Tapping Machine Spindle Reversal Correction
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Solution Overview
Problem
Existing tapping machines face synchronization errors between the spindle and feed axis, especially when the gain of the feed axis cannot be set high, leading to delayed response and increased errors during reverse spindle rotation.
Innovation Solution
A tapping machine with a spindle reversal detector and reverse correction amount production unit that adds a correction to the speed control loop of the feed axis motor to improve synchronization during reverse spindle operation, using a rotational angle detector and position detector to produce move instruction values and synchronize the spindle and feed axis motors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If the gain of the feed axis is set to be very large, then the response of the feed axis becomes fast, but the system becomes unstable or difficult to control
Solution Approach 1:
The patent applies preliminary action by detecting the reversal operation of the spindle in advance and proactively adding a reverse correction amount to the feed axis control before synchronization error occurs. The reversal detector detects when the spindle reverses rotation, and the control unit pre-adjusts the feed axis instruction value based on the screw pitch and detected reversal, allowing the feed axis to anticipate and prepare for the direction change rather than reacting with delay.
2Manufacturing precision
If the gain of the feed axis is set to be large, then the synchronization precision is improved, but the system complexity increases
Solution Approach 1:
The patent introduces an intermediary element - the reverse correction amount - that mediates between the spindle reversal detection and the feed axis control. Instead of directly increasing the feed axis gain, the system uses this intermediate correction value (calculated based on screw pitch and reversal detection) to adjust the feed axis instruction, thereby improving synchronization without requiring high gain settings or complex control structures.
3Reliability
If the feed axis follows the spindle with normal gain, then the system is stable, but synchronization error increases during reverse operation
Solution Approach 1:
The patent applies local quality by making the feed axis control gain variable rather than constant. During normal operation, the system uses standard gain settings for stability. However, when the reversal detector detects spindle reversal, the system locally adjusts the feed axis control by adding a reverse correction amount specifically at that moment and location in the control process, improving synchronization accuracy during the critical reversal phase without affecting overall system stability.
Data Source
AI summary
A tapping machine (1) executes a tapping operation by operating a spindle motor (21) and a feed axis motor (31) in synchronization, and includes a spindle reversal detector unit (34) for detecting the reversed operation of the spindle during the tapping operation, and a reverse correction amount production unit (35) for producing a reverse correction amount for improving follow-up performance of reversed operation of the feed axis at the time when the reversed operation of the spindle is detected by the spindle reversal detector unit (34). When the reversed operation is detected by the spindle reversal detector unit, the reverse correction amount produced by the reverse correction amount production unit (35) is added to the speed instruction on a speed control loop of the feed axis control unit (30) or to an integrator (41) of the speed control loop.