Note

Setting the G-code feed rate (either with an F word or call to Gcode::FeedRateSet) with the argument f does the following:

f > 0: sets the target feed rate to f (unless f is vanishingly small).
f == 0: clears the feed rate with no error. Use this to intentionally prevent feed-governed motion.
Otherwise: yields an error to indicate that the argument was rejected and clear the feed rate to prevent malformed motion.