Static-Bar Turning Sleeve With Ball-Screw Tool Positioning
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Solution Overview
Problem
Fixed-bar lathes face challenges with tool rigidity, precision, vibration, maintenance, and lubrication issues due to cantilevered arrangements, which affect machining precision and efficiency, and require frequent maintenance.
Innovation Solution
A turning device with a static bar design featuring a motor, driving shaft, sleeve, and secondary shaft coupled with a recirculating-ball screw and lead screw assembly, allowing precise tool movement without cantilevered arrangements, minimizing mass and vibration, and eliminating the need for lubrication of moving parts.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If the supporting arms of the tools are generously dimensioned, then the overall rigidity and machining precision are improved, but the rotating masses increase considerably, causing dimensioning and balancing problems
Solution Approach 1:
The patent inverts the traditional lathe architecture by making the bar stationary and the tool assembly rotatable. This inversion transfers the rotation from heavy tool supporting arms to a lighter tool holder assembly, reducing the rotating masses that need to be balanced while maintaining machining precision through the rigid stationary bar support.
Solution Approach 2:
The patent segments the system into a stationary bar portion clamped in the spindle and a separate rotatable tool assembly. This segmentation allows the heavy bar to remain stationary while only the lighter tool holder and tool need to rotate, significantly reducing the rotating mass that requires balancing.
2Weight of moving object
If more slender supporting arms are used, then inertia and vibrations are reduced, but deformations during turning operations increase, reducing precision
Solution Approach 1:
By inverting the system so the tool assembly rotates around a stationary bar, the patent eliminates the need for long slender supporting arms that would otherwise need to extend from the tool post to reach the bar. The rotation occurs at a fixed radius around the bar axis, allowing for shorter, stiffer support structures that resist deformation.
3Adaptability or versatility
If the tool movement is executed during rotation of the entire assembly, then continuous position changes are possible, but the movement becomes extremely complicated and precision is not ensured
Solution Approach 1:
The patent simplifies tool movement by making the tool assembly rotatable on its own axis rather than requiring the entire lathe assembly to rotate. The tool can be positioned radially and axially relative to the stationary bar, and then the entire tool assembly rotates to perform circumferential machining, providing continuous position changes with simpler mechanics.
4Productivity
If fixed-bar lathe architecture is used, then efficiency for specific machining kinds is improved, but continual and frequent maintenance with lubrication is required, causing machine stops and costs
Solution Approach 1:
The patent replaces traditional mechanical sliding contacts that require lubrication with rolling element bearings in the recirculating ball screw mechanism. This substitution reduces friction and wear, eliminating the need for frequent lubrication maintenance while maintaining the efficiency benefits of the fixed-bar architecture for specific machining operations.
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
The solution provides high precision, easy balancing, reduced maintenance needs, and efficient tool movement during operations, while maintaining low costs and safety, without requiring frequent lubrication.
Implementation Method 1
a secondary shaft (7) interposed between said driving shaft (3) of said motor (2) and said sleeve (4) and coupled to the screw (8) of a first assembly (9) which is constituted by a first recirculating-ball screw (8) and a respective first lead screw (10)
Data Source
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AI summary
A turning device (1) with static bar (A) of the type comprising a motor (2), a driving shaft (3) and a sleeve (4), which defines a seat (5) for temporarily accommodating at least one portion of the bar (A) being machined; a machining tool (6) is coupled directly or indirectly on the sleeve (4). A secondary shaft (7) is interposed between the driving shaft (3) and the sleeve (4) and is coupled to the screw (8) of a first assembly (9) which is constituted by a first recirculating-ball screw (8) and a respective first lead screw (10); the lead screw (10) is integral with the sleeve (4). The sleeve (4) and the first assembly (9) are coaxial and the axis of the driving shaft (3) is parallel to and separate from the common axis of the sleeve (4) and of the first assembly (9). The device (1) comprises an adjustment element (11), which is coupled to a pusher shaft (13) which is associated with the secondary shaft (7). The pusher shaft (13), through the secondary shaft (7), makes the screw (8) translate and the lead screw (10) of the assembly (9) rotate, with consequent rotation of the sleeve (4) and a movement in a radial direction of the tool (6).