Double Column Machine Tool Ball Screw Mounting for Beam Deformation
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Solution Overview
Problem
Machine tools with double column frames prone to downward flexing due to gravity, leading to unstable and inaccurate movement of movable units, especially when the upper guide rail deforms, affecting high-speed horizontal movement and workpiece machining accuracy.
Innovation Solution
A machine tool design featuring a double column frame with vertically mounted columns and a horizontally extending beam, supported by upper and lower ball screws mounted on both sides, allowing for stable and smooth horizontal movement of the movable unit with a tool rest, even when the beam deforms, and maintaining accuracy across the horizontal stroke.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the double column frame is made with a horizontally elongate steel beam, then the machine tool can handle larger workpieces and increase productivity, but the beam flexes downwardly by gravity causing guide rail deformation and reducing machining accuracy
Solution Approach 1:
The ball screw system is segmented into upper and lower separate ball screws, with the upper ball screw mounted on the movable unit and the lower ball screw mounted on the bed. This segmentation allows independent force application paths that prevent force transfer through the beam, eliminating the coupling between beam deformation and movable unit positioning.
Solution Approach 2:
The force transfer path from the beam to the movable unit is extracted and eliminated. The upper ball screw is mounted on the movable unit itself rather than on the beam, so that actuation forces are applied directly to the movable unit without being transferred through the beam structure, preventing gravity-induced beam flexing from affecting positioning accuracy.
2Device complexity
If forces are applied only to the lower portion of the movable unit by a single ball screw, then the structure is simpler, but the movable unit cannot move stably and smoothly at high speed
Solution Approach 1:
The single ball screw system is divided into two separate ball screws: an upper ball screw and a lower ball screw. The upper ball screw is mounted on the movable unit while the lower ball screw is mounted on the bed. This segmentation distributes the actuation forces to both upper and lower portions of the movable unit, improving balance and reducing vibrations during high-speed movement.
Solution Approach 2:
The force application is extended from a single lower point to two dimensions (upper and lower portions) of the movable unit. By mounting ball screws at both upper and lower locations, the system achieves better force distribution and balance, enabling stable and smooth high-speed horizontal movement.
3Device complexity
If the upper ball screw is mounted on the beam, then the structure is compact, but forces are transferred between the beam and movable unit causing positioning errors when the beam deforms
Solution Approach 1:
The upper ball screw is extracted from the beam mounting arrangement and relocated to be mounted directly on the movable unit. This removes the force transfer path through the beam, so that actuation forces are applied directly to the movable unit without being influenced by beam deformation, eliminating positioning errors.
Solution Approach 2:
The movable unit itself serves as the mounting intermediary for the upper ball screw, replacing the beam as the mounting surface. This intermediary relationship ensures that forces are transmitted directly to the movable unit without passing through the beam, preventing deformation-induced positioning errors.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
Enables stable and high-speed horizontal movement of the movable unit with accurate machining of workpieces, regardless of beam deformation, and ensures balanced support for the second main spindle in the transverse direction of the double column frame.
Implementation Method 1
an upper ball screw and a lower ball screw for moving the movable unit horizontally, the upper ball screw and the lower ball screw being mounted respectively on upper and lower portions of the double column frame
Implementation Method 2
The movable unit is supported and guided by the upper and lower guide rails for horizontal movement from side to side along the double column frame
Implementation Method 3
the beam extending horizontally along a Z-axis between upper portions of the columns... even when the beam is deformed by flexing downwardly by gravity
Implementation Method 4
the beam extending horizontally along a Z-axis between upper portions of the columns... when the beam is deformed by flexing downwardly by gravity
Data Source
AI summary
A machine tool has a pair of guide rails and a pair of upper and lower ball screws. No forces are transferred between a beam of a double column frame and a movable unit. The guide rails are spaced from each other and disposed on a bed, and the movable unit is horizontally movably supported on the guide rails. The upper and lower ball screws are mounted respectively on upper and lower portions of the double column frame for moving the movable unit horizontally. Even when the beam is deformed by flexing downwardly by gravity, the movable unit moves stably and smoothly at a high speed to machine a workpiece highly accurately without being adversely affected by the deformation of the beam.