dribble slime or bava!

[simmonsstummer 0]

Hi,

i'm printing some kind of jars.

What i notice is that the Ultimaker 2 leave some kind of dribble along his way. Not always but often.

This happen when cura make some kind of wrong path choice and go from a part to another. The nozzle bring back this slime and at the end of the print i have several slime!

Is that normal and how can i avoid it?

 

[simmonsstummer 0]

and that's the image

 

 

[illuminarti 18]

It's generally called 'oozing' or 'stringing'. Photos would help us make specific recommendations, but in general you need to enable retraction, and possibly also turn off 'enable combing' (die to bugs in how this works in current versions of Cura). In order to do those things, you will need to be using the 'full settings' mode in Cura, not Quickprint.

[simmonsstummer 0]

Ok, in the advanced settings retraction i can't understand if is able or not. Seems that combing is abled.

 

[illuminarti 18]

Ah, good. I see you added a photo already, thanks. Yes the lines on the outside is stringing due to retraction being off, or not working well.

The blobs on the inside of the print are Cura adding extra infill to ensure that sloping walls stay the right thickness (when measured at right-angles to the surface).

If this is intended to be a thin walled, open top, vase-like object, then go into the expert settings and enable 'spiralize'. That will print the outside as a continuous spiral, with a bottom layer, but no solid top, and none of the extra infill to thicken the walls.

[illuminarti 18]

Uncheck the checkbox next to 'enable combing'.

[simmonsstummer 0]

Uncheck the checkbox next to 'enable combing'.

 

the quick guide seems to say the opposite..

 

[simmonsstummer 0]

He you can find the other photo:

https://plus.google.com/116867274133488266077/posts/HQFfoWPtjke

So the blob you can see outside in the prints are due to the not "Spiralize" setting?

 

[illuminarti 18]

The blob on the outside in that print is due to a bug in Cura that causes the print head to move outside the print before a retraction. Unchecking the 'enable combing' option might help. Also, while in the retraction settings , set the minimum travel to 1mm, and the minimum extrusion to 0.

[gr5 2,265]

So the blob you can see outside in the prints are due to the not "Spiralize" setting?

 

Spiralize is a very special setting and can make a print much better or much worse. It is intended for vases and cups that have no holes in the sides.

What you have we call "strings". We don't call them blobs. "blobs" is something else that you will get to see later

There are 6 retraction related settings:

1) Make sure retraction is checked on basic/quality

2) In expert settings set minimum travel to 0mm or at least something small like 1mm.

3) In expert settings set "minimal extrusion..." to 0mm. I hate this setting right now.

4) In expert settings you can set "combing" on or off - it shouldn't make a huge difference for this part. Lately turning this "off" seems better in the current version of Cura but in the next version it might be best to turn it back on.

5,6) On the printer, you can control retraction there also Leave the retraction speed alone but change the retraction amount from 4.5mm to 5.5mm.

 

[illuminarti 18]

Blobs on the inside of hollow objects aren't caused by the state of Spiralize, but turning it on is the only way to get rid of them.

However, Spiralize is only for shapes with a single thin wall, solid bottom, and no top - like a vase or cup.

[Daid 306]

The blob on the outside in that print is due to a bug in Cura that causes the print head to move outside the print before a retraction. Unchecking the 'enable combing' option might help. Also, while in the retraction settings , set the minimum travel to 1mm, and the minimum extrusion to 0.

 

Note, this bug is only present in the 13.11.2 release, and will be fixed soon. It will also not effect this print.

What is preventing retraction here is the "minimal extrusion before retraction" in the expert settings.

 

[illuminarti 18]

Can I suggest defaulting that to zero - or something very close to it - for UM2's, Daid? In my tests, it just doesn't seem to be an issue on the UM2.

[Daid 306]

Yes, I've been adjusting the default. When I added the setting it was not really tuned yet. I've been tuning it better as I got feedback. The new default is 0.02mm now.

 

[simmonsstummer 0]

Daid,

Is there a way to add an extimation of the cc of the model?

All the lab set the price based on cc and could be more quick to have an estimation of the cc.

Something like netfabb..

 

[Daid 306]

cc? That's an odd value to use as cost, because objects are printed hollow.

Cura calculates the amount of filament used, which is a much better figure to use as costs.

 

[illuminarti 18]

Most places like shapeways do charge by the volume of material used in the print (not the enclosing volume of the object) - but expressed in cc's (since they aren't filament based printers).

If you assume a standard 2.85mm filament diameter, each mm of filament used is pi x 2.85²/4 = 6.38mm³ of plastic. Since there are 1000mm in a meter, and 1000mm³ in a cc, that makes for a direct conversion - every meter of filament used is 6.38cc. So not quite as simple as having the conversion built in, but it's not too hard to do from what Cura gives you.

 

[simmonsstummer 0]

cc? That's an odd value to use as cost, because objects are printed hollow.

Cura calculates the amount of filament used, which is a much better figure to use as costs.

 

Well, actually the volume of the object (the real volume not the enclosing) is the most "real" parameter because the weight is based on an assumed density that no one know if is real.

 

If you assume a standard 2.85mm filament diameter, each mm of filament used is pi x 2.85²/4 = 6.38mm³ of plastic. Since there are 1000mm in a meter, and 1000mm³ in a cc, that makes for a direct conversion - every meter of filament used is 6.38cc. So not quite as simple as having the conversion built in, but it's not too hard to do from what Cura gives you.

 

That's interesting.

I was just asking if there is a way to add a simple field for that kind of calculations.

 

[Daid 306]

You could do the math with the "price per meter" preference setting. As each meter of filament is 6.38cc, you could multiply your cc price by 6.38 and use that as "price per meter" setting in the preferences, and Cura will give you the exact cost of your print.

Or fill in 6.38 as "price per meter" and Cura will give you the CC as price value.

 

[ianlee74 0]

I'm fighting this problem also using Cura with my Mini Kossel. I've done as gr5 recommended and tried with "minimum travel" = 0, combing = off, and "minimum extrusion" = 0. The print was much better until eventually a blob built up and the hotend knocked the piece off the bed. However, the real downside was that these settings took my print from a 4 hrs to 10 hrs because it retracts after every move even the infill.

What really is needed here is a setting to have it always retract before making a non-extruding move when coming from an extruding move. This would ensure the moves off the edges get retracted but the infill doesn't. This seems like it should always be the default behavior.

Before...

http://sdrv.ms/1ieONpP

After...

http://sdrv.ms/199KILB

Any improvements to this problem would be greatly appreciated. I love the Cura software but this problem is making it almost impossible for me to make these types of prints.

 

[gr5 2,265]

Before printing a multi-hour print you should spend an hour doing some experiments - I have to run but...

You should experiment with amount of retraction amount and also with lower temperatures. Here is a sample experiment I did with retraction once:

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

The lower the temp, the better stringing will be but you might have to also slow down your print speed if you go too cold so it's best to find the warmest possible temp that has zero stringing.

Also you need to dial in retraction amount exactly. 4.5 is perfect for UM1, 5.5 is perfect for UM2. Your printer will vary. If you retract too much air gets in the hot end and causes problems. The correct amount should be visible by looking in the bowden carefully.

 

[illuminarti 18]

Setting the minimum retraction distance to 1mm should be enough to prevent all the retractions in the infill, while still letting the various shells print correctly without sticking together.

You might try using the newly released Cura 13.12, and turning on 'enable combing' - since that is supposedly working better now.

At the end of the day, I think the problem is more that the print is coming loose from the bed - you might tty printing with a brim to try and hold it down, but that will probably mean more clean up. on that first layer - but that's better than having the print come loose.

 

I'm fighting this problem also using Cura with my Mini Kossel. I've done as gr5 recommended and tried with "minimum travel" = 0, combing = off, and "minimum extrusion" = 0. The print was much better until eventually a blob built up and the hotend knocked the piece off the bed. However, the real downside was that these settings took my print from a 4 hrs to 10 hrs because it retracts after every move even the infill.

What really is needed here is a setting to have it always retract before making a non-extruding move when coming from an extruding move. This would ensure the moves off the edges get retracted but the infill doesn't. This seems like it should always be the default behavior.

Before...

http://sdrv.ms/1ieONpP

After...

http://sdrv.ms/199KILB

Any improvements to this problem would be greatly appreciated. I love the Cura software but this problem is making it almost impossible for me to make these types of prints.

 

[gr5 2,265]

Setting the minimum retraction distance to 1mm should be enough to prevent all the retractions in the infill, while still letting the various shells print correctly without sticking together.

 

Smart! Damn why didn't I think of that. :(