A wall that prints with a cavity

I am printing a cylinder. It was exported from fusion in both STL & OBJ. Printed on platform. When it prints a section of the side wall (very tiny) does not print. It leaves a cavity that is not uniform. I have scanned the file and the meshes or triangles on the file are all there. When uploading the STL file Preform says it needs repair. The OBJ does not say that. I have printed both with and without the repair from preform.
Anyone know what the cause could be?

A picture of the failed area would help troubleshoot this a bit more.

is this always in the same spot?

If you were to mode the location of the model on the platform would the error persist and still be in the same spot on the model?

If that is the case, then we would have to look at your STL or OBJ model and see what’s wrong with it.

The picture didn’t show up at first for me. Are you by chance printing directly on the build platform without supports?

That’s what he stated on the original post:

Yes, it’s always in the same spot. Printed about 18 of them. I even thickened up the wall. For some reason I thought the wall might have been too thin but it’s no where near being at that point. Believe it’s .08” thick. Both black and grey do the same. I have not tried rotating the print to see if it follows the same side or not.

When examining the STL, you just zoom in and look for imperfections on the mesh correct? The model is 100% a solid as is shows a volume amount.

No, you have to check the STL by software, e.g. netfabb. The software checks for holes, border edges and invalid orientation of triangles; errors you can’t see with your eyes.

Are the walls thin? Is that hole at about 5mm off the platform? The first 5mm are printed at a different exposure and when printing directly to the platform that change can cause some artifacts in the print.

If you’re printing directly on the platform the hole is probably a blow out. Tubes like this need a vent to print vertical on the platform. Sometimes they work and sometimes they don’t.

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It’s about 5/8” off the platform base

Wouldn’t errors show on the slice preview? I’ll have to try netfabb later tonight

Would be good to see the orientation your of this part in PreForm. To me it look like the vacuum effect…

I’ve gotten that type of thing on parts that are thin as well, about 1mm thick

I, too, have seen this effect on hollow parts without vent holes.

A tiny vent on your part at or near the build plate would probably get rid of the cavities you’re seeing. If that’s incompatible with the purpose for your part, it might still be preferable to plug a planned vent hole than patch a random cavity.

It’s not a hollow part. It does not require drain holes. I re-saved the STL file and printed 6 on a plate… 2 of them did not have the issue. The holes are all on the same side of the print but in different locations on the Z axis. I printed one more but rotated a 1/4 turn. If the hole shows up on the same location perspective to the build plate X axis then I think it’s safe to say a printer issue…?:thinking:

here is the part printed in grey… it does not show the holes. The walls were the holes are showing is 3mm thick

If that’s been printed on the build platform, then it could be a suction cup blowout. If that’s the case, then Ike is right that a vent hole would help.

So a blowout happens when the part forms a closed cup with the open end facing down on the tank. When the build platform comes down, the pressure inside the cup increases. Similarly, when the build platform goes up, the pressure decreases, until the lip of the cup separates from the tank. These pressure changes can be quite large, and can cause portions of the walls of the cup to “blowout”.

The one thing is that cup blowouts aren’t usually very consistent from print to print. If the hole always appears in the same place, then I would guess it’s probably something else.

Why not angle them and use supports? Besides risk of blowouts you also loose dimensional accuracy of the part when printing flat on the build platform due to initial compression layers.

That makes a lot of sense! I originally took it as he thought the walls were hollow…well that answers a lot! Thank you

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