Prusa i3 Mk3 - Top layer wrinkles (not on buildplate)

Question

Recently started using my kit Prusa I3 Mk3 and noticed that with large horizontal surfaces a wrinkling pattern is emerging.

As you can see in the image the wrinkles seem to run parallel, the surface is 10 mm above the build plate with all bridges fully supported.

Has anyone seen this before? All other areas seem to be doing well.

This print uses PLA filament @ 235 °C hotend temperature and clearly shows a wrinkled pattern on the top layer

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If it helps, I haven't changed the settings from the normal Prusa Slic3r 0.15 profile.

The problem reduced to an acceptable level by reducing the temperature to 205 °C but keeping the fan speed 100 %, I am printing PLA. I might reduce the fan speed if I feel troubled by the result.

Answer 1

Waves in printed surfaces with FFF are observed at either the bottom layer (common) or the top layer (less common).

Waves in bottom layer

Rippling/wave generation/wrinkling is a common problem for first layer to occur and has a direct relation to the print nozzle to bed distance; a too short of a distance or over-extrusion can lead to this effect. However, this effect is less commonly observed in top layer finishes. Bottom layer waves are described in more detail in this answer.

Waves in top layer

I have seen this defect before. It is caused by a combination of incorrect hotend temperature and print cooling fan settings. Please reduce the hotend temperature and reduce the fan cooling. The image below clearly shows the differences of such measures.

Answer 2

Might just be that you are bridging without collapsing but still have some visible sag. Things to try:

1) increase the support/infil density. If slic3r has a configurable setting like Cura does, you only need to increase the density for the last couple mm prior to the top layer.

2) increase the top plate thickness (number of extruded layers). This often allows the first extruded layer to sag, but the final layer or two to be quite flat.