13.03 vs 13.06.3 (a probably unfair comparison ;-)

[hp-65 4]

For your entertainment...

 

A few years ago, I bought a 3kg spool of a medium-rigid filament from eBay.

The best stuff I ever had:

Though it already got very soft above ~50°C, this filament had absolutely no warp.

 

I used it up and received a 2nd spool a few days ago.

After manually feeding the material through the extruder, I already noticed

that this filament was somehow different.

A lot of bubbles came out, even at completely ridiculous low temperatures.

 

I hoped the best and printed some solid parts.

Because I already used 13.06.3 for some other test prints, I did not pay special attention to the newer Cura version.

 

Nice! Not that much difference compared to the old, completely bubble

free material and 13.06.3 seemed to work great.

 

And then came this little case:

At first, I printed the shocking 13.06.3 version, the "old-13.03" print was done afterwards.

Same file, same material, same settings and same machine...

Cura 13.03 left and 13.06.3 on the right side:

After a while, I noticed that one part of the 13.06.3 print looked great too,

see lower part of the rear wall on the right.

And here's the reason.

The ugly top part, had this rapid move going through and the oozing material

from the nozzle sat right between the two walls and bent them apart.

Closeup (boosted dynamic contrast a little, doesn't look that glassy in real life):

 

The lower part only had the two walls:

Basically, two questions arise:

1)

Ok, beside all these filament caused problems, obviously because of a lot of

moisture in it, why didn't 13.06.3 fill the walls?

Wall thickness: 1.0mm

Nozzle size: 0.35mm

Infill overlap: 60%

Does it need the extra 0.05mm (3 x 0.35mm = 1.05mm)

Cura 13.03 does this:

2)

I printed about ~100kg of different PLA sorts, but I never had a problem like this.

Does it make sense to dry this filament?

According to this PDF (unfortunately in German only, but graphics on page 3 should be self-explainatory (moisture vs. time)), it would be required before each print:

http://atr-solutions.de/app/download/5785460138/I-PDF+Mann_Hummel_KU110937_KU4_12.pdf

Sorry for the subject, I just couldn't resist.

I really don't blame it on 13.06.3 (yet :wink:, just needed to share this.

Never experienced anything like this before.

 

[illuminarti 18]

I presume that the STL file you are printing actually has the walls modeled as thin structures - it's not a solid block, that you're only printing the outside edge of? If so, how thick are the physical walls in the model? The 'wall thickness' in Cura is now renamed skin thickness, which better indicates what it does - it's the thickness of solid plastic you want behind each finished surface. Typically you want this to be one or two times your nozzle size, to get either one or two passes of the head. This is nothing to do with the thickness of the walls in your STL file, unless you have a solid object that you want to just print a thin wall around (in which case you set the wall thickness here, and then set 0% infill). If, as I suspect is the case here, you have 1mm thick walls in your STL file, and have the 'skin thickness' set to 1mm, you're actually asking for something impossible - 1mm of plastic loops behind the outer wall, and a separate 1mm behind the inner wall, which would overlap. I expect that Cura is able to handle it, but it's worth bearing in mind.

The newer version has a totally different slicer engine, so it handles small gaps differently.To be honest, the gcode pictures you posted for 13.03 and 13.06 look to me like they were the wrong way round - usually 13.06 zigzags to fill in small gaps that earlier cura's left empty. Maybe your excessive wall thickness is confusing it, though - it is still in beta?

What I think is happening may just be that it's printing each layer a lot quicker, since it isn't doing the zigzag infill, and so the plastic isn't having time to cool between layers. Try setting a longer minimum layer time, so that the plastic can cool between layers.

 

[hp-65 4]

To be honest, the gcode pictures you posted for 13.03 and 13.06 look to me like they were the wrong way round - usually 13.06 zigzags to fill in small gaps that earlier cura's left empty. Maybe your excessive wall thickness is confusing it, though - it is still in beta?

Oh no, I did not swap them.

After some more experiments, it seems that the new overlap algorithm doesn't work as expected.

The walls have a thickness of 1.0mm

The nozzle width is set to 0.35mm, which leaves exactly 0.3mm in the middle.

With an overlap of 60%, the nozzle should travel 0.7mm * 0.6 = 0.42mm.

Enough to fit a 0.35mm tip.

The new slicer fills the gaps up to an infill value of 42%. One percent more (43%) fails.

Mhhh, let's see:

0.42 * 0.7 = 0.294mm

0.43 * 0.7 = 0.301mm

This exactly matches the gap distance between the walls.

Looks like the new slicer forbids the nozzle center to pass an already layed down string.

I guess that's not how it should work.

About to test some more, may be there are some more dependencies...

 

[gr5 2,234]

In the old cura it made sense to "lie" to it and tell it that the nozzle was .35 even though in reality it was 0.4.

The new slicer (I beleive) is better at this and you can tell it the truth - that the nozzle is .4. The gap will be 0.2 and it will make this crazy rattling shaking infill pattern but it should work hopefully. I believe it reduces the amount of plastic appropriately.

Regarding infill overlap of 60% - this seems crazy. 15 to 20% is a more reasonable value. Unless you have a lot of "play" aka backlash. Maybe that helped the old cura but I'm not sure if that's a reasonable value for the new cura.

Another way to make this all better:

Consider changing your STL so that the walls are either 0.8mm or 1.2mm thick (instead of 1.0mm thick).

 

[illuminarti 18]

Yes, but I think maybe you're missing the point about wall thickness settings... your STL has a 1mm wall defined in the file. But what is your 'skin thickness' set to? If that is also 1mm, while your nozzle is set to 0.35mm, then I think that Cura is going to probably change your nozzle thickness on the fly to 0.5mm (at least that's how it worked in older versions - see this write up for details. Note that the bugs described there are now fixed in the latest Cura, as far as I know, but I think it probably still works the same way in terms of nozzle/skin thickness interaction).

Because you can't fit two 1mm thick walls inside a 1mm space, I guess it's just doing a single pass in that area. Maybe with a bit of under-extrusion... but Cura probably doesn't think there's a gap in there that needs to be filled. Traveling along that thin wall may indeed be a problem though.

George is right that almost certainly you don't really want a 60% overlap - if its needed, then you're probably masking problems elsewhere (most likely backlash). If so, it would be better to solve the real problem - conventional wisdom says a 15% overlap is ideal.

And also, consider whether you really want a 'skin thickness' setting of 1mm if that's what you indeed have. I think it's going to cause problems in a model that only has 1mm as the physical thickness of some walls.

 

[hp-65 4]

Yes, but I think maybe you're missing the point about wall thickness settings...

 

Oh yes, you are right!

The new slicer isn't that forgiving any more.

The old Cura behaviour was to simply skip the inner walls and start with the infill rightaway.

13.06.3 behaves different.

But even after reducing the 0.7mm down to 0.35, the infill algorithm doesn't work as it should.

This is the old behaviour, with an infill setting of 50%:

This is the same in 13.06.3.

As you can see, a 50% overlap setting gives a 100% match with the perimeter walls:

 

I also tested 100%.

In this case, the infill crosses the perimeter walls and "leaves the object".

Someone forgot a divide by two here :wink:

 

George is right that almost certainly you don't really want a 60% overlap - if its needed, then you're probably masking problems elsewhere (most likely backlash). If so, it would be better to solve the real problem - conventional wisdom says a 15% overlap is ideal.

 

That's right. With Cura 13.06.3 I am going to divide this by 2 :wink:

No, seriously.

I spent a lot of time tuning all these machines and 60% gives perfectly strong and rigid results.