Factory ship

s were space capsules manufactured by the Daleks that contained automated assembly plants to grow new Dalek mutants and construct their casings.

History
The factory ships were sent out from Skaro by the thousands in the early days of the Dalek Empire. One ship could theoretically produce hundreds of Daleks within a few hours of planetfall. (PROSE: Dalek: The Astounding Untold History of the Greatest Enemies of the Universe)

One capsule crashed on the planet Vulcan where it was discovered by human colonists. Though the active Dalek crew managed to restore power to their ship, the Second Doctor ultimately destroyed it when he overloaded its static power feed. (TV: The Power of the Daleks) According to the Time Lords' Dalek Combat Training Manual, the capsule was infact a scout craft used for reconnaissance missions. (PROSE: Dalek Combat Training Manual)

Another, far more advanced, factory ship had landed on Vega 4. It had the resources to produce over 3,000 Daleks. (PROSE: Dalek: The Astounding Untold History of the Greatest Enemies of the Universe)

During the renewed civil war between the Daleks loyal to the Dalek Prime and those loyal to Davros, the former faction planted a dimensionally transcendental factory ship aboard a Thal ship returning to their own space. This was discovered by the Eighth Doctor who, aware that this would enable the creation of a new Dalek army in enemy territory, used the TARDIS to expel the factory ship through interstitial space, claiming that he had already dealt with it "in another time, and another place." (PROSE: War of the Daleks)