Corrugator Pull Roll Torque Control for Cut Length Accuracy

Resolve Bottlenecks,
Find Innovative SolutionsGenerate Solutions

Solution Overview

Problem

The existing corrugator dry end systems face challenges in maintaining accurate cut sheet lengths due to web tension changes, leading to inconsistencies in sheet length caused by varying forces applied during the cutting cycle.

Innovation Solution

A method is implemented to control cut sheet lengths by maintaining a high force level through the pull roll nip and adjusting it to a lower level when the leading edge reaches the outfeed nip, while operating the cutoff knife and simultaneously increasing the force level to ensure uniform tension throughout the cutting cycle, using torque control for the infeed pull roll and a web length measuring device to signal the cut completion.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If the first force through the pull roll nip is maintained at a constant high level throughout the cutting cycle, then the output web is pulled consistently into the cutoff knife, but web tension spikes occur when the leading edge reaches the outfeed nip, causing cut sheet length variations

Engineering Contradiction:

Improvecut sheet length consistencyVSAvoidweb tension variation

Core Design Contradiction:

ReliabilityVSForce

Solution Approach 1:

The first force through the pull roll nip is dynamically adjusted rather than maintained at a constant level. The control system reduces the first force when the leading edge of the output web reaches the outfeed nip and increases it when the sheet is being cut, creating a dynamic force profile that compensates for tension spikes and maintains consistent sheet length

Inventive Principle:

Principle #15Dynamics

Solution Approach 2:

A web length measuring device (such as a resolver) provides feedback about the position of the leading edge and the state of the cutting cycle. This feedback is used by the control system to automatically adjust the first force in real-time, ensuring that force adjustments are precisely synchronized with the cutting cycle events

Inventive Principle:

Principle #23Feedback

2Force

If the first force is reduced when the leading edge reaches the outfeed nip, then web tension spikes are minimized, but the output web may not be pulled sufficiently into the cutoff knife

Engineering Contradiction:

Improveweb tension uniformityVSAvoidweb feed speed into knife

Core Design Contradiction:

ForceVSSpeed

Solution Approach 1:

The first force is applied in periodic cycles that correspond to the cutting cycle. The force is increased during the cutting phase to ensure adequate web feed into the knife, then reduced when the leading edge approaches the outfeed nip to minimize tension spikes, creating a periodic force pattern that balances both requirements

Inventive Principle:

Principle #19Periodic action

Solution Approach 2:

The pull roll drive operates in torque limit mode at a slight overspeed limited by torque, allowing the system to respond dynamically to changing tension conditions. The drive automatically adjusts the first force based on the cutting cycle phase, maintaining adequate web feed during cutting while preventing excessive tension when the leading edge reaches the outfeed nip

Inventive Principle:

Principle #15Dynamics

Data Source

PatentUS9731927B2Cut sheet length control in a corrugator dry end

Publication Date: 2017.08.15 BARRY WEHMILLER PAPERSYST INC

AI summary

Tension spikes in a running web slit to direct output webs to respective upper and lower cutoff knives are minimized by anticipating the increased tension in the web when the lead edge enters an outfeed nip and offsetting the tension spike with a decrease in the force imposed by the infeed pull roll nip, whereby the sum of the web tensions is substantially uniform through the cutting cycle and the sheets are cut to a consistent length.