Solid State Additive Manufacturing Using Rotating Rod Friction
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Solution Overview
Problem
Additive manufacturing systems using melt pool deposition processes often result in metallic materials with defects such as thermally induced residual stress, fusion bond line flaws, and micro cracking, limiting their material properties compared to wrought materials.
Innovation Solution
A solid state additive manufacturing system and process utilizing a consumable rotating rod of metallic material, where pressure is applied to move the rod into a deposition zone, generating frictional heat while rotating, and preheating the rod to a near plastic state to reduce energy requirements and achieve defect-free deposition with full wrought properties.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If melt pool deposition processes are used to deposit metallic material, then material can be added to workpieces, but the deposited metal develops inherent defects including thermally induced residual stress, fusion bond line flaws, micro cracking, and poor microstructure
Solution Approach 1:
The invention fundamentally changes the thermal parameter by eliminating the molten melt pool state entirely. Instead of melting and solidifying metal (phase change deposition), the process uses solid state friction stir deposition where the deposition rod remains solid throughout, changing from a thermal-process to a mechanical-process parameter regime that avoids all melt pool defects
Solution Approach 2:
The invention replaces the thermal field (laser/electron beam melting) with a mechanical field (friction stir deposition). A rotating deposition rod mechanically stirs and consolidates the deposited material through friction and shear forces, substituting thermal energy with mechanical energy to achieve metallurgical bonding without melting
2Reliability
If a rotating deposition rod is used to generate frictional heat for solid state deposition, then defect-free material with fine grain structure is achieved, but the energy required to rotate the rod and generate sufficient frictional heat increases
Solution Approach 1:
The deposition rod is preheated to a temperature close to its melting point before the friction stir deposition begins. This preliminary thermal action reduces the temperature differential needed during deposition, thereby reducing the frictional heat generation requirement and the rotational energy needed to achieve the necessary deposition temperature
Solution Approach 2:
The invention merges the heating function with the deposition function by using the same rotating rod both to generate frictional heat and to deposit material. The rod serves dual purposes: as a heat source through friction and as the material source, combining thermal and material delivery functions into a single integrated tool
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 process enables defect-free deposition with a fine grain size and porosity-free microstructure, achieving full wrought properties in the deposited metal, comparable to forging, through the use of a consumable rotating rod and controlled heat application.
Implementation Method 1
rotating said rod while said pressure is being exerted to generate frictional heat when said rod contacts a surface of said workpiece
Implementation Method 2
exerting pressure at one end of said rod to move said metallic deposition material into a deposition zone
Data Source
AI summary
A process for solid state deposition of a material onto a workpiece includes the steps of providing a rod of metallic deposition material, exerting pressure at one end of the rod to move the metallic deposition material into a deposition zone, rotating the rod while the pressure is being exerted to generate frictional heat when the rod contacts a surface of the workpiece, and raising the temperature of the metallic deposition material to reduce the amount of frictional heat which needs to be generated during the rotating step and to produce a microstructure which is substantially free of porosity and which has a fine grain size.