Today, I was going to use a steel extruder to make some copper foils to produce circuit boards（I don’t want to do a Cluster mill, because it needs half a stack of materials, and the only function is to produce foil）, As a result, I put copper dust into the extruder and it didn’t working. (the steel extruder can handle the extrusion recipe of copper.) I checked the NEI and found that only rubber, plastic and wax have the extruder recipe of foil. Is this bug or is it intentionally set?
Extruder recipe for foil
I guess it was set to make Cluster Mill not so useless.
Correct, the Foil Extrusion Recipe is only for Plastic and Rubber alike Stuffs. That way you do not do what you were just about to do and skip the Clustermill.