3D Printing (Additive Mfg.)

3D Applications - Curvilinear structures

- less reinforcement -Compliment natural surroundings, organic natural feeling -Requires skilled workers -Special geometry leads to compression loads which are distributed evenly compared to straight structure, minimizing buckling and collapse over long period.

For a one-story building CAD model, all the 2D layers which are generated after the 3D model slicing, are always the same.

False

What is the most common concrete pump type used in construction 3D printing?

Progressive cavity pump

3D Application - Unconventional geometries and aesthetically appealing landscape

- Architects convey views in complex geometry form that is difficult for conventional construction. Turn their dreams to reality.

3D Application - Infrastructure Development

- Bridge construction (prefabrication industry) - Wind turbine construction 1. cost effective, 2. safer, 3. (up to 200 m) Taller towers (currently 100m or less)

Video - 3D Printed House built in 24 hours

Mighty Buildings - Palm Springs Cali 15 3D printed homes w/ advanced tech and sustainability, printer operate in 600 x 800 ft space. Reduced waste through using just as much concrete as needed.

What is the hesitation for using 3D printing in construction?

• Scale - large construction projects vs. other industries not comparable (small objects) • Involvement of different trades - collaboration leads to productivity issues and resistance to change • Lack of trained and technical work force - civil and construction trades aren't embracing skillsets involved • Need to design new printable material which is structurally viable - properties • Reinforcement of 3D-printed material - how to insert

Challenges of SBCP

- Design of shootable but printable concrete mixtures - Material loss because of rebound of aggregate and fibers during spraying - Achieving the high quality printed material, especially on the surface

Binder Jet Printing Challenges

- High porosity of printed parts - High dosage of fine powder particles in the job sites - Low experience on the large scale implementation - More suitable for off-site and small-scale manufacturing, less researched in large scale compared to EBP.

3D Applications - Space Colonies

- The ability to fabricate extraterrestrial habitats, laboratories or manufacturing facilities is the key element for long-term human survival on the Moon or Mars. - resources (challenge) Special C3DP systems are being developed that exploit in situ resources and can utilize, for example, lunar regolith as construction material.

Applications of SBCP

- This method is the newest construction technique, and it is gaining more popularity for a specific application - This method also offers 3D printing of overhangs and vertical surfaces with a fast printing rate. - For the fabrication of slender fully reinforced freeform concrete elements, potentially at scale for larger construction

Explain Binder Jet Printing (BJP)

-More suitable for off-site and small scale mfg, -Layer-by-layer fabrication process through jetting (spraying) a liquid, binder or adhesive agent on powder-based material• ----The powder-based materials are fine aggregate or a mix of sand and binder needing to be activated by a proper agent.• ---Fine aggregate (i.e., sand) or a mix of sand and binder (i.e., cement) needing to be activated by a proper agent.

Identify the 9 applications of 3D printing in construction

1. On-site construction (in one shot) 2. Precast 3D printed elements (on-site assembly) 3. Construction of houses 4. Emergency housing 5. Infrastructure development 6. Unconventional geometries and aesthetically appealing landscape 7. Curvilinear structures 8. Functionally Graded Materials 9. Space colonies

What are the typical main subsystems of a construction 3D printing system?

3D printing robot, Material preparation, Material delivery, Control system

3 3D Printing Arm Classes

1. Gantry Systems 2. Stationary Industrial robotic arm systems 3. Mobile Industrial robotic arm systems

Stationary Industrial robotic arm systems Vs. Mobile Industrial robotic arm systems

• 6-axis industrial construction arm robots - Six degrees of free movement, including three translational movements in X, Y, and Z directions and three rotational ones- Different sizes of these robotic 2 classes: 1. Stationary robotic arms: larger and heavier arms - prefabrication, off-site 2. Cooperative mobile robotic arms: a series of smaller, lighter, and transportable robots, on-site work together, can scale up

Explain Powder Bed Fusion (PBF) and it's applications

• An energy beam (laser or electron beam) is used to selectively melt a powder bed. • Once a layer is scanned, the next layer of powder is spread via a rolling mechanism. The subsequent layer is scanned, and is fused to the previous layer. • Direct metal laser sintering (DMLS), selective laser melting (SLM) and electron beam melting (EBM) are the most popular metal powder bed fusion techniques, commercially available since 2005. • SLM units typically contain higher-powered lasers than do DMLS (1000 watts vs 400 watts). SLM heats the metal powder until it fully melts into a liquid. DMLS does not melt the metal powder, so less energy is needed. • These processes initially create a powder bed via rolling or raking the powder fed from cassettes onto the built table. • Through heating and melting the successive atomized powders such as stainless steel, DMLS and SLM utilize a focused laser beam while EBM using a scanned electron beam. • The actual building process is done in a vacuum or inert environment in order to avoid metal oxidation. • DMLS and EBM parts are fully dense with high specific strength and stiffness.

3 Major Differences concrete EBP vs. conventional FDM

• FDM - Scale Smaller, nozzle size and layer thickness important • FDM utilizes heat to melt plastics, concrete EBP process mechanism isn't thermal based, uses hydration properties and chemical process to harden material • Material properties and delivery

Binder Jet Printing (BJP) Applications

Application: Smaller scale construction - Building exteriors: it can be used to create large-scale and complex building exteriors, such as walls, roofs, and facades. - Bridges: it can be used to create customized and prefabricated bridge components, such as piers and arches, that can be easily assembled on site. - Concrete structures: The technology can be used to create custom-fit concrete structures, such as foundation walls and retaining walls. Like modular homes and offices. - Customized building components: The technology can be used to create customized building components, such as stairs, balustrades, and columns. - Stone and masonry: it can be used to create precise and intricate stone and masonry structures, such as sculptures and fireplaces.

The software workflow in construction 3D printing includes:

CAD model > 2D layers > Toolpath planning > Sending G-code file to the robot

What is the most important challenge in toolpath planning for multi-robot construction systems?

Collision avoidance

Construction of houses

Companies such s SQ4D in NY are demonstrating the fast construction capabilities. Took 2 days. ICON is biggest company pursuing this. Low income and affordable options. Non profits such as UN looking in to mass constructing utilizing 3D printing. Temp or permanent housing for homeless.

What are the main functions of an ideal software system for construction 3D printing?

Controlling, coordinating, and monitoring the sub-systems

What is binder jet prinking known as; where was it founded and by who?

D shape printing, particle-bed printing, Enrivo Dini - Italy

WASP 3D Printing Video

Eco Sustainable home created w/ crane gantry system where multiple are operating at the same time - Tecla - Wasp Italy 3D natural earthen materials, self supported

3 Different categories of construction 3D printing

Extrusion-Based Printing (EBP), Binder Jet Printing (BJP), Shotcrete-Based Concrete Printing (SBCP)

3D Applications - Functionally Graded Materials (FGMs)

Fabrication of, tailored properties changing in different parts of a material for certain circumstances within design Ex- transparent glass w/ seamless joint joining load bearing cementitious material. Ex Video - looking to control density of concrete to maximize weight vs. strength properties using bio inspired.

The positioning accuracy of gantry robots is typically lower than robotic arms (articulated robots).

False

Guest Speaker info

Focuses research on higher level of reliability and automation Ongoing research at LUS- studying the hardening properties of printing mixtures, structural properties of printing mixtures, anisotropic behavior of 3D printed specimens under different loading conditions - published a few days ago, automated quality control techniques to enable fully automated process( shape fidelity- as built vs 3D model) capture dimensions of printed in real time and compare to designed - LIDAR sensors automate curing systems, embedded sensors to track curing and strength dev - computer vision using 2D cameras Planetary 3D printing - landing pads, research facilities, habitats, mars materials, in situ material, high level automation, Martian clay sulfur concrete Higher levels of automation are needed to achieve benefits, need extensive research on performance and long term durability, not just building shell, roofing and finishing need to be implemented, advanced monitoring systems fiber reinforcement - longitudinal only, need vertical reinforcement - research on mini rebars Full automation ? Manual reinforcement, inspection and QC/ adjustments

3D Application - Emergency Housing

For victims of a natural or man made disaster. Emergency hospitals in pandemics in future. 3D printed fabrication for isolation rooms in China for COVID patients.

Explain Gantry Systems including 3 Disadvantages

Gantry-like overhead frames and rails to mount the mobile extrusion nozzle Example: Contour Crafting technique - Used for contour wall forms (CC) - large scale desktop 3D printer Disadvantages: 1. The large size of the system makes its transportation and setup process challenging, time-consuming and costly 2. No rotational movement only (x, y, z) simpler geometries 3. The size of the gantry frame should be larger than the structures (companies looking to make process workable and flexible)

3D Applications - Military

ICON 3D w/ USMC @ Camp Pendleton - Gantry system for small housing structures and vehicle garages.

Video - 3D Printing for Homeless in Austin

ICON building homes at scale, community first community for homeless

What is G-code and how is it used in 3D printing?

Instructions used in computer aided manufacturing to control the automated machine tools.

Why "rebar reinforcement" is not considered as an acceptable reinforcement technique in construction 3D printing?

It is very difficult to automate rebar installation, and manual rebar reinforcement is not compatible with an automated construction process.

Video - Printed Reefs to restore biodiversity - North Sea

Kattegat North sea experiencing low cod numbers -> eel grass is struggling - combatting ocean's ability to combat climate change w/ 3D printing

Video - Den @ Mars The Competition

Marscrete Materials: Basalt Rock, Kaolinite, sodium, silicon, Ice Designed building and process simultaneously using AI and BIM - constructability - first 3D building completed including the roof

Name two materials that Dr. Kazemian Developed in his lab for the space project.

Martian Clay , Sulfur Concrete

3D Application Offshore

Purdue-Offshore applications such as turbines. - Help rescuing and restoring marine environment through 3D printed reef systems w/ sustainable bio receptive materials

Kuka Video - Robotic 3D printing of concrete components

Robotic shotcrete- facility, "the concrete aeditor" since 2020, no formwork needed, robot also smooths out surface, CAN be used as structural load bearing structure elements, prefabricate + on-site

When and where was Shotcrete - Based Concrete Printing (SBCP) created?

SBCP was firstly proposed at the Braunschweig University of Technology in 2017

Contour Crafting Video Behrokh Khoshnevis - First on the World

The best application for 3D printing is construction, layer by layer. Barriers against implementation in building sector: conservative low profit margin regulatory inspection and QC processes labor unions building shell only

In one of the research by Dr. Kazemian, he embedded some sensors between the 3D printed layers. Justify what his primary goal of this experimental setup was.

Track setting times and measure dimensions

The solutions for which classic optimization problem is commonly adopted for toolpath optimization in construction 3D printing?

Traveling salesman problem

Delta 3D printers consists of three arms on rails that move up and down independently to move the printhead.

True

To accommodate new construction materials and methods (like 3D printing) which are not addressed in the International Building Code, the building code compliance can be approved through product testing in accredited labs in accordance with peer-reviewed acceptance criteria.

True

Name advantages of having 3D Printing in construction

fast, affordable, complex models, accurate, safer, sustaiable-> leads to productivity and effectiveness

Video- Core Winding Reinforcement for shotcrete

force flow oriented fibre integration, University of Braunschweig

Large Scale EBP in Construction consist of 6 parts

mixer, pump, hose, nozzle, printing arm OR 1. Computer 2. Robot Controller 3. Robot 4. Dual Mixer + Pump 5. Extruder 6. Printed specimen

3D Print prefab or on site depends on: (Guest Speaker)

project at hand, location, weather

What is Contour Crafting (CC) and when was it developed?

• CC is the first construction scale 3D printing technology developed by Dr. Behrokh Khoshnevis at the University of Southern California in 1996. • The CC technology scales up the additive fabrication process from building small industrial parts to constructing buildings, like houses. • CC is an emerging technology that uses robotics to construct free form structures by repeatedly laying down layers of material such as concrete • Different names: freeform construction, additive construction, construction 3 D printing. • In FDM scale is smaller • Possibilities don't include just concrete

5 Barriers for EBP Implementation

• Conservative Industry •Process reliability and robustness (limited projects thus far show issues) • Regulatory barrier in terms of strict construction regulations, 3D printing not included in codes and permitting • Building shell (walls) cost reduced only, other aspects aren't automated • Shift in inspection and QC, need to be revised and redesigned

Explain Extrusion-Based Printing (EBP)

• In EBP, structural elements are created layer wise deposition of fresh construction material from a nozzle along a pre-defined path. Concrete, mortar, or formable material. • Important examples of EBP are Contour Crafting (CC) and Concrete Printing (CP) • The most popular 3D printing methods in construction industry • On-site, pre-fab, and large scale mfg. w/ large components • Larger scale construction, safety, and material property research ongoing

Explain Shotcrete - Based Concrete Printing (SBCP)

• It involves spraying pre-mixed fresh concrete with high-pressure air (like the wet-mix shotcrete process) from the nozzle to create layer-by-layer objects • It would improve the compaction of freshly printed materials and leads to high interlayer bond and mechanical performance of final products

Explain Fused Deposition Modeling (FDM) and it's applications

• Material extrusion is material being extruded through a nozzle. • Typically, the material is a plastic filament pushed through a heated. • Common Applications: Prototypes, electrical housings, form and fit testing, figs and fixtures, investment casting patterns, houses, etc. • Strengths: Lowest cost 3D printing method, a wide range of materials • Fused Deposition Modeling (FDM) invented in 1988 by Scott Crump • Creating layers by mechanically extruding molten thermoplastic material onto a substrate • Polymer 3D printing by FDM is now the most widespread 3DP technology • FDM requires high operating temperatures and the printed part typically shows high porosities.

5 Benefits to EBP in construction

• No need for formwork - 30-50% cost is eliminated from formwork costs • faster construction • high degree of freedom for design without needing to simplify structure for cost reduction • Customization without added cost • Reduces environmental impacts, related to optimizing design reduces use of concrete, and waste from formwork