Bifurcated Column Machine Tool Rigidity Design
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Solution Overview
Problem
Large plate mills face challenges in maintaining rigidity throughout their operational range due to the size and weight of the workpieces, leading to potential deformation and the need for varying process parameters based on tool location.
Innovation Solution
A closed force loop design with a moving bifurcated Y-axis column and X-slide configuration that maintains constant overhang of the spindle relative to the Y-axis column, supported by X and Z-axis drive motors mounted outside the workzone, enhancing the machine's rigidity and reducing distortion.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Area of stationary object
If the machine size is increased to accommodate large workpieces, then the workpiece capacity is improved, but the rigidity and resistance to deformation deteriorate
Solution Approach 1:
The machine structure is divided into modular components including a base, column, saddle, and overtravel mechanism. This segmentation allows each component to be optimized independently for rigidity while maintaining overall large workpiece capacity. The column is further bifurcated into upper and lower sections that can move independently along the Z-axis.
Solution Approach 2:
The patent introduces a moving bifurcated column that adds a fourth dimension of movement (overtravel along the Z-axis) to the traditional three-axis configuration. This dimensional addition allows the machine to accommodate larger workpieces while maintaining rigidity through the constrained movement paths of the column sections.
2Area of stationary object
If the machine envelope is increased to machine large workpieces, then the workpiece capacity is improved, but the rigidity varies throughout the working range
Solution Approach 1:
The patent employs a dynamically adjustable overtravel mechanism that allows the column to move along the Z-axis while maintaining constant rigidity characteristics. The upper and lower column sections can be positioned at different heights, and the system dynamically adjusts to maintain optimal rigidity throughout the extended working range, eliminating the need to vary process parameters based on tool location.
3Adaptability or versatility
If the spindle overhang is increased to extend the working range, then the versatility is improved, but the rigidity deteriorates
Solution Approach 1:
The movable bifurcated column provides dynamic adjustment capability where the upper and lower column sections can independently position themselves along the Z-axis. This dynamic configuration maintains a constant, optimized spindle overhang distance regardless of the tool's position in the extended workzone, thereby preserving rigidity while increasing versatility.
Data Source
AI summary
A rigid design for a machine tool having perpendicular X, Y, and Z axes includes fixed X-axis frame members at the back of the machine, fixed Z-axis vertical frame members at the front of the machine, and fixed upper and lower Z-axis frame members rigidly attached to the fixed X-axis frame members and the fixed Z-axis vertical frame members. The frame members form a fixed, rigid, closed force loop design. A movable Y-axis column is bifurcated and a headstock is mounted in the center opening of the column. The headstock is advanced and retracted relative to the workpiece by moving the Y-axis column and the headstock relative to the workpiece. Because the headstock is fixed relative to the Y-axis column, the unsupported portion of the headstock relative to the Y-axis column does not change as the Z-axis position of the headstock changes relative to the workpiece.