Insertion mechanism for drug delivery device

An insertion mechanism for a wearable drug delivery device that deploys a small gauge flexible cannula with support of a coaxial rigid trocar or hollow needle. After insertion, the trocar or hollow needle is withdrawn leaving the cannula in place for drug delivery. The insertion mechanism may also include an insertion mechanism housing having a proximal and distal end, a manifold configured to fluidly connect the hollow interior of the cannula and the fluid pathway connector, and a manifold guide carrying the manifold and movable between a first position and a second position. A hub carries the trocar and is removably connected to the manifold guide. An insertion biasing member may be initially retained in an energized state between the proximal end of the insertion mechanism housing and the hub, and a retraction biasing member may be initially retained in an energized state between the hub and the manifold guide.