Full Version: Boolean issue II

From: Derek (SANGKYU5) [#1]
1 Feb
To: ALL

Michael, I posted another one for boolean problem. I thought I fully understood what you showed me in my previous sample.
And I tested that myself and saw it work.
The attached one, however, doesn't seem to work that way(Putting the shape in the box and subtract(diff) it). I wonder if the shape isn't completely sealed
Could you diagnose one more time?

Thank you.

Attachments:
sample2.3dm

From: Michael Gibson [#2]
1 Feb
To: ALL

Hi Derek, yup the problem is exactly as you suspected - the shape you are using is not a completely sealed solid, it is only an open surface.

The quick way to diagnose this is to just look at the object type indicator here:

That's one of the new features for MoI v2.

That type indicator will show "Solid" when you have a solid selected - in your case it says "Joined srf" to indicate that you have several surfaces joined together but not totally sealed everywhere into a complete solid.

Then to get more specific information you can set up a keyboard shortcut with the script on it from here:
http://kyticka.webzdarma.cz/3d/moi/#SelectNaked

which will highlight "naked" edges - those are edges that are are not joined to another edge, making an opening in your object.

In your object there are quite a few of them:

How was your object created? There seems to be some pieces missing, like the side walls of the hole on the side are just not there.

- Michael

Image Attachments:
derek_edges.jpg solid_type_indicator.jpg

From: Michael Gibson [#3]
2 Feb
To: ALL

Hi Derek, was this possibly modeled at a smaller size and then scaled up to its present size?

There are a lot of pieces that just do not fit with each other with a very good tolerance.

For example here:

Those are 2 trimming edges of that surface which are supposed to be touching one another, but you can see there is a significant gap between them.

Similarly the edges of this piece does not line up well with the edges of its surrounding surfaces:

Several of those pieces are probably going to need to be reconstructed to have better accuracy and touch the surrounding geometry more closely.

- Michael

Image Attachments:
derek_tol1.jpg derek_tol2.jpg derek_tol3.jpg derek_tol4.jpg

From: Michael Gibson [#4]
2 Feb
To: ALL

Do you have any of the original curves used for constructing this model?

If you can post them, it may help me to give some tips on some more robust construction techniques, like trying to build larger surfaces rather than a lot of little slivered pieces or some stuff like that.

Try to build some pieces larger than you need initially, with fillets applied for the rounded edges, then slice away excess material with a boolean, rather than going around trying to fill in one little patch at a time.

- Michael

From: Michael Gibson [#5]
2 Feb
To: ALL

Hi Derek, here are some steps that would probably be easier for building a piece like this, working more with solids throughout rather than by going around filling in little patches.

To start with I drew a curve:

Then mirrored it and extruded it out into a solid block:

Now use Fillet to round off all the sharp edges:

Then prepare another curve, I used Construct > Offset to offset the original curve inwards a bit:

Then use Boolean Difference to cut the solid by the offset curve, to make a sharp inside cut, leaving the fillet around the outside to be rounded:

Things can tend to go more simply and quickly by working on a carving out pieces away from a solid like this. Hope this helps,

- Michael

Image Attachments:
derek_step1.jpg derek_step2.jpg derek_step3.jpg derek_step4.jpg derek_step5.jpg

From: WillBellJr [#6]
2 Feb
To: ALL

I just love these kinds of posts!

For me, that object type indicator is one of the most important features of v2 - I can tell at a glance if the object I have in hand is not a solid the way I expect it to be!

-Will

From: Derek (SANGKYU5) [#7]
2 Feb
To: ALL

Michael,

I really feel appreciated for your quick answer. I fully understood what you say.
I was designing a mobile device case for my own. This is the part of it.
I go to a local CNC club meeting in Portland, OR.
Next time I go there I plan to demonstrate MOI.

Thanks again Michael. I'll probably be back to ask you for technical issue.

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Full Version: Boolean issue II

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