Embed Size (px)
Citation preview
ADDITIVE LAYER MANUFACTURING AS APPLIED TO POROUS SURFACES ON MEDICAL IMPLANTS
CHALLENGES ASSOCIATED WITH CLEANING AND PROCESSING
Julius Bonini P.E., Senior Metallurgical EngineerKaitlyn Calaluca, Metallurgical Engineer
Lucideon M+P, Schenectady, NY
ALM - Challenges Associated with Cleaning and Processing
1. ALM process as applied to porous coated devices
2. General cleaning issues associated with ALM specific to porous coated devices
3. Unfused Particle Shedding
2
Tailored Porous Surface Structure
Additive Layer Manufacturing
3
− ALM - Otherwise know as 3D printing
− Titanium Components− Electron Beam Melting (EBM) or− Direct Metal Laser Sintering (DMLS)
− Several metallurgical issues need to be resolved for medical implant applications− Complex microstructural issues (won’t be addressed here)− Cleaning and processing issues
Additive Layer Manufacturing
4
Porous Surface Structures of Common Medical Implants
5
Accurate measurements can be made and parameters established per ASTM 1854
Sintered Wire and BeadHave Definable Porous Structures
6
ALM Structures Found to be Highly Variable
7
Cross-Sections Show Deep Porous Structures
8
Surface Porous Structures
9
Advantages of ALM Technologies
− Cost?
− Create any porous structure you want− Depth− Tapered porosity through section− Pore Size− Pore Density
− Complete flexibility for improved osseointegration
Components Manufactured via ALM Technology
10
Most Common Application of ALM Acetabular Cups
11
− How do you keep components clean during processing?
− How do you eliminate residues and prevent entrapment?
− How do you remove all processing fluids from final product?
Cleanliness Issues Related to Components Manufactured via ALM Technology
First You Need to Understand the Life of a Typical Component
12
The Life of an Acetabular CupConventional Porous CoatWire, Bead, Plasma Spray
ALM Porous CoatEBM, DMLS
Bar/Forging
Extensive Machining &Processing
Extensive Cleaning & Degreasing
Porous Coated
Final CleaningAnd Packaging
Coated Shell(porous)
Extensive Machining &Processing
Extensive Cleaning & Degreasing
Final CleaningAnd Packaging
Passivation
“Dirty” Parts
14
As-Received(Clean)
After Processing(Dirty)
− In-house processing operations will contaminate parts− includes applied cleaning procedures
− Think of ALM structures as sponges− Rough surfaces pick up surface debris− Substructures act as a sponge and absorb fluids and
humidity from air
− Removal of all these residues, liquids and debris is a challenge
Very Complex Issue
15
To remove these contaminates, you clean: Wash, Blast, Ultrasonics?
Debris Pick-up and Removal
16
Effective Cleaning of Complex Porous Structures is a Challenge
− Liquid exposures can be problematic
− Ultrasonic cleaning, rinsing, passivation
− Cleaning solutions, caustics, acids
− Problem becomes effective removal of cleaning liquids
17
Open Cell Structures Pose Less of a Challenge
Fluids In – Fluids Out
18
• Open Cells
• Closed Cells
• Semi-Closed Cells?
Closed and Complex Cell StructuresAre a Real Challenge
19
Processing Effects
− Thermal Effects
− Open (interconnected) cells stay open during all stages of processing− General problem that has to be dealt with− Any liquid exposure has to be effectively rinsed and dried
− Closed cells remain closed during all stages of processing− Shouldn’t be a problem
− Semi-closed – open when heated due to thermal expansion, then close upon cooling− Can be a very big issue
20
Processing Effects – Open Cells
21
− Typical Liquid Exposures
− Cutting fluids and coolants
− Solvents and cleaners used to remove above− May include ultrasonic with heat
− Rinse agents and water used to remove above
− Passivation
− All can be effectively removed with proper practice
Processing Effects – Semi-Closed Cells
− Semi-closed cells open at elevated temperature ( > 40 o C)
− Liquid infuses into now open cells at temperature
− Liquid remains trapped as cells close again upon cooling
− Liquid can be effectively rinsed from all open areas but not from now closed cells
− Subsequent thermal exposure can re-release liquid
− Particular concern during passivation step
22
Passivation Effects – Semi-Closed Cells
− Semi-closed cells – open when heated then close upon cooling
− Nitric Acid Exposure
− Slowly oozes out over time
Fully Porous Augment
23
Potential Solutions
− Effective dissolution and removal of all liquid agents
− Use of volatile alcohols
− Combined with ultrasonics + temperature to open those semi-open cells
− Followed by effective oven drying
24
Unfused Powder ParticlesLong Term Problem for all ALM Materials
• Nature of the material – it all starts with fine Ti powder
• Unfused particles are cleaned off of manufactured parts by blast methods using the same media
• Levels of effectiveness – surfaces look good
• Below the surface may be a problem – remember the complex porosity issue
25
26
Unfused Particles
Particles Collected fromCleaned Sample Surface
27
28
With Additional Surface BlastingAs Normally Processed
Unfused Particles
29
NoAdditionalBlasting
WithAdditionalBlasting
Conclusions
• A variety of particle cleanliness issues need to be addressed for evolving ALM components
• Stick your head in the sand?
• Test, evaluation and material standardizations specific to ALM material are needed
30
