Abstract: A recent development for manufacturing blankets of mineral fibers includes a system comprising a plurality of fiber forming and collecting modules spaced along a process line, each module designed to produce a relatively thin web of intertangled fibers and to deliver the thin web onto a common transfer conveyer to produce a plurality of superposed webs which can later be further processed to form a thick, uniform, mineral fiber blanket. The present invention provides an improvement in the above described system by permitting one or more of the modules to be operated independently of the remaining modules resulting in the manufacture of one or more secondary products when the primary product being made on the main transfer conveyer requires the operation of less than all the modules in the process line.