Nozzle scraping or scarring the top surface

Try these in order

Most likely and quickest to check first. Change one thing at a time so you know what fixed it.

1. No Z hop on travel moves

   Without a small lift, the nozzle drags through the surface it has just printed on its way to the next spot.

   • Turn on Z hop (retraction lift) of 0.2 to 0.4 mm, at least on top surfaces.
   • Turn on 'avoid crossing walls' so travel stays inside the part.

2. Too much plastic on the top layers

   Extra plastic piles up and the nozzle ploughs through the ridges on the next pass.

   • Calibrate the flow rate, and lower top surface flow to around 95% if it's still rough.
   • Use a monotonic top surface pattern.

3. Infill or edges curling up

   • Raise the fan speed for PLA so infill doesn't curl.
   • Slow down the infill, and print it with a thicker pattern like gyroid that doesn't cross itself in the same layer.

4. Ironing set too low

   • If you use ironing, lower its flow (10 to 15%) or turn it off to check whether it's the cause.