3D Printer – Retraction instellen en calibreren

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Op deze pagina vind je informatie over hoe je bij een 3D Printer “retract” kan instellen.

Informatie (ENG)

I was reading the discussion from Steesh and it occurred to me that I haven’t really tested the impact of retract yet.

On the web there is precious little information available, there is only this default value of 4,5 mm at 40 mm/s that everybody seems to use, including Craftware. But BonaFide shared a valuable insight in that thread – he advised us to reduce the retract to 0.5 mm or even disable it, since 4,5 mm was supposed to be used only with bowden extruders. I decided to test it.
I used this model on Thingiverse, it is very small, uses little filament and prints in five to ten minutes. I printed on a cold bed with glue stick at 200 °C with Craftunique PLA, 0.1 mm layer, 50 mm/s print speed, 0.5 mm nozzle.

I started with no retract:

retract 0mm

This is horrible. Clearly we need the retract if there is travel involved.

I then made a series of prints with different retracts: 0.7, 1.4, 2.8 mm at default retract speed of 40 mm/s:
1.4 and 2.8 mm:

retract 1.4mm 2.8mm

This is better than with no retract, but horrible nevertheless.

0.7 mm:

retract 0.7mm

I get a BIG difference: just some tiny stringing, MUCH smaller blobs.

I now tested the impact of retract speeds – is it better to go fast or slow?
0.7 mm at 20 mm/s:

retract 0.7mm 20mms

The blobs seem to be a bit bigger. It seems slower is not better.

0.7 mm at 80 mm/s:

retract 0.7mm 80mms

Blobs are smaller, it seems better to go as fast as possible.

So I will set the speed to 90 mm/s which seems to be top speed that Craftbot can handle for XY movement. Extruder can likely work much faster, but 90 mm/s is fast already – the retract of 0.7 mm should happen in about 8 milliseconds.
Now I wanted to find the optimal retract value.

I first tried 0.5 and 0.9 mm to find the direction I should take:

retract 0.5mm 0.9mm 80mms

Clearly 0.5 looks better. Maybe I can go lower?

0.4 and 0.6 mm:

retract 0.4mm 0.6mm 80mms

The pictures are not that good (sorry), but 0.4 clearly increases blobs compared to 0.5. To me it looks like 0.6 is the best value.

To recap:
You should set the retract on Craftbot to somewhere around 0.6 mm at high speed (90 mm/s works for me). It will increase the quality of your prints immensely, the blobs are all but gone!

There are two caveats:

  • If you print with different materials, these values likely change. I think normal stiff materials like ABS, PET and nylon should work fine with this setting, but stretchy materials like Filaflex likely need more retract.
  • Hot end temperature likely affects this too.

I will end this with the picture of all tests together – they are really tiny and so all imperfections are horribly exagerrated. What you see is a paper sheet about the size of A5:

retract overview

Edit: Be sure to set both Retract AND Prime settings to the same value, otherwise you get heavy over/underextrusion.

 

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