Teaching Points Backwards

Filed under: FANUC TP Programming Tips

I was with a customer earlier this week who needed a little help with one of their robots. It was a simple pick and place application, but for one reason or another, one of its placements had drifted and now the robot was fumbling that drop at overrides over 70%.

Pretty simple fix, right? Put the robot in teach, pick up a part and then step it through the place routine. Touch up the drop position when you get there.

That was my plan, but I was surprised when the part started hanging up on something I couldn’t see when trying to move to the final drop position.

Having never taken a close look at the application before, I didn’t realize that part of the drop fixture actually inserted into a small slot on the bottom of the part itself (it didn’t help that everything was painted black too). This was impossible to see from above, and given how tight the layout was, impossible to see from pretty much any other angle as well.

So what do we do? Teach backwards.

When dealing with a blind placement like this one, sometimes it’s easiest to place the part in its final position by hand and then teach the point like you would a pick position. Grip the part and step backwards through your programs until you can touch up the pick position like you would a drop.

I didn’t want to change the pick position on this one since it was used for several other drops that were working just fine, so I used a paint pen to mark where the robot gripped the part. I could then put the part in its final position and simply align the gripper with the marks to touch up the problematic drop.

Everything looked smooth in T1, so we put the robot in AUTO and bumped the override up to 100%– problem solved.

It’s easy to get stuck always trying to go from point A to point B, but sometimes it’s easier to start with point B and move backwards.

There's more where that came from.

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