OK so i've designed a palletization program.
The robot extends forward, down, a crowder pushes the box, the robot vacuum head touches, vacuum on, up, back to home position, other to the pallet directly over where it's to be placed, then linear movement all the way straight down, drop off.
The pattern is a 6 per layer, like :::
I start at the outside box first and move up one, then next line, etc, so the pattern is 1) . 2) : 3) :. 4) :: 5) ::. 6) :::
The problem is that even though the points are assigned by computer to position registers, and 1 and 2 have the same Y value, different X values, same Z, same W,P,R , they're coming in with box #2 at a 1 degree turn from box 1 and at least an inch off where it should be for Y.
Both are picked up apparently identically from the conveyor, which is in constant motion, so I cannot explain why they would have different Y values.
This problem seems to happen consistently between different patterns. The head is level at pick up, as far as i can measure (can't measure all points due to the rest of the robot getting in the way. The conveyor is level. The pallet is slightly off level because pallets suck (some are even different heights!).
My understanding of the User Frame used in setting position registers is that it's just based on x,y,z coordinates, and have nothing to do with W,P,R , so instead of using the world coordinates, I use the user frame so, say, the pickup might be at 0,0,0 (though it's not of course, as each box size is different).
So,
1) Is there a potential problem with the robot so that what should be a straight line becomes a curve, which would explain why the placement is off, i.e. maybe as it moves around the sphere that it can operate within, it's not properly interpreting a straight line?
2) If I'm already using a point at the top, reached by joint motion, then a point straight down from it, reached by linear motion (fine), do I have to have the top point set to FINE termination, or should it be correct already?
3) The venturi vacuum heads have spring motion and can move up and down with about 5 cm of movement. They are not exactly level to eachother, but all are engaged when the box is picked up. Would that affect the box's level when lifted off? If so, what can I do to combat that?