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
