EB-PBF Preheating with Stepped Current for Waste Powder Reuse
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Solution Overview
Problem
The inability to reuse waste powder from laser beam powder bed fusion (LB-PBF) machines in electron beam powder bed fusion (EB-PBF) machines due to electro-static charging, leading to instability and waste disposal issues, which is costly and hazardous.
Innovation Solution
A method of pre-heating the EB-PBF build chamber using stepped increases in electron beam current, allowing the use of waste powder from LB-PBF by gradually raising the temperature to the desired level, thereby dissipating static charge and preventing smoking.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of substance
If LB-PBF powder is used in EB-PBF machines, then powder cost is reduced by reusing waste powder, but powder stability deteriorates due to electro-static charging causing smoking
Solution Approach 1:
The patent applies preliminary action by pre-heating the build chamber and powder bed to a temperature of 200°C to 400°C before introducing the LB-PBF powder. This pre-heating eliminates moisture and reduces electro-static charging effects that would otherwise cause powder instability and smoking during the EB-PBF process.
Solution Approach 2:
The patent changes the temperature parameter of the build chamber and powder bed to a range of 200°C to 400°C, which is higher than conventional pre-heating temperatures. This parameter change fundamentally alters the powder's electro-static properties, allowing LB-PBF powder to remain stable during EB-PBF processing without smoking.
2Productivity
If conventional pre-heating is used, then process time is reduced, but powder stability deteriorates due to electro-static charging
Solution Approach 1:
The patent increases the pre-heating temperature parameter to 200°C to 400°C, which simultaneously achieves powder stabilization and maintains reasonable process speed. This optimized temperature range eliminates the need for excessively long pre-heating times while ensuring powder stability.
Solution Approach 2:
The patent implements a periodic pre-heating process that cycles through temperature zones, allowing the powder bed to reach optimal temperature uniformly. This periodic heating approach prevents hot spots that could cause premature powder instability while maintaining overall process efficiency.
3Stability of the object's composition
If higher pre-heating temperature is applied, then powder stability is improved by preventing smoking, but energy consumption increases
Solution Approach 1:
The patent optimizes the pre-heating temperature to a specific range of 200°C to 400°C, which is the minimum temperature required to eliminate electro-static charging effects. This optimized parameter range achieves powder stability while minimizing energy consumption compared to higher temperature approaches.
Solution Approach 2:
The patent maintains continuous pre-heating of the build chamber and powder bed throughout the powder handling process, ensuring that the powder remains at the optimal temperature range without requiring intermittent high-energy heating cycles. This continuous low-level heating is more energy-efficient than periodic high-temperature heating.
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
Enables the reuse of LB-PBF waste powder in EB-PBF machines, reducing costs and environmental impact by repurposing waste powder, while maintaining process stability and efficiency.
Implementation Method 1
pre-heating the build chamber to the predetermined preheated temperature, wherein the pre-heating the build chamber comprises: exposing a build plate within the build chamber to a plurality of streams of electrons
Implementation Method 2
an electron beam selectively melts and fuses the powder according to the respective current cross section of the CAD model
Data Source
AI summary
Electron beam powder bed fusion may be performed using waste powder from laser beam powder bed fusion by pre-heating a build chamber using stepped increases of electron beam current. To perform the pre-heating without smoking the powder, a plurality of predetermined interim temperatures, ranging from an ambient, resting temperature of the build chamber to a predetermined preheated temperature, are determined. A build plate within the build chamber is exposed to a plurality of streams of electrons, one at a time, while the build plate is surrounded by the waste powder. Each stream of electrons has a progressively increasing current, with the current being increased each time an actual temperature of the build chamber reaches or exceeds the next predetermined interim temperature. The actual temperature of the build chamber is monitored during the pre-heating, to compare the actual temperature of the build chamber to the plurality of predetermined interim temperatures.