[DerekFromm]

When applying an [N,T,S] approach to a curve follow project, anytime a non-zero value is used for the [S] component, unexpected tool orientations occur for the entire curve follow project.

Context/Background:
My team is using this style approach so that we may apply Rx rotation to tool offsets for curve projects via the API, as opposed to updating the curve object itself. It allows us broader control of tool orientation for variable weld types on our robot welding cell. We found that we then needed to modify the approach vector for curves to match modified Rx rotation, so that the welder approaches in the same plane as it will travel during the weld. To do this we started using [N,T,S] approaches where [N] and [S] components are calculated from the Rx angle value we apply to the tool offset in the curve follow project. Upon trying this method we noticed odd tool orientation changes. 

Here are the findings so far:

• NTS application for curve approach affects tool orientation for the entire curve, but using NTS for retract has no effect.
  
• Non-zero N and T values can be used with no unexpected change to tool orientation.
  
• Using non-zero S values applies a path to tool Z rotation to tool orientation, but this rotation is dependent on your values of N and T. See the following:
  
• Changing values of N has NO effect on Z rotation, meaning N values of zero and non-zero terms, when combined with non-zero S values, will result in the same tool behavior. The following bullets list that behavior:
  
•   Using a [-] S value applies a -90 path to tool Z rotation
  
• Using a [+] S value applies a +90 path to tool Z rotation
  
• Non-zero T values, when combined with non-zero S values, create variable rotations that change between approach and path
  

While we have a current solution for this issue, utilizing the -90 path to tool z rotation, we aren't sure if this is a bug or a result of the math involved with the NTS approach vector. We'd like to have full control of an NTS approach with all components, but have not figured out all the workarounds for each combination of NTS components.

I've attached a simulation of this behavior.

[Albert]

If you use the algorithm Tool orientation follows path, the orientation of the TCP will be defined by the approach orientation. If you select the + button you have the option to ignore certain curve angles that define the tool orientation.

To avoid this type of behavior I recommend you to change the algorithm to Minimum tool orientation change.