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[Solved] Layer missing / underextrusion due to retraction

tankenland
(@tankenland)
Member

I am having layer missing issue on one of my ender 5 pro machine. The layer missing was inconsistent and occurs randomly.

Here is my printing parameters:

1. Material: PLA

2. Nozzle Temperature: 210 c

3. Bed Temperature: 50 c

4. Printing speed: 80mm/s

5. Retraction speed: 45mm/s

6. Retraction distance: 5mm to 6.5mm (my other ender 5 pro use 6.5mm)

7. E step and flow have been calibrated.

 

Here is some of the examples: 

Example 1: 

image
image
image

Example 2: 

image
image
image

Example 3:

image
image
image

For the retraction tuning, I have try with retraction speed from 45 to 80mm/s and retraction distance from 5 to 6.5mm. The problem is the stringy still happen while the part is underextrusion (normally my part will underextrusion when i put too much retraction.

The same file have been printed using another ender 5 pro without any problem.

So far what have I try:

1. Clean hotend and nozzle

2. Check PTFE tubing

3. Check extruder (cold end)

Any suggestion to fix this problem?

 

Regards,

Ken

Quote
Topic starter Posted : 30/09/2020 10:35 am
Luke
 Luke
(@lmf5000)
Expert Moderator

Hi Ken,

The first step is to observe the extruder while it's printing one of those lines, as its behaviour will give you a clue as to what's happening. Do you see it slipping and grinding the filament or skipping steps?

Something like this is normally caused by either an intermettently/partially blocked nozzle (which you can troubleshoot by swapping the nozzle for a new one, or performing a few atomic/cold pulls to clean out your existing nozzle), or a problem in the extruder (dirty extruder gear, slipping gear due to grub screw not tightened, insufficient drive current to motor, overheating stepper driver etc.).

Check also that the end of the PTFE tube is absolutely, perfectly straight (the cut of the end of the tube must be perpendicular to the axis of the tube and nozzle), and check that the nozzle is tightening against the end of the PTFE tube, not being stopped by the heat block before it forms a tight seal to the PTFE. The issue is that if the PTFE isn't sealing right up against the end of the nozzle, filament will leak out of that gap and cause blockages there.

As for the stringing, it will be impossible to eliminate that completely (especially once the filament has aged a bit and absorbed a bit of moisture, even if you keep it in a sealed bag with dessicant). You can easily burn off the fine strands with a heat gun or hair dryer.

Looking forward to your feedback 🙂

Regards,
Luke

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Posted : 01/10/2020 9:08 pm
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