Numerical Controller Workpiece Mounting Error Compensation
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Solution Overview
Problem
Three-axis machine tools cannot accurately compensate for workpiece mounting errors, particularly rotation errors, due to the absence of rotary axes, leading to incorrect machining at the tool center point.
Innovation Solution
A numerical controller with a workpiece mounting error compensation unit that calculates and compensates for translational and rotational errors in the X, Y, and Z axes, ensuring the tool center point is correctly positioned by adjusting the linear-axis positions based on pre-set error values, allowing precise machining despite the absence of rotary axes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If five-axis machine tool control methods are applied to three-axis machine tools, then tool position compensation is attempted, but tool direction compensation cannot be achieved leading to incorrect machining
Solution Approach 1:
The patent applies local quality by differentiating between three-axis and five-axis machine tool compensation needs. It recognizes that three-axis machines only require position compensation (not direction compensation) and develops a specialized compensation method tailored to this specific capability, rather than forcing a universal five-axis approach.
Solution Approach 2:
The patent inverts the conventional approach by not attempting to compensate tool direction (which five-axis machines do) but instead focusing exclusively on compensating the tool center point position through coordinate system transformation. This inverted approach matches the actual capabilities of three-axis machines.
2Ease of manufacture
If conventional workpiece offset compensation is used, then simple position adjustment is achieved, but rotation errors cannot be compensated leading to machining inaccuracies
Solution Approach 1:
The patent transitions from simple translational offset compensation to a more comprehensive solution by introducing rotational error compensation through coordinate system transformation. This adds dimensional complexity to the compensation approach, enabling correction of both position and orientation errors.
Solution Approach 2:
The patent introduces an intermediate coordinate system (workpiece coordinate system) as a mediator between the machine coordinate system and the tool path. This intermediate system allows for systematic compensation of both translational and rotational errors through transformation matrices, bridging the gap between simple offset methods and complex five-axis compensation.
Data Source
AI summary
A numerical controller controls a three-axis machine tool that machines a workpiece, mounted on a table, with at least three linear axes. The numerical controller includes a workpiece mounting error compensation unit that compensates a mounting error caused when the workpiece is mounted. The workpiece mounting error compensation unit performs an error compensation with respect to an instructed linear-axis position with amounting error which is set beforehand, in order to keep a position with respect to the workpiece at a tool center point position, based on the instructed linear-axis position of the three linear axes to obtain a compensated linear-axis position. The three linear axes are driven based on the obtained compensated linear-axis position.