Scars on 3D prints

[JavierCM 0]

Hi! I've been having this issue where I get the scars showed in the attached pictures in all my prints. I'm more like an amateur in 3D printing, so I've been doing some research but I don't seem to find the solution (nor similar problems) to this. I've tried checking my belt tension and making sure there are not any loose screws, but everything seems ok. I've been playing with my retraction settings and calibrated the extruder steps/mm, but with no results.

 

Does someone know what this problem is and how could I fix it? Thanks in advance!

[gr5 2,004]

Three thoughts:

1) retraction.  Check the print in layer view and try to find these spots and see what happens there and in particular if there are any light blue lines in these spots which are retraction moves - you might need to play with the retraction distance.  Retracting too much or not enough can cause spots just like these.

2) speed.  Try printing at half speed - it's amazing how much better the quality can be.

3) slicer.  Try cura 15.04.  I'm not sure but it seems like some of these blemishes don't happen in cura 15.04.  I don't understand why as it's the same slicer engine but some setting or something may have changed.  Many people (many!) have had better luck with cura 15.04.  However I have had excellent results with cura 3.X so I don't know what's going on.

 

What kind of printer is this?

[JavierCM 0]

46 minutes ago, gr5 said:

Three thoughts:

1) retraction.  Check the print in layer view and try to find these spots and see what happens there and in particular if there are any light blue lines in these spots which are retraction moves - you might need to play with the retraction distance.  Retracting too much or not enough can cause spots just like these.

2) speed.  Try printing at half speed - it's amazing how much better the quality can be.

3) slicer.  Try cura 15.04.  I'm not sure but it seems like some of these blemishes don't happen in cura 15.04.  I don't understand why as it's the same slicer engine but some setting or something may have changed.  Many people (many!) have had better luck with cura 15.04.  However I have had excellent results with cura 3.X so I don't know what's going on.

 

What kind of printer is this?

 

It's a Anet A8, I'm slicing with Cura 3.3.1. I was playing around with the slicer's options when I found out about coasting. It turns out that when I enable this experimental feature, it shows in the preview the exact same scars that are found in the print. I'm really confused about it. For example, the wing picture that I attached earlier was sliced without coasting being enabled; though it was printed with the scars that shows Cura when I turn coasting on. With this feature off, it just shows the smooth surface it should be printing instead. 

 

Any ideas about this?

[JavierCM 0]

So for everyone having this issue, I finally understood what's going on. My printer was not extruding enough plastic, so when it came to a layer change it left a gap without filling, the ones you can see in the pictures and with coasting enabled (as coasting substitutes the last extrusion movement with a travel path). So basically the solution is to extrude more plastic. I printed the same model in Simplify3D cranking up the extrusion multiplier and it came just perfect. I'm currently adjusting the Flow setting of my Anet so I can get back to Cura. 

 

Hope it helps!