There are no set rules in the DfA practice, however, there are some criteria you can use when trying to decide whether or not your design qualifies:

• Parts need to be simple enough where they cannot be easily assembled by hand; i.e., screws need to be self-tapping (no pre-tapped holes), joints need to be over-designed, parts need at least one flat surface to provide a "key" etc.
• Features must be designed so that they do not require any additional tooling which can increase manufacturing costs (e.g., holes requiring custom tools, screws needing custom taps)
• Minimum tolerances need to reflect the tightest tolerances in your product design.
• The assembly needs to be able to be completed without any errors