Press Brake Optical Monitoring for Shadow-Induced False Detection
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Solution Overview
Problem
The existing optical safety devices for press brakes often incorrectly detect foreign bodies due to shadow enlargement caused by temperature gradients, leading to reduced working efficiency and productivity, especially when a long upper die is used with a long optical path length.
Innovation Solution
An optical safety device with a projector and photodetector system that includes an invalidation unit to prevent false detection by determining if the shadow of the upper die extends to the photodetectors, using a determination unit to assess the shadow's enlargement and invalidating the light receiving elements when necessary, thereby preventing erroneous foreign body detection.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Area of stationary object
If the optical path length of the monitoring light is increased to monitor a long upper die, then the monitoring coverage is improved, but the shadow of the upper die is enlarged due to temperature gradient, causing false detection
Solution Approach 1:
The photodetector array is divided into multiple independent detection regions, each corresponding to a specific spatial position. By segmenting the detection area, the system can identify which specific photodetectors are affected by shadow enlargement and exclude only those from foreign body detection, rather than invalidating the entire detection system.
Solution Approach 2:
Different regions of the photodetector array are treated differently based on their light receiving characteristics. The invalidation determination unit selectively invalidates only the photodetectors whose shadows extend to them, while maintaining the validity of other photodetectors. This local differentiation allows the system to maintain high detection accuracy in unaffected regions while compensating for shadow effects in affected regions.
2Adaptability or versatility
If the upper die length is increased to handle larger workpieces, then the processing capability is improved, but the shadow enlargement effect increases, leading to more frequent false detections
Solution Approach 1:
The system continuously monitors the light receiving state of each photodetector and uses the invalidation determination unit to analyze whether shadow extension is occurring. Based on this feedback analysis, the system dynamically adjusts which photodetectors are valid for foreign body detection, allowing continuous operation without false stops and maintaining high productivity.
Solution Approach 2:
The system changes the operational state parameter of photodetectors from valid to invalid based on shadow analysis. By dynamically adjusting the validity parameter of individual photodetectors rather than the entire system, the press brake can maintain continuous operation with long upper dies without experiencing productivity loss from false foreign body detections.
3Reliability
If the optical safety device is equipped to ensure bending work safety, then the safety is improved, but false detection due to shadow enlargement causes frequent stopping, reducing working efficiency
Solution Approach 1:
Before foreign body detection is performed, the invalidation determination unit preliminarily determines which photodetectors should be excluded from detection due to shadow extension. By performing this preliminary invalidation based on shadow analysis, the system ensures that subsequent foreign body detection is not interfered with by shadow effects, maintaining both safety and productivity.
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 solution effectively prevents the upper table from being stopped due to shadow enlargement, enhancing the working efficiency and productivity of the press brake while maintaining safety by accurately distinguishing between shadow enlargement and actual foreign body presence.
Implementation Method 1
when a monitoring light B passes through the air layer having a temperature gradient, the monitoring light B is bent toward the cold air region CA due to the difference in a refractive index of the air
Implementation Method 2
a layer of air with a temperature gradient is generated
Data Source
AI summary
A determination part determines whether or not a shadow of an upper mold is expanded to a photodiode by laser beam projected to a light receiver side based on a light receiving state of a photodiode positioned in a vicinity of the upper mold. When it is determined that the shadow of the upper mold is expanded to the photodiode positioned in the nearest vicinity of the upper mold, the invalidation unit invalidates the photodiode. A detection unit detects a presence or absence of a foreign body between the upper mold and a lower mold based on light receiving states of the effective plurality of photodiodes during a lowering operation of an upper table.