how to determine surface centroid

[deenigeechtepatrick]

hi,

I need to locate the centriod of a surface in order to generate (through offset) a curve which will be the trajectory of a spinal bend, and which will also generate the correct length op the part. I need the centroid to create the exact length of a part. Can't use mass properties, since they change after the spinal bend, and thus generate an error.

Does anyone know if there is a function for an 'Integral' in Pro/e? then I could find the centroid... or does anyone have another solution?

 

[mloew]

deenigeechtepatrick,

Sounds like an optimal application for Behavioral Modeling (BMX). You will need to create an analysis feature that computes the centroid. The nice thing about using this technique is that it sensitive to where you place the feature in the model tree, so you can have the centroid calculation done before the spinal bend feature, in your example. There are some good tutorials available on the net. Check out the PTC Pro/ENGINEER and Pro/MECHANICA internet resources (faq554-468) on this site and from PTC (

http://www.ptc.com/products/proe/bmx/faq.htm).

Good luck! Best regards,

Matthew Ian Loew

Please see FAQ731-376 for tips on how to make the best use of Eng-Tips Fora.

 

[deenigeechtepatrick]

Thanks Matthew, but currently the BMX module is not available to me...

Isn't there another way to work around this?

the problem is that initially the part is correct, but after regenerating it isn't anymore.

I used the centre of gravity of a protrusion, I put the spinal bend trajectory on this c.o.g., evaluate the curve length, and the protrusion is made the correct length through 'replace surface' with the use of an offset datum plane, offset from the original sketching datum plane.

However, when regenerating the part the centre of gravity is recalculated, and, depending on how I model it, it results in an error or in an incorrect lenght of the bend curve.

Now I was thinking to use the centroid of a surface, but I just can't find the right function (e.g. 'integral'or 'y-coordinate area centroid') to put in the relations file.

 

[peglor]

You can find the centroid of a surface by creating a section through the surface and calculating the section properties. I don't know whether this can be built into an analysis feature, as I haven't tried it.

Analysis features should only operate on the features above them in the model tree too. The problem you describe is not something I have experienced.

I have used it to find the centre of pressure for a gasket seal.