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Cannot dimension arc lengths of a 3dSketch? 2

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tmalinski

tmalinski

Mechanical
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Oct 14, 2002
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424
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I have a 3dSketch consisting of three arcs. Kind of like an s-curve. All have "tangent" relations and "on-surface" relations to keep them glued to a plane. I need to dimension their arc lengths but SW greys them out as if they were driven but I have no other driving relations or constraints that I'm aware of. Can I not do this? or is there another way to nail down the length of the arcs on a 3dSketch?
Thanks,
Tom

Tom Malinski
Dell Prec 670, Xeon 3.8,2GB Ram, Nvidia Quadra FX 3450/4000 SDI
SWorks Pro & PDMWorks 2007 SP3.0
 
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Click on your display/delete relations button to make sure that you don't have any other driving relationships. Perhaps a point is coincident?

Jeff Mirisola, CSWP
SW '07 SP2.0, Dell M90, Intel 2 Duo Core, 2GB RAM, nVidia 2500M
 
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You may have inadvertently created inferred relations when placing the centres or endpoints of the arcs.

[cheers]
 
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I get the same.
It seems you can't get the true dimension of an arc in a #d sketch.......

Remember...
[navy]"If you don't use your head,[/navy] [idea]
[navy]your going to have to use your feet."[/navy]
 
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TOOLS/MEASURE will show length of 3D Sketch spline.

Chris
SolidWorks 07 4.0/PDMWorks 07
AutoCAD 06
ctopher's home (updated 04-21-07)
 
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If all 3 arcs are "on surface" of one plane, could you not convert them to a 2D sketch and then apply the arc lengths? You would have to delete the relations created by converting though.

Either way an ER may be in order.

[cheers]
 
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Thanks all for your replies, I really need to leave this as a 3d sketch because there is more to this than a simple s-curve as I used in my example. What I ended up doing is dimensioning from endpoint to endpoint of the arcs, this fully defined them, although not as I would have preferred. It is the arc length that is important.

This sketch defines two ends of a lofted surface that looks like a wavy carpet. However, I need the ability to change one of the arc segments length where everything else would move reletive to the change but would keep their own lengths preserved.

I wonder, is it possible to "fix" geometry relative to other geometry without using relations? The normal "fix" relation fixes everything in its current position. If I could fix geometry but then drag it around as a group that would be cool. I can do this using a block in a 2d sketch, but 3d sketches will not allow blocks.

Thanks
Tom

Tom Malinski
Dell Prec 670, Xeon 3.8,2GB Ram, Nvidia Quadra FX 3450/4000 SDI
SWorks Pro & PDMWorks 2007 SP3.0
 
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Tom,

You can put an arc length dimension on a 3D sketch; it will just need to be a driven dimension if my quick attempt at it is any indication. You may be able to add these driven dimensions in addition to the dimensions you added to define the sketch. Future modifications won't be as straightforward because you'll need to iteratively modify the driving dimensions until you get the arc length you need.

If what you really need is to dimension the arc lengths you will have to figure out a way to use a 2D sketch to define the loft sections. Maybe use 2d sketches to create your lofted surface and then another 2D sketch to generate your surface boundary? I'm not sure what your end goal is, but with a little messing around you may be able to get there with 2D sketches. You'll probably need more features, but I'd rather have more features that yield what I want instead of a nice short feature tree that is a compromise in terms of the resulting geometry.
 
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I must be missing something tmalinski,

If you are able to use ..
"on-surface" relations to keep them glued to a plane.
Click to expand...

Why do you need a 3D sketch at all?
A 2D sketch on the 'plane' in question would still give the results you need.

Remember...
[navy]"If you don't use your head,[/navy] [idea]
[navy]your going to have to use your feet."[/navy]
 
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Meintsi here you go!!
Here is a quick shot of my surface loft. Note the construction line attached to the nose of the loft. In my 3d sketch, I must be able to dimension the angle between the line and the loft nose to twist the loft and change it at will. It's currently at 96 deg. When I modify the angle or twist all of the arc lengths must stay preserved except for the very last arc on either side where it connects to the flat tail area. Those arcs simply lengthen or shorten to take up the difference from the twist of the nose. The tail always stays stationary no twist.
so having the loft geometry and the controlling twist geometry in the same 3d sketch seemed like the best way to go for this.
Hope this makes sence to you.


Tom Malinski
Dell Prec 670, Xeon 3.8,2GB Ram, Nvidia Quadra FX 3450/4000 SDI
SWorks Pro & PDMWorks 2007 SP3.0
 
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Tom ... I don't know if it will give the control you need but, have you tried using the Flex tool on a regular extrusion?

[cheers]
 
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CBL, yes I have played with the flex tool and I thought I had it, but when compared to the twisted loft it was different, so I abandoned the idea

Tom Malinski
Dell Prec 670, Xeon 3.8,2GB Ram, Nvidia Quadra FX 3450/4000 SDI
SWorks Pro & PDMWorks 2007 SP3.0
 
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Twisting material between the two fixed planes of a loft will not accurately reflect what is really happening to material when it gets twisted. Unless the material can stretch, the end points at the twisted end will move closer together laterally.

[cheers]
 
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CBL, there is more to this than what meets the eye. I do a surface trim to round the back flat area and then the sides are trimmed away and tapered down to the nose to where the nose is almost pointed. then I thicken it. The end result is very very close to an actual formed Sheetmetal part. Because I'm thickening the surface the thickness stays normal to the surface so it looks very real. see the attached jpeg


Tom Malinski
Dell Prec 670, Xeon 3.8,2GB Ram, Nvidia Quadra FX 3450/4000 SDI
SWorks Pro & PDMWorks 2007 SP3.0
 
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A surgical blade for the Da Vinci Robotic surgery

Tom Malinski
Dell Prec 670, Xeon 3.8,2GB Ram, Nvidia Quadra FX 3450/4000 SDI
SWorks Pro & PDMWorks 2007 SP3.0
 
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As a work around to make it easier to modify, could you create a 2D sketch with driving dimensions for the arc length and driven dimensions for the dimensions in the 3D sketch and then link them?

Eric
 
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