Pre-Planning to acomplish mate and alignment.

I have just recently viewed a Solidworks model of a very modernistic
styled sports car. I noticed that the spacing of all the surface
created parts relative to each other was perfect. Spacing between
trunk and rear fenders, hood and front fenders, etc. I am wondering,
is an understructure, or chassis needed to be created first in order to
mate all these parts together with the perfect alignment and spacing?
Without an understructure of some kind, what would ultimately be
assembled and mated would be no more than a shell, with wheels
free-floating in empty space, with the edges of these surface created
parts not sufficient enough to be used to accomplish mates, much less
the uniform spacing. Are axels needed in order to mate the wheels and
tires perfectly in the wheel well openings? Certainly provisions must
be made while creating the individual parts that would come into very
important play later on at assembly and mating time. Much thought and
pre-planning must certainly be done in the drawing stage of the
individual surface parts.
Will one of the many expert advanced modelers here enlighten one who is
not so expert?
Thanking you,
Erika Layne

 

All the blank-sheet design I've done with styled surface products were
done top-down using common coordinate system to define part geometry.
Parts were locked with common coordinates and modelled "in-position".
If you took the parts and dropped them into a new assembly and lined up
the base planes, the parts were in place.

This method was used extensively in the computer industry. Also, all
the automotive interior designs I made parts for were designed this
way. It is a very effecive method when a team is working on a product
that has "A" surface definitions that span across more than one part.

 

Yes- in cases that you want surfaces to align together into a cohesive
product, designers will use a "top-down" approach. You design the over
all shape how you want it to look and then start splitting it up into
different parts(Insert>Feature>Split). This splittingis ueually done
with surfaces that cut across the solid part.

Simultaneously though you can have a bottom up design taking place -for
instance with standard wheels, and axles put together designed from
stock components. Both methods have their strengths, but for the
cohesiveness that you describe where complexly curved surfaces are
aligning together, you need to design top down.

http://www.productdesignforums.com/index.php?s=1bf9e8512c1a52b83b1649b6f8575508&showforum=25

has some links to models, and tutorials describing the process (perhaps
it was these models you were referring to?)

 

Thank you sir/madam. After I spend a time learning surfaces as I did
learning solids, I will hope to run across some literature or tutorials
describing this "Top-Down" procedure in more detail, and more attuned
to my beginner's level of skill. At least I know what I am looking for
now, many thanks to you.
Erika Layne