First there was an initial phone screen, then an initial interview with a lead regarding my portfolio / resume. After that was a more in depth technical interview with multiple members of the mechanical team.

The onsite interview consists of many stages. The first being interviewed by 5 engineers simultaneously. They will ask anything from your experience to analyzing free body diagrams. The next phase is with some of your collogues that you would be working with. The final phase is with upper management and mangers of different departments. They'll ask a slew of questions about various specifics things you've done, strengths/weaknesses, etc. Total time for the onsite was around 5 hours for me.