Sketch Tangency to a Sphere

[ktsrocket]

Hi, I am running NX 3 on Windows 2000

I need to punch parameterized holes into a spherical surface, so that the holes are Normal to the surface at their centreline.
I then need the ability to move the hole position and stay Normal to the surface in the new position.

Any help would be appreciated.

Regards
Ken

 

[cowski]

Draw a line from the center of the sphere through a point on the surface that you want a hole, make a tube feature using the line you created using the desired diameter of the hole, subtract the tube from the sphere. You can now edit the line to go through a different point on the surface (leave the other end point at the sphere's center) and everything will update.

This works well for spherical surfaces, if the surface is more complex this method fails.

 

[JohnRBaker]

A much simpler way is to create a Point on the face of the Sphere and then create a Datum Plane by first selecting the Point and then the face of the Sphere which will create the Datum Plane tangent to the Sphere and through the Point. Now create your Hole feature by selecting the Datum Plane as the 'Placement Face' and the Point as the origin.

If you created an associative Point, you can now move it by editing the u and v parameters as Expressions. If you created a 'dumb' Point, you can move the Point by using Edit -> Transform -> Transform and use the Point to Point method.

Attached is an example part using the above method (using an associative Point).

John R. Baker, P.E.
Product 'Evangelist'
NX Design
Siemens PLM Software Inc.
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.

 

[ktsrocket]

Thanks for your replys.

I will explain more when I am less busy.

Ken

 

[ktsrocket]

Hi Guys,

The problem I have is with more complex surfaces, I have attached an NX3 part showing my work around.
My method gives good parameters for adjusting the position of the holes on the surface, but it actually creates conic holes and not cylindrical ones.

John, I believe your solution is the way I need to go but if I put a point on my complex surface and then add a Plane it does not come out as a Tangent to Surface Plane.

I have loaded your file but I cannot adjust the position of the Point using X,Y,Z in Point Constuctor. If you change the X -50 to 50 it does not re-position the plane. Also when modelling it is unlikely that you would know the X,Y,Z coordinates of the hole position.

Ideally the point would be contstrained as follows:
1. To the Surface
2. Dimensioned to the X Plane
3. Dimensioned to the Y Plane
Then you could adjust the X or Y values and the point would move either along or up/down the surface.

I hope this makes some sort of sense and once again thank you for your replys.

Ken

 

[JohnRBaker]

Points on surfaces are not controlled by absolute X,Y and Z coordinates, but rather what's called parametric, or U,V space. So when you place a point on a surface the location is defined by expressions representing what you can think of a 'percentage' of the parametric sense of the surface. Perhaps if you thought of the surface as a grid with 100 graduations along each edge and now think of 'mapping' any location on that surface by giving two numerical values, one along each edge.

In the attached example (note that the Datum Planes are blanked), if you wish to move the points do NOT try and edit their X,Y and Z values, but rather go to the expression system and edit the U and V values for each point (this can also be done from the Part Navigator by selecting the point in feature list and then editing it's U and V 'parameters' in the Details panel of the Part Navigator).

BTW, this entire task will be much easier starting with NX 5.0.2.x since there will no longer be any need for the Datum Planes as you can now place a hole normal to any surface at a point, all in a single step.

John R. Baker, P.E.
Product 'Evangelist'
NX Design
Siemens PLM Software Inc.
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.

 

[ktsrocket]

Hi John,

Thank you for the informed response.

I can get the planes and adust their positions in your example, but I cannot get the Planes to go Normal to their surface in my example.

Could you try to add Surface Normal holes to my CAD file please.

Regards
Ken

 

[JohnRBaker]

You really need to upgrade to at least NX 5.0.2.x ASAP for something as complex as this. Using NX 5, putting holes in a part like yours is trivial.

John R. Baker, P.E.
Product 'Evangelist'
NX Design
Siemens PLM Software Inc.
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.