- Motorized valve assembly for extrusion coating automatically regulates back pressure
- System uses closed-loop control to maintain back pressure within a desired range for coating and laminating
- Valve assembly with human / machine interface
A new patent-pending motorized back pressure valve assembly for extrusion coating and laminating is the first such system to provide closed-loop control, minimizing human error and the possibility of injury when making manual adjustments, it was announced today by Nordson Corporation.
Patent-pending motorized valve assembly uses closed-loop control
Although extrusion coating operates at higher melt temperatures than other extrusion processes and requires use of a back pressure valve to reach these temperatures, excess back pressure can lead to polymer degradation. Installed between the extruder and the die, the new patent-pending EDI PolyStream motorized valve assembly uses closed-loop control to maintain back pressure within a range targeted to ensure optimal processing. The drive for the valve responds to a controller that receives a continuous flow of signals from a pressure transducer, causing the valve to open at varying degrees in accordance with whether back pressure is trending too high or too low. When the valve reaches its limit of opening as a result of excessive contaminant buildup on the filtration screen, an automated warning indicates that it is time to change the screen.
Valve assembly with human / machine interface
The PolyStream assembly includes a motor, breaker plate screen pack, linear valve, melt pipe, control system, and optional display panel. A human / machine interface (HMI) enables the operator to specify process conditions or to use specifications from a recipe. The valve assembly can be run manually, although Nordson recommends automated closed-loop operation.