Geometry added to model

vikingtone · November 19, 2020

I printed a model on my Creality CR10 mini, it came out with a very large piece of additional geometry in a place which should have been a cylindrical void. I checked the appearance of the model on the Cura build plate - no problem. But on (very) close inspection I see the additional artifact in the Preview view. I re-sliced it and printed it using Prusa slicer, and the artifact is not there. I thought it may be a function of printing with Tree supports, but the preview shows the additional geometry, with both Tree and Normal support. The artifact of additional geometry is not support material, which came away very easily, the artifact is solid with the skins, walls and infill of the rest of the model.

gr5 · November 19, 2020

In this case the printer is irrelevant. So what you describe sounds like a common and easy to fix issue. But first, could you describe the problem in pictures better? Please use PREVIEW tab (as you did) but please set "color scheme" to "line type" which is just on the line under the PREVIEW tab. Also scroll part way up your model so we can see an example layer where it is printing in an area where it shouldn't be. Also make sure that travel moves (blue) is enabled to eliminate the possibility it is stringing like crazy (I doubt it).

So I'm going to attempt an answer even though I don't understand the problem fully. I'm pretty sure there is something wrong with your model. The Prusa slicer figured out what you meant to do (despite the error) but the Cura slicer did not. There are many types of errors but one of the most common is that the "normals" are wrong. For example in Sketchup (but there are 3 other CAD packages I know of that has this issue - most cad do not have this issue) you have to have all surfaces have the gray side facing into solid parts of the model and white surfaces facing out. If this is backwards you right click and select "reverse faces". This is one possibility.

So

1) please tell us the CAD you used (if you created this model).

2) Please show better what the issue is with arrows or something and with color scheme set to "line type".

Some other ways to fix this quickly without fixing it in cad:

There is a free model repair service (but you have to create a free account) at netfabb

https://service.netfabb.com/login.php

Here's another service - drag and drop mesh repair service:
https://3d-print.jomatik.de/en/index.php

Cura has an amazing plugin to test your model to see if something is wrong with it and can repair a very few of the many potential problems:
In the upper right corner of Cura click "marketplace" and make sure you are on the "plugins" tab and install "Mesh Tools". Then restart Cura. Now right click on your model, choose "mesh tools" and first choose
"check mesh", then "fix model normals" and "fix simple holes" to see if that helps.

gr5 · November 19, 2020

OH! It just clicked in my mind. The first two photos I believe show the model properly and wrong. Is it possible that in Cura you selected "make overhang printable"?? If so, uncheck that. That is a very dangerous feature.

vikingtone · November 21, 2020

On 11/19/2020 at 5:57 PM, gr5 said:

OH! It just clicked in my mind. The first two photos I believe show the model properly and wrong. Is it possible that in Cura you selected "make overhang printable"?? If so, uncheck that. That is a very dangerous feature.

Sir - thank you, so much. Everything you suggest has been massively helpful. let me begin: I got the model from ThingiVerse, so don't know the original CAD prog. I messed with it in TinkerCad, because I'm a retired old fart on a limited budget. It has been great for me, though I accept 'proper' makers would scoff. I downloaded the mesh plugin for Cura and did as you suggested, and it says the model is not watwertight - so you got that totally correct. It also said, after I went through your guidance, that it was not repairable with the plugin - I guess I'm not surprised. Yes, the photos I sent are one from Cura which didn't work, one from Prusa which did. Final throw of the die - turn off 'make overhangs printable,' artifact disappears. 🙂 I have other parts with similar problems, and I'm confident thay will now print properly. The astronaut glove has a new pyramid on the surface. Pictures enclosed. Thanks again for taking time and trouble to offer support - I am deeply grateful One screenshot is cut at the artifact and shows it clearly, the second is a pic from the Mesh analysis, and the third is the full model with 'make overhangs printable.' turned off and the artifact is gone. 🙂