Chitin autodoor

A chitin autodoor is a Vanilla structure made from the chitin material, added in the Vanilla Factions Expanded - Insectoids module.

Strategy
By the time autodoors become prevalent in your colony, it is likely that plasteel will also be readily accessible. Thus, the chitin autodoor is only an alternative to stone autodoors if the small flammability does not matter, but the tiny improvement to speed does.