Automatic PID Mode for Filament Extrusionline

Hello, my Name is Dennis and I have a Startup for Filament production. Most important thing for the filament is the accurate diameter + roundness. This depends / realize on the speed of the extruder and the speed of the tractor. ( and laser measurement ) The machine runs with installed Delta PLC, programmed on Simatic WinCC flexible. Right now i have the opportunityto run the machine in manual mode ( set seperate extruder and tractor speed ) or automatic mode. In the Touchpanel i can change PID values of the system to get a good diameter but its not the best way. Although i can turn on an "automatic mode" ( which only regulates the tractor speed ) i often dont get good results of diameter. So often even the automatic mode is not able to get the filament to a good diameter i have to test / change the PID values and hope its getting better. I will produce many different materials ( plastic ) for the filaments ( different viscosity ) and because of that i will need a really good working automatic mode where extruder and tractor will match perfect with each other. For me its most important that i dont have to experiment / test to the PID settings every once i will produce a new material to get a good quality. The machine has to do this PID changes full automatically! Hoping for someone who can help me to create a good program for my requirements. Greetings Dennis