The document discusses the differences between top-down and bottom-up design processes in CAD modeling, highlighting how each approach serves different needs based on the components' nature. Top-down design is preferred for assemblies where components are interdependent, while bottom-up design is suited for off-the-shelf parts. It also mentions a hybrid approach for large assemblies and recommends specific PTC Creo CAD software packages based on the design method employed.

1. TOP-DOWN VS. BOTTOM-UP DESIGN:
TOP-DOWN VS. BOTTOM-UP DESIGN:
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CHOOSING THE BEST APPROACH
CHOOSING THE BEST APPROACH
FOR YOUR PROJECT
FOR YOUR PROJECT

2. In working with clients that span
multiple industries, we have found
that designers and engineering
departments for most mid-sized to
small companies in Discrete
Manufacturing are more focused on
hitting deadlines and don’t have the
time to change or update their
process or the way they work.
However, adopting a Top-Down
design process (rather than Bottom-
Up) for your PTC CREO CAD models
can save a lot of time downstream
from building a better parametric
model.
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3. Here is the difference between a
Bottom-Up design process and a
Top-Down process.
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A Bottom-Up process focuses on
the individual parts that make up
an assembly. Each part is designed
independently and in isolation
from the other parts. They are then
combined into an assembly as the
last step.
A Top-Down design process
focuses on the entire assembly
from the start. Individual parts are
modeled referencing the assembly
with each parts geometry tied
back to the assembly.

4. So, when does it make sense to
use one process over the other?
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The Bottom-Up design is
ideally suited when most of the
parts or components are off the
shelf items. In this scenario it is
much more difficult to adjust or
change the individual
components.
Top-Down design is ideal for
designs where the components
are not “off the shelf” and their
dimension or function is driven
from the assembly itself.

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There is also a hybrid approach that
uses both Top-Down and Bottom-
Up, which is more common when
modeling very large CAD
assemblies (assemblies with a lot of
parts). In this case the top-level
assembly is generally Bottom-Up
but the critical unique sub-
assemblies use Top-Down design.
How can PTC Creo CAD software
help with Top-Down and/or
Bottom-Up modeling processes? If
you are manufacturing/designing
simple component type parts and or
assemblies.

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Using the Bottom-Up method, then
Creo Design Essentials package is
the best solution for you since it’s
the basic license of Creo, but very
feature rich.
If you are manufacturing larger
assemblies or hybrid assemblies
using the Top-Down approach you
will want to utilize the capabilities of
Creo’s Advanced Assembly
Extension (AAX). Creo’s Advanced
Assembly Extension does more than
just Top-down design and skeleton
models. Advanced Assembly also
improves communication regarding
design criteria.

7. www.3hti.com
Advanced Assembly also improves
communication regarding design
criteria and assembly references, as
well as providing a concurrent
design process.

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