When printing dual extrusion, the ooze shield seems to be very helpful... and you need either that or a prime tower to make sure the extruders are primed.
However the gcode generated by simplify 3d does not have the ooze shield (or prime tower, for that matter) print before the layer.
Expected behavior: Ooze shield should print before any of the actual model features in each layer, at least once, so that it fulfills its purpose of wiping ooze off of the idle nozzle while printing. IMO prime tower, if chosen, should also print a layer before the first layer of print to make sure the chosen extruder is primed and ready to go.
Observed behavior: When printing with ooze shield or prime tower enabled, the shield/tower is only printed at the first tool change, or AFTER the first layer.
This behavior seems particularly bad when using the ooze shield because of two things:
1. Shield does not protect first layer at all, allowing any ooze on idle nozzle to be wiped on edge of print and potentially cause things to fail downstream
2. For the same reason the shield is frequently 1 layer shorter than the model outline and features being printed - again leading to it not serving its purpose and having idle nozzle ooze be wiped on the print edge instead of the shield.
I suspect it is the intended behavior - it's certainly what the gcode says - but it doesn't make sense to me. The only mitigation I see is to print a skirt as well as the ooze shield - but this only helps with the first layer problem, and it it raises the possibility of the skirt lifting and causing print failure (that is, another potential point of first layer failure).