which type of machines are used in sandpaper production line?where can I find them?

Answer 1

Somehow, I envision this process to be a web handler that applies adhesive to one side of a heavy paper, and then a shaker to apply the grit.

Avery-Dennison has a number of types of equipment they use for web handling. Search them on-line, along with 'web handling" and "paper line".