Tips to prevent "scars" from travel moves?

[mitchfx]

I'm getting some very nasty looking "scars" (aka artifacts or trace marks) on the outer shell of my prints where the nozzle moves to and from the supports. I'm looking for a way to either prevent this by redirecting the path that the head takes when changing from outlines/infill to laying down support pillar layers. I was also wondering if it is possible to force a retraction or wipe at this phase. Here is an image that shows the effect of these moves going right across a very prominent surface area of my sculpture, which unfortunately needs supports to hold up the nose and chin.

It is worth noting that the resulting scars are NOT at the attachment point where the supports meet the outline. Instead they are a few mm to the right or left and due to some very VERY fine strings of PLA left behind I can tell the exact path the nozzle took. Judging from the fact they are more pronounced on the right side (looking at printer bed) I would have to guess they are from the travel move AFTER adding a support layer as it moves to the next support pillar (ear) in a counter clockwise direction.

[KC_703]

Maybe choosing a "start point" towards the back of the head will make it less noticeable... thats assuming you're using the "Choose start point closest to specfic location" option. Instead of making the change to the profile, you could also rotate the model so a less obvious spot is identified.

Also could be ooze build-up or slight over extrusion:
- For ooze, increase retraction slightly or possibly experiment with coast and/or wipe
- For over extrusion, decrease extrusion multiplier (.95-.97) or sample the diameter of the filament and adjust filament diameter.

The strings may be from too high an extrusion temp... descrease or increasing the retraction (above) could "suck" up the ooze more.

[mitchfx]

KC,

Thanks for the reply. I actually do have the start point in the back of the model. This artifact isn't a start/stop seam in the outline...it is a mark made by the nozzle traveling diagonally across the outline after the support layer is laid down on its way to the next support pillar. I've tried coast and wipe for fixing other small issues but not sure you can force a wipe or coasting for the end of each section of support (mine is in a few different disconnected areas around the model). I feel my extrusion rate is pretty good and I've calibrated it carefully for this specific spool of PLA using a thin wall cube.

I will play with retraction settings tonight a bit.

[mitchfx]

Here is a screenshot showing the travel moves from one support to the next. As you can see it crosses right over the outlines. I've tried using the option "Avoid crossing outline for travel moves" but it doesn't appear to actually change anything even if I set the detour factor to 10.0.

[JoeJ]

I would add Z-lift or retract more so that there isn't anything to deposit on the outlines to create the defect

[jimc]

X2

plus adding a little more retraction may help also

[jzatopa]

I have the same problem with some flat surfaces. I will get a perfect finish and then the head is dragged accross the top of it making a mark.