When designing something complex in CAD you will find there is a bit
of a process. First you design parts. Then you build the parts into
Sub-Assemblies. Next you build sub-assemblies into Groups. Then you
build the groups into the machine. It is a logical pyramid process. You
can also think of it like a file structure inside of a computer.
Designing Parts
Parts are your building blocks. Without this level, nothing could be
produced. The part level breaks the entire “thing” down to its simplest
form. You also manufacture at the part level. You make parts, and then
assemble them into other things. Parts are generally made out of raw
materials.
Think of a differential on the rear axel of a car. The differential
is made up of gears and a housing. Each of these are parts of the
differential and the differential is the assembly of these parts.
Designing Sub Assemblies
Sub Assemblies are the next level up and I am guessing you are
getting the idea. You first design parts, then put them together into
sub assemblies. In the car example above the differential is a sub
assembly in the axel “Group” of the car. Sub Assemblies are put
together to form groups.
Designing Groups
Moving up the design chain, groups are usually things you can
identify with. It could be a door, engine, transmission, or cooling
package on a car. Above we used the example of an Axle as a Group.
Groups are put together into machines. Our example is a car, which is
at the machine level.
Designing the Machine
Finally, the top level of all your designing, the machine. The
machine could be built for the end user or be sold to another
manufacturer. That manufacturer could use your “machine” as a sub
assembly or group. You can see all this is just a matter of viewpoint.
You can consider just about anything a sub assembly, group or final
machine. It is all just semantics and what you are using the item for.
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