Use specified Area to control sketch

[janhansen]

Hello NX´s

Does anybody know if it is possible to control the size of a sketch with a specified Area ?

I know (and have tried) that it is possible to control the size of a closed skecth profile by using the Perimeter dimension, and by inc. or dec. the Perimeter value the sketch profile change size by moving the non-dimensioned objects in the skecth.

But can the same be done by specifiyng the Area of the closed profile in the sketch?

I would use this "Control sketch by Area" to make a deformable part for an O-ring, that can be stretched in Diameter , and also show in 4 different build in shapes ( 1: Axial (Flat on top and bottom) , 2: Radial (Flat at inside and outside diameters) 3: Inside corner (Triangle shape) and 4: Outside Corner (Triangle shape)

And when the O-ring is deformed (strechted and shaped) the section area should be correct. (When the o-ring strecht, the section area is getting smaller).

I first thought I could just calculate an "Strecht Ratio" by dividing the nominal Diameter with the stretched Diameter, and multiply the Perimeter of the Section with this factor.... BUT when the O-ring build in shape is not circular, the Perimeter and Area is not the same as when the O-ring section is still circular...

So I realized that I need to be able to control the Section sketch by an Area that is reduced by the "Stretch Ratio" , to be able to keep the Volume of the O-ring the same, wether it is stretch in Diameter and/or deformed to one of the 4 build in shapes.

Do anybody have an Idee??

I have attached the Partfile as it is now, still with the Perimeter Dimension in the sketch. It consists of 4 different sketches , that is supressed 3 of 1 by changing the Build_in_Shape expression to 1,2,3 or 4.

Best Regards

Jan Hansen
Denmark

 

[jerry1423]

yes, it is possible.
I did it a long time ago.
I don't remeber how I did it, but I may have time today to experiment a little bit and get back to you.

 

[JohnRBaker]

OK, attached is an example that uses a totally different approach.

To start with, I created the model using a Sweep instead of a revolved body. This way I can use a 'Law' to control the 'cross sectional area' of the model. One of the nice things about this is that you do NOT have to create your profiles to be the correct size, they simply have to be the correct shape. In fact, in my example I created three different profiles which are much larger than they need to be just to prove the point. When I created the Swept Body I used the 'Black' circle as the 'profile' but I used an Area Law, set to 200 mm^2, to control the 'Cross Sectional Area' of 'O-Ring' (controlled by an Expression named 'Area'). Now to change the 'shape' of the O-Ring simply edit the Swept Body replacing the 'Profile' (the 'Black' circle) with either the 'Blue' or 'Green' profile and you will get a new 'O-Ring' still with a 200 mm^2 profile but with the same 'shape' as the colored profile that you selected.

Anyway, give it a try and see what you think.

John R. Baker, P.E.
Product 'Evangelist'
Product Engineering Software
Siemens PLM Software Inc.
Industry Sector
Cypress, CA
Siemens PLM:
UG/NX Museum:

To an Engineer, the glass is twice as big as it needs to be.

 

[janhansen]

Hello Jerry and John.

Thanks for your replyes.

Jerry, if you some day remember how you did it, please post it here.

John, I looked at your proposal, and I did not know this possibility!

But the problem about it, is that i cannot keep some of the section segments steady , while the rest adjust to the new area. f.ex. In the Axial build in type, I need to maintain a constant height between the top and bottom face while stretching the O-ring.

The Main reason why I want to have this function that reduce the Cross section Area when Stretching the O-ring, is especcially for the Triangle types, to make it really visible to the designers, about how much of the "touching areas" of the o-ring that is left, if they stretch the O-ring a lot, and still use our Standard "build in" values for the grooves/Chamfers for the choosen O-ring Section size.

So my problem is to find a solution that can adjust the cross section area, by adjusting only the "non-constrained" non-touching faces...

Best regards

Jan