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I did calibrate the extruder to extrude exactly 50/100 mm and it is fine. I have replaced the old (prehistorical) extruder that was giving me the problem with a new one. The issue does not go away. It is severely under extruded. The nozzle is a 0.4 mm, if I extrude manually the extrusion is nice and clean but when printing its a mess. I have the following setting in Slic3:

  • Layer height: 0,16
  • First layer height: 0,16
  • Filament diameter: 2,94
  • Extruder temperature: 184°C
  • Extrusion multiplier: 1
  • Fill density: 15%

In Marlin I have the following setting for the extruder:

  • Steps per unit: 1450 (I use micro steps)
  • Default acceleration: 3000
  • Default retract acceleration: 3000
  • Default Ejerk: 5

How can I solve this problem?

enter image description here

This is a 20 mm cube I stopped after 15 layers!

Here is another 20 mm cube, the dimensions are perfect but is absolutely a mess. enter image description here

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  • $\begingroup$ Does your extruder constantly push out filament, just not enough? Or does it just irregularly extrude? $\endgroup$
    – kamuro
    Oct 20, 2016 at 6:58
  • $\begingroup$ Slic3? Do you mean Slic3r? $\endgroup$
    – Peter Mortensen
    Oct 31, 2016 at 21:16
  • $\begingroup$ See also Test print coming out spongy $\endgroup$
    – Greenonline ♦
    May 31, 2019 at 1:43

3 Answers 3

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Assuming your filament dimension settings are correct and your extruder is correctly calibrated...

Your extruder temperature may be too low. While 184C can be hot enough, it is very near the bottom of the range for PLA and it appears your filament isn't melting quickly enough to keep up with your other settings. Your extruder may even be running slightly cooler than you think so your 184C setting may actually be printing at 180C or less.

To solve this:

  • Raise your extruder temperature. I suggest raising your print temperature to 220 degrees and then gradually lower it until other aspects of your print quality are acceptable (bridging, oozing, etc).
  • Slow down your print. Slowing down reduces the volume of melted plastic your extruder has to deliver in a given amount of time. This allows more time for the plastic to melt and allows you to use a lower print temperature

Your filament feed mechanism may be slipping. Even if you have adequate temperature and perfectly calibrated firmware and print settings, if your filament feed mechanism (the thing that pushes filament into your extruder) is slipping, you will have under-extruded parts.

To solve this:

  • Make sure you have adequate tension on your filament feed mechanism. If your feed mechanism is too loose, filament may slip and cause under extrusion. The part to check is the part the pushes the filament into the rotating hobbed bolt or friction wheel...make sure it applies adequate pressure. "Adequate pressure" or "adequate tension" will vary depending you your printer's design, but it should be enough to provide a firm grip on the filament.
  • Verify your feed mechanism is clean. A hobbed bolt or similar filament drive mechanism that has become clogged or otherwise contaminated may cause filament to slip and under-extrude.
  • Ensure the end of your filament is not damaged from slipping. Once your filament has slipped, it may be damaged with a worn spot, a bulge, or some other defect that can prevent proper feeding even after you fix the root cause of your problem. So, as tbm0115 pointed out, be sure to clip off the damaged end to make sure you have good filament feeding into your extruder.

I hope this helps!

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  • $\begingroup$ Thanks for the good hints. I will try. I also start suspecting the robbed bolt in the extruder which is quite old. $\endgroup$
    – FeliceM
    Oct 19, 2016 at 14:23
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    $\begingroup$ As a result of under extrusion, the end of the filament may also need to be snipped if the drive gear has dug into the filament. $\endgroup$
    – tbm0115
    Oct 19, 2016 at 14:38
  • $\begingroup$ Good point tbm0115. And check the hobbed bolt and clean off any filament that has become ground into the grooves. $\endgroup$
    – Chris Thompson
    Oct 19, 2016 at 15:18
  • $\begingroup$ Updated answer to include the slipping filament issue and solutions...inspired by tbm0115. Important. $\endgroup$
    – Chris Thompson
    Oct 20, 2016 at 4:27
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    $\begingroup$ Glad that solved it for you! Another possibility (for future readers), is any setscrew(s) connecting your hobbed bolt, gear, or whatever to the extruder motor shaft. Mine loosened up once and it was (of course) the last thing I thought to check... :( $\endgroup$
    – TextGeek
    Oct 28, 2016 at 17:07
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Looks to me like you have your slicer set to 3mm filament when you're using 1.75mm filament. Confirm that your slicer has its filament setting set to 1.75mm and not 3mm (this obviously assumes you are using 1.75mm filament..)

Failing this:

  • Test extruder steps/mm
  • Ensure nozzle diameter is set correctly (usually doesnt make too much difference anyway...)
  • Ensure extrusion multiplier is set correctly.
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  • $\begingroup$ The filament is 3 mm. The nozzle is 0,4 mm and as I said in my question the multiplier is 1. $\endgroup$
    – FeliceM
    Oct 19, 2016 at 10:52
  • $\begingroup$ Fair enough. I provided the other things even though you'd already said in case somebody else came to this answer and hadn't checked those. $\endgroup$
    – James T
    Oct 19, 2016 at 11:34
  • $\begingroup$ What plastic are you printing with? $\endgroup$
    – James T
    Oct 19, 2016 at 11:35
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    $\begingroup$ PLA, black, 3 mm $\endgroup$
    – FeliceM
    Oct 19, 2016 at 12:19
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Short addition to the already great answers:

Check whether the gear wheel on your extruder motor axle is spinning with the motor. It can seem to be quite fixed, but when under load the motor is turning nicely but the gear slips on its axle.

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