Why ABB robot doesn't follow set coordi accurately?

RobotStudio
1

Hello, I couldn’t find a solution using search so I have created a new topic.
I have been testing the robot(and the software that comes with it) in my university lab for a few days. I have faced rather a queer problem with RAPID command line “MoveL”. My aim is to draw a square as an example on a 2-D board which is near the robot. So whenever I use “MoveL” function I set only position in x and y directions, and z coordinate is always set to 0. But when I run the code on the robot it moves in z direction as well even though it shouldn’t. By moving 50 mm in x direction it moves 5 mm in z direction. So if I used a pen it would draw only two lines of a square as the tool goes up approx 5 mm and the pen couldn’t reach the board. This occurs even if I don’t have a tool mounted. Here I attach some simple code I am using.

PROC l()
ConfL\On;
StartMove;
IF i=0 then
MoveL RelTool(init,0,0, 0\Rx:=0\Ry:=0\Rz:=0),speed,fine,tool1\WObj:=wobj1;
i:=1;
ELSEIF i=1 THEN
MoveL RelTool(init,50,0,0\Rx:=0\Ry:=0\Rz:=0),speed,fine,tool1\WObj:=wobj1;
i:=2;
elseif i=2 then
MoveL RelTool(init,50,-50,0\Rx:=0\Ry:=0\Rz:=0),speed,fine,tool1\WObj:=wobj1;
i:=3;
ELSEIF i=3 THEN
MoveL RelTool(init,0,-50,0\Rx:=0\Ry:=0\Rz:=0),speed,fine,tool1\WObj:=wobj1;
i:=0;
ENDIF
StopMove;
ENDPROC

2

Hello,
This can have 2 possible reasons:

1.Probably your tool1 coordinate system is not aligned with your wobj1, because if your tool is turned 5 degrees to your wobj1, making the robot move relative to the tool , it will move in the coordinate system of the tool and not the wobj.
If you want to move with offsets in your wobj, you should use the command:
MoveL Offs(init,50,0,0),speed,fine,tool1\WObj:=wobj1;
then the tcp will move in the coordinate system of the wobj.
Make sure your wobj1 is aligned with your 2D table, if not then you have to redefine your wobj
2. your robot is not calibrated well, try to redo a “revolution counter update” and check your “motor offsets” that are on the back of axis 2 of the robot.