Variable Helix 4

[Blase_McK]

Hello, So im trying to add a Helix to a screw that has a MIN thread depth that runs at an angle for 11.2mm and then runs out straight for the remainder of the shank.
I have attached a snip of the drawing. The line highlighted orange, is the spline i am trying to run the helix along.

any idea on how to get it to follow this spline?

Thanks in advance!

 

[Toost]

What NX version are you running ?
This is a typical job for a radius by law curve.
I have attached an NX12 example.
The sketch is the law for how the radius evolves. The total length ( the X- direction) of that sketch is = 100% of the helix height.
i.e if you make this say 100 mm and the helix should be 14 total, and the "bend" at 7 mm, the sketch should bend at 50 mm. ( I hope you understand this.) the height from the base line is 1:1 to the selected radius/diameter in the helix dialog.

Edit : - You should probably add a fillet ( possible even a G2 Spline ) in the sketch between the lines , else the helix might have a sharp corner which in turn might affect the sweep you do on that helix.
Regards,
Tomas

 

[Blase_McK]

Toost, Thank you for the reply I'll give this a try and see what I come up with.
I feel like i have tried Law curve and it says spline has multiple loops... not sure why it says that, but it errors out the helix.

As for the version, I'm Running NX12.

 

[Blase_McK]

So i got the Helix to follow the spline i have set for the minor Diameter,
but its following the spline as if its the minor Diameter. The Major Diameter is constant but the minor is variable

 

[Blase_McK]

I GOT IT!!!!

Thanks
Blase

 

[Toost]

Good !
But what on earth is the usage of this thing ?

Regards,
Tomas

 

[Blase_McK]

It's a bone screw.
The Tapered ID is only to strengthen the screw, The OD stays the same diameter.

Thanks
Blase