Paper web processing: slitter-rewinder
A relocated paper web processing machine requires previously unused edge position control sub-system redesign and deployment to production. This series covers system evaluation, control scheme prototyping, and production form factor system completion to production go-live. Design Task A paper slitter-rewinder purchased from one factory and relocated to another arrived at the new site with a …
All the drive and sensor systems are installed and in-place. An Allen-Bradley PLC contractor indicates there is resident code to enable, and there’s a ladder logic printout in a document binder that arrived with the machine. First try: tune what’s there. First Try: Enable and Test Resident PLC Logic An Allen-Bradley PLC technician with tools …
Observing incomplete code around the LVDT and poor results tuning the existing scheme, the effort transitions to a redesign. We might still employ the existing PLC, or we’ll evolve a new stand-alone controller for the edge control function. Regardless, the resident Allen-Bradley Programmable Logic Controller (PLC) is not convenient for system analysis and design candidate …
Neglecting for now the ultrasonic Edge Guide sensor we first seek a model from hydraulic servo valve amplifier voltage command input to LVDT output. This will give us a plant model for the input role lateral position rack. The Edge Guide will provide additional state feedback for our eventual controller, subject to transport lag as …
The goal is to be suitably responsive and stable in regulating the web edge to the null point of the ultrasonic sensor given the mechanics, drive system, and the sensors provided. We’re not starting with a specification on output roll side-face (0.030 inches for example) and designing a new machine. We’ll analyze the given equipment, …
The distance between the web tangent-point departure from the stock roll and the edge guide sensor is roughly 1m. The operational range of 100 feet-per-minute (fpm) to 2000 fpm converts as 0.5 m/s to 10m/s web speed range. With a 1-meter sensor distance, the lag at a low speed of 100 fpm (0.5m/s) is 2 …
During slow-speed setup or when an input roll is near empty a, “hold” switch is asserted on a tethered pendant. This puts the control system in an LVDT-only feedback mode with the reference position as the LVDT position at the time of hold-mode entry. While in hold mode, left- and right-pushbutton switches jog the reference …
The laptop-hosted National Instruments NI USB-6001 is great for system identification and candidate controller design prototyping. A production solution requires an industrial-grade controller with minimal interfaces for simple, reliable operation. Platform: Automation Direct P1AM-100 Below is a rendering of an Automation Direct P1AM-100 Arduino platform main controller with peripheral modules. This is not the module …
The controller form factor installs on a DIN rail in a cabinet. Design iteration and debugging against the live system is not practical. To simulate the entire assembly from analog and counter inputs, through C-code to command output we again use the National Instruments USB-6001 as shows here. In this configuration, the code behind the …
Production Run Here we see production operation slitting a single input roll into 4 output rolls with no edge trim! Output roll side face remains clean within ~50 thousandths, or visually acceptable based on operator experience. We’re satisfied with this as, “production complete”. Hold-Jog mode for setup and reload is not shown. Design Walk-Through (Again) …