Sheet Conveyance Speed Control for Accurate Cutting
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Solution Overview
Problem
Existing methods for manufacturing wearing articles, such as diapers, fail to accurately position components like absorbent bodies and tapes due to misregistration caused by stretching and contraction of continuous sheets, leading to inconsistent cutting positions and product quality issues.
Innovation Solution
A method and apparatus that control the conveyance speed of sheets by using markers and a rotary blade to establish a given positional relationship between markers and cutting positions, adjusting the rotation speed of a driving roller based on detected angular differences to ensure accurate cutting and component placement.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If continuous sheets are conveyed and cut at intervals, then productivity is improved, but misregistration between cutting positions and markers occurs due to stretching and contraction
Solution Approach 1:
The system performs preliminary detection of markers on the continuous sheet before cutting occurs. By detecting the position of markers upstream and calculating the required conveyance speed in advance, the system prepares the correct speed adjustment before the cutting action takes place, ensuring accurate positioning despite sheet stretching or contraction
Solution Approach 2:
The system implements a feedback control mechanism where the actual position of markers is detected, compared against target positions, and the conveyance speed is adjusted based on the detected angular difference. This closed-loop feedback ensures that cutting positions remain accurately registered with markers even when sheet dimensions vary during conveyance
2Manufacturing precision
If sheet conveyance speed is adjusted to compensate for stretching and contraction, then manufacturing precision is improved, but device complexity increases due to speed control mechanisms
Solution Approach 1:
The system replaces complex mechanical speed control mechanisms with a computational approach. Instead of using variable speed drives or mechanical feedback linkages, the invention uses a control unit that calculates the required conveyance speed based on detected marker positions and angular differences, then controls the driving roller through software-based speed adjustment
Solution Approach 2:
The system changes the operational parameters of the conveyance system dynamically. By continuously adjusting the rotation speed of the driving roller based on detected marker positions and calculated angular differences, the system adapts to sheet stretching and contraction without requiring complex mechanical adjustment mechanisms
3Manufacturing precision
If markers are used to detect position, then manufacturing precision is improved, but device complexity increases due to detection systems
Solution Approach 1:
The detection system serves multiple functions: it detects marker positions, calculates conveyance distances, determines angular differences, and provides feedback for speed control. By making the detection system multi-functional, the invention reduces the need for separate detection and control mechanisms, thereby reducing overall device complexity while maintaining high manufacturing precision
Data Source
AI summary
A method for controlling a conveyance speed of a sheet comprises the steps of: setting a reference rotation angle; rotationally driving a drive motor (8) and a rotary cutter (15); detecting a marker (2a) of a backsheet (2); detecting a rotation angle of a rotary blade of a cutting member when the marker (2a) is detected; ascertaining an angular difference between the detected rotation angle and the reference rotation angle; and controlling rotational driving of the drive motor (8) to reduce the angular difference.