Cylindrical Workpiece Machining with Internal Kelly Drive
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Solution Overview
Problem
Current machining methods for cylindrical workpieces face challenges in achieving high concentricity between outer and inner surfaces, leading to increased manufacturing costs and deformation due to inadequate support and friction issues during grinding processes.
Innovation Solution
A method and apparatus that support the workpiece on a driving center and a centering center, with a kelly engaging the workpiece within its inner bore, allowing for simultaneous machining of the entire width and reducing frictional forces, thereby improving concentricity and roundness while minimizing deformation and equipment costs.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the workpiece is supported by both centers with friction-based rotation, then the workpiece can be rotated for machining, but the contact friction force is insufficient leading to extended machining time and increased manufacturing cost
Solution Approach 1:
A driving member is introduced as an intermediary between the driving center and the workpiece. This driving member engages with the workpiece (through a hole or groove) to directly transmit rotational motion, eliminating reliance on insufficient friction force between the centers and workpiece surface, thereby enabling high-speed machining without extending the machining time
2Stability of the object's composition
If the pressing force of the centers is increased to increase contact friction force, then the rotational stability improves, but the workpiece deforms especially in thin-walled workpieces
Solution Approach 1:
The driving member acts as a mediator that transmits rotational motion without requiring high pressing forces. By engaging internally with the workpiece (through holes or grooves), it provides stable rotation while minimizing contact pressure on the workpiece surface, thus preventing deformation and maintaining roundness in thin-walled workpieces
3Ease of operation
If the kelly is used to support the workpiece for grinding the outer circumferential surface, then the workpiece can be rotated for machining, but the entire width of the workpiece cannot be ground by one process
Solution Approach 1:
The driving member is extracted from the traditional kelly positioning system and repositioned to engage with the workpiece internally. This allows the grinding wheel to approach from the end of the workpiece without interference from a kelly, enabling the entire width to be ground in one continuous process and improving machining efficiency
4Manufacturing precision
If additional machining steps are performed to ensure desired accuracy after heat treatment, then the manufacturing precision improves, but the machining steps and manufacturing cost increase
Solution Approach 1:
The driving member is pre-installed in the workpiece before heat treatment, and the outer circumferential surface is machined with high precision using this driving member before heat treatment. This preliminary high-precision machining, combined with the stable rotational support, ensures that the desired concentricity is achieved in one process, eliminating the need for additional corrective machining steps after heat treatment
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
This approach enables efficient machining of cylindrical workpieces with improved concentricity and roundness, reducing machining time and costs by allowing the entire width to be machined in one process and minimizing the need for additional equipment, such as hydraulic devices.
Implementation Method 1
since the contact friction force between the centers 60 and 61 and the workpiece 56 is smaller than the machining force
Data Source
AI summary
An apparatus for machining a cylindrical workpiece has a hollow spindle with a driving center on its tip end. The hollow spindle is rotationally journaled within a spindle unit. A tail stock spindle, with a centering center on its tip end, is rotationally supported and axially movable within a centering unit. A shaft-like kelly is non-rotationally and axially movably supported within an inner bore of the spindle. A drive rotates the spindle. Cylinders axially drive the kelly and the tail stock spindle, respectively. The spindle, the tail stock spindle and the cylinders are arranged on the same axial line. The cylindrical workpiece is sandwiched between the driving center and the centering center. An outer circumferential surface of the workpiece is finish machined while rotating the workpiece under a condition where the kelly engages the workpiece within an inner bore of the workpiece.