Undercut Detection

Is there anyone out there who uses the "Undercut Detection" in SW05? Has anyone noticed that it's completely wrong?
Here's a very simple example part: www.dezignstuff.com\swparts \undercut.SLDPRT (using the default config)
Here's how the undercut analysis should read for this part:
Dir1 undercut: 0 Dir 2 undercut: 0 Occluded undercut: 0 Straddle undercut: 0 No undercut: 17
But instead, it reads this way:
Dir1 undercut: 5 Dir 2 undercut: 5 Occluded undercut: 0 Straddle undercut: 0 No undercut: 7
Looking at it, the part obviously has no undercut faces when the Front plane is the direction of pull. SW seems to think that the only types of faces that cannot be undercut are faces with no draft, in other words, ALL DRAFTED FACES ARE UNDERCUT.
I don't have any problem with the calculations, I just have a real problem with the classifications. Instead of "Direction 1 undercut", the interface should read "Pulls from Direction 1". Likewise for Direction 2. What most people think of as "undercuts" are actually listed under "Occluded undercut". See "Other" config for occluded undercuts.
Anyway, is there something I'm not getting or has this function always been simply wrong?
Matt
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Matt,
It's very hard to understand (and I don't).
To me, an undercut is an area of a feature that will require a slide or some other type of moveable form,,,that's it...
This thing doesn't seem to give you any usefull information. Or if it does, it's obfuscated to the point of uselessnes.
Probably looks real slick in a demo though :(
Regards
Mark

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been
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You're right and I hear ya, the wording is incorrect, the results are misleading and the help description contradicts itself.
This is what it should be, imho...
Pull Faces and Undercuts: (Undercut Faces)
Pull Faces Dir1: (Direction 1 undercut; light blue) Pull Faces Dir2: (Direction 2 undercut; dark blue) Undercut Faces Dir1: (Occluded undercut; red) Undercut Faces Dir2: (Occluded undercut; orange) Undercut Faces Dir1 and Dir2 (Straddled undercut; blue) No Undercut (no draft): (No undercut; grey)
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(correction/addition)
Pull Faces and Undercuts: (Undercut Faces)
Pull Faces Dir1: (Direction 1 undercut; light blue) Pull Faces Dir2: (Direction 2 undercut; dark blue) Undercut Faces Dir1: (Occluded undercut; red) Undercut Faces Dir2: (Occluded undercut; orange) Undercut Faces Dir1 and Dir2 (Straddled undercut; blue) No undercut Dir1 (no draft): (No undercut; grey) No undercut Dir2 (no draft): (No undercut; dark grey)
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Matt:
I think the mistake you are making is to think that when you use a plane to define the direction that Solidworks interprets it as a parting plane. If you want to get the results that you are expecting you need to insert a parting line and use that in the Undercut Detection. It then gives the results as you predict.
Mike
matt wrote:

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snipped-for-privacy@trudellmed.com wrote in

The same discussion is going on in the SW subscription forum. It works differently, but still incorrectly when done with a Parting Line feature. Anyway, the help describes its use with pull direction and with PL. With the PL feature, two faces of the undercut side core from the part "undercut2" are identified as undercuts from the same direction, but the other 3 faces of the side core are shown as not undercut. This is the biggest giveaway that the "undercut" concept has not been understood by the folks who defined the function.
I'm not making the mistake you point out. I understand the difference between parting plane and pull direction. Just by identifying a pull direction, SW should be able to tell if a face is fully or partially obscured by the solid in the direction of pull without identifying the PL. If a face is not obscurred by the solid in the pull direction, and it is drafted in the direction of pull, then it is not undercut.
Part of the problem is that SW says that all faces on side B are undercut when viewed from side A. That's not useful information. Useful information would be telling me which faces cannot be pulled from side A or side B.
They should get rid of the "Diretction" part of the undercut face identification. Either a face can be pulled from A or B or neither, there is no distinction unless a set of undercut faces are fully surrounded by side A faces.
Just out of curiousity, what part of the information given do you find useful?
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Don't agree, you can have a mold which draws away in multiple directions, not simple A-B. You can do some interesting pulling/lifting/sliding.
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That's true, but what benefit do you get in distinguishing "Undercut" from "Direction1 Undercut" unless it allows you to knit surface bodies from the various types? If you're going to do that, you might want to go the route of doing the same for the draft as well, so you'd have no-draft faces grouped into no draft, no draft dir1, no draft dir2.
Better yet, instead of grouping by direction or side, it would be cool if they could group faces into sets that constitute a single "undercut feature", so you'd have "Undercut1", "Undercut2" which would help you construct lifters or slides. Really, the direction or the side of the undercut doesn't matter.
Matt
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Just to add a little here, if you ever use Splitworks, it groups faces and knits surface bodies after doing a draft analysis, and allows you to create custom groups and move faces between the groups manually. I don't think it would be too difficult to automate this somewhat so that the sets of contiguous undercut faces are automatically grouped and knit into a single surface body.
Anyway, that would be slick and solve some of the difficulty in making slide/lifter geometry.
Matt
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Ok, yeah, beyond analysis, it would be very nice (and easy thing to ask for and get, I would think??) to have the option to utilize the pull direction results as a selection set (copy offset "0") for other mold design use!
Maybe a copy faces check box per undercut detection results? Similar to the parting line feature or assoc or non-assoc and grouped into folders?
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Just did a test, added parting line, on Matt's part and no, although better, it also does not give the correct results.
IMHO, Undercut detection should be initially about Analysis, quickly understanding what faces will be involved with Pull direction choosen (testing planes). Setting up parting lines would be secondary and the undercut analysis would help with understanding what faces need to be drafted or split.
I have to agree with MM, I'm sure it looks good at a demo.
Anyhow, this tool provides 3 ways to set/test for undercuts,.. -Coordinate input -Direction of Pull -and, Parting Line
And it ain't working right.
Seriously,.. Undercut Detection needs to be fixed.
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http://www.zxys.com/misc/undercut_fubar.avi
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I wonder if there is a difference depending on the service pack? When I inserted a parting line and ran it I did get the correct results (SW2005SP1.1).
I don't actually find it particularly useful. I generally use the draft analysis instead.
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It's possible, I'm using sp3.
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snipped-for-privacy@trudellmed.com wrote in

This has been this way since it was implemented. I complained about it to SW and got the old "this is functioning as designed" routine. Apparently the people who design the functions are infallible.
Anyway, I'd be interested in what you think "correct results" are.
I love the draft analysis tool, but it doesn't tell you directly where undercuts are. You can only infer that from seeing red faces in a sea of green. Unfortunately the undercut tool doesn't give that info either.
matt
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"Anyway, I'd be interested in what you think "correct results" are."
What I referenced as correct results are what you indicated in your first post:
Dir1 undercut: 0 Dir 2 undercut: 0 Occluded undercut: 0 Straddle undercut: 0 No undercut: 17
Except that for No undercut I get 19.
Mike
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Just noticed the undercut2 part. You're right it does screw up the side core.
Mike
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