gfcaim

6mm @ 30mm/sec worked for me but by far the biggest thing was as GregValiant says 'turn off Z-hops'

Trying to understand. I make a simple box of height 8mm (50 x 0.16 which is my layer height. Add a letter to the top surface of it. When i slice instead of getting smooth surfaces up to the layer where the letter printing starts i get 'impressions' of the letter below the letter layers (see pic) How do i avoid this?