Bambu-Studios handling of parts seems broken

I am trying to understand how to make an object with parts…

So I designed this as a crude test:

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I saved one object as this:

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And another this:

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If I then open both into Bambu at the same time I get this:

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Which leads to this:

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And if I assign the 2nd part a different colour, this:

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So we are all good… This is exactly what I want… But lets say I couldn’t open both parts at the same time… First I open the 1st object:

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And then I “Add part” for the 2nd:

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I get this:

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And the only way to move the J inside is manually dragging it around, and it’s a total pain as its almost impossible to accurately as you are working to 1/100th of mms… You can use the Move Co-ordinate system, but that doesn’t seem to work right, as even if i give them the same numerical value, they are about 0.5mm out.

Even if you get it almost right, you get this:

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But lots of double walls.

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So I checked how Prusa would handle this……

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Tada…

That’s how I expected this to work… So what does this mean? Bambu broken? Different? Feature I am overlooking??

Any thoughts on how you use the ‘add part’ feature and get the parts ot line up?

I think the difference is that prusa is just leaving the origin alone on instantiation but bambu wants to treat it like a new part so it moves it to avoid overlap.

I bet if you select the P in studio and then select ‘Move’ and set the P to whatever the other object is set to, so they again have the same origin and line up perfectly.

Seems like the Z is just a bit off on your test screenshot and the J is a bit buried.

And finally, I think the first way is the way, load them at the same time, they were created together in a 3D modeler to mate, that info is lost if you load them separately and you are just relying on how the slicer is going to treat separate part imports. If you’re saying well I’m going to take this one design and add another to it in STL mode so I’m just going to use the slicer to do it, then OK but I would not expect this to be user friendly, the slicer is not a 3D modeling program. In this case you could be left with having to dial in those origins down to the fractional milimeter.