PLC screen changer controls

Screen Feed Controls for Melt Filtration

Sophisticated PLC touch screen controls, with descriptive graphics deliver maximum flexibility to adapt to varying processing conditions. Both operational parameters and hardware conditions are continuously monitored, with discrete alarms that can be fully integrated with the operation of the line. The controls algorithm detects real time processing conditions and automatically adjusts the operational parameters for optimal screen advancement, thereby maintaining the highest possible level of continuous production.

screen changer closed loop controls

Pressure Override™ Controls

The Pressure Override™ controls algorithm uses our proprietary Screen Guide & Resolver Assembly™ to monitor screen movement and ensure a consistent rate of advancement. The rate (inches or mm per hour) of screen travel is programmable and is automatically maintained by means of a feedback loop – the Resolver Assembly™.

The Pressure Override™ (or Differential Pressure ΔP) feature maintains uniform processing pressure by continuously monitoring the pressure before the screen (or the differential pressure (ΔP) across the screen) and automatically increasing the rate of screen advancement to maintain uniform processing pressure. The distance of screen advancement is programmable to achieve a precise rate of movement, allowing for fine-tuning to the specific process parameters of a given application.

The screen changer’s controls provide a comprehensive system to monitor the machine’s operational status and provide continuous feedback on operating parameters. Complete automation of the filtration function means the screen changer becomes a fully integrated element in the extrusion process. The screen changer’s functions are completely automated allowing for months of non-stop operation, with no process disruptions

Features of the AB 1400 processor with 9” color touch screen:

  •  The program allows for automatic setting and calibration of the major parameters – screen travel, timers, pressure, temperature, operational limits – based on the polymer melt temperature and available coolant temperature & flow rate via the touch screen selection.
  • All operational parameters – cycle steps, screen travel increments, temperatures of each section of the machine, pressure or differential pressure across the screen, coolant flow rate – are monitored and permanently displayed on the HMI screen.
  • All steps of the operational program – heating, cooling, screen advancement – are shown in real time with descriptive graphics.
  • The program stores and displays trends of the machine’s critical parameters (temperature, pressure, cooling flow, amperage) collected for the preceding 48 hours of operation, as well as any alarm conditions.
  • UL construction; fail safe wiring, alarms and E-stop for integration with OEM controls.
  • All associated instrumentation – thermocouples, pressure transducers, flow meter, etc. – are field connected via multi-pin plugs and supplied cables.
  • The logic of the program is multilayer password protected to prevent an accidental or unauthorized change of operational parameters.
  • Safety features prevent the possibility of operating the screen changer in an incorrect or unsafe mode.
  • Easy to trouble shoot: multiple protective alarms immediately alert to a system malfunction and facilitate trouble shooting by pinpointing the source of any failure (e.g. loss of heating or cooling)
screen changer time based controls

Time Cycle™ Based Controls — Unitonics Microprocessor Controls with Touch Screen

The controls logic generates an operating cycle that allows the screen to advance on TIME BASED cycles. The rate of screen movement (inches or cm per hour) is established to suit the process at a rate that maintains uniform head pressure and melt temperature over months of non-stop operation, without operator attention.

  • The program allows for automatic setting and calibration of the major parameters – screen travel, timers, temperature, operational limits – based on the polymer melt temperature and available coolant temperature & flow rate via touch screen selection.
  • All operational parameters: cycle intervals, screen advancement increments, temperatures of each section of the machine, coolant flow rate are monitored and permanently displayed on the HMI screen.
  • All steps of the operational program: heating, cooling, screen advancement are shown in real time with descriptive graphics.
  • The program stores and displays trends of the machine’s critical parameters (temperature, cooling flow, amperage) collected for the preceding 48 hours of operation, as well as any alarm conditions.
  • UL construction; fail safe wiring, alarms and E-stop for integration with OEM controls.
  • All associated instrumentation – thermocouples, flow meter, etc. – are field connected via multi-pin plugs and supplied cables.
  • The logic of the program is password protected to prevent an accidental or unauthorized change of operational parameters.
  • Safety features prevent the possibility of operating the screen changer in an incorrect or unsafe mode.
  • Easy to trouble shoot: multiple protective alarms immediately alert to a system malfunction and facilitate trouble shooting by pinpointing the source of any failure (e.g. loss of heating or cooling)