Cura retraction during fill?

[fishpepper 0]

Hi!

When cura changes the xy position while inside an object it does not seem to retract. Can i enable that somehow?

The problem with the current behaviour is that the infill that gets printed over the stripes/dots caused during those moves results in an uneven finish :(

regards,

Simon

 

[Daid 304]

Disable "combing"

 

[fishpepper 0]

Hi!

Thanks! That looks much better. However i still get some oozing...

The same retraction (30mm/s, 4mm) for my kossel delta (bowden) work fine with slic3r.

When i use cura (13.11) and the same settings i get a lot of strings.

Even if i set it to 70mm/s 6mm it looks still bad.

What does Cura differently than slic3r?

Another thing i noticed with cura: At the continuation point after retraction i get a weak (incomplete) fill.

Very strange... Any ideas?

Too bad, i really like the way cura calculates its toolpaths :( I do not want to switch back to slic3r :-

Regards,

Simon

 

[gr5 2,071]

There are several things you can do to reduce stringing. Lower temps help:

http://umforum.ultimaker.com/index.php?/topic/1872-some-calibration-photographs/

 

Slow speeds helps. Change retraction back to 4.5mm and 40mm/sec. 70mm/sec actually moves slower because of a Marlin bug. 6mm is too much and lets in air into the nozzle. Also add this to your extruder to keep the tube from moving up and down at the extruder:

http://www.thingiverse.com/thing:46157

 

Try 20mm/sec at 190C? I know that's extremely slow but you are likely to see zero retraction with that setting. You should be able to go much faster depending on the type of filament, layer height, and more. But at 190C you can't squeeze as much filament out so if you want to print faster you might have to increase the temp a bit.

 

[fishpepper 0]

Hi!

Thanks for your suggestions, i will try them tonight.

To me it looks like there is some timing issue (?) with cura.

The prints look really really bad compared to slic3r, even printing at 210°C in slic3r looks way

better than 190°C in Cura (talking about stringing issues).

To me it looks like cura times the retracion in a wrong way, it seems that the retractions happens "too late"

-> i get strings when the head starts to move to a new position

-> after reaching the new position i do not get enough material being pushed out resulting in not closed infill

I will post pictures today from the tests i printed yesterday.

Maybe i will dig into the produced gcode, mayber i get a clue what cura does differently.

I might try older versions of cura to see if this helps.

Regards,

Simon

 

[fishpepper 0]

Hi!

I did some experiments. I think there is something going wrong....

If i print the hollow calibration pyramid, the first layers where the arms start to be printed work fine,

then cura changes to a strange behaviour:

1) it prints one arm

2) retracts (E=Eold - 4mm)

3) prints a very small part from infill

4) moves E=Eold

5) moves to next arm position

It should retract after the infill print?!

I see the minimum extrusion kicking in, if i st that to 0.0 it retracts after 4 as well but i get a lot of retractions.

Any clues?

Regards,

Simon

 

[Daid 304]

What you are describing should be impossible. At least, if you are saying:

1) Cura prints a bit

2) Cura retracts

3) Cura moves to infill

4) Cura prints infill

5) Cura pushes back from the retract at 2)

This piece of code:

https://github.com/Ultimaker/CuraEngine/blob/master/gcodeExport.cpp#L175

Always adds a push-back before printing anything if it was retracted.

 

[fishpepper 0]

Oh sorry i made a mistake in my ordering, i swapped 3 and 4.

what i see in your notation is:

1) Cura prints a bit

2) Cura retracts

3) Cura moves to infill

4) Cura pushes back from the retract at 2)

5) Cura prints infill

and now the bad part:

6) Cura moves to the next (far away, parameter crossing) section

 

The move from 5 to 6 is without retract. The behaviour i would expect is

1,3,5,2,6,4

(= retraction only for the big move and not for the infill)

 

So the detection when to retract goes wrong. If i set the minimum travel/extrusion values before retraction to

very small values i get many retractions but at least it adds the right one between (5) and (6)

 

I just found out 13.10 does not do it wrong, it starts with 13.11.

You can observe it with this file:

http://www.thingiverse.com/download:86621

 

The first (5 or so) arm layers after the base are ok, then cura starts to show the wrong behaviour.

 

Regards,

Simon

 

[Daid 304]

Which combination of settings? As I'm seeing proper retractions.

 

[fishpepper 0]

Hi!

Oh sorry, it looks like i deleted my config during testing/playing around with 13.06 and 13.10 debugging the problem with infill directions.

Unfortuantely i can not reconstruct my settings where i got that behaviour...

I just reinstalled 13.11 and the problem does not seem to happen with my current settings.

If i ever encounter them again, i will post the settings here. Thanks for looking into it!

Regards,

Simon