Weird sphere shape printout

I’m having a problem with printing the lower portion of a 2" diameter spherical shape.

One section, always at about the 10 o’clock position, is flat or concave while the opposite side has the correct convex shape. To make things more peculiar, this only happens on the first (lowest level) shape when printing a stack of such shapes.

I am printing ABS using Cura v17 running on a TAZ 5 with 0.35mm nozzle.

I’ve tried different bed temps, different filament temps and raising the first print off the bed; all to no avail.



Pic 3.png
Pic 4.png
I’ve included an STL file that I’ve used to do tests with in case anyone else wants to try to duplicate my result.

Any suggestions greatly appreciated.

Thanks,
t
sphere bottom deformed.stl (9.84 MB)

Try printing with support touching build plate only. It’s also looking kind of hot down there with those brown discolored blobs underneath on that middle(ish) photo. Might even try 30-50% fan for those lower layers.

Scott

I have found that the problem is apparently with the STL file.
The design was created using Autodesk 123d design and used to generate the STL file which is about 10mb in size.

I loaded the STL file into slic3r then exported a new STL file which is about 1/5th the size! :astonished:
When I printed using the new slic3r STL file in Cura, the printout turned out much better.

The STL files are obviously very different but I have no understanding of the STL file contents.
I have posted the slic3r STL file for comparison should anyone have that knowledge/bent to investigate.
It appears that Cura doesn’t correctly interpret the 123d STL file but slic3r can.
I’m not sure if I should contact autodesk since slic3r can process the file or if this is a Cura issue.
sphere bottom deformed slic3r.stl (1.77 MB)

Your first file was in STL-ascii and the last was a STL-binary format that are usually a lot smaller. I also see that your first file is three separate parts but in your Silc3r file you have them combined into one part.

“Apparently” it’s not as I thought (or hoped I guess.) The print with the slic3r STL did print better but today when I started to print the real part with the only change to be using a Cura fine profile instead of a medium profile, the deformity re-appeared.

This seems to be a path issue as the only way I can imagine the concave result in one quadrant of the circle would be if the tool head is not following the correct path. But how this could only be for the first copy and not for the copies stacked on top is beyond me.

This just shouldn’t be a big deal. Stock Lulzbot Cura profiles, pretty simple design elements … sigh.

I’m trying to generate some slic3r gcode now to see if that’s any better - easier said than done I’m finding … Ah, to be on the bleeding edge :slight_smile:

t

Still can be a temp issue. Particularly when you say the problem reocures when you switch to fine. This allows the lower layers to be ‘baking’ longer as the fine prints take more time. You might try adding some fan cooling, perhaps 50%.

Scott

I’m pretty much out of ideas, so I will add this to my list of solutions to try with Cura. The reason I haven’t pursued the temperature settings more aggressively is that this only happens in one quadrant (between the 9-12 o’clock position) and it only happens on the first of several stacked items even when the first item is elevated well above the bed (the fan is on by that point.) … But thinking about this a little more, the fan is on the right side of the print head and the deformity is on the left/back portion of the print … Thanks Scott.

I have successfully generated gcode using slic3r with promising initial results. If This isn’t repeatable, I’ll try cranking up the fan.

I have been able to confirm that the #1 contributor to this problem is the wobbling head on the X axis rods.
This post https://forum.lulzbot.com/t/linear-bearing-backlash-big-x-axis-issues/966/1 among others pretty much describes my symptoms, just not to the extreme that I’ve been having with the spherical shape.

I can’t afford at the moment to make the mods to replace the bushings and rods identified in this and other posts so I took a different tact and printed myself a counter balance to hang off the back of the print head assembly. While only a temporary fix, I immediately saw improvements. To further improve things, I then followed up with a number of tweaks in slic3r including turning on the fan full time (thank you for the suggestion Scott), slowing down the outer perimeter printing, and reducing the filament flow to 95%.