Machine Tool Control Device for Curved Surface Machining Accuracy
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Solution Overview
Problem
Conventional machine tools face challenges in accurately controlling the feed rate during machining, particularly when machining curved surfaces, leading to potential inaccuracies and elongated machining times, as the feed rate of the moving axis may not match the speed of the tool relative to the workpiece, affecting the precision of the machining surface.
Innovation Solution
A control device for machine tools that estimates the fastest moving point along the tool path and sets the feed rate for the moving axis to ensure the relative speed remains at or below a specified speed, optimizing the machining process by adjusting the feed rate based on the time it takes to move between specific relative positions, including rotational movements.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If the feed rate is lowered to improve machining accuracy, then the machining accuracy of the machining surface is improved, but the machining time is elongated
Solution Approach 1:
The patent dynamically changes the feed rate parameter based on the actual relative speed between the tool and workpiece during machining operations involving rotational movements. By calculating the fastest moving point and adjusting the feed rate accordingly, the system maintains optimal machining accuracy while avoiding unnecessary time elongation that would occur with uniformly low feed rates.
2Ease of operation
If the feed rate of the moving axis is used directly, then the control is simple, but the relative speed of the tool to the workpiece does not match the desired speed, affecting machining accuracy
Solution Approach 1:
The patent implements a feedback mechanism where the actual relative speed between tool and workpiece is calculated based on the tool path and workpiece information, and this calculated speed is used to adjust the feed rate command. The system continuously monitors and adjusts the feed rate to ensure the relative speed matches the desired speed, resolving the discrepancy between simple control and machining accuracy.
Solution Approach 2:
The patent performs preliminary calculation of the fastest moving point along the tool path before machining begins. By pre-determining the maximum relative speed that will occur during machining, the system can set an appropriate feed rate in advance that ensures the relative speed never exceeds the desired threshold, maintaining machining accuracy without requiring complex real-time adjustments.
3Device complexity
If linear interpolation is performed without considering angle change, then the control calculation is simplified, but a position deviation occurs on the tip end of the tool due to rotational movement
Solution Approach 1:
The patent calculates the position deviation that will occur due to rotational movement during linear interpolation and adds this deviation to the distribution moving amount in advance. By performing this compensation calculation before the machining operation, the system maintains simple control calculations while ensuring position accuracy on the tool tip end is preserved despite rotational movements.
Data Source
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AI summary
The machine tool control device is provided with a calculation unit for estimating, on the basis of the tool path for machining using a tool and information on the workpiece, the portion of the tool that will form the final machined surface. The control device is provided with a feed rate-setting unit for estimating the fastest moving point, among multiple moving points contained in the portion that will form the final machined surface, for which the relative velocity of the tool with respect to the workpiece will be maximal and setting the feed rates for the machine tool movement shafts so that the relative velocity of the fastest moving point is at or below a previously specified relative velocity.