Page "Top-down and bottom-up design" Paragraph 5

For perspective, for a product with more restrictive requirements ( such as weight, geometry, safety, environment, etc ), such as a space-suit, a more top-down approach is taken and almost everything is custom designed.

However, when it's more important to minimize cost and increase component availability, such as with manufacturing equipment, a more bottom-up approach would be taken, and as many off-the-shelf components ( bolts, gears, bearings, etc ) would be selected as possible.

In the latter case, the receiving housings would be designed around the selected components.