Variable offset on complex A-Surfaces

[adam1986]

We are currently having issues with creating a variable offset on complex surfaces.

We have created the Bottom side of a formed material, which is fully constrained, allowing us to wavelink into the appropriate tooling for the component. We have since found issues with the thinning of the material, due to a large draw process, so we now need to accuratly create the top surface which has been thinned in various places.

I have tried to use the variable offset tool, but due to the complexity of the surface it is unable to create anything. I have also tried to individually create every surface at different offsets, but the bridge curves are not accurate enough when joining the surfaces which creates folds/creases in the tool.

Does anyone have any other suggestions using the standard tools available (ie, no molding specific tools) (As an engineering depeartment we try and stay away from freeform modelling as much as possible)

Regards

Adam

 

[JohnRBaker]

What version of NX are you running?

John R. Baker, P.E.
Product 'Evangelist'
Product Engineering Software
Siemens PLM Software Inc.
Industry Sector
Cypress, CA
Siemens PLM:
UG/NX Museum:

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

 

[adam1986]

Nx8.5

 

[JohnRBaker]

Have you looked using...

Insert -> Offset/Scale -> Rough Offset...

You should also try running...

Analysis -> Minimum Radius...

...to see if the minimum radius of the surface is LESS than the desired offset distance. If so, it will be very difficult, if not impossible to create an exact offset and you will need to use tools, such as 'Rough Offset', which will be more forgiving when it comes to surfaces with small radii or local inflections.

John R. Baker, P.E.
Product 'Evangelist'
Product Engineering Software
Siemens PLM Software Inc.
Industry Sector
Cypress, CA
Siemens PLM:
UG/NX Museum:

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

 

[adam1986]

the rough offset tool isnt available using our standard license set?

 

[JohnRBaker]

Yes, it requires an 'Advanced Free-Form' license.

John R. Baker, P.E.
Product 'Evangelist'
Product Engineering Software
Siemens PLM Software Inc.
Industry Sector
Cypress, CA
Siemens PLM:
UG/NX Museum:

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

 

[Toost]

What does A-surface mean in this case ?
Generally the term Class A (-surface(s) ) or Class 1 means very "clean" surfaces where "clean" means as simple and mathematically simple as possible.
- and one of the benefits is that for example offset surfaces doesn't give you headaches...

Anyway,
it's quite common that the supplied data isn't really usable for tooling and similar work due to over-complex or poorly defined surfaces.
- The more complex the underlying surface is the smaller the chance that an offset operation will work.
I have been through a few cases where prototypes should be manufactured but the supplied surfaces simply wasn't good enough. We had to ask for better models before we could do anything.

It's difficult to propose any tools/ methods without seeing the case,
Is there any piece of your data that you can share ?


Regards,
Tomas

 

[adam1986]

The data is pretty sensative so i cant share anythign at this stage, but if you can invisage something simiar to a bath.
As the plastic deforms towards the top, it will not have a uniform wall thickness due to the 60cm or so draw and the deformation of the material.

We class an A-surface as a surface that is visable on the product, so an external side of the skin. This surface/side of the material needs to be as "clean" as possible.
The underneath also needs to be relativly tidy as any deformation on this side, can cause shrinkage or creasing due to the thin wall section created by the draw.