22 feb. 2017

Tasty buns and good tree structures


When I was a little boy my mom sent me to do the daily shopping. I got a handwritten purchase list with approximately ten issues. There was variation but the last entry was always the same, " 4 tasty buns ". I can still remember my confusion and irritation. Surely the buns should be "tasty", who would buy four " disgusting " buns voluntarily? But how to find the tasty buns among all by the master baker?

I can imagine that a Catia pupil, being told repeatedly to use good structure for the specification tree, perceives the same confusion and irritation. Everybody demanding good structured trees but never or seldom any particular guidelines.  Sure I want to achieve a good structured tree but what is it more exactly?

An exactly answer can not be given, since the usage of Catia is so extremely diverse. However there are topics, which should be evaluated to define your convenient guide lines, how to structure your trees. Let us look upon some important issues.
When should you define a tree structure?

If you are working professionally with Catia the answer is easy, always!  There are very few parts, which are so uncomplicated, that they not deserve a considered specification tree structure. The necessary time to plan a structure is proportional to the complexity of the part. Simple part - short time, complex part - long time.

However the importance of having a good tree structure is increasing non linear but exponential with the complexity. Real complex parts from the daily job in the design office necessarily need logical tree structures. The handling of the geometry will otherwise be too costly.

When you want to define the ideal tree structure evaluate first:



Templates

Before you start anything, find out about templates at the department. Use the best suited and invest a couple of minutes to understand the structure. Normally you have geometrical sets for
                Tooling
                Externally copied Features
                Features to be copied outside the part
                Important References
                ….
Respect this structure since it is major guide line for the company. Building up a different structure interfering with the defined template is not a good idea.

Existing Structures

Are there structures already defined for this kind of parts in other used CAD/CAM systems or documentation of the company? If existing and well known by the colleagues and if they are adequate reuse them.

 Skeletons

If and what kind of skeleton is needed?
Look for a skeleton structure, in which you easily can select the reference features with the main important parameters regarding modifications.

Major Parameter

If there is a major parameter, such as e.g. material thickness, create the corresponding parameter in the Parameter branch. This to avoid inefficient search for that important parameter.

Frequent Modifications

Ask yourself what will be the most frequent modifications of this part and which features are concerned?
Define a structure which can separate this major features from features of minor importance.

Dominate order topology or chronology

Should the dominate guideline be to divide the part into separate areas or rather follow the chronological order in which the features have been created. The first alternative would be to have a separate branch for each geometrical area, left, right, center, .... or represent the features regarding the order in which they must be created, e.g. first branch: sections, second branch: untrimmed surfaces, third branch: trimmed surfaces.
Take a decision and try to use it consistently!

Show/Hide Combinations

Consider what kind of combinations of features you want  to show. Are they available with your tree structure?

Working Method

Start with a template and complete it with your rude tree structure. Do not get in detail. You have to see, if your structure really do work. When you are satisfied complete, rename and clean up the tree.

Rename

Rename the geometrical sets and a number of features to support the visual navigation. You do not necessarily have to rename a big number but what is reasonable to orientate inside the tree. Do not entry the feature type. You can identify the feature type by the symbol in the tree. Use significant words or letters at the beginning, since the program can be limited to display a certain number,  e.g. the first eight letters.

And remember, there is not only one type of tasty bun.  Different solutions can be equivalent good. It is a matter of taste!

Have a splendid time in the trees
Thomas

14 feb. 2017

A new Grand Touring starts

This is the start of grand touring inside the country of Catia V5.

Here you will read and discuss topics as methodology, best practices, lessons and user experience.

Thomas Pärsson, Unico's Catia master, and Johan Fleischer, Technology Area Manager  CAD, will do most of the writing. We hope to make this place an Arena where we can meet new and old friends how like us are working with CAD and more specific with Catia.

Let's start the grand touring now!