Can one use mixed dimensional units in an Expression somehow? 1

[LinuxFreak]

Hi All,

I am often creating sketches that involve arcs and angles where the angle required is dependant on the arc radius. I use a simple formula as follows:

Angle (deg) = Chord Length (in) [÷] .017453 [÷] Radius (in)

I've shown the units in the formula to help explain my issue. The chord length is defined but the radius would change depending on loading conditions of the part. I'd like to use such a formula in the Expression Editor in order to drive the angle as I make changes to the radius. However, I haven't found a way to use mixed dimensional units in this fashion.

Does anyone know of a work-around? I hate having to manually change the angles all the time when I make changes to the radius.

Thanks,
Drew

 

[jerry1423]

What version of NX are you on?

 

[JohnRBaker]

Attached is an NX 5.0 part file showing an Expression scheme which will do what you're asking.

John R. Baker, P.E.
Product 'Evangelist'
Product Design Solutions
Siemens PLM Software Inc.
Industry Sector
Cypress, CA

http://www.siemens.com/plm

http://www.plmworld.org/museum/

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

 

[LinuxFreak]

John,

Thanks a million! That works great, and so simple. I wouldn't have imagined your idea of just creating a dimensionless value for the calculation and then making an angle equal to that value. I'm fairly new with NX and really wanting to learn a lot of tips to make life a bit easier.

What version of NX are you on?

I am using NX 6.0.5.3. Since posting my original thread I figured it'd be smart to add that information to a signature so it's always known. It should show up now. If you have anything different to offer from John, I'll certainly consider it. Thanks!

Drew

Win VISTA-64 / NX6.0.5.3 MP5 / NX7.5.1.5 MP1 / Algor 23.1 / ANSYS 13.0

 

[JohnRBaker]

Now that I've thought about it awhile I've concluded that your problem was in how you ordered the variables in your equation.

Take a look at this second example where I avoided the intermediate expression altogether (I knew taking Algebra back in high school would pay off someday ;-)

John R. Baker, P.E.
Product 'Evangelist'
Product Design Solutions
Siemens PLM Software Inc.
Industry Sector
Cypress, CA

http://www.siemens.com/plm

http://www.plmworld.org/museum/

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

 

[jerry1423]

You are able to set the units in the expressions so maybe that will help you do what you need.

 

[LinuxFreak]

John,

That last example was also excellent. Thanks. At first I failed to see how that would work since I've tried doing something similar before and it failed. However, by grouping the two linear dimensions in the brackets as you've done, perhaps that's allowing the units to cancel out first before completing the equation and assigning new units. Hmmmm.

Well, I certainly appreciate your help!

Drew

Win VISTA-64 / NX6.0.5.3 MP5 / NX7.5.1.5 MP1 / Algor 23.1 / ANSYS 13.0

 

[JohnRBaker]

That's why I mentioned high school Algebra since cancelling out the units in an equation was one of the things you learned, although I have to admit that until I took Chemistry and was introduced to balancing chemical equations, I didn't really appreciate why learning the basics of Algebra was so important. I guess it was then that I realized that one could actually understand how things worked by decovering the variables, determining how they were related and how this effected the answer.

As for the parentheses, while it is true that there is a precedent in the order that operations are applied in a computer programming equation (learned that 40+ years ago when I studied FORTRAN), you quickly learn that you can force the order of evaluation by the use of parentheses and while I've been critized at times for using more than what were technically needed, I feel that, at least for me, they make it easier to understand what's happening and if needed, makes debugging expressions more straightforward.

John R. Baker, P.E.
Product 'Evangelist'
Product Design Solutions
Siemens PLM Software Inc.
Industry Sector
Cypress, CA

http://www.siemens.com/plm

http://www.plmworld.org/museum/

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