Twin-Spindle Lathe Cut-Off Detection via Speed Fluctuation
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Solution Overview
Problem
Conventional methods for determining whether a workpiece is normally cut-off in a lathe take longer due to the need to reduce spindle rotation speed before detection and change speeds between spindles, prolonging the cycle time of workpiece machining.
Innovation Solution
A lathe that synchronously operates first and second spindles and adds a rotation speed fluctuation to the first spindle, allowing immediate determination of cut-off success by checking if the resulting fluctuation in the second spindle's rotation speed falls within a predetermined range.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a workpiece detecting pin is advanced to check cut-off status, then cut-off determination can be made, but the spindle rotation speed must be reduced first which prolongs the determining time and cycle time
Solution Approach 1:
The patent replaces the mechanical detection system (detecting pin physically contacting the workpiece) with a sensor-based detection system that monitors rotation speed fluctuations. This substitution eliminates the need to reduce spindle rotation speed for detection, as the sensor can detect cut-off status through vibration signals during normal high-speed rotation, thereby resolving the contradiction between detection accuracy and cycle time
Solution Approach 2:
The patent introduces rotation speed fluctuation as an intermediary parameter to indicate cut-off status. Instead of directly detecting whether the workpiece is separated, the system detects changes in rotation speed caused by the cut-off process. This intermediary approach allows detection during normal rotation without requiring speed reduction, solving the time loss problem while maintaining determination capability
2Measurement precision
If phase difference control is used to detect cut-off status, then determination can be made, but the spindle rotation speed must be changed between spindles which prolongs the determining time
Solution Approach 1:
The patent extracts the essential detection information (rotation speed fluctuation) from the complex phase difference control system. By focusing only on monitoring rotation speed changes rather than managing synchronized phase differences between spindles, the system simplifies the detection process and eliminates the time-consuming speed changes required by phase difference methods, resolving the contradiction between accurate detection and quick determination
3Measurement precision
If the detecting pin method is used, then cut-off status can be determined, but additional detection apparatus is required which increases device complexity and cost
Solution Approach 1:
The patent makes the rotation speed sensor serve multiple functions: it not only controls the spindle rotation but also detects the cut-off status by monitoring rotation speed fluctuations. This multi-functionality eliminates the need for separate detecting pins or additional detection apparatus, reducing device complexity and cost while maintaining accurate cut-off determination capability
Data Source
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AI summary
A lathe capable of shortening a cycle time of workpiece machining. A lathe 1 includes a first spindle (12) rotatable on a spindle axis AX1 and holding a workpiece W0, a second spindle (22) opposite the first spindle (12) to be rotatable on the spindle axis AX1 and holding the workpiece W0, a tool post 31 on which a cut-off tool T1 is provided for use to cut-off the workpiece W0 held by the first and the second spindles (12, 22), and a control unit U1 which controls rotation of the first and the second spindles (12, 22) and further controls relative movement of the first and the second spindles (12, 22) and the tool post 31 to cut-off the workpiece W0. The control unit U1 adds a rotation speed fluctuation to a rotation speed of the first spindle (12) after rotating the first spindle (12) and the second spindle (22) synchronously and detects a rotation speed of the second spindle (22). The control unit U1 determines that the workpiece W0 is normally cut-off upon determining that a detected fluctuation (ΔV2) in the rotation speed of the second spindle (22) is within a predetermined range.