Broach Cutter Grinding Rake Angle Control
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Solution Overview
Problem
Existing methods for forming turbine engine disk slots, such as those using firtree attachment roots, suffer from variations in rake angle during machining, leading to inconsistent chip generation, increased forces, and reduced precision due to uneven material properties and residual stresses.
Innovation Solution
The use of a rotating quill with a lateral surface to grind the teeth of a broach, allowing continuous reorientation to achieve a uniform rake angle of 7.5° to 8.5° over a majority of the cutting edge, forming a peripheral trench to deflect chips and improve machining efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional grinding methods are used to form broach teeth, then the teeth can be manufactured, but the rake angle varies during machining leading to inconsistent chip generation and increased cutting forces
Solution Approach 1:
The grinding wheel is rotated about an axis that is offset from the broach tooth centerline, creating a dynamic grinding motion that varies the rake angle during the grinding cycle. This dynamic approach allows the rake angle to be systematically varied to achieve optimal chip generation and reduced cutting forces, resolving the contradiction between manufacturing precision and productivity.
Solution Approach 2:
The invention changes the grinding parameters by offsetting the grinding wheel axis from the broach tooth centerline and controlling the rake angle variation during grinding. This parameter change enables consistent rake angle control across multiple teeth, improving chip generation consistency and reducing cutting forces while maintaining manufacturing precision.
2Manufacturing precision
If conventional grinding methods are used, then broach teeth can be formed, but residual stresses and uneven material properties reduce machining precision
Solution Approach 1:
The dynamic grinding motion with offset wheel axis creates a systematic variation in rake angle during machining. This dynamic approach ensures more uniform material removal and reduces residual stresses by distributing the cutting forces more evenly, thereby improving both manufacturing precision and material property uniformity.
Solution Approach 2:
By changing the grinding parameters to include rake angle control through offset axis rotation, the invention achieves more uniform material properties and reduces residual stresses. This leads to improved machining precision and reliability in slot formation.
3Productivity
If tight tooth spacing is implemented to increase throughput, then productivity improves, but machining precision deteriorates due to varying rake angles
Solution Approach 1:
The dynamic grinding approach with offset axis allows for tight tooth spacing while maintaining cutting edge consistency. The systematic rake angle variation during grinding ensures that each tooth receives appropriate machining, even in tight spacing configurations, thereby maintaining precision while increasing throughput.
Solution Approach 2:
By implementing rake angle control through parameter changes in the grinding process, the invention enables tight tooth spacing without sacrificing precision. The controlled rake angle variation ensures consistent cutting edge quality across all teeth, allowing increased productivity while maintaining manufacturing precision.
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 method results in more uniform chip generation, reduced cutting forces, improved surface finish, and increased precision by maintaining a consistent rake angle, facilitating tighter tooth spacing and higher throughput.
Implementation Method 1
grinding the first face of each tooth of a plurality of said teeth with a lateral surface of a rotating quill
Data Source
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AI summary
A broach (20) or broach segment (20) has a spine (22). A longitudinal array of teeth (40-1...40-n) protrude from the spine (22), each said tooth (40-1...40-n) having: a first face and an opposite second face; and a distal surface joining the first face and second face; and at least some of the teeth (40-1...40-n) being firtree teeth (40-1...40-n) and have a peripheral trench adjacent the cutting edge of the at least one tooth (40-1...40-n).