How to lock dimensions from different sketches

[creo1234]

Im trying to create a Optimisation analysis where there are changes in certain dimensions within their own sketches. However there is a dimension (the overall width of the part) that I dont want to change in this analysis. Its fine that other widths and heights change when optimising just as long as the distance from one surface to another remains the same. As there is no sketch in my model tree that has both surfaces together I cannot find a way to lock them together.

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[JamesBurcham]

Do you have some screen shots or a file we can look at to help understand what it is you are trying to do?

[creo1234]

Not right now but this is similar:

http://www.cimdata.com/newsletter/2012/6/03/images/clip_image005.jpg

I want to optomise the thickness/ width of this part using an optomisation analysis in creo simulate, but in doing so its going to change the distance between the two holes at the top and bottom of the picture (the top having the purple load applied, and bottom with that orange circle on it). Their separation distance cannot be altered. Im not sure how to conduct this analysis without the distances between them changing, so how do I lock them in their original positions relative to each other? Hope that helps

[JamesBurcham]

I would recommend using relations to locate the two features. Without knowing how its modeled I can't make any specific recommendations on how to do that, but Antonius' descriptions of parameters and relations should be helpful for you.

[TomD.inPDX]

I do not know the simulation package for Creo.

I am not sure how it determines which parameters are allowed to change.

If indeed it uses locked dimension in your feature creation, then yes, the method I describe should work.

However, if this is managed through the analysis process independent of the model generation, you probably need to create boundary conditions for the analysis process to keep certain faces fixed.

The forum does have an analysis specific section that might be more appropriate for your question. It is second tot he last entry when you hover on the Creo tab.

[TomD.inPDX]

Hello and welcome to the forum.

There are many ways to accomplish what you need but the question is rather broad.

First, you can use references in your sketches that are fixed. Next, you can use a parameter or a relation to provide a fixed value in all your sketches.

If you have a common datum plane for the one side, you can offset a datum plane for the other. In your sketches, you can reference this new datum plane to constrain your sketch. This will not change until and unless you move the datum plane.

You can create a parameter named "distance" with a value of 10.5. You can create this parameter by creating a relation "distance=10.5" or entering this parameter directly in the parameter dialog. in the sketch, you create a relation (now tied to the sketch) by selecting the applicable sketch dimension, say "sd4" and create the statement "sd4=distance". Again, this value will remain until changed.

This is pretty much core functionality for Pro|Engineer. Relations, parameter, and references are what makes parametric modeling in Creo what it is.

[JamesBurcham]

Great explanation Antonius.