1 Topic by 3d-oodler (edited by 3d-oodler 2013-04-16 05:17:47)

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Topic: Little to no filament extruding for the first several mms

[Solution was to lower PLA printing temp from 185C down to 145C.  Sending code M302 to override cold extrusion prevention is a quick way to see the impact before you update the firmware with a lower min temp]

Once my SD3 gets going it prints pretty well, but when the print starts the filament is barely dribbling out.  To compensate I set slic3r to skirt several loops, but this can vary per size of the object.  I also tried the slic3r setting to extrude a minimum amount before completing the skirt, and that didn't seem to make a difference (though the max value I tried was 20mm).

Eventually the filament starts flowing well and consistently, but for small object this can be more than half way through the first layer.

This is using PLA between 180C and 190C, and the extruder is brought up to temperature before starting the job.

FWIW I have:
- Calibrated the extruder (steps went from 138 down to 98.5).
- Changed the multiplier setting in slic3r to 1.0 from the default .79 (I also tried .95 and 1.05 after I calibrated the extruder)
- Checked the that belt tension is equal (I was having a skipping problem)
- Tightened the pulleys
- Leveled the bed
- Calibrated the z-axis

It may or may not be related, but the perimeter of my first couple of layers is not clean, it almost looks like the PLA is either melting on the bed (though this still occurs when the bed is not heated), or too much filament is being extruded (which is clearly not the case), and/or the bed, z-axis, is too high (which I also believe not to be the case).

Any ideas?

2 Reply by ronsii

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Re: Little to no filament extruding for the first several mms

I have found that you need a good 'prime' of PLA because of how runny it is it tends to drip out of the extruder once it is up to temp... if it sits for any length of time (not printing) when it is at temperature it can lose a lot of filament, so I set mine to 'dump' about three inches(70mm) in the front corner of my build plate.

3 Reply by 3d-oodler

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Re: Little to no filament extruding for the first several mms

Thanks. 'Priming' helped a lot.  First layer could still be better, but it's an improvement.

4 Reply by 3d-oodler

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Re: Little to no filament extruding for the first several mms

Increasing my post count

5 Reply by 3d-oodler

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Re: Little to no filament extruding for the first several mms

Increasing my post count

6 Reply by 3d-oodler

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Re: Little to no filament extruding for the first several mms

Increasing my post count

7 Reply by 3d-oodler

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Re: Little to no filament extruding for the first several mms

Increasing my post count

8 Reply by ronsii

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Re: Little to no filament extruding for the first several mms

3d-oodler wrote:

Thanks. 'Priming' helped a lot.  First layer could still be better, but it's an improvement.

So is your print still missing spots...like the filament is not primed all the way or is it something else?

9 Reply by Manx

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Re: Little to no filament extruding for the first several mms

I've had this problem it could be that the bed is to high and rubbing against print head

10 Reply by 3d-oodler

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Re: Little to no filament extruding for the first several mms

ronsii wrote:
3d-oodler wrote:

Thanks. 'Priming' helped a lot.  First layer could still be better, but it's an improvement.

So is your print still missing spots...like the filament is not primed all the way or is it something else?

I've improved the first layer by adjusting the widths in slic3r.  I set the extrusion multiplier to 1, and then tune the perimeter, infill, and first layer widths to extrude less.

Since my original post I had a clog and have been working to recover from that.  Things are improving, but I'm still not to the overall quality I had before the clog.  However with the width adjustments at least the first layer is now better than before the clog.

I need to experiment with lower extruder temperatures.  I'm now wondering if perhaps my post-clog issues are due to a change in the thermistor placement resulting in a hotter extruder.  I'm also wondering if this may help with overall flows.  It seems odd to me that I can turn on the printer, bring it up to temperature, and extrude about 60mm with nothing coming out of the extruder for a bit (this happened before and after the clog).

11 Reply by 3d-oodler

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Re: Little to no filament extruding for the first several mms

Changing the extruder temp from 180-185C down to 145C made a big difference.

I no longer see a delay between when I ask filament to be extruded and when it actually comes out of the nozzle.

12 Reply by elmoret (edited by elmoret 2013-04-16 05:16:57)

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Re: Little to no filament extruding for the first several mms

.

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