Actual element not updating (2026.4.1.5)

[[Jo...]]

Hello,

I am changing the selected surface area on the cad to change some sections and the actual sections are not updating.

I tried recalculating the project, changing aligments, restarting inspect and a couple more randoms stuff.

Anyone had this problem before and found a solution other than deleting and recreating the elements?

[[TI...]]

You probably used the 'actual section' measurement principle  instead of using 'Reference Construction'

[[Jo...]]

Hello Tim,

That is right.

So you are saying that this is intended behavior with the measurement principle "actual section"?

I was under the impression that a parametric software would also change the calculation when creating the actual section, when underlying parameters are changed.

I will have look into that, thank you.

[[TI...]]

You don't want to use actual section, you want to use reference construction. Actual section isn't parametric, but reference construction will be.

The programmer I took over for didn't really know what they were doing and used actual for everything. I eventually just rewrote all the programs. Once you switch it to reference it will also lose its alignment and that caused me problems with parts with threads that could be rotating with a local alignment.  

[[Be...]]

Please understand the difference between 'Actual Section' and 'Referenced construction' before you simply change the measuring principle: "Actual section" ensures that the nominal plane is used as cutting plane. For many evaluations you need this! "Referenced construction" would replace the nominal cutting plane with an associated actual plane (if you are using a nominal plane with a measuring plane to determine the actual plane). This could result in a nominal and actual section which have not the geometrical same plane which leads to "invalid" inspection evaluations or evaluations which gives you weird values.
If you still want to use "Referenced Construction" and you need to have the same cutting plane use a nominal plane with no applied measuring principle ("No measuring principle").

[[TI...]]

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 We never use actual section. I'm sure there may be some cases when you need it, but I have never encountered one.  Sometimes we cut on the CAD X,Y, Z plane so using actual vs reference it almost irrelevant, but I'd still use reference on X,y,Z planes b/c if you change them somehow the won't break as easily as the OP poster here saw.

I'm assuming if you wanted to use actual due to a poor stabilized plane, you could instead find a way to stabilize it(ie directing it based on a primary datum) or some machined feature and still use reference.  Other than that, I don't see a use case for ever using Actual Section.  Can you give me an example when it is desirable to use Actual Section?

 

[[Be...]]

E.g. if you want to have an Inspection section. Nominal and actual plane must be geometrically identical to get a deviation result. If you have applied a measuring principle to a nominal plane, e.g. Bestfit you usually will get an actual plane which is not geometrical the same plane as the nominal plane (otherwise you wouldn't habe to measure your specimen). If you create a section on nominal and actual with the combination of nominal and actual plane and 'Referenced construction' you will get not the expected deviations in the Inspection section (usually you want to have a section on the actual data which is geometrically exact at the nominal plane geometry).
There a lot of industries which requests that: Automotive, Airfoil, etc.

[[TI...]]

I'm not in aerospace, but a fan blade for instance, wouldn't you want to establish a primary height datum and measure incrementally from that surface certain heights up?

Maybe you are saying they best fit the overall part, in this case the blade, so Datums are irrelevant, and then you section a certain height up from the CAD Z origin, which then using actual so the nominal section and real section are cut on top of each other.  That seems strange to me b/c we are always analyzing section cuts and profiles from proper robust datums.  I hope turbo fan blades are measuring section cuts from datums 😉.

 

 

 

 

 

 

 

 

[[Be...]]

Yes, this can be true that the nominal and actual plane are geometrical "equal" due to an established alignment/datum system. Nevertheless, in general you are not forced to do that, e.g. in the automotive industry an RPS alignment is usually established and not a planar datum in a Geometric alignment and then it happens often that the nominal and actual plane can differ.
Even for advanced evaluation processes with a 'Geometric alignment' you can simulate a different alignment to see how the deviation would change. In all of these situations 'Actual section' as measuring principle can fit better to the application of the customer.

If 'Referenced construction' fits better to your application simply use it! But please be aware when to use what due to the expected differences.

Regards