1. Additive Manufacturing Technology Overview
Mike Klecka
United Technologies Research Center
East Hartford, CT
June 18, 2014

2. Presentation Overview
Additive Manufacturing Technology
Comparison of Additive Manufacturing Methods
Typical Post Processing Requirements
Multiple Material Designs
Additive Manufacturing with Cold Spray
Suitability of Parts for Additive Manufacturing
Design and Redesign for AM
AM Process Selection

3. Increasing Pressure on Manufacturing
Requirements
Shorter time to market
Higher performance requirements
Increased product life, durability
Reduced weight
Lower cost
Higher yield and quality
Improved energy efficiency
Less waste, environmentally friendly
Additional challenges
Increasingly complex part geometries and systems
Expanded material options
Manufacturability concerns
Slow adoption of new techniques
Qualification of new processes
Potential benefits from additive manufacturing
Reduced machining time, energy, & cost
Reduced material consumption
Material solutions and combinations not otherwise possible
Increased part complexity

4. Additive Manufacturing Overview
Additive manufacturing is broadly defined as the addition of functional material to a substrate, after which is either incorporated into the substrate as the finished part or is separated from the substrate to yield a free standing part
Added ribs to a sheet or panel for stiffening
Added lugs to a tube for mounting
3D printing of entire components on a build plate
Majority of techniques utilize powder feedstock
Some use wire, sheet, or strip stock
Powder Bed Techniques
Laser powder bed, DMLS, EBM
Advantages – Small features, tight tolerance, fully inert environment
Disadvantages – Low deposition rate, limited part size, single material
Powder Deposition Techniques
Cold spray, LENS, Laser applied powder
Advantages – Moderate part sizes, in situ alloying, moderate deposition rates, dissimilar materials
Disadvantages – Lower dimensional accuracy, less tolerance control
Build Core
Added Material
Non-Powder Based Techniques
Laser wire feed, EB wire, ultrasonic, laminated object
Advantages – High deposit rates, low cost feedstock
Disadvantages – Poor part tolerance, required post machining, moderate property potential

5. Comparison of Additive Manufacturing
Powder Bed
DMLS, LPB, EBM, powder bed fusion
Potential for widest variety of geometry
Limited to one material
Low deposition rates ( kg/hour)
Part size limited by dimensions of powder bed
Advantages – Small features, tight tolerance, high geometric fidelity, fully inert environment
Disadvantages – Stress relief & heat treatment often required, slow build rates, limited part size
Laser Powder Injection
LENS, laser applied powder (LAP)
Multiple build directions
Multiple material deposition
Moderate deposit rates (0.5 – 1 kg/hour)
Advantages – Moderate geometric fidelity, shield gas environment, cladding/repair/resurfacing
Disadvantages – Moderate feature size, moderate property potential, gravity concerns with build direction
Laser Applied Powder

6. Comparison of Additive Manufacturing
Cold Spray
High plastic work during deposition
High deposition rates (3 – 15 kg/hour)
Limited to line-of-sight processing
Lower geometric fidelity
Advantages – Solid state processing, good mechanical properties, multi-material, bonding of dissimilar materials
Laser/EB Wire Additive
Ultrasonic & Laminated Object
LAW, MIG, EB Wire
High rates (3 – 10 kg/hour)
Low cost feedstock
Low feature tolerance
Moderate property potential
UC, UAM, LOM
High build rates
Sheet, strip feedstock
Limited geometry
Solid state
ASM Handbook, Vol.6A, Welding Fundamentals and Processes (2011)
Granular Material Bonding
Powder bed inkjet & binder jetting
3D printing sand, casting molds/cores
Plaster based printing (PP)
Low material properties, low cost
Sintered metal, polymer, & ceramics

7. Comparison of Additive Manufacturing
Direct Write
Conductive ink printing, conformal surfaces
Potential for wide variety of geometries
Excellent resolution depending on technique
Multiple material deposition
Micro cold spray
Actuators, Motors & MEMS
Sensors & Arrays
Fused Deposition
Thermoplastic-based (neat or filled)
Layer-by-layer deposition
Extrusion & shrinkage limits high resolution
Capable of complex geometries and low density cores
Multiple material deposition, limited properties
Cores
Prototype parts
Stereolithography
SLA, Large Area Maskless Photopolymerization (LAMP)
Ceramics and polymers, UV curing materials
Complex geometries with good resolution
Restricted material selection, resin is often expensive

8. Metal Based AM Comparison
AM technology publicizes less raw material waste compared to conventional machining
Cold Spray: Deposition efficiency and overspray can vary significantly based on material
Laser Applied Powder: Capture rates between 40% and 80%, depending on process conditions
Powder Bed: Un-sintered powder has potential to be reclaimed and reused - gives rise to additional questions of repeatability and quality
Wire Feed: Captures better than 90%, similar with ultrasonic; often requires post machining
Common constraints for each AM technique
Part Size: Powder beds limited in size, typically less than 12 inches, while wire feed can accommodate foot long sections or more
Build Speed: Powder beds often take many hours (often more than 24 for large structures), LAP may take up to 12 hours or more, wire feed less than 6 hours
Material Properties: Melting processes result in strength similar to cast, solid state processes (cold spray & ultrasonic) may be better
Deposition Rate
Feature Resolution
Laser Powder Bed
Electron Beam Powder Bed
Laser Applied Powder
Wire Feed Techniques
Cold Spray
Ultrasonic Fabrication 8

9. Typical Post Processing Requirements
Example: Powder Bed
Often overlooked aspect of AM: Post processing requirements
Stress relieving via heat treatment to prevent part distortion
Due to rapid cooling rates, AM parts often contain large residual stresses
Conducted while part remains affixed to build plate
Removal of part from build plate, typically via EDM
Heat treatment to reach required microstructure and mechanical properties
As deposited, AM parts often resemble cast microstructures
Directionality is common, with grain structures oriented in the build direction
May require HIP to reduce porosity and improve density
Homogenization and solution treatment to reduce grain orientation
Hardening/precipitation/strengthening/quench/temper heat treatment, as required
Finish machining to meet required geometry and tolerances
Peening, grit blasting, and tumbling to improve surface finish
Inspection for defects/flaws
Part distortion in laser applied powder after removal from build plate

10. Multiple Material Designs
Additive techniques offering multiple material solutions:
Injected powder laser additive (LAP, LENS, etc.)
Cold spray deposition
Ultrasonic consolidation
Multiple material part fabrication
Weight reduction
Light weight base/core material
Hard, wear resistant surface
Integrated component designs
Potential for advanced materials

11. Additive Manufacturing with Cold Spray
Potential for buildup of uniform section possible through proper gun manipulation
Support with sharp drop-off
CS deposit
Cold spray tensile sample, deposited on steel mandrel with engineered release layer
More complicated geometries possible through mandrel concept
Level of Finish Machining Required
Mandrel design
Material used
Dimensional requirements
Accuracy of spray path

12. Case Study: Optimization of Additively Manufactured Structural Mount
Component: Structural mount
Process: Cold spray additive manufacturing
Structural modeling & optimization indicate preferred geometry
Critical factors:
Material properties and layout
Process parameters
Structural performance
Geometric process characteristics…
Trapezoidal cross section θ1
Substrate is flat θ2
Substrate drops off 12

13. Additive Manufacturing Process Dependence
Different outcomes by process and properties
Design for the cold spray process using removable mandrel
Design for direct metal laser sintering (DMLS) powder bed process
Design conception for the laser applied powder (LAP) process 13

14. Suitability of Parts for Additive Manufacturing
AM makes sense for some, but not all components
Existing clear business case for using AM
Many processing steps, intensive machining
AM saves time, has less raw material waste
No existing business case, but redesign could create one
Current design more expensive with AM
Redesigned part could be more cost effective using additive technique
Consolidation of multi-part assembly into single component
No existing business case, low likelihood that redesign could impact
Low cost conventional processing (e.g., stamping)
Satisfactory performance
High part volumes required
Redesign may improve the performance independent of cost

15. Redesign for Additive Manufacturing
Parts suited for additive manufacturing may look different than traditional counterparts
Conventional manufacturing
Well-established limits in feature shape and complexity
Casting
Forging
Machining
Higher cost often associated with feature complexity and low weight
Additive manufacturing
New areas of design space
Often no penalty for more complexity
Possible lower cost associated with higher feature complexity and lower weight
Redesign for AM requires creativity and new ways of thinking

16. Additive Manufacturing Technique Selection
Some key considerations
Size of part
Geometric tolerance
Surface finish
Throughput
Geometric complexity
Feature size
Single- or multi-material
Mechanical properties
Microstructure …
AM technologies are rapidly evolving
Deposition Rate
Feature Resolution
Laser Powder Bed
Electron Beam Powder Bed
Laser Applied Powder
Wire Feed Techniques
Cold Spray
Ultrasonic Fabrication

17. Thank You