Systems engineering detail design help!

[rbamfordz]

Hi,

I'm reading some books about engineering design but I can't find out how systems are detailed.

During conceptual design I know you can create a design which describes the top-level mechanisms for a system but leave the internal workings of them undescribed.

My question is what is the procedure for continuing design for the inside of those mechanisms?

Thank you!

[jboggs]

I'm not sure I follow your question exactly... But:
In the mechanical world we have assembly drawings and subassembly drawings. The same design principles apply to both. The only difference is that a subassembly can conveniently be assembled, stored, handled, and installed as a single component of the larger assembly. For example, Your car's gas tank is an assembly of several components. It is also a component of the entire car assembly. The fuel pump inside your gas tank is itself another subassembly. Each of these components and subassemblies would have their own drawing and can be designed on its own.

Is that what you were asking?

[rbamfordz]

I'm not sure I follow your question exactly... But:
In the mechanical world we have assembly drawings and subassembly drawings. The same design principles apply to both. The only difference is that a subassembly can conveniently be assembled, stored, handled, and installed as a single component of the larger assembly. For example, Your car's gas tank is an assembly of several components. It is also a component of the entire car assembly. The fuel pump inside your gas tank is itself another subassembly. Each of these components and subassemblies would have their own drawing and can be designed on its own.

Is that what you were asking?

Yes! exactly, how do you go about designing a subassembly for example the fuel pump. Do you completely start a new design for that subassembly? i.e. back to requirements analysis, concept design.etc?

[Kelly_Bramble]

Yes! exactly, how do you go about designing a subassembly for example the fuel pump. Do you completely start a new design for that subassembly? i.e. back to requirements analysis, concept design.etc?

If the subassembly does not exist a development effort may be required to create the end item or a sourced subassembly is identified, specified and procured for installation in the top assembly.

In general, subassemblies are best developed as a next generation iteration where lessons learned in the existing subassembly are incorporated into the design and manufacturing changes are incorporated.

[jboggs]

"how do you go about designing a subassembly for example the fuel pump. Do you completely start a new design for that subassembly? i.e. back to requirements analysis, concept design.etc?"

As I said, the design principles are the same. You start by identifying the functional, dimensional, and other requirements for your finished subassembly design. Start by defining where you want to end up. Then examine any existing subassembly designs to see how closely they might meet those requirements. You might get lucky and be able to use an existing subassembly design with no changes at all. More likely, you start with the existing subassembly that most closely matches your new requirements, then modify whatever features are needed to meet those new requirements.

In the process you might notice that an existing subassembly would work in the higher level assembly if a small change were made to that higher level assembly to accept it. Your higher level assembly has a particular bolt pattern for mounting the subassembly. An existing subassembly meets all the requirements except for that bolt pattern. Then by simply changing the bolt pattern in the higher level assembly you enable usage of the existing subassembly.

[rbamfordz]

"how do you go about designing a subassembly for example the fuel pump. Do you completely start a new design for that subassembly? i.e. back to requirements analysis, concept design.etc?"

As I said, the design principles are the same. You start by identifying the functional, dimensional, and other requirements for your finished subassembly design. Start by defining where you want to end up. Then examine any existing subassembly designs to see how closely they might meet those requirements. You might get lucky and be able to use an existing subassembly design with no changes at all. More likely, you start with the existing subassembly that most closely matches your new requirements, then modify whatever features are needed to meet those new requirements.

In the process you might notice that an existing subassembly would work in the higher level assembly if a small change were made to that higher level assembly to accept it. Your higher level assembly has a particular bolt pattern for mounting the subassembly. An existing subassembly meets all the requirements except for that bolt pattern. Then by simply changing the bolt pattern in the higher level assembly you enable usage of the existing subassembly.

Thank you!