Involute Curve in NX 9

[Kim K]

Hi! I have gotten access to a file "involute_curve.prt" and was wondering if you could help figure out how to change it. I am unsure what 't' represents. I am fairly certain 'r' is my generating radius. Can you help? Please and thank you! - Kim

 

[JohnRBaker]

Don't mess with the 't' expression! It's value in under the control of the Curve function.

John R. Baker, P.E. (ret)
EX-Product 'Evangelist'
Irvine, CA
Siemens PLM:
UG/NX Museum:

The secret of life is not finding someone to live with
It's finding someone you can't live without

 

[cowski]

The involute curve is a parametric equation (a "law curve" in NX terminology). The "t" is the parameter that ranges from the value of 0 to 1 that helps drive the curve definition. The "t" must appear in the equation for the curve, but as JohnRBaker points out, it is under the control of NX.

www.nxjournaling.com

 

[Kim K]

Ok - T expression untouched!

Why can't i use the extrude function and have this involute as the driving curve to build it?

 

[cowski]

You should be able to do that. Does it give any sort of error message?

www.nxjournaling.com

 

[Kim K]

Yes, invalid string.

I had used the part file as a linked composite curve and it failed. So I went into the part itself and chose the law curve and it had the same error.

 

[cowski]

Can you post a link to the involute_curve.prt file or attach your file?

www.nxjournaling.com

 

[Kim K]

I think that should be the file... I am new to the site so unsure if i did this correctly. Thanks for the help!!

 

[SDETERS]

For some reason it crashes where the curve is at the 0,0,0??? I do not know why. Sketch a line across it and do an extrude with stop at intersections is turned on. I attached a PRT file. Thanks

 

[Kim K]

I am using NX 9 and can not open that file SDETERS.

 

[cowski]

If the "turns" parameter is set to 2.55 or less, it works. I'm not sure why it won't accept a larger value...

www.nxjournaling.com

 

[JohnRBaker]

That was a limitation which I personally found and reported as a PR, and which I was under the impression that this was fixed in either NX 10.0 or NX 11.0

John R. Baker, P.E. (ret)
EX-Product 'Evangelist'
Irvine, CA
Siemens PLM:
UG/NX Museum:

The secret of life is not finding someone to live with
It's finding someone you can't live without

 

[Kim K]

Thank you for all the input!!! After the holiday I will be looking into this further to see if the involute part i downloaded can actually work with what we are designing!

 

[BubbaK]

If the Law Curve approach isn't working, there is an alternative. If you look in some location like C:\Program Files\Siemens\NX 10.0\UGOPEN\SNAP\Examples\More Examples\Gear on your system, you will find a SNAP program that creates simple spur gears. Part of this is the construction of an involute curve.

 

[Toost]

Try change the start angle from 0 to say, 0.1 or 1 or ...
It will probably do the trick, if you can accept it.

Regards,
Tomas