Flat Film Nozzle Gap Control for Cross-Web Thickness Deviations
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Solution Overview
Problem
Existing methods for controlling the thickness profile of film webs in flat film machines fail to consider lateral effects, leading to quality issues such as piston rings and uneven thickness distribution, which are not efficiently addressed in current manual or automatic adjustments.
Innovation Solution
A method that continuously monitors the thickness profile across the transverse direction, identifies local deviations, and implements control interventions at locations separate from the deviation site, considering cross-relationships to adjust the nozzle gap and redistribute extrusion material to correct profile deviations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If adjusting devices are positioned only at the deviation section to correct thickness profile, then the local correction is achieved, but lateral effects are not considered leading to control oscillations and insufficient correction
Solution Approach 1:
The control system divides the film web transverse direction into multiple sections (deviation section and intervention section) and applies different control strategies to each. The deviation section identifies where thickness correction is needed, while the intervention section applies the actual control adjustments, allowing targeted correction without over-complicating the entire control system.
Solution Approach 2:
The control system performs preliminary identification of deviation sections through continuous monitoring, then proactively applies control interventions in adjacent intervention sections before the deviation fully develops into quality defects like piston rings. This anticipatory approach improves precision without requiring complex real-time adjustment at every point.
2Reliability
If continuous monitoring of the entire thickness profile is implemented, then quality issues are detected earlier, but measurement and control complexity increases
Solution Approach 1:
The system extracts and focuses measurement efforts on critical sections of the film web where piston rings and thickness deviations are most likely to occur. By identifying and monitoring specific deviation sections rather than uniformly monitoring the entire width, the system achieves high reliability without the full complexity of comprehensive continuous measurement.
Solution Approach 2:
The control system implements continuous feedback monitoring of the thickness profile, comparing measured values against target profiles to automatically identify deviation sections. This feedback mechanism ensures consistent film quality by continuously detecting and responding to thickness variations without requiring manual intervention or overly complex measurement systems.
3Manufacturing precision
If adjusting devices are placed at every section for precise control, then local thickness control is improved, but the system becomes more complex and costly
Solution Approach 1:
The control system applies adjusting devices only in specific intervention sections adjacent to identified deviation sections, rather than distributing adjusting devices uniformly across the entire film web. This localized approach maintains precise control where needed while reducing overall system complexity and cost in areas where adjustments are not required.
Solution Approach 2:
The intervention section acts as an intermediary zone between the deviation section (where thickness problems occur) and the normal operating sections. Control adjustments applied in the intervention section indirectly correct thickness deviations in the adjacent deviation section, eliminating the need for direct adjusting devices at every location while maintaining effective local control.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach effectively reduces unwanted thickness variations, prevents the formation of piston rings, and enhances the quality and efficiency of film production by minimizing control oscillations and ensuring smoother transitions in the thickness profile.
Implementation Method 1
Applying a defined target temperature, electrical target voltage, or heating time as a control intervention can lead to the thermal expansion of the respective adjusting bolt, so that it reduces the exit gap by mechanically acting on a nozzle lip.
Data Source
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AI summary
The invention relates to a method for controlling the thickness profile (DP) of a film web (FB) along a transverse direction (QR) by means of a plurality of setting means (120) for setting a gap opening (112) of an outlet nozzle (110) of the flat film machine (100), said method comprising the following steps: − detecting a thickness profile (DP) along the transverse direction (QR) of the film web (FB) transverse to a production direction (PR) of the flat film machine (100), − comparing at least one partial section of the detected thickness profile (DP) with a predefined profile (VP), − determining at least one local profile deviation (PA) in a deviation section (AA) as a result of the comparison, and − generating at least one control intervention for adjusting at least one setting means (120) in an intervention section (EA) that differs from the deviation section (AA).