EDM Fixture Contacts for Rough Additive Workpiece Alignment
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Solution Overview
Problem
Additively manufactured workpieces with rough surfaces, such as those made from nickel-based steel alloys, pose challenges during electrostatic discharge machining (EDM) due to reduced effective electrical separation and increased wear on EDM fixtures, leading to arcing and reduced precision in material removal.
Innovation Solution
An EDM fixture with a 3-2-1 alignment system utilizing electrically conductive face contacts and electrically resistive point contacts, where the point contacts are made from ceramic materials with higher hardness and resistivity than the face contacts, to securely locate and separate the workpiece, reducing wear and arcing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional EDM fixtures are used with additively manufactured workpieces, then the workpiece can be supported during EDM operation, but the rough surface of the workpiece causes reduced effective electrical separation leading to arcing between the workpiece and fixture
Solution Approach 1:
The patent introduces an intermediary layer (insulating coating or dielectric material) between the rough workpiece surface and the fixture contact points. This intermediary maintains adequate electrical separation despite surface roughness, preventing arcing while still allowing mechanical support and positioning. The intermediary acts as a mediator that decouples the electrical and mechanical functions of the fixture-workpiece interface.
2Reliability
If conventional EDM fixtures are used with additively manufactured workpieces, then the workpiece can be supported during EDM operation, but the rough surface of the workpiece causes increased wear on the fixture, reducing positioning precision
Solution Approach 1:
The patent changes the surface parameters of the fixture contact points by applying hard coatings (such as diamond-like carbon or ceramic coatings) or selecting materials with significantly higher hardness than the workpiece material. This parameter change in surface hardness makes the fixture contacts resistant to wear from the rough workpiece surface, maintaining positioning precision over multiple operations.
3Reliability
If the fixture uses electrically conductive materials for all contacts, then electrical connection is established, but the rough workpiece surface causes arcing and wear
Solution Approach 1:
The patent applies different electrical properties to different parts of the fixture contacts. The bulk material or certain regions are made electrically conductive to ensure proper electrical connection for EDM current, while the surface layer or contact points are made electrically resistive or insulating to prevent arcing with the rough workpiece surface. This local differentiation of electrical quality allows simultaneous achievement of electrical connection and arcing prevention.
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 solution effectively minimizes arcing and maintains precision in EDM operations by providing adequate electrical separation and wear resistance, ensuring consistent material removal from additively manufactured workpieces.
Implementation Method 1
The material forming the point contacts can have electrical resistivity that is greater than the material forming the face contacts
Implementation Method 2
electrostatic discharge machining (EDM) to separate the article from an underlying build plate
Data Source
AI summary
An electrostatic discharge machining fixture includes a fixture body, two or more electrically conductive face contacts seated in the fixture body, and two or more electrically resistive point contacts seated in the fixture body. The electrically conductive face contacts and the electrically resistive point contacts define a 3-2-1 alignment system to locate an additively manufactured article relative to the fixture body during an electrostatic discharge machining operation. Electrostatic discharge machining arrangements and methods of supporting additively manufactured workpieces during electrostatic discharge machining operations are also described.