Print defects in stacked face masks

[sajidarali 0]

We're in the process of 3D printing headbands for face shields to donate to hospitals. We're stacking the models vertically in order to print 24hrs straight without user intervention to maximize our printing, as these prints are needed urgently. However, every third row in the stack has loose filaments that makes it a defect. In those layers, the first few slices of filament become loose at specific locations and gradually this effect lessens until halfway through that piece, then the top half prints ok (see attached image below).

 

We changed so many settings, but yet the effect is still occuring. When the speed is reduced dramatically from 70mm/s to 30mm/s we see a great improvement, but this slows down our production, and we think that there might be a better solution. Has anyone faced similar issues or could possibly help?

 

We're using Ultimaker S5 Bundle with latest firmware. I'm attaching the stacked print Cura model in case that helps.

 

Thank you.

 

UMS5_C19_x6_T18_19hr_293g.3mf

[rcfocus 0]

I don't have S5. But did you "preview" the sliced result in Cura?

[gr5 2,192]

What is the yellow matieral?  That's the problem I think.  For some reason it's not working well.  Is that breakaway?

 

Breakaway should work well.  Alternatively you could use PVA but it's important to get the calibration perfect so clean the nozzles at the start of the print - and clean the bed.  PVA needs to be extremely dry.  When it gets wet, steam bubbles get into the PVA and it doesn't work as effectively.  It can be dried out but that can take a long time (e.g. in an electric oven with carefully controlled temperature at 80C for 24 hours and with the spool unwound a bit (loosened))

[sajidarali 0]

@rcfocus  Yes we previewed the sliced results in Cura and everything looks fine.

 

@gr5  The yellow material is yellow PLA which we're using as breakaway support, but we did also use actual Breakaway material and still made the same result. The issue is still persistent. It's worth mentioning that there's a 0.4mm gap between the parts in the vertical stack to break them apart, and we also tried 0.3mm and 0mm, but they all yield the same issue. We even tried manipulating the STL file in 3DS Max but still the same issue.

 

Since some layers work, we hope that we can do the entire stack the same way. It's weird that this is happening every 3rd layer.

[JohnMatthews72 0]

It might be to do with layer heights.  I have removed fine inconsistencies with stacks by ensuring that I am using layer heights that are multiples of 0.04mm. This is because the Z axis servos hold better when asked to lock into steps of this size.  (Yes, microsteps work, but are less reliable than full steps.

If you are printing at a layer height of say... 0.15mm, try going up to 0.16 mm.  If you are printing at 0.25mm, try coming down to 0.24mm.  Because of the modulus of your print errors, I'd suggest this may be the case.
 

[Carla_Birch 116]

Having printed headbands for face shields myself before on my S5's and seen others trying to stack print, i personally just kept to not doing a stack and just doing 3 at a time in the basic layout you have done.

 

You have a gap between each one what's asking the printer to print full layers in mid air, if that gaps to big you get what you have, if its to small then you will have a problem with getting them apart.

 

My personal view on this, is that the item is going be in use on someones forehead for 12 or more hours, and stacking as little time benifit in printing than just doing a none stack, eg you have no need for support so its a faster print time as no core swapping, you also have far less clean up and a far better product without bad undersides thats going be pushing into someones forehead. Print 3, swap out build plates and print 3 more why the other cools and pops free ready to then swap out the build plates again.

 

I was in a printing group for the bands in the UK when the virus first started and i bugged me how some was taking it as a comp to see how fast they could print the bands, not caring about the drop in quality. Most would have been rejected as not fit for end use, or cut peoples foreheads to bits.