mirrored surface isn't symmetric wtf? 1

[Manifolddesigner]

Howdy all,
I'm working with some boundary surfaces and after running into some weird filleting errors, ran a symmetry check. noting something was asymmetric, rolled back to the point where i mirrored a couple of bodies. Immediately after i mirror the bodies, when i run a symmetry check (i double checked that it's mirrored and symmetric about the same surface!) it isn't symmetric!! WTF????
Is there some hidden resolution setting I can change somewhere?

Any suggestions?

Jason
CSWP, adv mold, adv surf, adv weld, etc.

 

[Manifolddesigner]

running SW 2k10, sp0. x64.

 

[kellnerp]

I've been saying that for years. This problem has been there for years (since the late 90's). I think Ed Eaton addresses it in one of his Curvy Stuff presentations.

At the last WMSWUG meeting a guy had an optics package which he used to compare surfaces from SW with the optically perfect surfaces the addin created. Pretty eye-opening.

TOP
CSWP, BSSE

http://www.engtran.com

http://www.niswug.org

"Node news is good news."

 

[Manifolddesigner]

bloody hell! that wasn't the answer i was looking for!!

 

[ctopher]

I'll never be able to look at mirror again!
A few years ago I experienced this once, but not since.
My guess it's small? How asymmetric is it?

Chris
SolidWorks 09 SP5.0
ctopher's home
SolidWorks Legion

 

[Manifolddesigner]

i honestly am not sure how asymmetric. Maybe in the millionths. Enough to make nice really complicated features like "fillet" refuse to work.

 

[lumenharold]

This is a link to a thread in the SW forum that contains the SPR and SR numbers for the surface accuracy (if interested):

https://forum.solidworks.com/message/158307#158307

This is a link to the presentation (again, if interested):

http://wmswug.files.wordpress.com/2010/05/wmswug-may-11-2010-upload.pdf

The presentation does not go into much detail on surfacing or the models. For more info on surface accuracy you might surf for the SWW2010 presentation from Mark Biasotti "Advanced Modeling 301".

Harold
SW2010 SP3.0 OPW2010 SP1.0 Win XP Pro 2002 SP3
Dell 690, Xeon 5160 @3.00GHz, 3.25GB RAM
nVidia Quadro FX4600

http://www.lumenflow.com

 

[mjcole]

I'd recommend using Planes rather than faces for the *Mirror Plane* Selection. This can be compared well with the accuracy of a helix curve compared to a *Convert Edge* of the same curve in a 3d Sketch which can calculate the curvature correctly and display the curvature combs.

In sheetmetal sometimes you were forced to use faces instead of planes for Mirror command which I think has changed since 2010. From parts I've modeled on multiple CAD systems Planes work better for Mirrors than Faces even supposedly flat surfaces.

Michael

 

[Manifolddesigner]

it's a plane i'm using, but thanks, good info. Interesting note about the convert entities. Greaaaaatt....another weird inaccuracy.

 

[KevinDeSmet]

Well, computers are deemed "perfect" but there is no such thing. If they were, drawing a circle would take 2 hours

CSWP-Surf

 

[lumenharold]

Just rec'd notice that my SPR 558639 is Closed (Implemented). Good news! It's in 2010 SP3.0. Not really since I'm already on 3.0 although that's what the Customer Portal tells me. I've requested more information via the forum.

Harold
SW2010 SP3.0 OPW2010 SP1.0 Win XP Pro 2002 SP3
Dell 690, Xeon 5160 @3.00GHz, 3.25GB RAM
nVidia Quadro FX4600

http://www.lumenflow.com

 

[Theophilus]

I get huge problems of this sort all the time when modeling half a widget and then mirroring the bodies across a main plane.

Often I'll cap the open surfaces on half the part with a planar surface first, knit to form a solid body, and then mirror the solid bodies. Join often fails because of zero thickness geometry (or whatever)--this is essentially the loose tolerance problem creating microscopic voids of some sort even though ALL the work is done across the main (Right, Top, Front) planes throughout the feature tree! So how could there be any gaps anywhere? Zero should at least represent zero, but often does not.



Jeff Mowry

http://www.industrialdesignhaus.com

A people governed by fear cannot value freedom.

 

[Theophilus]

By the way, Harold, I just caught up with the discussion on the SW forum. I've just gotten v2010 SP3.1 installed--but haven't yet tried much of my typical swoopy stuff with it yet for production work (still in v2009).

Anyway, this is interesting and I'll keep an eye on it. I thought my surfacing work was demanding, but yours is a few notches above mine in terms of requiring precision.

Good luck.



Jeff Mowry

http://www.industrialdesignhaus.com

A people governed by fear cannot value freedom.

 

[lumenharold]

Thanks Jeff. The surfaces are not all that swoopy they just need to be accurate in order for the light rays to calculate correctly. I suspect there is no change in the software since the issues I submitted were generated using SP3.0. Like I mention in the SW forum, I'm not sure what was gained by going through the exercise of submitting the files, etc.

When it comes to real swoopy designs I prefer to let the IE people handle that. I am a form follows function person at the tube.

Harold
SW2010 SP3.0 OPW2010 SP1.0 Win XP Pro 2002 SP3
Dell 690, Xeon 5160 @3.00GHz, 3.25GB RAM
nVidia Quadro FX4600

http://www.lumenflow.com

 

[Theophilus]

What was gained could be as simple as false assurance that something has been done (gain for SolidWorks and not for you?). So it might be worth pressing them just a bit on this in the main forum to see why the issue is closed with the SP in which the problem exists--since clearly it hasn't been closed legitimately (as resolved) given what you've seen.



Jeff Mowry

http://www.industrialdesignhaus.com

A people governed by fear cannot value freedom.