Difference between the Boolean operations "Assemble" and "Add" in CATIA

3D Design Volume Model
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Hello

Since then, I've been interested in the bodies of a piece under catia.

What differences do you make between the Boolean operations "Assemble" and "Add"?

If I take two different parts bodies, to which I assign each a different material. Independently I find their mass but when I combine them ("Assemble" or "Add" operations) the total mass is not equal to the sum of the masses of the parts bodies, do you know why?

What interest do you see in the use of part bodies (pyramidal rather than linear construction tree)?

Thank you for your answers.

Kind regards;

André Montéra

 

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Catia V5 - Boolean operations in Catia - A modeling asset

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Design office / CAD

Image Relimitation Partielle.

The Boolean operations in Catia are a real "plus" compared to its competitors for the design modeling of mechanical parts. They make it possible to separate the different functions of the part into distinct parts of bodies, thus limiting unnecessary references between the different parts of the part, and provide a very appreciable flexibility of design.

These Boolean operations are mainly used in 2 very distinct situations:

  • Grouping of functions in order to facilitate a duplication operation (symmetry, repetitions, etc.).
  • The isolation of a part of the part in order to simplify its definition and limit the references necessary for its modeling.

However, it must be kept in mind that a part body is destined to be integrated into the main body at one time or another. A Catia room is supposed to consist of only one main body.

The different operations available when assembling the part body into the main body are the big advantage of this design method:

  • Assemble: Default operation to integrate the part body while respecting its polarity.
  • Add : A forced operation in Add Material mode.
  • Remove : Forced operation in Subtract Material mode.
  • Intersection : allows us to obtain the solid resulting from the intersection of the bodies concerned.
  • Partial relimitation (the most interesting operation for the simplification of the design): assembly operation with the relimitation of the parts bodies between them during the operation.
  • Volume withdrawal: allows you to remove a piece of isolated solid, obtained for example after a withdrawal operation (in the event that a partial relimitation could not be considered, you can fall back on a withdrawal followed by a volume withdrawal).

These famous partial relimitation operations, which allow part of the part to be assembled and can then be simplified, require a little practice, especially with regard to understanding and correctly using the "to keep" or "to remove" faces. But they are an undeniable advantage for modeling complex parts.

To illustrate the use of these Boolean operations, here is one of the guided exercises I use in my training room to demonstrate their effectiveness.

- See more at: http://www.cti-formation.fr/cti/catia-v5-les-op%C3%A9rations-bool%C3%A9ennes-dans-catia-un-atout-de-mod%C3%A9lisation#sthash.UjR21esm.dpuf

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Same material of the 3 parts in your initial assembly?

Otherwise, there is surely also fusion of materials and therefore of 3 different densities, you go to one...?

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Hello

01- As it is written in @gt22's reply:

Assembling it respects the polarity *  ( * explanation if the first function of a body is a removal of matter "pocket, groove, etc"  the body icon takes a sign - if this function creates matter the body icon takes a + sign)

So with the assemble of a field "+" operation we add, with the assemble of a "-" field operation we subtract.

Whereas with operations:

Add (add matter whether the body is + or -)

Withdrawal  (removes matter whether the body is + or -).

For my part I use: "Add" only  with body +, "Removal"  only  with body - and "Assemble when the body itself is the result of association of Boolean operation. (I rename the "Assemble-add-shape" function......" or "Assemble-Shrink-Shape......"  as the case may be.

02 - Total mass:

The mass is deduced from the (volume) x la (density).

If no material is applied to the part body at the highest default level, the value is 1g_cm3.

If the part is multi-material, we don't assemble the bodies , which allows us to have the right rendering on each body, and if we want the total mass, we keep the measurements of the 2 bodies, we create a user parameter of total mass = the sum of the two measurements.

03 -  Linear VS Boolean design:

Linear, this is the normal design also used inside bodies.

As soon as the model becomes complex (many topological operations), its modification is + delicate, so we try to structure the graph (pyramidal structure, Boolean operation), this makes it easier to read, allows us to group topological operations by "mechanical functions", e.g. all the fixing clips, all the reinforcement ribs (by the way on the latter the partial relimitation with method is just great).

To allow design independently of the rest of the model (which makes changes, recalculation time and reuse in another design more flexible and faster), etc.

 

 

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