Isothermal Fixture for Chatter Reduction in Precision Machining
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Solution Overview
Problem
In the high precision machine tool industry, large, thin cross-section, contoured, and complex work pieces experience significant challenges with chatter and thermal expansion due to machining heat generation, leading to dimensional inaccuracies and surface finish irregularities, especially in dry machining processes where coolant or lubricant is not used.
Innovation Solution
An isothermal work piece holding system utilizing a rigid, non-visco-elastic material with vacuum clamping and integrated isothermal cooling/heating systems to maintain the work piece at a stable temperature, reducing vibrations and thermal expansion, while allowing for precise and rigid support during machining and assembly operations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If compliant or visco-elastic materials are used to damp work piece vibrations, then vibration damping is improved, but rigidity in supporting the work piece deteriorates
Solution Approach 1:
The work piece support system is segmented into multiple independent vibration damping elements distributed across the support surface. Each element provides localized vibration damping without compromising the overall rigidity of the support structure, allowing the system to address chatter while maintaining structural integrity.
Solution Approach 2:
The invention employs composite material structures combining rigid support elements with vibration damping characteristics. This composite approach enables the support system to simultaneously provide the rigidity needed for accurate machining and the vibration damping capability to reduce chatter, resolving the contradiction between these two opposing requirements.
2Object-affected harmful factors
If elastic materials are used to damp vibrations through partial compression, then vibration reduction is achieved, but rigidity in holding the work piece deteriorates
Solution Approach 1:
Vibration damping capability is applied locally at specific contact points between the work piece and support structure, rather than throughout the entire support system. This localized approach allows vibration reduction at critical areas while maintaining overall rigidity for accurate positioning and holding of the work piece.
3Manufacturing precision
If shallower depths of cut at slower tool rotation are used to mill cleanly without waves or sharp shoulders, then surface finish quality is improved, but productivity deteriorates
Solution Approach 1:
The work piece support system is pre-configured with vibration damping elements and rigid positioning features before machining begins. This preliminary setup prevents chatter and vibration during the machining process, enabling the use of more aggressive cutting parameters such as deeper depths of cut and faster tool rotation speeds without compromising surface finish quality, thereby improving productivity.
4Object-affected harmful factors
If non-linear metallic springs, gas and hydraulic shock absorbers, or tuned resonant structures are used for chatter reduction, then vibration damping is improved, but device complexity and cost deteriorate
Solution Approach 1:
The invention employs simple, inexpensive vibration damping elements that can be easily manufactured and integrated into the work piece support system. These elements provide effective chatter reduction without the complexity and high cost of non-linear metallic springs, gas and hydraulic shock absorbers, or tuned resonant structures, making the solution economically viable for widespread implementation.
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
The system effectively reduces machining errors, increases precision, and enhances dimensional accuracy, enabling deeper cuts at faster speeds, reducing cycle times and costs, and ensuring consistent quality by maintaining the work piece isothermally stable, thus preventing thermally induced dimensional changes.
Implementation Method 1
The work piece is held firmly on the holding body by a vacuum
Implementation Method 2
conduits, channels or grooves formed or emplaced in the holding body... for use with a non-corrosive fluid coolant for maintaining the entire work piece truly isothermal during machining
Data Source
AI summary
Isothermal work piece holding system uses vibration-damping, low thermal conductivity, low TCE polymer-composite holding body(ies) to damp machine tool vibration and chatter while accurately, rigidly maintaining the work piece in position by vacuum and/or mechanical clamps during machining. Cooling fluid channels having high thermal conductivity plates in contact with the work piece transfer thermal energy to/from it to maintain it isothermal during machining, inspection and assembly, eliminating dimensional changes and increasing process repeatability. Minimizing chatter reduces cycle time and improves surface finish which eliminates manual re-work. The system employs vacuum and coolant fluid pumps, heater/cooler(s), temperature sensor(s) and controller(s) to achieve highly accurate dimensional tolerances machining of parts which reduces error stack-up and assembly costs. Isothermal fixtures are disclosed for assembling parts and automated rivet settings in precise locations with reduced use of shims. The inventive isothermal system is applicable to control of TCE/I2R effects in linear induction motors.