1
general::
Phrase(s): churn something out
to produce something in large numbers, perhaps carelessly. • We churn toys out by the thousand. • This factory can churn out these parts day and night.
McGrawhill's American Idioms And Phrasal Verbs
2
general::
Produce in an abundant and automatic manner, as in He churned out a novel every six months. This idiom transfers the turning of milk into butter to other kinds of production. [Early 1900s]
American Heritage Idioms