Spindle Encoder Layout to Reduce Run-Out Detection Error
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Solution Overview
Problem
The existing arrangement of encoders near the rear end of the spindle in machine tools leads to adverse effects on detection accuracy due to spindle run-out, which affects the rotational angle detection precision.
Innovation Solution
A machine tool design where the rotational angle detector is positioned between or on the side of the bearings relative to the rotation driver, allowing for improved detection accuracy by integrating the sensor gear with the bearing spacer or lock nut, reducing the influence of spindle run-out and facilitating assembly and maintenance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If the encoder is arranged near the rear end of the spindle, then the detection position is simplified, but the detection accuracy deteriorates due to run-out affecting the encoder
Solution Approach 1:
The encoder is extracted from the rear end of the spindle and relocated to the front end, separating the detection function from the problematic run-out zone. This extraction allows the encoder to operate in a region with minimal run-out influence, thereby resolving the contradiction between detection simplicity and accuracy.
Solution Approach 2:
A gear is introduced as an intermediary element between the spindle and the encoder. The gear is rotatably coupled to the spindle and engages with the encoder, allowing the encoder to detect rotational position indirectly through the gear rather than directly from the spindle, thus eliminating run-out interference while maintaining detection functionality.
2Volume of moving object
If the encoder is arranged near the rear end of the spindle, then the structure is compact, but run-out adversely affects detection accuracy
Solution Approach 1:
The encoder detection function is shifted from the axial dimension (rear end of spindle) to a different spatial location (front end of spindle), changing the dimensional arrangement to avoid the run-out zone while maintaining system compactness. This dimensional repositioning resolves the contradiction between compact structure and detection accuracy.
3Measurement precision
If the rotational angle detector is positioned between or on the side of the bearings, then detection accuracy is improved by reducing run-out influence, but the device complexity increases
Solution Approach 1:
The gear and encoder are merged into an integrated assembly where the gear is rotatably coupled to the spindle and the encoder is positioned to engage with the gear. This merging consolidates multiple functions (spindle rotation, gear transmission, and angle detection) into a single compact unit, reducing overall device complexity while maintaining high detection accuracy.
Data Source
AI summary
There is provided a machine tool for suppressing the adverse effect of run-out of the rear end of a spindle on the rotation detection accuracy when processing a workpiece within a processing area. The machine tool includes a rotation driver, the spindle that is rotated by the rotation driver, a rotational angle detector that is provided to face a part forming the spindle in order to detect a rotational angle of the spindle, and at least two bearings that support the spindle and are arranged on a side of the processing area with respect to the rotation driver. The rotational angle detector is arranged at a position on the side of the processing area with respect to the rotation driver, the position being on the side of the processing area with respect to the bearings, on a side of the rotation driver with respect to the bearings, or between the bearings.