Flexible length part w/ relations

[Br2]

Hoping someone can help me out.  I have a steel C channel that I would like to use flexibility for length.  This will have a hole pattern about each interior datum plane and then within an assembly another assembly attached to the datum planes. 

I've tried to accomplish what I want by using relations, and a dimension pattern, or a combination thereof, but I'm not getting it, if it can even be done.  What I'd like to accomplish:

• (2) Datum planes at each end would never be <4.25 from outermost datum plane
• Subsequent datum planes (up to 4) would be >= 6.00 spaced intermittently

>26.50 in .prt (30” in .asm) = (4) datum planes for flexible channel length

<26.50 thru >20.50 = (3) datum planes for flexible channel length

<20.50 thru >14.50 = (2) datum planes for flexible channel length.

<14.50 = (1) datum plane for flexible channel length

I think that explains everything, but if someone is able to help and has questions please let me know.  Thank you!

[BenLoosli]

A steel C-Channel part is not a flexible component. What you have described is more of a family table type of part.

A flexible component would be like a corrugated tube between 2 fittings where the shape and length may change depending on the assembly. Wire routings could also be considered flexible components.

[tbraxton]

If you are asking to make a flexible part, that is not necessary to change the length of the C channel. Since the feature is parametric you can set the length as required and use relations to locate your datums based on test conditions.

Use conditional statements in the relations to manage the # and location of your datum planes.

http://support.ptc.com/help/creo/creo_pma/usascii/index.html#page/fundamentals/fundamentals/fund_sev... 

Keep in mind the the number of instances in a pattern can be managed via relations so you can change the number of planes based on a conditional test of the channel length.