Solid DNA blog

Blog about stuff on Solid Edge CAD software

Lexis

New discussions raised by Synchronous Technology makes me use words/expressions in which readers may not be familiar. So I think about building lexis, giving me the chance to define those new words/expressions.

As an example, all solid modeling implies a history because they keep track of what you are doing, yes even ST. AutoCAD, on the other hand has no history. Well if you count undo/redo,  may be it has a history……

Also traditional modeling does not automatically mean that the design is parametric.

Since Synchronous Technology introduces new paradigms, new thinking comes along and gives us the chance to review our way of doing things.

History modeling

History modeling refers  to the type of modeling where actions are kept  in a bucket to be later edited. History modeling implies  the use of a container. Those containers come in two major flavors:

  • Feature (Traditional modeling)
  • Procedural feature ( Synchronous modeling)
History modeling can or cannot be Parametric.

Non history modeling

Non history modeling refers  to the type of modeling where no information is kept.Therefore no container is need. A well known, non history CAD program is AutoCAD.

Linear Modeling

Type of modeling where a structure is built (feature tree) and parent/child relation is established between features. Moving features (re-order) need recalculation. Also because of the parent/child relation, it may be impossible to reorder features

Linear modeling can or cannot be parametric.

Non linear modeling

Type of modeling where a structure is built (feature tree) but no parent/child relation is established between features. Therefore moving features (re-order) have no impact ( no recalculation).

Non linear modeling can or cannot be parametric.

Parametric Modeling

Use parameters to drive a design.

Usually parameters are uses in formulas.

Parametric modeling is often associated to part design, where parts serve as a container for the parameters.

Example of formula using parameters: Length/2=width

Parametric modeling can also be found in assembly. It is mostly used to establish links between parts. Parts can still be the container of parameters but in some cases, the assembly can act as a container for the parameters. They are store in the variable table of the assembly.

Other types of parametrics involve assembly constraint, where a part has a defined position in regard to the whole assembly (assembly reference planes) or in regard to other parts.

“Yes” is the answer to the question asked by Matt Lombard. Parametric modeling can exist without histories the same as histories can exist without parametric modeling.

Import a non native files inside Solid Edge, apply PMI dimensions and create a equation, you have use parameters to drive a non history model.

OR

Import a model inside Solid Edge, add few operations and use only the steering wheel to  modify the model, you did not use any parameters to drive the history model.

Parameters

Parameters come in different flavors:

  • Number
  • Equation/formula
  • Physical
  • Morphology

Each of them are an evolution of the of the precedent one. Basic level being numbers.

Parameters – Number

The simplest of all, a table containing values that are changed by the user to modify the part

Parameters – Equation/formula

Numbers define variables that are used in formulas to define behavior.

Parameters – Physical

Parameter is not any more a number but a physical entity. An analogy for this is when you look at yourself in the mirror; numbers are not involved in our reflection. This reference in 3D CAD has includes edge or geometric constraint ( the action of giving mechanical behavior inside a 2D sketch)  etc…. In many cases the “Z” is not taking in account for this type of parameter.

Parameters – Morphology

Here we talk using the 3D shape  to establish a parameter. Often we refer to “Insert part copy”. This is the action done from within an assembly, while editing a part. We copy a portion of another part inside the actual part we are editing.

Variables

Two types of variable are used

  • Dimensional variables
  • User Variables

Variables – Dimensional

These came from a 2D sketch. Each time users place a dimension, dimension variables are placed  in a table named “Variable Tables”

Variables – User variable

These are created by the user directly in the variable table. Taken alone they  have no effect on the design. They have to be incorporated inside a formula to drive/modify the design.

Exposing

Making variables available outside their container ( variable table). When exposed variables become properties (metadata). Those can later be accessed through other documents (associativity)

Metadata (Properties)

From Wikipedia:

«….Metadata provides context for data.

Metadata is used to facilitate the understanding, characteristics, and management usage of data. The metadata required for effective data management varies with the type of data and context of use. In a library, where the data is the content of the titles stocked, metadata about a title would typically include a description of the content, the author, the publication date and the physical location….»

The umbrella of metadata (for the purpose of this lexis) includes any properties associated with 3D files (part, assembly,draft etc…)

To make a better image of what is metadata, just think about the information stored inside a picture like the name, the camera model, exposure time, GPS location , etc…..

Associativity

Where associativity is involved:

  • Part to Draft
  • Assembly to draft
  • and so on as long it is associated to a draft or similar document (Word for example).

When 3D modeling was introduced,  the term «Associative» was meant to describe the link between the 3D and the draft (2D design for the manufacturing or transmission or for the transmission of informations among people inside the lifecycle). Modifications in the 3D, were reflected in the 2D.

With time the concept of associativity slowly migrated/merged/changed/mixed… with parametric and vice versa.

Inter-part associativity

Here we talk about establishing a link between two parts.  Changes made inside one part reflect inside the other one. It is best when directions of changes are in one direction. However, in most complicated scenarios, bi-directional exchanges are involved. This can be accomplished by linking parts through  parameters.

Conclusion

Are you keeping information so you can it edit later?

Yes…. so you are in history base modeling.

Can operations be modified (re-order) without any impact on the designs?

Yes… so you are in non-linear modeling.

Do you keep track of the dimensions inside a table?

Yes… then you have variables, those can be exposed to be reused as a part properties( metadata).

When producing a document containing information (word document), does this document update when sources change?

Yes… so you have established associativity between documents.

This is a work in progress…..

1 Comment »

  1. If you don´t mind I will translate this to article Spanish and publish them as a 3d modeling terms definitions in our portal related to CadCam.

    Comment by SERGIO | 8 April 2009 | Reply


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