Lesson 1 – Introducing SolidWorks
Section I – Preliminaries 1.4 The SolidWorks Interface
Parts, Assemblies and Drawings
An assembly is a group of parts that together make the complete product or a portion of the product.
For example, an automobile is an assembly of parts, but for convenience, it can be subdivided into a
frame sub-assembly, a powertrain sub-assembly, the air conditioning sub-assembly, etc. The
powertrain sub-assembly can be further subdivided into the engine sub-assembly, the transmission
sub-assembly, the wheel-tire sub-assembly, etc.
Parts and assemblies are a convenient way to subdivide a product because they allow division of
labor and specialization. If production resources, including employees, equipment and facilities, are
dedicated exclusively to producing only one or a few parts or assemblies they can achieve efficiencies
that are not possible otherwise. Specialization is the basis of mass production. The engine block, for
example, is usually a casting. The engine camshaft is machined from a steel bar and the pistons can
be cast or forged. Each manufacturing process requires different equipment and expertise. A typical
automobile today has thousands of parts and dozens of sub-assemblies produced in manufacturing
facilities located all over the world.
Designers and design engineers create detail or part drawings primarily to enable the manufacturing
of parts by different people in different locations. This requires that each detail or part drawing have all
the information needed to make the part, and nothing extraneous that can cause confusion. For
example, the part drawing for a camshaft must have one or more pictorial views of the part, derived
from the solid model, and additional information such as dimensions and tolerances, material, finish,
etc. On the other hand, there is no need for information about other engine parts such as the valves.
Thus, the camshaft, the valve detail or part drawing will have all the information needed to make the
parts but no information about how they fit together. The information needed to assemble the
camshaft and the valve together belongs on the engine sub-assembly drawing.
The first step when modeling a product is to break down the assembly into parts. This is a very
important step that will impact the quality and cost of the final product and the complexity of the model.
Although there are exceptions to the rules, the following are important considerations when deciding
what should be a part:- Components made of different materials should be different parts. For example, a part
should not be made of sheet metal with rubber bushings or bumpers. Instead, create a sub-
assembly that contains sheet metal and rubber parts. - Components made with different manufacturing processes should be different parts. For
example, a typical steel file drawer has many sheet metal and machined parts assembled
into drawers, cabinets, etc. This is also true for the finishing process. A part should not be
painted and also chrome-plated. It is more appropriate to have an assembly of painted and
plated parts. - Weldments should be drawn as parts, with all final dimensions, tolerances and other
information. A wood frame, such as a book shelve, could also be drawn as individual detail
drawings for each shelf configuration, plus an assembly drawing. The choice can be based
on the degree of control required for the assembled dimensions and tolerances. - Use sub-assemblies when the parts complement to enable a function. For example, the
wheel and tire together will enable the automobile to roll over the pavement. There are a
minimum of four identical wheel and tire sub-assemblies.
In addition to the detail or part drawings used to make the parts, the design organization must create
assembly drawings to provide information about how the parts assemble together. The information in
an assembly drawing is different than the information in a detail drawing, but the process for creating
them is similar.