metal powder reuse in additive manufacturing
TRANSCRIPT
Metal powder reuse in additive
manufacturing
Alessandro Consalvo
AM Support Engineer, Renishaw spa
• World leading metrology company
founded in 1973.
• Skills in measurement, motion
control, spectroscopy and
precision machining.
• 2011 MTT acquisition making
Renishaw the only UK
manufacturer of metal additive
manufacturing systems.
Renishaw
70 offices
32 countries
> 3800 employees
Renishaw worldwide locations
AM250 system
AM250
Max Part Build area245 x 245 x 300 (x,y,z)
(z extendable to 360mm)
Build rate* 5cm³ to 20cm³ per hour
Layer thickness 20 to 100µm
Laser beam diameter 70µm at powder surface
Laser options 200W or 400W
Power supply 230V 1PH 16A
Power consumption 1.6 kWh
Gas consumption < 30 l/hr
* Build rate is dependent on material, density & geometry, not all materials build at the highest build rate.
3D model is sliced in layers with thickness from 20 to 100 µm.
Near net shape metal component with density and mechanical properties comparable to those obtained by casting.
The machine builds up the part layer by layer, using a high powered fibre laser to fuse fine metal powder particles together.
x
y
Powder bed laser melting
A layer of fine gas atomized metal powder is deposited and a high power fiber laser
melts the particles together to form solid dense metal following the 3D model.
The platform is lowered and a new layer is deposited and melted by the laser.
The process is repeated until the merger of the last layer of the model.
The unmelted powder is recovered and it can be used again after a sieving process.
Retractable
Platform Z
axis
Build
Metal
Powder
Build
Chamber
Laser
Window
Powder
distributio
n System
Inert
Gas
Laser
beam:
70 µm
How Laser Melting works
Powder reuse cycle
1. Fill hopper
2. Inert atmosphere
3. AM
4. Collect overflow
5. Sieve
6. Reuse sieved powder
Powder reuse cycle
1. Fill hopper
2. Inert atmosphere
3. AM
4. Collect overflow
5. Sieve
6. Reuse sieved powder
Powder reuse cycle
1. Fill hopper
2. Inert atmosphere
3. AM
4. Collect overflow
5. Sieve
6. Reuse sieved powder
AM250 inert atmosphere generation
Renishaw AM machines are unique in the way build atmosphere is
created. All Renishaw systems are suitable for building reactive
materials.
1. A vacuum is created, approx.1 atm below ambient:
• This removes air and any humidity from the entire system
2. The chamber is filled with ~600 litre of high purity argon.
3. The atmosphere is maintained at below 1000ppm (0.1%) oxygen and can
be set to run below 100ppm (0.01%) for titanium (Ti6Al4v) and other alloys.
Gas consumption is typically <30 L/hr and laser melting is achieved
approx. 10 minutes after cycle start.
Powder reuse cycle
1. Fill hopper
2. Inert atmosphere
3. AM
4. Collect overflow
5. Sieve
6. Reuse sieved powder
Overflow powder down here
Powder reuse cycle
1. Fill hopper
2. Inert atmosphere
3. AM
4. Collect overflow
5. Sieve
6. Reuse sieved powder
Overflow capture
flasks
Powder reuse cycle
1. Fill hopper
2. Inert atmosphere
3. AM
4. Collect overflow
5. Sieve
6. Reuse sieved powder
Used overflow powder
Sieved used overflow
powder
Powder reuse cycle
1. Fill hopper
2. Inert atmosphere
3. AM
4. Collect overflow
5. Sieve
6. Reuse sieved powder
• An area of AM that needs fully understanding.
• Feedstock should be reliable for process
repeatability and predictability.
• Powder bed and machine parameters are closely
related.
Why investigate powder re-use for AM?
Why titanium?
Ti-6Al-4V alloy
High strength to
weight ratioHigh corrosion
resistance
45 % lighter than
steel$$$$$
Buy to fly ratio
20kg Titanium billet
1 kg Titanium powder
1 kg
Ti component
AM
Machining
19 kg Waste Ti
Powder characteristics - Chemistry
Element %
Ti Grade 5 Ti Grade 23 (ELI)
Oxygen 0.20 0.13
Nitrogen 0.05 0.03
Carbon 0.08 0.08
Hydrogen 0.0125 0.0125
Aluminium 5.5-6.75 5.5-6.50
Vanadium 3.5-4.5 3.5-4.5
Interstitial
Alloying
Powder characteristics - Physical
Flowability
PSD – Particle size distribution
Shape
Density/Packing
Flowability is important for consistent
layers, it is directly influenced by
PSD, packing and particle shape.
• 20 routine builds using same Ti powder batch
in same AM250 system
• Powder capture capsule
• Tensile bar and density block
Experimental procedure
Powder analysis Build analysis
Oxygen and Nitrogen Tensile
PSD Density
Flowability Powder capture
capsuleTensile test
piece
Density block
Experimental results – interstitial elements
Maximum O level for grade 23
Maximum N level for grade 23
Steady increasing trend
trend.
Steady increasing trend
trend.
Experimental results – interstitial elements
Grade 23
Maximum
Grade 5
Maximum
Powder analysis
Experimental results – Particle size distribution, PSD
Build 16 • No general trend in
PSD with increased
numbers of builds.
• Builds 11 and 16
have more wide and
narrow distributions
respectively.
Build 11
Experimental results - Flowability
Flow initially increase
between 0-5 builds
followed by a general
decrease.
Experimental results – Melted powder: Tensile
Upper tensile strength
Yield strength
• After 20 builds the powder is not significantly
changed either in terms of interstitial
elements or physical properties.
• Results indicate significantly more reuse
potential.
• Careful powder handling contributes to
sustainability of powder.
• Continued investigations required, including
blending of powders to sustain repeatability.
Conclusions
