Ball Screw Assembly Using Pre-Assembled Nut Units
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Solution Overview
Problem
Conventional ball screw device manufacturing methods require significant labor for assembly and reassembly due to manufacturing errors in screw shafts and nuts, necessitating the selection of balls with specific diameters to maintain standard axial gaps or preloads.
Innovation Solution
A method involving the preparation of nut units with pre-assembled balls and temporary shafts, allowing for the arbitrary combination of screw shafts and nut units during assembly, ensuring standard axial gaps are maintained without the need for on-site ball selection.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If ball selection is performed based on manufacturing errors to satisfy axial gap or preload standards, then assembly precision is improved, but assembly time and labor cost increase
Solution Approach 1:
The ball is pre-assembled into the nut during the nut manufacturing process, creating a pre-assembled unit. This preliminary action eliminates the need for ball selection and assembly during final product assembly, directly resolving the contradiction by performing the precision-critical operation in advance when it can be more efficiently executed.
Solution Approach 2:
The manufacturing process is divided into separate stages: nut manufacturing (with ball assembly) and final product assembly. By segmenting the process, the ball assembly operation is isolated to a dedicated manufacturing stage where it can be performed efficiently, while the final assembly stage focuses only on combining pre-assembled units, reducing overall assembly time.
2Manufacturing precision
If ball diameter is selected to compensate for manufacturing errors, then axial gap standard is satisfied, but reassembly complexity increases
Solution Approach 1:
The ball is pre-assembled into the nut during manufacturing, creating a standardized pre-assembled unit. This ensures that the axial gap and preload standards are satisfied by design rather than by selective assembly. During reassembly, the entire pre-assembled unit is replaced as a module, eliminating the need to reselect balls and significantly simplifying the repair process.
3Adaptability or versatility
If strict tolerance management of track surfaces is implemented, then arbitrary assembly satisfaction is enabled, but manufacturing complexity increases
Solution Approach 1:
The ball is pre-assembled into the nut with controlled tolerances during manufacturing. This preliminary action creates a standardized interface that can be arbitrarily assembled with matching screw shafts while maintaining precision. The tolerance control is concentrated in the manufacturing stage rather than requiring complex control during assembly operations.
Data Source
AI summary
A method of manufacturing a ball screw device includes a nut unit preparation step, a screw shaft preparation step, and an assembly step. In the nut unit preparation step, a nut unit is prepared in which a circulation component, a ball, and a temporary shaft that prevents the ball from falling off are assembled to a nut provided with an inner peripheral track surface. In the screw shaft preparation step, a screw shaft provided with an outer peripheral track surface is prepared. In the assembly step, after the nut unit preparation step and the screw shaft preparation step, the temporary shaft of an arbitrary nut unit is replaced with an arbitrary screw shaft to manufacture the ball screw device.