to the floor becomes loose, the end effector becomes loose or damaged, and so on. Gearboxes wear, and the backlash changes. You need to try to do a root cause analysis to find what has changed.
So then is it the part changing or the fixturing? Depending on the pose of your repeatabilty check, you might be missing where there is excessive backlash. You have not mentioned the robot type, only the controller.
Robtarget position gets shifted suddenly
How far is it being shifted? Is it consistently the same distance or is it a uniquely incorrect position every time?
program not running as per its taught position
How far off is it? 1mm? 100mm? 100 km?
What is the size of your zone?
Whenever you execute a move instruction there are several arguments that must be passed into the instruction in order for the movement to be executed. For example:
MoveJ p1, v20, z30, tool2;
This instruction tells the robot to move to robtarget p1 at a velocity of 20mm/s with the zone radius of 30mm with reference to the TCP of tool2.
Here is a visual description of zonedata:
All of this information is very well documented in the Technical Reference Manual - Rapid Instructions, Functions and Data types
Take note of the robtarget values when it is "right". When you see that it is "wrong", take note of the values and compare them to the previously noted "right" values. Are they the same or different?
Is it only the one position instruction that is shifted 20-30mm?
If so, please post the entire instruction.
Step thru the program in Auto to get to the position to ensure you are selecting the right position instruction to modify. Could be running a different position instruction in Auto than in Manual.
Just a shot in the dark, are there any pdisp instructions being used in the program? Any chance that the reset is not being performed, and you are stacking pdisp instructions for greater accumulated
Along the same line of thought, is there a vision system being used to modify work objects? Or more specifically, is there any evidence that the Uframe or Oframe of the workobjects are being modified on the fly?
Are you positive that the correct TCP is being called? have you checked TCP accuracy?
hello Egalesky,
I have faced a similar issue,
it took a lot of time to realize it just was some error in the program.
I think it will be better if you share your code here.
