how to maintain parametric relationship of creo rounds dependent on depth modifications?

[pimm]

I need to maintain the length of 4 locked flats on a locked shape.  The depth of the locked shape is variable and is controlled in a family table.  I have 8 rounds which are applied to the transition between horizontal and the locked flats.  If I increase the thickness of the shape the 8 constant radii will alter the position of the 4 flats that I need to maintain.

Normally I could keep a parametric relationship of these flats within a sketch.  To avoid reworking my geometry and just for the sake of curiosity I am wondering if there might be a way to parametrically have the inside corner radii to decrease and the outside corner radii to increase based on the thickness change that was made to the shape?

Below is an image of this shape which defines the solid rounds and identifies the flats that need maintained.

If this isn't parametrically possible I will modify the model to develop the relationship that I need using a sketch with all of the radii and apply the thicken command.  I just find from time to time it would be helpful to maintain parametric relationships on a solid rather than within a sketch.

[tbraxton]

The design intent if I understand your post is to define a function such that the inside and outside radius of a feature vary with the thickness. This can certainly be controlled with feature and or part relations assuming that you can write the function such that the radii are driven by the thickness.

As a side note I would strongly encourage you to avoid using sketcher relations (other than for trajpar in VSS features) as it makes debugging models a complete nightmare. There are of course exceptions but for this specific scenario I would not use sketcher relations.

[pimm]

Tbraxton: 

I believe you have exactly described what my intention would be.

If the overall thickness changes by .125 this means that each side would  thicken by .0625.  This would also mean that for all the flats to stay the same that same relationship would need to change with each of the radii.  If the radii is on an inside corner it would be .0625 smaller.  If the radii is on an outside corner it would need to be .0625 larger.

I am very unsure of how to use feature or part relations how would something like this be done?  Would this be developed in a relations table that would have an individual dimension feature define the mathematical increase or decrease to the entire set of outside or inside radii? 

[tbraxton]

The process would be as follows:

Identify the driving dimension(s); in this case it would be thickness (obtain the dimension name of this dim in the model i.e. d123)

Identify the driven (dependent) dimensions in the model; the radii and get the names for those dimensions (i.e.  Rd123 and Rd124 for inside and outside radii respectively)

Use Tools->Relations: this will open the relations editor

Write relations for each dependent variable as a function of the driving dimension in the relations editor this is where you use the dimension names noted above in the relations i.e. Rd124=d123+d123/2 (this would make the outside radius equal to 1.5* the thickness (d123) as an example.

Verify the relations; use the icon with a check mark on the sheet to verify in case there are errors

Then regenerate the model(s)

About Relations (ptc.com)

[Catalina]

Hi @pimm,

I wanted to see if you got the help you needed.

If so, please mark the appropriate reply as the Accepted Solution. It will help other members who may have the same question.
Please note that industry experts also review the replies and may eventually accept one of them as solution on your behalf.
Of course, if you have more to share on your issue, please pursue the conversation.

Thanks,

[kdirth]

One could definitely create a relation with trig functions to determine the correct radius.

However, I would suggest creating a sketch on the end before adding the rounds referencing the walls and defining the flat length.  A reference dimension on the radii would be the dimension to relate to the rounds.