Cura's perimeter welding

[chopmeister 0]

As I understand, Cura welds perimeters with small gaps between them by rapidly zigzagging the printhead throughout those gaps. Can that feature be switched off?

Besides sometimes doing that when completely unnecessary or unimportant, I just tried to print a thin walled (double perimeter) object for the first time with Cura 13.11 and it completely destroyed the inner skin of the object. It seems that for some reason those welds appear on the inner side of the walls as can be seen in the picture.

The result was of course a totally messed up print.

I do like the feature for most prints, but I would like it even more if I can shut it off sometimes.

 

[illuminarti 18]

That's not 'welding' the perimeters, it's just adding extra infill on the inside of the object where needed to support overhangs etc. It's been like this since the early 'SteamEngine' versions of Cura, and actually works quite well for its intended purpose, but is damned annoying when you're doing a hollow print like this, and it can't be turned off directly :-)

However, Cura 13.11 brings back the Joris/Spiralize option that will specifically avoid doing this infill, and also extrude the wall as a single continuously climbing pass of whatever width you specify (even if that thickness is, say, 0.8mm, that it would usually do with two passes - it just forces out more plastic than usual to give a wider bead, so be sure that you adjust speed downwards accordingly).

I think that it's maybe a little bit buggy, as it's a brand new feature, but it can't be worse than all the crap on the inside of your vases, so it might be worth trying.

 

[chopmeister 0]

Ah. Since this is the first such object I'm printing since the old Cura versions, I wasn't aware that infill can kick in even if it is set to 0%, so I presumed it was randomly welding those. I'll give Spiralize a try, but still, I would love 0% infill to actually do no infill whatsoever.

Thanks for the clarification!

 

[cor3ys 28]

Hi

I tried spiralize with a wall thickness of 0.8, but when it done the base it left what looks like a nozzle width gap between each row so the base ended up like a sieve, to get a solid base i had to set a wall thickness of 0.4.

So i don't understand how to get a thicker wall thickness ? do we have to manually increase the material flow on the um2 control panel to achieve this ?

 

[illuminarti 18]

@cor3ys - I haven't tried using it yet with it, but I imagine it's just a bug. You also need to make sure that you're bed leveling is precise, since you're relying more than usual on spreading the plastic out into a wider bead.

 

[cor3ys 28]

Hi Illuminarti

Yes bed was level so i assume like you there must be a bug in this feature...

 

[illuminarti 18]

Actually it might be under-extrusion. The base is printed with the first layer height, and the wall width you specify. So if you have say 0.3mm as the height, and 0.8mm as the width, that's 6 times the extrusion volume per second, compared to a normal 0.4mm-wide bead, and 0.1mm layers at the same speed. (i.e., 0.3 x 0.8 x s = 6 x 0.4 x 0.1 x s).

So, you may need to slow your first layer down a lot, to be able to extrude enough plastic. Otherwise, you'll get gaps, because the printer can extrude as much plastic as it is supposed to every second, so the lines of plastic it lays down aren't the right size to fill the space between them.

I just finally tried a spiralized print on my UM2, and it printed fine - and I checked the math in the gcode, and the first layer was calculated correctly.

 

[cor3ys 28]

Hi illuminarti

My settings were as follows am i asking to much from the machine ?

Base settings

0.3 layer 20mm/s speed

Build settings

0.06 layer 0.8 wall 50mm/s speed

 

[gr5 2,172]

As illuminarti mentioned, you have to print about 3X slower than normal (and first layer 6x slower). Do your normally print 150mm/sec with .06 layers? If so then you should be fine. Note that this print will still come out fast as it is basically printing 200% flow (personally I would try something more manageable like .6mm wall).