Separating Disjoint Bodies Into Parts

[justindove]

I'm new to Inventor and I'm having a bit of trouble doing something I figured should be pretty basic.

I have a solid that I have cut up into multiple disjoint pieces using revolve cuts with a tolerance I specified in the sketch by giving the revolve profile a thickness. So now I have a "single" solid, but it is really separated into a bunch of pieces by empty space. I just want to make all of these disjoint pieces into separate parts. I guess making them into separate solids would be the first step. I tried making a revolved surface at the center of the revolve cut but I can't use that to split the solid. It appears you can't split a solid through a disjoint space. Is there any way to do what I'm trying to do?

Thanks!

[justindove]

@johnsonshiue O_o *facepalm* I should have thought of that. Brilliant! This is why you are an employee! Thank you so much!!! However, with good news comes bad news. The main issue with this is that it takes n(n-1)+1 operations (which is O(n^2) complexity) whereas since there is such a simle workflow, there really is no excuse why this isn't a feature. Now, why am I complaining about the complexity of the number of operations? Well I happen to have 122 disjoint lumps so we are talking on the order of over 10^4 operations. That said it is still a wonderful workflow and I believe it might even have some advantages over splitting the solid all at once (were this a feature) THEN extruding the air gap (the motivation for Issue [#1]), particularly when you don't have the original cutting tools available. Thank you very much for this extremely useful and clever flow!

Now it happens that of my 122 pieces only 4 are unique and I only have to print copies of those 4 pieces so it really will take me 4(122-1)+1 which is on the order of (10^3)/2 or so. Furthermore, I could get rid of the duplicate lumps before I do the rectangular pattern and then have it done in 122+4(4-1)+1 which is 135 operations. That's still a lot but, at least its feasible. Is there anyway to select all other lumps except one of interest? If so I could reduce it to 4+1=5 operations which is good for this specific case.

This is all contingent on the fact that I have duplicate lumps and don't need to actually have a full multi-solid model of the entire project for any reason. If either of those conditions were false, it would be completely impractical to do this. If there is a "select all other lumps" feature for the delete face tool then it can be reduced to n+1 steps which is linear but that's still 123 steps if I had unique parts or needed a virtual assembly of the whole thing...

It's really kinda ridiculous that such a simple and intuitive feature (separate disjoint bodies) has quadratic complexity on the user. At the very least this quadratic workflow should be automated. There isn't any way to code workflows in Inventor right?

@Paul.Normand This doesn't apply to the case where you started with a single solid and cut out the gaps since it would just make solids out of the cutting tools (which doesn't help). The only case where it works is when you could have already trivially made them separate solids in the first place (i.e. they are each separate extrudes/revolves). So this doesn't really address either issue but thanks anyway since the "make a new solid" button is something I probably would have forgotten to hit when doing something that is initially multibody in the future!

@BMiller63 I don't see the equivalence between the technique in the video and John's technique. In the videos you posted the objects were already separate solids. The only circular patterning that was used was to make an interesting cut into a solid. Did I miss something?

John has given me a workflow for Issue [#2] (albeit an unfortuately cumbersome one for large numbers of parts and even cumbersome for me if there is no "select other lumps" feature). This still leaves Issue [#1] open which is given a solid and a bunch of surfaces (or a circular/rectangular pattern of a surface) how to cut up the solid with all surfaces simultaneously to obtain separate but flush solids. I was suprised to see a solution to [#2] that couldn't deal with [#1]. Fortunately I need the tolerance for practicalities sake anyway, but I could easily see myself needing flush disjoint solids in the near future. In fact it may turn out that my parts work best flush and my only solution right now would be to take a very very small tolerance which is fine for practical application but not a solution to the modelling problem.

[BMiller63]

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@justindove wrote:

@BMiller63 I don't see the equivalence between the technique in the video and John's technique. In the videos you posted the objects were already separate solids. The only circular patterning that was used was to make an interesting cut into a solid. Did I miss something?

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in the video they use the circular pattern tool to create a new solid. that was the part I was referring to as being the same thing. I'll have to review Johnson's suggestion a little closer when I get a chance.

but, really the point I was trying to make was the need for the split tool do this. even if Johnson's solution fits the need 100%, it's very unlikely that a new user would ever figure it out on their own, and that should be reason enough for autodesk to improve this (imo).

...There isn't any way to code workflows in Inventor right?

actually there is, iLogic is the way to do that.

[justindove]

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@BMiller63 wrote:

 I'll have to review Johnson's suggestion a little closer when I get a chance.

but, really the point I was trying to make was the need for the split tool do this. even if Johnson's solution fits the need 100%, it's very unlikely that a new user would ever figure it out on their own, and that should be reason enough for autodesk to improve this (imo).

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Well, his method works if the lumps are all separated by a non-zero gap. It does NOT work for splitting on flush surfaces. So it does not repeat the functionality demonstrated by Solidworks in the video. Nevertheless it greatly helps me for my special case.

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@BMiller63 wrote:

...There isn't any way to code workflows in Inventor right?

actually there is, iLogic is the way to do that.

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They wouldn't happen to have a free student version of that would they?

@john I was able to reduce the number of steps for my very specific case by another order of magnitude. Since all 4 of my unique parts are close to one another, I just setup my revolve cut to only cut a large enough angle to catch at least one copy of each. This means it only cuts up a few duplicates and leaves the rest of the solid as a single lump. Again this only works in this special case since I had parts close together that didn't require full revolves (and again that I only care about a small number of unique parts). I'm still interested in hearing about a "select other lumps" feature if its there.

Summary of new extremely useful features that I or someone will have to formally request:

-Split solids on multiple surfaces simultaneously

-Separate all lumps of a solid into separate solids

-Select all lumps EXCEPT one of interest

EDIT: It turns out that it's a **** good thing that I thought of the partial revolves because I actually had more lumps than I realized. Because of the way I cut the parts, it leaves some tiny tiny disjoint lumps at the intersection of male and female cuts that I intended on just throwing away. However, they are indeed separate lumps and there are 480 of them...and they are miniscule.....talk about tedious and room for messing up. Now there are far less to manage but it's still on the order of 40 or so.

[JDMather]

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@justindove wrote:

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@BMiller63 wrote:

...There isn't any way to code workflows in Inventor right?

actually there is, iLogic is the way to do that.

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They wouldn't happen to have a free student version of that would they?

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iLogic is included in Inventor 2011.  Students can download free Inventor Professional 2011 from http://www.autodesk.com/edcommunity

I suspect there is a relatively simple (Inventor) solution to the problem (flood fill with Sculpt) - but without the file.....

[Paul.Normand]

OK - this thread has raised an interesting issue and you have our attention. I can request adding this functionality, but my voice doesn't carry as much weight as you all!

If you want to see this functionality added, please request it:

http://usa.autodesk.com/adsk/servlet/index?siteID=​123112&id=1109794

Your votes count!

Thanks,

Paul

[justindove]

@JD I have the student version of Inventor, that's why I asked. So iLogic is completely integrated into Inventor 2011 by default now? And is it accurate to say that I could use it to automate John's workflow for getting my result?

I'm sorry that I can't give you my ipt. The design isn't public yet so I can't have CAD files for it floating around. I can set up one with a very simple example of the issue if you really want but I think it's just as easy for you or anyone to build an example. Just make a solid block of any shape. Then make a thin rectangle (or anything similar) sketch and extrude cut all the way through the block with it, leaving two disjoint lumps separated by a gap. Then linear or circular repeat that cut. Now you'll have a single solid made of a bunch of disjoint lumps separated by gaps. Now try your solution for making each lump a separate solid. That's the Issue [#2]

And example of Issue [#1] is start with a block of any shape, then make a 1-D sketch and turn that into a surface that passes all the way through the solid block. Then linear/circular repeat that surface. Now you have a bunch of surfaces running through a single solid. Then see if you have the solution for splitting the solid with all of those surfaces without manually splitting each one one at a time.

Turn's out I had a lot of those little scraps I mentioned (>40) even after the simplification. But I cranked through it all and have the parts I need to continue working. Nevertheless, the issue is still very important to me. There is a design I may be working on in the very near future that has a lot more unique parts making me need a more efficient solution.....right now I'm heasitant to start that at all because I still have no way of efficiently tackling the issue and its not feasible to crank through John's workflow for all of those parts.

@Paul I agree, we should definitely request these features (simultaneously cut, separate lumps, and select all but one lump). I take it they should be requested individually? I would greatly appreciate any pushing you do on the employee end as well. I just can't believe this issue hasn't been brought up before...it seems like a very logical and necessary feature for many design projects.