Self study quiz

• Additive Manufacturing refers to the process, in which the workpiece is built up in successive layers or units. It's called additive manufacturing when an object is made by adding material rather than subtracting or reforming it.

In Additive manufacturing, components are built up layer by layer and are not created by removing or reforming material as in conventional processes .

Rapid Prototyping and Rapid Manufacturing and repair

Customization, decreased costs, sustainability, efficient supply chains

Computer science, CAD technology, laser technology, material science

In the production of complex, individualized and small components as well as in small series production

Single-stage AM processes

Multi-stage AM processes

Material type

Machine architecture

Energy input strategy

Material state

Increasing product complexity and embedded functionality

Decreasing time to market

Aerospace

Medical / Dental

Motor vehicles

Consumer goods

A model is a representation of a product that is used to test and refine its design before the final product is produced. A prototype, on the other hand, is a working model of the final product that is used to test its functionality and performance.

Types: 1. visual model/ prototype, 2. functional model/ prototype

Tool that decomposes the component into individual layers.

Why: cutting of 3D geometry by planes with constant distance (=layer height)

• Layer-by-layer build process induces a geometrical error (steps in z-direction) -How: ➢Increased geometric accuracy ➢ Increased build time (= increased costs) 

Material Extrusion (MEX) (Metal and plastic)

Powder Bed Fusion with Metals (PBF-LB/M)

Vat Photopolymerization (VPP)

Material Jetting

Why: increases statik strength

Engürel heat dissipation

1. Necessity of support structure

2. Geometric accurancy

3. Surface quality

4. Mechanical properities

The number of layers and layers height

Active laser medya can emit radiation when their atoms drop from an excited energy state to a lower energy state. The energy between the two states corresponds to the energy of the emitted photon.

1. Reflection R

2. Refraction

3. Absorption A

4. Transmission T

The Rayleigh length (zR) is a parameter that describes the divergence of a focused beam of light.

There are 4 states of material (all metals) : plasma, gas, liquid and solid (crystallin or amorphous)

Effect is explained by the Drude theory of metals, also known as the electron gas

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+

• Electrons are delocalized which results in electrical and thermal conductivity

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+

• Electrons are present in a gas like state and interact with the positively charged ions → characteristic for each type of metal

+

+

• As the kinetic energy is higher than the electrostatic force of attraction

→ Particles repel each other

Cubic

Hexagonal

Tetragonal

Solidification

Thermal treatment

Cooling rate (size)

Crystallite shape:

planar

cellular

columnar dendritic

Microstructure in Casting

1. Outer equiaxed dendritic

2. Columnar dendritic

3. Inner equiaxed dendritic

Should have a defined and consistent particle size distribution.

Metal alloy composition should be well-defined and consistent.

Steel And iron-based alloys

Titanium and titanium-based alloys

Nickel-based alloys

Aluminium

Inconel is mainly used for high temperature applications. When heated, a thick stable oxid layer is formed, which protects the surface.Corrosion Resistance

Metal Powder Production

-Mechanical Crushing

-Atomization

-Electrolysis (rarely used)

-Chemical Reactions (rarely used)

Directed Energy Deposition (DED)

1. **Rapid Build Rates:**

2. **Material Variety:**

3. **Repair and Cladding:**

• 1 Laser-based Directed Energy Deposition

• 2 Directed Energy Deposition with an Arc

• 3 Cold Spray

WAAM = source of fusion, electric current And build rate, resolution, layer height bigger than DED-LB

DED-LB = source of fusion, laser

Cold Spray Additive Manufacturing

Source of fusion = Speed of gas

Feedmaterial = powder

Transport of Feedmaterial = Gas jet

Powder bed fusion processes are additive manufacturing processes in which thermal energy selectively and layerwise fuses regions of a powder bed.

As thermal energy, lasers or electron beams can be used.

Powder coating is a dry finishing process where pigment and resin powder, applied electrostatically, are cured on a surface at high heat for a durable and uniform finish, commonly used on metal.

Powder tank:

Powder is conveyed from above through a powder tank and then distributed by the coater, also tanks as part of the coater are established.

Dosing platform:

Powder is conveyed from the bottom to the top and distributed by the coater.

Scan strategies within one layer

Targeted influencing of the heat balance by adjusting the scan strategy

Scan strategies of different layers

• Compensation of anisotropic microstructure

• Symmetrical distribution of shrinkage and stress effects

• Control eigenstress and material density

1. Keyhole formation:

High intensities and powers cause vapor capillaries.

The process drifts off to a deep penetration welding process

The consequences are overheating and development of gas pores.

1. (welding depth bigger than width of the weld pool) t/b > 1

keyhole formation

gas pores

balling

lack of fusion

• lack of fusion exposure speed + Beam power -

• the keyhole effect exposure speed - Beam power +

Layer by Layer build up

• Material used : Metal Powder

• high tempereture necessary for AM of metals

• laser is used at the main heat source

• Reduced Material waste: unmelted powder is removed

Build process = layer-by-layer additive technique in vacuum

Source material = powder: metal alloys

PBF-EB/M process runs under high vacuum, since the electron beam can only be operated in this atmosphere

→ no protective gas flow but high vacuum

Fusible: eriyebilir, soluble: çözünebilir

Amorphous: low E-Modulus, transparent, no structure, soft

Semi-crystalline: high E-Modulus, partly structured, hard,

MEX: Thermoplastic polymers, Composite filament

PBF - LB/P: Plastic powder, filled Plastic Powder.

Plastic powders often exhibit (sergilemek) better flowability and self-supporting properties compared to metal powders.

Plastic Powders have besser stabiliy in powder bed.

The isothermal laser sintering model processes semi-crystalline thermoplastics in a specific temperature range, allowing the material to be both molten and solid simultaneously in part building.

Impacted by the energy density: Layer Connection

Energy density too low: Bad Surface finish

Energy density too High: Smoke and decolorization / yellow regious

Vat Photopolymerization = liquid resin

Binder Jetting = liquid powder, binder

Material Jetting = liquid resin

1. Digital light processing VPP

2. Laser Vat Photopolymerization

Direction of incident light:

Free surface approach: light from up

Constrained surface approach: light from down

CLIP has less steps. It skips on steps like Separation, Re-Coating and Re-positioning.

advanced light and oxygen control

Machine

Process

Heating conditions

Powder

Limitations

• Lower temperature resistance

• Materials slightly brittle (thermosets)

• Low UV-resistant (embrittlement and discoloration possible)

• Restrictions in the geometric freedom

DED