The primary goal of the controls package is ultimately determined by the process and what level of integration is required.
For example, a standalone central granulator that is used intermittently may only require manual controls whereas an integrated beside the press or under the press system may need I/O capabilities for system regulation. If a conveyor belt is feeding a granulator, as the granulator approaches maximum capacity, this feedback may need to be relayed to pause the conveyor feed.
One initiative in the plastics industry is coined “Industry 4.0”, as in the fourth industrial revolution driving the integration of systems, processes and operators. This parallels what is currently being done in other industries such as water/waste-water reclamation with SCADA systems.
The Germany based IKV – Institute for Plastics Processing – describes it this way: “The key factors are horizontal integration to interlink not only different process steps, but also different companies along the entire value chain, and vertical integration to connect individual part-systems of the production cells to form a single, holistically controllable production system.”
The result for OEM equipment manufacturers is offering solutions on size reduction equipment that cater to both basic controls packages as well as smart system provisions.
Cumberland’s latest smart control used on the T50 model granulator illustrates the growing capabilities of this technology. The HMI (human-machine interface) allows interface with the PLC, allowing adjustments of settings and ability to view status of the PLC. The graphic display provides a realtime visual representation of the entire grinder system.
The HMI displays component trending such as granulator motor load current and bearing temperatures. This can be used to extend the life of the unit and minimize downtime. For example, when the knifes are dull, the motor load current will increase to give you an indication that knives are due to be serviced. If the bearing temperature increases to above normal values, it can create an alarm to notify the operator to check for grease or bearing failure and avoid a more serious problem and ultimately enhancing safety. If a service event happens unexpectedly, historical trends allow you to look back in time at different parameters to help diagnose or troubleshoot the problem.
Thermoforming Granulator Control Loop
A closed loop system can have many configurations, but the logic of any closed loop is really the same.
In the case of thermoforming, a controller has an input for line speed and measurement devices at the feed roll and process line. By comparing the values it calculates an error and regulates the speed of the feed rolls to the speed of the process line. It’s the same logic your car uses on cruise control.
This thermoforming granulator is shown with a dancer bar option which is used to regulate the speed of the feed rolls.
With a mechanical device such as the dancer bar, the tension in the sheet causes the bar to index and temporarily pause the feed rolls to avoid pulling material too fast.
For more info on PID loops, here is a good read: https://blog.opticontrols.com/archives/344