If you melted your initial test piece your spindle speed is to fast, or your feed rate is slow. I would try slowing the spindle speed and increasing the feed rate with a single flute tool. Some form of cooling directed at the cutter helps remove heat generated by the engraving process and removes the waste which is important as you do not want to keep re-cutting the already machined chips.
You failed to mention your speed and feed rate, what are you running?