After few good prints with my new Ender 3, I noticed that prints with longer shell straight lines (> 5 cm) have extrusion problems in the middle of those lines.

I figured that this might be because the printing speed (70 mm/s) and filament temperature (210 °C for PLA). So I increased my filament temperature about 215 °C and lowered print speed to 60 mm/s. I am using Cura v3.5.1. For the next few smaller prints everything was perfect.

Now I am printing a bigger 128 mm X 48 mm rectangular shape. In the middle of the 128mm line of the outer shell, I have signs of under extrusion. Looks like dents.

I also notice that the head is really fast during this 128 mm travel. No way ~2 seconds would take 60 mm/s to travel 128 mm. It is more like 1 second or less.

Why would my head travel at such speeds?

I am attaching my speed settings.

Speed settings

I am attaching the image of the printed piece and the defect generated.

The problem generated

up vote 2 down vote accepted

Your travel speed is set to 120mm/s so it would make sense the 128mm travel takes ~1 second. You most likely have combing turned on so that it doesn't not need to retract on travels. This makes it ooze plastic as it travels and would mimic underextrustion.

  • Interesting point. Combing is turned on indeed. You might be right. I am not sure. I have a knob on the extruder motor and seems that is extruding during the fast move. I might be wrong. I have to reprint this tomorrow and take into consideration your suggestion, so I can accept your answer. Thank you! – sanyi Nov 6 at 22:16
  • @sanyi After looking at the image it doesn't really look like a combing issue, although i still think it is related to the travel. – Perplexed Dipole Nov 6 at 22:35
  • Travel speed is the speed at which the nozzle travels when it is not printing. Print speed is how fast the nozzle travels while printing. At a print speed of 60mm/s, it should take just over 2 second to complete the 128 mm side. You also have more advanced speed settings, including inner wall and outer wall settings, that should effect the time to print the side. – Verl Humpherys Nov 6 at 22:43
  • I did not have time to reprint the previous print, but i did print a small beam simulating the 120 mm long lines. Disabling combing on skin, I was not able to reproduce the problem. I will reprint the initial piece eventually, for now I accept your answer as correct. – sanyi Nov 7 at 19:10

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