Ender 3 seemingly speeds up too much on straight long shell lines

  • 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

  • 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 After looking at the image it doesn't really look like a combing issue, although i still think it is related to the travel.

    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.

    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.

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Content dated before 7/24/2021 11:53 AM