Machine Tool Feed Axis Control for Stable Spindle Load Torque
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
In machine tools, maintaining a desired load torque on the spindle motor is challenging due to varying load torque caused by reaction forces from the workpiece, leading to potential tool breakage or processing inefficiencies.
Innovation Solution
A control apparatus that includes a load torque estimation unit to estimate the load torque based on the spindle motor's torque command and speed, and a speed control unit to adjust the feed axis motor speed to maintain a prescribed load torque target value, using a configuration that includes a position command generation unit, speed control unit, and current control unit to manage the spindle and feed axes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the feed axis speed is increased to enhance processing efficiency, then productivity is improved, but the load torque on the spindle motor increases causing tool breakage or work abnormality
Solution Approach 1:
The control apparatus uses feedback control by continuously monitoring the actual load torque on the spindle motor and adjusting the feed axis speed accordingly. The load torque estimation unit estimates the actual load torque based on spindle motor torque command and speed, and the speed control unit adjusts the feed axis speed to maintain the estimated load torque within the target range, preventing tool breakage while optimizing processing efficiency
Solution Approach 2:
The system dynamically adjusts the feed axis speed based on real-time load torque conditions rather than using a fixed speed. The speed control unit changes the feed axis speed command value in response to varying load torque, allowing the system to adapt to changing processing conditions and maintain optimal performance without exceeding tool load capacity
2Reliability
If the feed axis speed is decreased to reduce load torque on the spindle motor, then tool integrity is maintained, but processing efficiency deteriorates
Solution Approach 1:
The feedback control mechanism continuously monitors the estimated load torque and adjusts the feed axis speed to maintain it within the target range. This allows the system to operate at the maximum safe speed without exceeding tool load capacity, optimizing processing efficiency while ensuring tool integrity
Solution Approach 2:
The system changes the feed axis speed parameter dynamically based on the estimated load torque. By adjusting the speed parameter in real-time according to actual loading conditions, the system maintains optimal processing efficiency while preventing excessive load torque that could cause tool breakage
Data Source
AI summary
A control apparatus of a machine tool including a feed axis, which is driven by a feed axis motor, includes a load torque estimation unit configured to estimate a load torque acting on a spindle motor, based on a torque command to the spindle motor which drives a spindle axis of the machine tool, and a speed of the spindle motor; and a speed control unit configured to control a speed of a feed axis motor such that the load torque estimated by the load torque estimation unit follows a prescribed load torque target value.