Trochoidal Grinding for Rotor Disc Blade Slot Finishing
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Solution Overview
Problem
Existing finishing processes for blade slots in rotor discs, such as broaching and super-abrasive grinding, face issues like burr formation, residual tensile stress, thermal damage, high tool costs, and inflexibility, which compromise surface integrity and efficiency.
Innovation Solution
A finishing process using two super-abrasive grinders with a trochoidal path for the sides and a disc grinder for the bottom, where the grinders move in a cycloidal or elliptical trajectory to alternately contact the sides, reducing thermal stress and allowing for flexible machining with reduced tool wear and improved surface quality.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If super-abrasive grinders are used for finishing slot sides with continuous contact throughout the length of the pass, then finishing quality can be achieved, but a large quantity of heat is generated causing local overheating and compromising surface integrity
Solution Approach 1:
The grinder is fed with a rectilinear intermittent motion that alternates between advancing toward the workpiece and retracting from it. This periodic contact allows the grinding zone to cool down between passes, preventing heat accumulation and local overheating while maintaining finishing quality through repeated controlled contacts.
Solution Approach 2:
The grinder performs multiple passes over the same slot side, with each pass removing a small amount of material. This preliminary action approach distributes the total material removal across several intermittent contacts rather than one continuous contact, allowing heat dissipation between passes and preventing thermal damage.
2Productivity
If broaching process is used to make blade slots, then slot surfaces can be formed, but burrs are generated on slot edges requiring subsequent removal operations
Solution Approach 1:
The invention replaces the mechanical broaching process with an abrasive grinding process. Instead of using a broach with defined cutting shapes that mechanically shear material and create burrs, super-abrasive grinders remove material through abrasion, producing a burr-free surface finish and eliminating the need for subsequent burr removal operations.
3Productivity
If broaching process is used to make blade slots, then slot surfaces can be formed, but residual tensile stress is left in the rotor disc material
Solution Approach 1:
The invention replaces the broaching mechanical cutting system with an abrasive grinding system. The grinding process removes material through abrasion rather than mechanical shearing, significantly reducing the induction of residual tensile stresses in the rotor disc material while maintaining slot formation efficiency.
4Productivity
If broaching process is used to make blade slots, then slot surfaces can be formed, but white layer is generated on machined surfaces altering crystalline grain and micro-structural integrity
Solution Approach 1:
The invention replaces the broaching process with super-abrasive grinding. The grinding process produces a different surface layer characteristic that avoids the formation of the harmful white layer with altered crystalline grain structure, while still achieving the required slot geometry and surface quality.
5Manufacturing precision
If broaching tools and machines are used, then slot surfaces can be formed, but high tool costs and long procurement times are incurred
Solution Approach 1:
The invention replaces expensive, complex broaching tools with relatively simple super-abrasive grinders. The grinder tools are more economical and have shorter procurement times, accepting that they may require replacement after a certain number of passes, but overall reducing tooling costs and lead times while maintaining slot surface quality.
6Manufacturing precision
If broaching machines are used, then slot surfaces can be formed, but long setting times and very high costs for purchasing new machinery are required
Solution Approach 1:
The invention replaces complex broaching machines with simpler super-abrasive grinding machines. The grinding equipment requires less complex setup procedures and has lower acquisition costs, while still achieving the required slot surface quality through the abrasive process.
7Device complexity
If a single grinder is used for finishing slot sides, then tool complexity is reduced, but finishing time increases due to sequential machining of each side
Solution Approach 1:
The single grinder performs multiple intermittent passes over each slot side, alternating between advancing and retracting. This periodic action allows one grinder to efficiently machine both sides of the slot by repeatedly processing each side, achieving the required surface quality without the need for multiple grinders while minimizing total finishing time.
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 process minimizes thermal damage, reduces finishing times, extends tool life, and achieves higher surface integrity with lower residual tensions, enabling more efficient and flexible production of rotor disc slots with improved quality and reduced costs.
Implementation Method 1
the use of super-abrasive grinders
Implementation Method 2
the grinders move in a cycloidal or elliptical trajectory to alternately contact the sides, reducing thermal stress
Data Source
Figure 1~4
Figure 2~3
AI summary
A rotor disc (1) has a plurality of slots (5), each defined by a bottom surface (9) and by two lateral surfaces (10), which are connected to the bottom surface (9) and are symmetrical with respect to a symmetry plane (11); each slot is machined performing a bottom finish, in which the bottom surface is ground by means of a disc grinder (12), and a lateral finish, in which the sides are ground by means of a finger grinder (13); the lateral finish is performed with a pass of the finger grinder (13) along a trochoidal path, which includes the combination of a translation component and a revolution component along a loop trajectory (B), which is set up so as to bring the finger grinder (13) into contact with the sides (10a) alternatively and remove stock from both sides during the same pass.