Inner Shaft Boring Bar With Guiding Pads for Deep Bore Accuracy
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing machining tools are inadequate for internally machining shafts with varying inner bore diameters and hard materials like hardened steel, as they lack proper support, leading to poor surface finish and dimensional accuracy due to bending and collision issues.
Innovation Solution
A machining tool with a radially extensible cutting insert and rotatable guiding pads, supported by an external bar support device, allows precise machining by maintaining tool rigidity and preventing collisions, while a CNC-controlled system adjusts the cutting insert and pads for accurate operation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a long shaft is machined using conventional support devices, then the shaft can be fixed during machining, but the support rollers may damage the inner surface and the tool requires much space
Solution Approach 1:
The patent introduces guiding pads as intermediary elements that contact the outer surface of the shaft instead of support rollers contacting the inner bore. These pads are mounted on the boring bar and provide guidance and support during machining, eliminating direct contact between support devices and the inner surface that needs to be protected.
2Manufacturing precision
If the boring bar diameter is increased to improve rigidity, then machining precision improves, but the tool cannot pass through narrow openings in the inner bore
Solution Approach 1:
The boring bar is designed with a collapsible or telescopic structure that allows it to change its effective diameter. During insertion, the bar can be compressed to a smaller diameter to pass through narrow openings, and during machining, it extends to provide the necessary rigidity and precision for accurate cutting.
3Length of moving object
If the boring bar is made longer to reach deep inner bores, then machining capability improves, but the bar bends under its own weight causing poor surface finish
Solution Approach 1:
Guiding pads mounted on the boring bar serve as intermediary support points that contact the outer surface of the shaft. These pads provide continuous support along the length of the boring bar, preventing bending under its own weight and maintaining rigidity for high-quality surface finish throughout the machining process.
4Device complexity
If conventional machining tools are used without proper support, then the tool structure remains simple, but bending and collision issues occur leading to poor surface finish
Solution Approach 1:
The boring bar is designed to perform multiple functions: it serves as both the cutting tool carrier and the mounting platform for guiding pads. The guiding pads provide support, guidance, and collision prevention, while the boring bar maintains its primary function of holding and positioning the cutting insert, creating a multi-functional integrated system.
Data Source
Figure 1~2
Figure 3~4
AI summary
Machining tool for internal machining of a shaft (2) with an inner bore (3), such as an aircraft engine turbine shaft (fan mid shaft). The machining tool has an external boring bar (6) support device (5), and a boring bar (6) having a diameter smaller than a smallest opening on one side (4) of the inner bore (3) of the shaft (2). The boring bar (6) has a radially extensible cutting insert (7), and an end part (6b) of the boring bar (6) is rotatably connected to a main part (6a) of the boring bar (6). The end part (6b) is provided with one or more radially moveable guiding pads (8).