NC Tool Path Deviation Detection for Reject Workpieces
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Solution Overview
Problem
Existing numerically controlled workpiece machining systems struggle with geometric deviations in workpieces, particularly those obtained through forming processes, leading to inaccuracies that can cause tool collisions, process interruptions, and costly manual corrections, and fail to detect defective components early in series production.
Innovation Solution
A method and device that adaptively determine an optimized target tool path by analyzing deviations between the actual and target tool paths, identifying rejects based on predefined tolerances, and updating the tool path using data from previously machined workpieces, without requiring additional CAD specifications.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a fixed target tool path is specified by the control system based on CAD data, then the machining process follows a predetermined path, but workpiece geometric deviations lead to collisions or process interruptions
Solution Approach 1:
The system performs preliminary measurement of the workpiece surface geometry before machining and uses this information to pre-calculate an adapted target tool path that anticipates geometric deviations. This preliminary action allows the machining process to follow a path that accounts for actual workpiece variations, preventing collisions and interruptions while maintaining process reliability
Solution Approach 2:
The system implements a feedback loop where the actual workpiece geometry is measured during or before machining, and this measurement information is used to dynamically adjust the target tool path. The control system continuously compares the planned path with actual surface deviations and modifies the tool path accordingly, enabling the system to adapt to geometric variations while maintaining reliable machining
2Adaptability or versatility
If the control parameters of the distance control system are kept relatively low to handle larger workpiece inaccuracies, then more workpiece variations can be processed, but the correction capability is insufficient leading to collisions or process interruptions
Solution Approach 1:
The system performs preliminary measurement and analysis of workpiece geometric deviations before machining begins. By calculating the expected deviations and pre-adapting the target tool path in advance, the system can handle larger workpiece variations without requiring high real-time correction parameters, thus maintaining both adaptability and precision
Solution Approach 2:
The system dynamically adjusts the target tool path based on measured workpiece geometry while maintaining stable distance control parameters. The adaptability comes from the flexible tool path calculation rather than from increasing distance control parameters, allowing the system to handle variations without compromising manufacturing precision
3Reliability
If manual correction of the target tool path is performed during machining to handle workpiece deviations, then the machining process can continue, but the process becomes cost-intensive and time-consuming
Solution Approach 1:
The system performs automatic measurement, analysis, and tool path adaptation without requiring manual intervention. The control system independently handles workpiece geometric deviations by automatically calculating and adjusting the target tool path based on measured data, enabling continuous machining while eliminating time-consuming manual corrections
Solution Approach 2:
The system implements automatic feedback-based tool path adaptation where measurement data from the workpiece surface is continuously fed into the control system, which automatically recalculates and adjusts the tool path. This closed-loop approach maintains reliable continuous machining while eliminating the need for manual corrections, saving time and reducing costs
4Measurement precision
If all components are inspected using current measurement methods to detect contour errors, then defective components can be identified, but the inspection process is costly
Solution Approach 1:
The system performs measurement and quality assessment during the machining process itself rather than as a separate post-processing step. By integrating measurement and evaluation into the machining workflow, the system identifies contour errors and defective components in real-time, maintaining high measurement precision while eliminating costly separate inspection processes
Solution Approach 2:
The system combines the machining process with measurement and quality evaluation functions into an integrated process. The same equipment and data streams used for machining are also used for measuring contour accuracy and identifying defects, thereby maintaining precise detection capabilities while eliminating the need for separate costly inspection operations
Data Source
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AI summary
The invention relates to a method for detecting rejects during processing of identical workpieces (14) by means of a numerically controlled workpiece processing apparatus (10), comprising the following steps: a) processing a workpiece (14) according to the specification of a target tool path (34) for a tool (12) of the workpiece processing apparatus (10) and b) closed-loop control of a working distance (22) of the tool (12) from the workpiece (14) to a defined target distance such that during processing of the workpiece (14), the tool (12) is moved along the target tool path (34) on an actual, distance-controlled tool path (36), wherein according to the invention it is examined whether the distance-controlled actual tool path (36) deviates from the target tool path (34) which applies to said workpiece (14) at selected contour sections (40), in particular contour sections which lack tracking errors, by less than a predefined tolerance value. If yes, processing of the next workpiece (14) continues or, if no, a notification is output that the processed workpiece (14) has been identified as a reject.