Missing filament in outer surface - Z axis problem

[AlwynTurner]

I've noticed a fault in CURA that very rarely it is missing filament on the outer surface of a print. I thought at first it was a printer problem but noticed that the filament was missing in exactly the same place when printing multiple copies of an item at different times. It seems to occur when CURA is placing support material or printing complex objects elsewhere in the print and the fault appears just at the point where the support material ends or where complex details exist at a different point in the object, it's as if it loses track of what it was doing with the outer surface and skips a bit. I have noticed this on several different prints so it's not an artifact from just one print.




Just so that no-one else doubts their sanity like I did.

Alwyn

[wibblywobbly]

Try adjusting the rollers on your printer, it looks like a z height issue, when the printer gets to a certain height the rollers might be sticking which is messing up the layers. It isn't Cura, there would be a thousand people on the Ultimaker forum mentioning it if it was.

I would also look at the support material settings, you may need to adjust the distances between the support material and the surface, it looks like your filament isn't peeling away cleanly.

[AlwynTurner]

Hi Rob, thanks or the advice and I certainly need to have a look at the support material settings as they are giving me a few problems. I am not sure about a z-height problem though, this problem only occurs where there are complexities on the inner surface of an object, which seem to cause issues with the outer surface. I may play with the retraction settings though and maybe try a print without retraction as this may be the source of the problem. I've sent the photos and stl to ultimaker to see see what they say.

Many thanks again
Alwyn

[wibblywobbly]

There are so many variables in the Cura settings, and options that aren't even visible unless they are made active, that when things aren't printing correctly it can take a bit of digging to find out what needs adjusting. On top of that there is always the possibility that it isn't the printer or Cura, but some weird anomaly in Openscad that is producing an STL file that has holes in it that can't be seen on screen.

There is an option in Cura to fill holes, but that is masking the problem rather than finding out why it is happening. Those fuel drums in the pic above are junk ones, I printed one that came out perfectly, and then took about five attempts to get a perfect second one....it became a matter of rotating the drum in Cura, and moving it across the print bed to a 'perfect' position.

One way to see if the horizontal bar is level is to print two cylinders, one on the left of the print bed, and one one the right, bang on the centre line of the bed. If one of them prints better than the other then either the bed isn't level or the cross bar is drooping on one side.

[AlwynTurner]

I suspect this is a retraction problem. I've compared four diffrent hubs that I've just printed and all four have the same exact problem at the same position in the print, and I've just watched the print, and at the point of the problem it is doing both a retraction and a z-lift, maybe I need to give the z-axis spiral a thorough clean and light oil.....

Alwyn

[wibblywobbly]

Do you have a join between two sections of the Openscad model at that point, and if so are the two parts against each other. Check that Openscad does not display a 'manifold' warning.

If Openscad says that it is a valid model, then try closing it down, opening it again, F5 > F6 and then resave the STL under a new name.
Then delete the old STL, reload the new STL into Cura, generate the Gcode and watch what happens.
STL files can be created with faults in them, and Gcode can be generated with flaws. I have had this happen occasionally.
By recreating the files from scratch you may eradicate the problem.

[AlwynTurner]

I've just heard from Ultimaker and basically because I'm not using an Ultimaker printer then they are very sorry but can't help. I'm a bit disappointed with the response but they are a printer maker/seller not a software house. I'll just have to fiddle with settings when the problem happens on a part where the fault shows. Luckily it doesn't show on the wheel hubs.

Alwyn

[gisalook]

Alwyn in Cura you can view in layer mode it's good for this sort of thing. Just go to view, layer view and you can check each layer.

[AlwynTurner]

Yes I considered that, but the missing filament is so miniscule it would be hard to spot, and where the bits were missing didn't matter so I left it. Even If I found it there's nothing I can do about it, so c'est last vie as the French say.
Alwyn

[igotit]

i recently had similar issuses with cura and tinkercard,they both lag on my old laptop.
but i had a few print with missing layers in the same spots on multiple prints,i had remove all of my wheels published at thingi because some parts were printed outta place,on tinkercad it was good,and in cura 3.0.2 in layer view everything checked out.
so i ran both part files on my cr-10 and my a8,both printed the same wheel nicely....but the 5mm hex was now 5.8 mm.
i fought this issue all week,fix one issue,then another aspect of the part would be wrong,1 bead ring shifted,1 bead ring oversized,on 2 seperate printers.
i dont know what was going on but it seems to be fine now,no more lagging on tinker or cura at the moment.
i wasted about 150 meters rolling out wheels n stock pilling,after a few days of both printers running 12 hour non stop 4 wheels at a time,i started removing support n cleaning up and was shocked,and confused.
in tinker and cura they looked perfect.
i blew close to 90 hours of time and filament because i got complacent and confident in my printers/prints.
now i do 1 part at a time and clean up ,inspect,before making multiple parts.
hard lesson learned