Machining Fixture Force Balancing to Prevent Part Lift-Off
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
In the machining of gas turbine engine components, such as blades and vanes, the forces from grinding tools can cause parts to lift off the fixture, leading to dimensional and geometric tolerances issues, which are often detected late and can be challenging to diagnose, especially with thin material cross-sections and reduced rigidity.
Innovation Solution
A method and apparatus for configuring a machining fixture that involves computing reaction forces at part contact references and modifying clamp forces, clamp positions, part contact reference positions, and machining movements using a model of the part and fixture to prevent negative reaction forces, thereby ensuring accurate machining.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If high-force grinding operations are performed on thin-walled parts, then machining precision can be achieved, but the part may lift off the fixture causing dimensional and geometric tolerance violations
Solution Approach 1:
The system performs preliminary computation of reaction forces at part contact references before actual machining occurs. By analyzing the model of the part and fixture with planned machining movements, the system identifies potential lift-off conditions in advance and adjusts clamp forces or contact reference positions preemptively to prevent tolerance violations during high-force grinding operations
Solution Approach 2:
The system computes reaction forces at part contact references during simulated machining movements and uses this information to modify clamp forces, clamp positions, or part contact reference positions. This feedback loop ensures that negative reaction forces (indicating lift-off) are eliminated while maintaining manufacturing precision throughout the machining process
2Measurement precision
If multiple datum features are used to fully constrain the part, then positioning accuracy is improved, but the complexity of the fixture increases
Solution Approach 1:
The system dynamically adjusts parameters such as clamp forces, clamp positions, and part contact reference positions based on computed reaction forces. By modifying these parameters rather than permanently complicating the fixture structure, the system maintains positioning accuracy through software-controlled adjustments while avoiding unnecessary mechanical complexity
3Weight of moving object
If weight reduction is achieved through thin material cross-sections, then component performance is improved, but part rigidity decreases increasing susceptibility to lift-off during machining
Solution Approach 1:
The system computes reaction forces at part contact references and uses this information to adjust clamp forces that counteract the lifting forces generated during high-force grinding operations. By applying compensating clamping forces at strategically positioned contact references, the system prevents lift-off of thin-walled parts while maintaining their weight-reduced design and inherent performance benefits
Data Source
AI summary
A method for configuring a fixture for use in machining of sequential parts via a machine tool, for a planned machining movement of the machining element, uses a model of the part and fixture. Respective reaction forces at the plurality of part contact references are computed. Responsive to computation of a negative reaction force at a said part contact reference, a modification is made to a machining parameter.