So those very skinny long spikes kind of complicate the cleanup, the pieces that the skinny spikes are emerging from have to be cleaned up as well.

- Michael

Hi Stefan, I've attached here an edited version of your object with those degnerate "slit" boundaries removed and those little thin spiky fragments cut off, this version should work better for you now when cutting off a chunk to do a test print.

Hope this helps, - Michael

Many thanks - that was very helpful. I was able to export that part and will print it now.

Regarding my statement about the bug - I still think there is something wrong. When I selected the part to be exported, it was visible. That's how I saw in the preview that it was broken. But the exported file was still "empty".

The reason why this part is so messed up is because it was first designed to fit an aluminium extrusion that had the wrong size. After I had found a .step file for the correct part, I imported it and thought first to "fill" the area with the wrong sized cutout in order to cut out the new aluminium extrusion. I did this with a square that was extruded down and then merged into the main object. The thin lines with the two faces attached to them were some artifacts of this (probably silly) change that I introduced.
I think it would have been better to separate the main object and then delete the faces and edges of the cutout in order to have the cutout filled up.

Hi Stefan,

re:
> Regarding my statement about the bug - I still think there is something wrong. When I
> selected the part to be exported, it was visible. That's how I saw in the preview that it
> was broken. But the exported file was still "empty".

I'm not able to repeat that bug over here... Here's what I did - I opened up your "broken_after_isect3.3dm" file that you attached above, then clicked Edit > Hide to show objects since they are all hidden to start with, then selected one of the large pieces and did File > Export to a test 3DM file, and then when I opened that file it had the object in it as expected.

Did it happen with a previous saved version of this file? If so can you please send that one to me so I can try to reproduce the bug over here?

I won't likely be able to fix the bug unless I can reproduce it.

- Michael

Yes it did. I have uploaded an unlisted Youtube video:
https://youtu.be/Q3la-k24Pxo


And I have attached the original file here.

Hi Stefan, thanks for posting the file and the video. I am able to reproduce that bug over here now - it seems to be due to the intersected solid being malformed probably because of those doubled up faces. The object ends up with a broken region where the "is void" flag is set for both the exterior and interior regions, and when MoI goes to write an object it wants to go through the solid (is void == false) region but doesn't find any solid pieces.

It looks like it's not just File > Export that fails, File > "Save As" doesn't write the intersected piece either.

So it seems that the bug is in the boolean intersection calculation but it will be difficult to fix because booleans can get confused in general when an object has self intersecting pieces...

A couple of tips from the video - if you want to show only the one named object a shortcut for doing that is to go its entry in the scene browser and right-click on the eye. The right-click on an eye hides everything else other than that one object so that saves the step of separately hiding other things.

Also when you do a boolean you can just do it using the rectangle curve, the booleans will automatically extrude it out as needed during so you don't have to extrude it as a separate step, unless you want to make it go to a limited depth instead of all the way through.

- Michael

Alright, thank you for the tips Michael. And good luck with the bug.

Sorry for hijacking this thread again. I'd like to ask for advice on the best practice for this scenario.




I have the orange part where I did a cutout of the v-slot (the grey part). After I printed a small portion of the orange part (the one with the cutout) I realized that the cutout is too narrow. So I need to enlarge the coutout. My actual workflow looks like this:
1. Enlarge the grey part.
2. Fill up the cutout on the orange part (hardest step because it is prone to errors and can produce a malformed solid).
3. Do a bool diff of the grey and orange part.
4. Print

Is there a way to streamline steps 1-3? Ideally I'd only like to enlarge the cutout or maybe find a way to fill up the cutout without breaking the orange part :)

Thanks again!
Stefan

Hi Stefan - I tried one version attached here with erasing the cutout by drawing the same kind of rectangle that you had done previously for the boolean intersection, then extruding it just like you had done in your steps (because boolean union does not auto extrude 2d profiles like the difference or intersection does), then doing boolean union and I seemed to get an ok part with the cutout entirely removed.

Are you trying to do something like only restore some upper portion of the cutout while leaving some of the inner structures on the inside bottom intact?

Anyway the attached file has the cutout removed, if that's not what you need I'll probably need some more information.

- Michael

Thanks Michael,

I am trying to remove the cutout right until a certain height (until it meets the yellow faces). I had hoped there was another "trick" like selecting the inner faces of the cutout and offsetting them or something.

Hi Stefan, does the attached version have it set up how you need?

For this one I did the same process that I described earlier - drawing a rectangle just like in your previous video and extruding it down, but I stopped the extrusion at the top of the area you show above and then did the boolean union.

re:
> I had hoped there was another "trick" like selecting the inner faces of the cutout and offsetting them or something.

It's pretty unlikely that offsetting is going to be able to clean something like that up... The best way that I can think of for filling the area is to do a boolean union with a slightly larger box.

Please let me know if the attached version is still not what you're trying to get.

- Michael

Yep, this works. Many thanks!