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Assistance with print - not just first layer  

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yggsson
(@yggsson)
New Member
Assistance with print - not just first layer

Having issues with all prints. Have done numerous first layer calibrations. They _seem_ okay, but...

I figure the best way to convey the issue is to illustrate it, so here are two pics. The first is the top. They look decent. The second if the bottom, and looks like [email protected] I've read a fair amount and made adjustments given in various threads. The uppers have gotten better, but lowers just pretty much suck.As well, there appears to be a tapering to the edges. They are not "squared" as modeled. I'm sure this has been dealt with before. I just haven't found that thread yet.

Advice welcomed.  Thank you.

 

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Posted : 28/08/2020 3:46 pm
yggsson
(@yggsson)
New Member
Topic starter answered:
RE: Assistance with print - not just first layer

Well, this is not encouraging. After some more reading, I decided to download Cura. I did not touch the settings. Simply loaded the saved project from PrusaSlicer into Cura, resliced, reposted, and printed. The results are excellent, considering.

Why would Cura print better than PrusaSlicer on a Prusa printer? Seems a bit ridiculous. So what am I missing?

( supports were more numerous as well as being immensely easier to clean up, too )

 

Posted : 29/08/2020 2:03 am
Peter M
(@peter-m)
Noble Member
RE: Assistance with print - not just first layer

Make a first layer calibration and make a picture for us, first layer looks strange.

Picture how model sits on the bed?

Did you print with infill?

Do you have the prusa project file?

Possible better to make a top model and bottom model and glue/screw it together.

 

Posted : 29/08/2020 12:02 pm
Diem
 Diem
(@diem)
Noble Member
RE: Assistance with print - not just first layer

@yggsson

It looks as if your first layer has been printed in mid-air as a bridge.

Can you check your stl/amf file, is there a second object or a microfine extrusion placed below the part (-z)? 

The problem is especially common with complex .stl files; some avoid them for this reason but they are still the most convertable format for exchange.

If a part is designed by subtracting shapes from another then sometimes segments which have been calculated to be the same height might not be due to irrational numbers differing in (say) the tenth decimal place - so there is a micro-thin, unprintable, unwanted remnant left outside the body of the wanted part.  The slicer sees the remnant and despite not being able to reproduce it in plastic it honours the entire shape and so places the part you wanted in mid air.  Usually this is obvious but sometimes the remnant is no nore than a millimetre below the main body and it's not obvious unless you are looking for it.

This phenomenon can be useful too:  by putting micro-fine cut through the body of a part it's possible to print with little or no fill and yet have the slicer detect the internal perimeters and so place internal reinforcement just where you want it.

- and make sure you have 'Detect bridging perimeters' ticked.

Posted : 01/09/2020 3:49 pm
bobstro
(@bobstro)
Illustrious Member
RE: Assistance with print - not just first layer
Posted by: @yggsson

[...] Why would Cura print better than PrusaSlicer on a Prusa printer? Seems a bit ridiculous. So what am I missing?

Short answer is: They are different. Each has strengths and weaknesses. PrusaSlicer is derived from the much older Slic3r which -- for a variety of reasons I don't recall -- does supports this specific way. At one point in time, this may have been a great solution, but other slicers definitely handle supports for large, flat surfaces better. Here's a comparison of PrusaSlicer with 3 other popular slicers available today (Cura, ideaMaker, Simplify 3D):

Team Prusa is actively making improvements on the old Slic3r code base, but doesn't seem to have gotten around to supports yet. I know they're working on top infill quality and ironing now. You might drop a feature request over on the Prusa github page where the devs will actually see it (odds are low here as this is user-user support) and add your voice.

In the meantime, I'd say another slicer is the way to go if you do a lot of these prints. Right tool for the job and all that. PrusaSlicer is definitely my preferred slicer, but this is one situation where I might use another.

 

My notes and disclaimers on 3D printing and miscellaneous other tech projects
He is intelligent, but not experienced. His pattern indicates two dimensional thinking. -- Spock in Star Trek: The Wrath of Khan...
Posted : 01/09/2020 4:59 pm
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