Cause(s) for print failure?

[jam896549 0]

Hi guys,

 

I'm fairly new to 3d printing. I printed a few premade models from the web with varying success, fiddled a little with printer settings, made my own smaller models/prints and decided to go for a more complex print.

For that I made my own model in Blender, imported into Cura 5.1.0, applied my usual print settings, did a few tweaks and started the print.

The first few layers looked good, although I was accepting a little warping on the far left end (x=75, y=220, z=0). I noticed that on earlier prints too, but I decided to keep going (big mistake?).

However, on the next morning (after about 12hrs of printing) I encountered a print that has gone well for the most part, but then totally failed.

I decided to stop the print at this point.

 

Printer: Anycubic Mega X

Filament: Basicfil PLA black

Bed Temp: 60°C

Printing Temp: 190°C (a little higher on the initial layers)

 

This is my model in Cura:

 

Thats the warping on the "far left corner":

 

And those are the topmost layers of the print:

 

Eventually, the left half of the print has detached from the print bed and shifted a little.

At least that's what I decipher from this (and also the previous) area of the print:

 

These are the questions going on in my head:

• Is it solely a problem of the print, or could/should I also do some improvements on the model? The lower parts of the walls (between the cutouts of the box) are rather thin and maybe too flimsy?
• Is it only a problem of bed adhesion? Could that alone lead to the weird printing issues?
• Maybe it's also a problem of a clogged nozzle or something?
• Is it a problem of air drafts during printing? The printer was operating in a rather small, closed and heated room without any people inside. So I guess the answer is rather "No"?

 

I wouldn't like to just jump in and print it again with a few tweaks on my own, because the problems (besides the bed adhesion) only started to appear after ~8-10hrs printing time.

I'm very grateful for any hints on improvements! I also attached my 3mf project file and can provide any further pictures or information that might be necessary.

 

Thanks a ton,

jam

AI3MX_air_tower.3mf

[ahoeben 1,948]

Did you stop the print outright, or did you observe what was going on for a little while?

 

It looks like those pilars are very thin. They are always going to wobble (try placing a piece of paper on its side, supporting it only at the bottom). If this building would be build, there would be (temporary) scaffolding in place at least until the arches are completed.

 

You also seem to have had a layer shift. I was not there when it happened, but I would guess that the printhead hit one of the wobbling walls, and a stepper skipped a couple of steps (or a belt slipped) because of that.

[dsp 18]

Bed adhesion is the issue with the corner on the  bottom, this could be due to the adhesive used, but if I look at the model a brim would certainly help (there are pretty thin walls on the base of your model).

 

an other issue is stability , because you have quit high, but thin pillars the print head will cause these to move while laying a new layer (yes the brim will also help this a little) but i think upping the temp just a little will help the new placed filament to cause less stress on the pillars. if you are worried about the bridges you can up the cooling a bit.

 

 

 

 

[jam896549 0]

Thanks a lot for your suggestions and input!

 

4 hours ago, ahoeben said:

Did you stop the print outright, or did you observe what was going on for a little while?

I did stop it after about half a layer, because due to the model having already moved on the bed, the print was partly going into empty space.

 

4 hours ago, ahoeben said:

It looks like those pilars are very thin. They are always going to wobble (try placing a piece of paper on its side, supporting it only at the bottom). If this building would be build, there would be (temporary) scaffolding in place at least until the arches are completed.

I was thinking about maybe putting some T-shape onto the lower parts of the walls. So basically a 90° wall, sticking towards the inside of the model. This should also help with stability, right?

What exactly did you mean by "try placing a piece of paper on its side, supporting it only at the bottom"?

 

4 hours ago, dsp said:

Bed adhesion is the issue with the corner on the  bottom, this could be due to the adhesive used, but if I look at the model a brim would certainly help (there are pretty thin walls on the base of your model).

Actually, there is already a brim on the outside AND the inside of the model. Here are the parameters i used for that:

Would it make sense, to increase the brim line count? I remember having read on many occasions that five lines should be enough?

 

What I'm taking away from this so far is:

• Improve bed adhesion
• Make walls sturdier

Thanks,

jam

[GregValiant 1,251]

I checked the model with @ahoeben's Mesh Tools plugin and the model has some minor issues.  This is the Cura Prepare stage in X-ray View.  The red areas around the base are errors in the model.  MS 3D Builder was able to repair it.

 

 

They are minor errors and didn't seem to affect the slice, but it's good practice to check for errors before putting a lot of time and effort into a print.

 

Your nozzle looks to have started under-extruding at around layer 230 or so.  That didn't fix itself as the print continued upward and so things got weak as it grew taller.  That really needs to be addressed before you try again.  I would guess that the bowden tube isn't tight against the nozzle and a plug of plastic is causing a partial blockage there, but it can be caused by other things as well.  Going along with that I would turn off "Retract before Outer Walls" and increase you "Z-Hop Distance" to 0.5mm.  You really don't want the nozzle hitting those tall skinny pillars.

 

Wobbling prints.

A brim 8mm wide (with the brim distance set to 0.1mm so it's easier to break off).  Make sure the bed is clean and you may want to use hairspray or a glue stick to aid the bed adhesion.  If that print lifts at all then the walls won't build straight.

 

The front wall has buttresses that help hold it vertical.  The rear does not.  Your printer is a "bed slinger" and as the bed starts and stops in the "Y" those pieces that will comprise the back wall will want to wobble as they get taller and top heavy.  After slicing you can go into the Gcode file and at about layer 200 add the line "M201 Y250".  When the printer sees that line it will drop the Maximum Y Acceleration to 250 and so the starts and stops of the bed will be a lot smoother than at your default 400mm/sec².  (If you don't enable Accel Control in Cura then the printer will use it's defaults and for your printer that is 400 (from the printer definition file).)

 

Here is what I would do.

I added 3 x 25 x 115 support blockers and placed them at the rear wall pieces.  Then I configured them to "Print as Support" with an XY distance of 1.0 and a "Z" distance of 0.  Next I added more blockers but configured to "Print as Normal Model".  They are small at 1.2 wide by 6mm long x 0.6mm tall.  There is a set at 35mm off the build plate and another set at 70mm off the build plate.  What will happen is the supports will grow and the little tabs will connect the model to the supports at Z=35 and Z=70.  So as the back wall grows it will be glued to the supports and keep them from wobbling.

I think that needs to be done for at least the rear walls.  The side walls are wider in the Y and shouldn't wobble, but as AHoeben says, the nozzle can whack them and they will want to move as they get taller.

 

So there you have it..."break off" supports that are only attached to the model at intervals.  I changed the Brim to Inside and Outside and "Brim Replaces Support" is enabled as those support pillars are only 3mm wide and could use some help.

 

Good luck.  This isn't an easy model.  You could also build some custom supports in CAD and set those models to "Print as Support" with the Cura "Per Model" settings.

 

 

 

Edited November 25, 2022 by GregValiant

[ahoeben 1,948]

1 hour ago, jam896549 said:

What exactly did you mean by "try placing a piece of paper on its side, supporting it only at the bottom"?

I meant it as a mental exercise.