Breaking up 3d solids that have been joined

[Frana]

Is there a way to "disassemble" a 3d model that has been joined together using union?

 

For an example, viewing the pic, I have used the union command to "connect" a handful of 3d objects for easier movability in my model floorplan. But, after doing so, I find if I need to make alterations to one of these grouped objects, I can't break them back apart to their original seperate forms... Does this make sense?

 

The only thing I can think of is to explode the object, but that makes way to much of a mess to clean up...

 

[mdbdesign]

I got no answer for your question but I like this machine. Used to work on one like that for 13 years (ALLSTELL)...

[ReMark]

It sounds like you didn't retain any of the underlying geometry (separate profiles) for the machine. Right?

 

DO NOT EXPLODE IT! Hope I said that loud enough for you.

 

Your only option might be to use the Slice command to carve up the machine into the necessary pieces. Do it on a copy and save the unioned original.

[Frana]

So, I guess the way it sounds once you've unioned two objects, without keeping original geometry, the originals are sorta erased?

 

This is a bummer. The good news is, what I need to alter is a simple crane rail extension, the slice command will work on doing what I need, I was just hoping there was a way to revert back to those original individuals for other incidents that may come up... I will need to keep layers for backup original geometry I guess.

 

I still think that there has to be a way? There's always more than one way, right ReMark?

[ReMark]

Look up DelObj in your AutoCAD Help file regarding retaining geometry.

 

Altering the crane rail extension. In what way? Are you lengthening it?

[nocturne00]

Sad but yes, after union,its foing to be difficult to split up to its original components. usually for simple geometry, I tend to use slice to separate, but in this case it would be better to redo it. but im not sure with the newer versions. pelase do correct me if im wrong.

[fuccaro]

First time I was faced with this problem I copied the drawing, than I exploded it and I recreated the solids from the exploded surfaces lines and arcs. A lot of work, I would say.

[marmo]

If solids are physically attached you have to use the SLICE command. SLICE allows you to cut solids.

If solids are not physically attached to (this can happen at work) you must use the command SOLIEDIT> BODY> SEPARATE.

For practical work instead join objects with UNION you can use GROUPS SELECTION, with switch ON/OFF the effect of variable PICKSTYLE (value 0,1,2 or 3).

 

Another way: Try to use explode..

We have to do these steps:

If you use explode obtain a lot of 3DFACE or Surface or REgions.

If you have 3DFACE or regions must then be converted to surface.

The surface, corresponding to the part you wanted to separate, should be merged with the Union command.

Now you have one surface, which should correspond to the solid surface that you wanted to separate.

The surface must be converted in solid.

[ReMark]

I think a lot of newcomers to 3D solids editting assume the SEPARATE command is the equivalent of an UNUNION command which it is not. We've even had people ask if there is such a command as UNUNION. AutoCAD users need to become familiar with the system variable DELOBJ.

 

"Controls whether geometry used to create 3D objects is retained or deleted."

 

The default value, which is saved in the Windows' Registry, is 3. This setting...

 

"Deletes all defining geometry, including paths and guide curves used with the SWEEP and LOFT commands if the action results in a solid object."

 

Users might wish to change the setting to "0" instead. This will retain the underlying geometry.

 

Source: Quotes are taken directly from the AutoCAD Help file.

[Frana]

There is much to learn from this discussion, and I appreciate all the input. I do know now that the "group" function is more practical to what I was shooting for in the first place. I dabbled a bit with that this morning and I like how you can add and subtract objects from the group. "newcomers, right!?" lol

 

Also, as ReMark stated, I should start utilizing DELOBJ. I've only messed with this once and, at the time, didn't see a good reason I would want it at 0, having to erase all the left over lines and arcs! funny, huh. Sorta wish at this point I hadn't already unioned as much as I have in this layout I'm working on. Lesson learned however.

[fuccaro]

Also you can create a new solid that contains a part of the unioned solids. And use INTERFERE with the option to create new solid where the two ones intersects. Hard to explain... better give it a try.

[marmo]

Interfere!

Good strategy!

Very fast for subdivide complex models!

[busseynova]

Don't newer version (post 2010) retain a goemoetry history? I know the OP is on 2008, so that's not much help.

 

That's the way it seems when I draw models and it flashes up the outline of the shape I just subtracted. Although I've not dont much 3D modelling recently.

[ReMark]

The default setting on your system may have been changed. Perhaps a rogue lisp routine could reset the variable setting and neglect to change it back.