weight is easier to hit at the slow speed. The vibratory feeders have
problems if you change speeds, at different speeds, they feed a different
depth of chemical in the vibrating troughs. Running coarse and fine on
vibratory feeders causes waves in the chemicals, causing the rate of feed to
go up and down, hard to predict infly.
....

Ah, you bring back memories. I used to work with cellulose acetate
flake. Couldn't use air to move it - explosive that way. Augers didn't
work, it would just compact. Vibrating troughs was the only way.
management wanted to speed up. Very hard to speed up a trough without
just building another. We were doing about same thing you are, mixing
acetate, plastisizer, several small ingredients, then running through
a pelletizer. Last improvment I worked on was going direct from raw
material to extruded film. You know the product, that roll of magic
tape on your desk. The factory I worked in averaged 1,000,000 finished
rolls of tape packed out every day.

karl