MECH502

Consider infill paths A and B. Which infill will produce a smoother outside surface on this part (the upper most face, facing upward, in these figures)?

(No overlap)

7 different AM process Categories

1. Binder Jetting 2. Direct Energy Deposition 3. Material Extrusion 4. Material Jetting 5. Powder Bed Fusion 6. Sheet Lamination 7. Vat Photopolymerization

General AM Process

1. Engineering Design 2. Pre-Processing 3. Additive Manufacturing 4. Post_Processing

FFF (Evolution and Impact)

1988 - First prototype developed & patented (1989) as FDM by Scott Crump, founder of Stratasys, in the 1980s Idea came to Crump as he was creating a toy frog for his daughter using a glue gun 1990s - First commercial system available 2003 - FDM became the largest Additive manufacturing process 2012 - Stratasys merged with Objet 2013 - Stratasys acquires Makerbot 2014 - Stratasys 3d printed the exterior of an electric car with Objet1000

When testing bending stiffness of a 3D printed ceramic object which type of testing is best?

4-point bending

An Andrew Number is...

A measure of applied energy density in powder bed fusion printing

Photospeed is...

A measure of how quickly a photopolymer cures

The term "Dynamic precision" refers to...

A measure of the smallest feature a particular printer can create with its most accurate material, all other factors being held constant

Topology Optimization is...

A method of reducing the weight of parts

In the context of 3D digital modeling, what is a "manifold" model?

A model that is completely closed between the inside of the model and the outside. If it were a physical object, it could hold water.

Additive Manufacturing

Additive manufacturing represents processes where we transform the part from Form A (most of the time 'nothing') to Form B by addition of material. The fundamental concept is that we augment the volume of materials throughout the process. Composite manufacturing, 3D Printing, SLS, SLA, FFF are examples of Additive Manufacturing processes

Which of the following statements are true about CLIP technology?

All above choices are true about CLIP.

Which type of sintering is characterized by the coalescence of powder particles of more than one material without full melting?

All of the above: Indirect sintering, liquid phase sintering, chemically-induced sintering

This object was printed using melt extrusion. Your boss is in a hurry (as always) and wants to keep costs down (as always). You are told the object will be stressed in tension in unknown directions. Being aware of the time and cost needed to do adequate tensile testing to achieve statistical significance, which of the following directions would you recommend doing tensile testing on this object?

All three directions (X, Y, and Z) independently

Which of the following structures would be the toughest (as in its structural material property)?

BRICK

Why is it so difficult to print an object using viscous extrusion that is both high resolution (minimum feature size) that is strong and/or tough?

Because the materials need high content loading to be strong/tough, which results in high viscosity && Because high resolution requires a small needle (orifice) radius

You friend shows you this statue that someone 3D printed and wants to know what 3D printing process was used to make it. It is full, continuous color and has a granular surface. It's fairly heavy because it seems to be solid material, not hollow. (Wedding)

Binder Jetting

Direct sand castings are most often made using which AM Process?

Binder jetting

The name of the additive manufacturing process in which a liquid bonding agent is selectively deposited to join powder material is:

Binder jetting

Your colleague asks you which AM process was most likely used to make this object. It has a rough, grainy surface that appears to have been post-processed with a coating that gives it the shine you see. What do you tell her? (see heart model image on desktop)

Binder jetting

Build Orientation

Build orientation focuses on the virtual & physical placement of the part on the build platform. It is very important and have effect on multiple parameters like build quality, material properties of the printed part & even speed of manufacture. It has to be understood that slicing and build orientation depend on each other. Build orientation can have significant impact on how much support material/structure is needed. An experienced engineer can save significant rework and material waste by strategically using build orientation to optimize the support needed for overhangs and such.

Your boss wants a part as soon as possible that you make using your photopolymer printer. Which of the following would increase the scan speed in a photopolymeric AM process?

Buy a material that has a lower critical exposure with other properties as similar as possible

New/Other Am methods

CLIP: photopolymer curing w/ oxygen permeation control light is slower 50x faster oxygen inhibits free radical polymerization ofo acrylates - note - this requires acrylates 25-1000mm/hr control of - speed of print and resolution Mark forged: melt extrusion continuous composite as well 2.5D metal nano particles in polymers Voxel-Based define volume instead of surface middle step HP - Multi Jet Fusion biner -> detailing agent -> sinter -> chemical sinter -> thermoplastics (PA12 and PAnylon) Desktop metal single pass process binder jetting -> debinding (sinter prep) -> sinter

Your boss emails you the following picture and asks you how this object was made using additive manufacturing. The part is made of a ceramic composite. The following lists AM Processes you have available in your company. Which of the following is the best answer to the question?

Choices (a) or (c) could have made this object, but (a) is the better choice if it is available.

The new 3MF file format supports which of the following characteristics of a model:

Color & material type, Curved triangles, Instancing of structures like unit cells, are all supported in 3MF

Which set of metrics lists two of the most important considerations when deciding to make a product using additive manufacturing, or if subtractive or formative manufacturing may be a better choice?

Cost per complexity, Cost per quantity

You are making a photopolymeric part for a paying customer and you run out of material. So you buy some replacement material. You want to be completely certain the new material will perform exactly the same as the prior material you were using, in the same printing conditions. What should you do?

Create a working curve for the new material and compare it to a working curve of the prior material.

Your boss emails you the following picture and asks you how this object was made using additive manufacturing. The part is made of a ceramic slurry. Which AM process was most likely used to make this object? (see small scaffold image on desktop)

Direct-write

Which AM process is most often used to enable variable metallurgy of custom metal alloys and functional grading of material properties within a single part

Directed energy deposition

Your colleague asks you which AM process was likely used to make this object. You can easily see its corrugated, shiny surface that the technician says is direct from the printer (i.e. there was no post-processing on these parts), and your analysis lab says the parts are fully-dense. What do you tell her? (see boeing image on desktop)

Directed energy deposition

Generalized AM process (Engineering Design)

During the engineering design phase, specific limitations of AM have to be considered (e.g., support structure). • Create CAD file • Create STL-Data file

Extrusion Based Systems

Extrusion - like forming modular t slot melt extrusion "ram" - lost cost, low precision head - feed controlled 1) screw extrusion 2) ram 3) gas pressure head weights and build size effect of precision How filament made? helical worm gear -> compression -> filament out -> buy -> print

FFF (Application)

FFF can produce a variety of parts & products with a broad range of applications, ranging from designs, to prototypes & functional parts. Industrial Automotive: transparent front/back light covers, mirror casings, etc. Aerospace: lightweight composite (complex) parts

True or False: Bioprinting usually uses a jetting process with a very fine spray of material.

False

True or False: Solid-state metal powder sintering uses two different metal powders with nearly the same glass transition and melting temperatures

False

True or False? A material with a relatively low heat deflection temperature would require more thermal energy to extrude.

False

True or False? Our guest speaker from General Motors said they expect 98% uptime from all their equipment, including additive, and they can usually achieve this goal with their additive manufacturing machines.

False

Minimum self-supporting angle

For Fused Filament Fabrication(FFF) features, it is necessary to set a minimum inclination angle to ensure that angled faces will not collapse without support material.

Maximum vertical aspect ratio

Fused Filament Fabrication (FFF) feature cannot have a vertical aspect ratio exceeding a maximum value. The aspect ratio is defined as the proportional relationship between feature's height and width. Continuation of the recoating process will eventually result in the feature's bending.

unstopped feature

Fused Filament Fabrication (FFF) cannot extrude material above open air, so it requires external support structures for overhang, bridge and horizontal hole. The figure below shows these three types of unsupported features, and the red arrows mark the decisive dimensions involved

FFF (Process)

Fused Filament Fabrication (FFF) is "a material extrusion process used to make thermoplastic parts through heated extrusion and deposition of materials layer by layer." Other commonly used and closely related terms are: Fused Deposition Modeling (FDM) (© Stratasys) FFF processes are widely in use due to relatively low initial cost of the system, availability of low cost materials and low maintenance

Grouping/Nesting

Grouping describes the strategic arrangement of different (or multiple of the same) parts of an assembly to be printed in one setting. Well placed parts during grouping can significantly enhance the output of the AM process. Badly placed parts can not only 'waste' valuable AM capacity but also cause built quality problems. An example of such an arrangement that can cause quality issues is placing parts too closely together. Depending on the process (e.g., SLS), the dispersed energy can negatively effect the material property of too close placed part.

SL (Application)

High build quality and a increasing variety of materials in combination with multi-material prints allow for a wide variation of applications. Visual prototypes Great surface finish / variety of materials Full engine design prototypes Some (fully) functional parts Industrial casting molds Materials can be cleaned and reworked - therefore, parts with (micro) structures are possible. Test/functional prototypes Medical applications (e.g., test models for surgeons) Dentistry

Pros Additive Manufacturing

High degree of flexibility Ability to manufacture complex, near-net shapes Ability to manufacture assemblies Low ramp-up investment Reduced lead time Ability to manufacture multi-material/multi-color parts* Excellent mechanical properties* Little/No wasted material

In powder-bed fusion, a "Melt Flow Index" is used to help determine...

If powder is reusable

Minimum Spacing

In powder bed fusion (SLS/SLM) processes, if two surfaces are too close to each other, heat from one side may influence the properties of the other side. Therefore, it is necessary to specify a minimum spacing between two different surfaces.

Minimum Feature size

In the additive manufacturing process, thin wall or small size structures are subject to significant thermal dissipation, which may cause various defects, such as un‐melted powder inclusions, internal voids, cracks and shape irregularities. Therefore, it is necessary to specify a minimum dimension for thin wall and holes.

Generalized AM process (Pre-Processing)

In the preparation (pre-processing) phase, it has to be checked if design contains critical flaws (e.g., gaps). • Preparation of files (e.g., close holes, support structure) • Extracted layered model of design

A scan pattern is used to...

Increase layer adhesion, Minimize the amount of uncured resin, &reduce the amount of part distortion.

What is the best approach to decrease the total print time for a photopolymer part that you have printed before, maintaining its exact mechanical and behavioral properties and high precision?

Increase the scan speed and increase exposure

Which type of sintering is characterized by the coalescence of powder particles of more than one material, without full melting?

Indirect processing, liquid phase sintering, and chemically inducing sintering

Sheet Lamination

LOM - laminated object manufacturing bonding, -glue, thermal hold (plastic), clamping, ultrasonic welding "Bond the form" - (less popular) no heat to cut non toxic, low cost have to "dig out" inside no overhangs "Form the bond" fully dense arts materials paper, plastic, metal?, ceramic, composites ballistics, DOD, embedded systems

Considering the process parameters controlling material flow in melt extrusion-based systems, if you want to minimize the attachment/adhesion of support material at the interface regions (between model and support material), assuming primary support material, the best approach would be:

Make print/scan speed faster when printing the interface regions than when printing anything else, all other parameters stay the same

One of your colleagues is asking you how to get good bonding between layers in a photopolymer process. Of course you want to give good advice, so you say...

Make sure your cure depth is about 30% greater than layer thickness

Cons Additive Manufacturing

Not economical for large batch sizes Manufacturing time required high* Skill and expertise needed to prepare design Requires post-processing (e.g., removal of support structure) Materials available limited & expensive (improving!) Systems (and maintenance) cost is high (improving!) Limited mechanical properties* Some waste materials can be hazardous*

Powder Bed Fusion

Nylon Pa12 metal 3d printing began here roller -> laser sinter CO2 laser - sinter fibre laser - melt (40 um scan width -& 10um spot size) galvometric control heated enclosured to 40C less than Tg Post Process support down to table - b/c warping EDM to remove bead blast or material finish Powder Fusion full melt - direct laser melting deeper than layer thickness Sintering - 0.5Tm < T < Tm driving force: like water droplets coming together varying porosity b/c layer energy drop "green parts" - only sintered then HIP to get 99.7% dense Direct sinter - 1 material, homogenous Indirect - 2 materials, eg. Nylon + Ceramic - sinter nylon, not hot enough to ceramic Variants: low temp laser - optimal for polymer sintering only high temp laser ground part to bed inert atmosphere 10 MW laser vacuum radiative or resistant heater Electron Beam Melting electron interact w/ gases mag field control (galvanometer?) part conductive potential negative charge could build can heat by going out of focus Andrew number Powder Recycling: fraction mixing fine sives -> blower -> light particles go further -> cutoff Melt flow index - can tell us if powder is reusable

Topology Optimization

Optimization of topology space based on functional requirements Shape is no longer the initial step, but rather the boundary conditions and mating/matching surfaces Algorithms to interpret the 'grey' matter, enhancing the performance of final part (stiffness and strength)

FFF (tools)

Overall FFF is comparably low-cost / maintenance and thus most wide-spread Most common & available FFF system: MakerBot Replicator (various var.) can be bought 'everywhere', e.g., Sam's Club (2016) Resolution: 100 microns Building Vol: Z18 11x12x18 in to mini+ 4x5x5 Variety of materials available (D=1.75mm) Comparable low-cost (~$500 - $5,000) / Ease of use (offer own software suite) / plug'n'play Commercial systems (~$25,000 - $100,000+) like Stratasys Fortus 900mc allow for: Larger build area (36x24x36 in) More variety of materials & thus material properties Smaller tolerances (=/- 0.0015 in/in) / build quality Faster throughput

Which additive process involves the use of light to cure/harden a liquid polymer?

Photopolymerization

Laser melting is a type of which of the following additive processes?

Powder Bed Fusion

An artist wants to know what 3D printing process was used to make the artwork in this picture. It's some type of plastic, about 8 inches tall and has a granular surface. The chain of caged-ball structures fully articulates (the balls are loose in the cages). Considering the fine detail of the chain and the other complex, interchangeable (on lego bases) articulating objects in the piece, it appears to have a high precision of about 30 microns. What type of printer would you most likely need to make this object in the same material?

Powder Bed Fusion - sintering

Your boss wants to buy the company's first commercial printer that can make the widest variety of true 3D parts at precisions down to 30 microns in the widest variety of metallic and polymeric materials. Nylon would work well for most of the parts you want to make. What type of printer from the following list do you recommend?

Powder Bed Fusion - sintering

Your colleague asks you which AM process was most likely used to make this object. He tells you it's made of fully dense titanium and has a rough, grainy surface. What do you tell him?

Powder bed fusion

Of the following, which Am process is mot often used to create production parts that have more than one material in a single part (i.e. NOT one material in each of multiple parts of a build)?

Powder bed fusion - indirect processing

SL (Tools)

Previously, Stereolithography systems were comparably expensive and required high maintenance. In recent years, a few lowcost, low-maintenance systems emerged) Desktop variants (e.g., Formlabs Form1+/2) Low-cost (~$3,000 - $7,000) Resolution (layer thickness): 25 microns Building Vol: Form2 13.5x13x20.5 Expensive and limited material availability Commercial/Industrial systems High cost Investment (~$50,000 - $1,000,000+) Maintenance: (~$89,000/year*) Example 3D Systems ProX 950 Large build area (59x30x22in) Accuracy 0.001 mm

Which set of characteristics provides the best list of the things to consider when deciding which additive process to use to make a particular part?

Purpose of part (e.g. functional requirements), material requirements, size of part

SLS (Tools)

SLS tools are some of the most expensive and complex variation within the AM space. Just now, first lower-cost variants (e.g., Formlabs Fuse1 or Sinterit Lisa) are announced (pre-order) to entry prices around ~$13,000 - $$15,000. Commercial/Industrial systems High cost Investment (~$250,000 - $1,000,000+) Maintenance (~$30,450/year*) Example EOSINT P760 (~$800,000) Medium build area (27.6x15x22.9in) Limited selection of materials Good resolution/layer thickness (min. 0.0024 in) / build quality

SLS (Application)

SLS, allowing for a wide variation of materials, (surface) finishes and high accuracy leads to broad applications. Possibility to directly create fully functional parts/products from metal, ceramic or polymer with good material properties Industrial Automotive: Engine parts

SLS (Process)

Selective Laser Sintering (SLS) is "powder bed fusion process used to produce objects from powdered materials using one or more lasers to selectively fuse or melt the particles at the surface, layer by layer, in an enclosed chamber." Other commonly used and closely related powder bed fusion processes are: Selective Laser Melting (SLM) Direct Metal Laser Sintering (DMLS) Historically, SLS and SLM are often used to describe the same process - however, some argue that SLS is associated with polymer/ceramic powders while SLM focuses on metal powders

The material shown in this image changes shape in response to changes in temperature. What type of material if the object printed with?

Shape-memory

Slicing

Slicing transforms the solid CAD model of the to-be-manufactured part to the set of individual layers that will ultimately make up the part & defines the tool path. There are various software solutions available that aim to support the engineer during the slicing process & decision (freeware: Cura & Slic3r). There have to be some decisions made that have an impact on the final outcome of the part (printer speed

Consider photopolymer Working Curves A and B in this figure. Which photopolymer will polymerize at a lower exposure

Steeper Slope boi

SL (Process)

Stereolitography (SL) is "a vat photopolymerization process used to produce parts from photopolymer materials in a liquid state using one or more lasers to selectively cure to a predetermined thickness and harden the material into shape layer upon layer." SL processes can manufacture products/parts with high surface quality from many materials. Originally mainly used for design and/or test prototypes, today there are applications where a fully functional parts/products. Often are considered one of AM processes with highest (yearly) maintenance effort/cost.

Our guest speaker from Otterbox made which of the following important comments about their ability to produce crystal clear, completely transparent parts?

The can get transparent parts by polishing the printed part, but it only stays transparent for a short while before yellowing.

The slope of a photopolymer's working curve represents...

The distance a given irradiance will decrease by an amount equal to the half-width of the gaussian, as it penetrates a given photopolymer

curing time

The length of time it takes for paint or varnish to "set" or reach its ultimate, stable state.

The terms "precision" and "resolution" are used interchangeably to refer to:

The smallest feature that a particular 3D printer can print, independent of any particular material.

4D or "smart" polymers respond to which of the following stimuli:

Thermal, pH, and Electric

Why does one use "location targets" in scanning?

To provide reference registration points to help the software fit surfaces together

True or False: Hot iso-static pressing (HIP) is a method for densifying metal parts created with powder-based fusion processes.

True

True or False? A material with a relatively low thermal expansion coefficient would provide a more accurate part (printed part matches CAD model), all other factors being equal.

True

True or False? Durometer is a measure of resistance to deformation in elastomeric objects.

True

Your boss emails you the following picture and asks you how it was made using additive manufacturing. He is amazed that the object is 10 µm long and 7 µm high, made of urethane acrylate. What is most likely the AM process used to make this part? (see 2 photon bull image on desktop)

Two-photon photopolymerization

Fusion/Consolidation

Usage of lasers, electron beams, extrusion heads to create the localized solid entity

Cut/restart

Usage of mechanisms and cutting knives that enable the cut/restart process

Motion Control

Usage of mechanisms to ensure deposition/addition location and feedback to system

Pressure

Usage of pressure mechanisms in certain processes to 'sinter' components

Containment Chamber

Usage of volume separation to contain heat/cold depending on process. I.e. Cold chamber manufacturing.

In which of the following processes do you need support material to hold the part up while it solidifies?

Vat Polymerization

Your boss wants to print electronic circuitry directly and conformally onto non-planar surfaces. You have the following AM processes available in your company. What do you tell her?

We could use: (Our Direct Write printer will work), but (The Aerosol Jetting printer will do an excellent job with these circuits.) is more precise

Which of the following terms is used to characterize the difference between the dimensions of an as-printed part and the dimensions of a digital, as-designed (CAD) part?

accuracy

Liquid Photopolymers

are available in a basin and are cured into solid polymers by means of laser constitutes the family of Stereolithography (SL) (sometimes referred to by the machine producing it as Stereolithography Apparatus (SLA) ) ... are typically a mix of monomers with oligomers and photoinitiators. ... are the raw material for the stereolithography process that solidify when cured by exposing them to UV light - typically using a UV laser - and thus become polymers. ... are rather costly, however with a decreasing tendency. For liquid photopolymer a wide variation of specialized materials are trademarked and available only from the respective provider: CeraMax (© 3D Systems): ceramic-reinforced composite EPU60 (© Carbon): Elastic Polyurethane (EPU) 18420 by SOMOS: Allows creation of RTV moulds etc.

Bio Printing

biomimicry - form not function direct writing importance in bioprinting - curve surface/circuitry

buid vol vs bounding box

build vol - max size of printable volume for printbounding box - smallest box size to fit a part inside

Bulk vs structural properties

bulk - raw materials structure - properties of mat'l's structure

Photopolymerization

can't print in color - brittle

Direct Write System

circuits small scale viscous extrusion collodial inks w/ metal nano particals - caulk on table - flattens like solder meltings + fine line - non planar large variation of materials - tough post processing - chemical 98% density - 60% ceramic robo casting - meh quill type - super super micro scale aerosol systems - automixation curved surfaces - strain gauges

Viscous Extrusion

delivery systems: merged delivery - calcium phosphate + phosphoric acid Solidification processes - maintaining size and shape of road gravity, surface tension, cooling material nonlinear effect nozzle geometry - temp, shear, material profile temp - convection and conduction - bw roads and environmental conditions u_PLA > u_ABS -> need high P for PLA Pressure die sweel ooze road spreading - lower alpha -> more spreading nozzle interaction -> error propagate -> gross corners of prints Bonding of layers - thermalls driven sintering process

Material Jetting

droplets of build material are selectively deposited

Direct Energy Deposition

focused thermal energy is used to fuse materials by melting as they are being deposited

Direct Energy Deposition

fully dense material melted multi nozzle - can gradient material materials - weldable are best; gold - bad; high k - bad; no plastics Powder Feed Systems excess powder common less warpage/shrinkage HIP to densify (hos isostatic press) Wire Feed Systems 100% efficiency simple geometry cladding can make very large parts - rocket nozzle Notes: low resolution, high part cost, gast, gradient microstructure, machine post processing, residual stresses

high level considerations

life cycle -shelf life duty cycle - durability physical factors mechanical, stiffness precision - min feature size color/transmissivity - discrete or full color? behavior properties - chemical, optical, thermal, electrial magent environment? - chem resistant temp

Binder Jetting

liquid bonding agent is selectively deposited to join powder materials."

Vat Photopolymerization

liquid photopolymer in a vat is selectively cured by light-activated polymerization.

Material Extrusion

material is selectively dispensed through a nozzle or orifice.

foam vs lattice structure

random, stoic -controllable - stucture width posisty and heights etc - known stress strin curve to FEA

Sheet Lamination

sheets of material are bonded to form an object

Photopolymer Systems

solidify with radiation still need support material transparent polymer ideal to improve cutting scanning - vector scan, mask projection downward vs upward projection 2 photon - 1 not strong enough, 2 is - 200nm material acrylates - most popular epoxy vinylethers high accuracy good surface finish Curing Eqns spot size, irradiocce, line width curing depth, Ec

Filaments

that are introduced by an extrusion head, and fused together constitutes family of FFF Filaments are widely available in a range of different qualities and prices Common filament materials: Polylactic Acid (PLA) Acrylonitrile Butadiene Styrene (ABS) Other filament materials: Nylon / Reinforced nylon / Metal / carbon fiber / ... Polyethylene Terephthalate (PET) / Poly Propylene (PP) / Thermoplastic Polyurethane (TPU) Common filament sizes: 1.75mm 3mm

Powder

that are spread and fused together using a laser or electron beam constitutes family of Selective Laser Sintering (SLS) Metal powder as a raw material for SL are increasingly available yet still expensive Depending on process, there might be certain safety precautions necessary Common metal powder variations: Aluminum alloys Cobalt based alloys Nickel based alloys Stainless steel / Tool steel Titanium alloys Common other powder variations: Ceramics (e.g., Silicon Carbide (SiC) ) Polymers (e.g., Ultrasint PA6 - X028)

Powder Bed Fusion

thermal energy selectively fuses regions of a powder bed

cost of ownership

true cost - install +mat'l + initial cost+ disposale

Generalized AM process (Post processing)

• Remove support structure(s) • Add. processes to achieve, e.g., tight tolerances (machining/grinding), desired material properties (sintering), surface finish (polishing/painting)