Frustration: Drawing involute internal splines to spec

[St0RM33]

Hello guys. I am fed up. In the last couple of days i am trying to create a correct internal involute gear. A little background:
I have a power steering pump pulley that i happen to want to change some of the parameters. After i found the specs for the poly micro-v profile (PK belt) and reversed engineered the pulley i am only left with the internal spline that mates to the power steering pump shaft. After some reading and measuring i found out that it has 17 involute teeth (side fit - flat root from the looks of it), modulus 0.75 (so 12.75mm pitch diameter) and probably 20 degree pressure angle (JIS automotive spec) (since it has been made in japan about 1990) or 30 degree (ISO, DIN, JIS spec) (not sure how can i confirm the pressure angle, only with measurement over pins i guess).

So after finding out the various standards i went into modelling with Siemens NX:
- Hidden china-only market gear tools hidden in NX: Internal gear tooth minimum limit of ~34 teeth - can't use it
- GRIP program i found in this forum: Does external gears correctly, however internal gears seem to have a programming limit maximum (aka programming error in this case) for addendum as i cannot make it give me out the correct Dii (minimum minor diameter, internal spline). Dedendum works fine (i make 2 circles in a sketch, one for Dii and one for Dei max flat) - i've attached a pic to show the problem with both the correct external gear and the wrong internal gear
- Other programs i found online that spit out dwg/dxf files either won't work right/have demo limits/unobtainable)

I still don't understand how CAD suites don't have gear creation modules based on all the common standards. This is unacceptable! I am stuck now, and i don't know what to do. Any ideas?

Kind regards

 

[Toost]

A little trick, NX7.5 did not have a separate license for the china toolkit.
I do not know when the special license was implemented but i know that 7.5 didn't demand one.
It will require a KF_execute .

Regards,
Tomas

 

[SDETERS]

We have a standard part that uses base diameter and gear tooth thickness and the other standard information for a gear. You have to modify these values in the expressions. I will upload If you are interested in it. It creates the splines by using law curves.

 

[Toost]

I tested 7.5 again today on the 34 teeth limit, is this something you have discovered or ?
I played around with it and noticed that it will, when it no longer produces a gear, create curves which might (?) be used for manual extrusion.


Regards,
Tomas

 

[BubbaK]

There is an example gear program that ships with NX. It's in ...

\Program Files\Siemens\NX x.x\UGOPEN\SNAP\Examples\More Examples\Gear

It produces an external spur gear. It's pretty simple, and you might be able to change the code to produce internal gears.