Worm Gear Indexing Error Detection from NC Torque Feedback
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Solution Overview
Problem
Current methods for diagnosing indexing errors in NC machine tools are labor-intensive and time-consuming, requiring manual measurement with rotary encoders, which hinders efficient and quick identification of accuracy issues.
Innovation Solution
A worm gear abnormality determination system that uses a numerical controller to rotate the spindle and monitor drive torque commands and position feedback, allowing for quick identification of indexing errors without the need for additional measuring devices, by comparing the monitoring results with pre-defined normal values and calculating abnormal index angles.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If manual measurement with rotary encoder is used to diagnose indexing errors, then measurement precision can be ensured, but labor intensity and time consumption increase significantly
Solution Approach 1:
The system enables the NC machine tool to self-diagnose indexing errors by automatically comparing the actual index angle with the theoretical index angle during automatic operation, eliminating the need for manual measurement with rotary encoders. The control unit automatically detects and identifies abnormal index angles, allowing the machine to perform its own diagnostic function without external intervention.
Solution Approach 2:
The invention replaces the mechanical measurement system (manual rotary encoder measurement) with an electronic/digital system that uses the existing encoder already present in the NC machine tool. The control unit processes electrical signals from the encoder to calculate and compare index angles, substituting mechanical measurement operations with electronic computation.
2Measurement precision
If manual measurement methods are used for indexing error diagnosis, then accurate error detection is possible, but operation complexity and labor requirements increase
Solution Approach 1:
The system enables the NC machine tool to self-diagnose indexing errors by automatically comparing the actual index angle with the theoretical index angle during automatic operation, eliminating the need for manual measurement with rotary encoders. The control unit automatically detects and identifies abnormal index angles, allowing the machine to perform its own diagnostic function without external intervention.
3Measurement precision
If additional measuring devices like rotary encoder are attached for diagnosis, then measurement capability is improved, but device complexity increases
Solution Approach 1:
The invention makes the existing encoder in the NC machine tool serve multiple functions: it not only performs its original function of position feedback for control but also simultaneously enables indexing error diagnosis. The control unit utilizes the encoder signals for both motion control and diagnostic purposes, eliminating the need for separate measuring devices.
4Loss of information
If comprehensive error measurement is performed every 1 degree for 360 degrees, then complete error distribution is obtained, but time and manpower requirements increase
Solution Approach 1:
The system enables the NC machine tool to self-diagnose indexing errors by automatically comparing the actual index angle with the theoretical index angle during automatic operation, eliminating the need for manual measurement with rotary encoders. The control unit automatically detects and identifies abnormal index angles, allowing the machine to perform its own diagnostic function without external intervention.
Solution Approach 2:
The diagnosis process occurs continuously during the automatic operation of the machine tool without interrupting the useful work. The control unit continuously monitors and compares index angles as the spindle rotates, obtaining complete error distribution information while the machine performs its primary function, thus maintaining continuous useful action.
Data Source
AI summary
A system determining whether the feed shafts are normal or abnormal, the system including: a command generation unit that moves the feed shafts in a forward direction at a predetermined speed from a lower limit value to an upper limit value of a range of feeding movement by the numerical controller; and a feed shaft abnormality determination unit that monitors a drive torque command during the movement of the feed shafts in the forward direction by the command generation unit, compares a monitoring result during the movement in the forward direction with a normal value of the drive torque command, determines that abnormality occurs when the drive torque command deviates from the normal value, and outputs the determination result.