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Thursday, June 16, 2016

CONTOUR CRAFTING

1. INTRODUCTION
Since the early years of 20th century automation has grown and prevailed in almost all production domains other than construction of civil structures. Implementation of automation in the construction field has been slow due to:a) Unsuitability of available automated fabrication technologies for large scale products b) Conventional design approaches that are not suitable for automation c) Significantly smaller ratio of production quantity/ type of final products as compared with other industries d) Limitations in the materials that could be employed by an automated system e) Economic unattractiveness of expensive automated equipment.
Current construction industry still remains labor intense and craft oriented industry. It causes several problems in the areas ofproductivity, quality, safety and skilled labor shortages. In order to overcome these issues, various types of automation and robotics technologies have been proposed and implemented. Automation of various parts and products has evolved in the last two centuries. The various conventional methods of manufacturing automation do not lend themselves to construction of large structural members. A promising new automation approach is layered fabrication, known as rapid prototyping. The current layered fabrication methods are limited by their ability to deliver a wide varieties of materials to the construction.
 Currently Contour Crafting (CC) seems to be one of the layered fabrication technology that is applicable to construction of large structures such as houses. The construction automation will require a paradigm shift in process technology. The Contour Crafting construction process, fits in this category and has the potential to revolutionize the industry, changing it from the conventional “cast-in-place” paradigm to a layer by layer approach.

2. CONTOUR CRAFTING
Contour Crafting is a building printing technology being researched by Behrokh Khoshnevis of the University of Southern California’s Information Science Institute. Khoshnevis stated in 2010 that NASA was evaluating Contour Crafting for its application in the construction of bases on Mars and Moon. After three years, in 2013, NASA funded a small study at the University of Southern California to further develop the Contour Crafting 3D printing technique.
Contour Crafting is an additive fabrication technology that uses computer control to exploit the superior surface-forming capability of troweling to create smooth and accurate planner and free-form surfaces. The key feature of Contour Crafting is the use oftwo trowels, which in effect act as two solid planer surfaces, to create surfaces on the object being fabricated that are smooth and accurate. The craftsmen have effectively used simple tools such as blades, trowels, putty knives with one or two planer surfaces for forming materials in past form since ancient times. Surface shaping knives are used today for industrial model making.
In CC, computer control is used to take advantage of the superior surface forming capability of troweling to create smooth and free-form surfaces.  The layering approach enables the creation of various surface shapes. It is a hybrid method that combines an extrusion process for forming the object surfaces and injection process to build the object core.

Fig 2.1 Simple Historical Construction Tools
The extrusion nozzle has a top and a side trowel. As the material is extruded, the traversal of the trowels creates smooth outer and top surfaces on the layer. The side trowel can be deflected to create non-orthogonal surfaces. The extrusion process builds only the outside edges of each layer. After completion of extrusion each closed section of a given layer, if needed filler materials such as concrete can be fill in the area defined by the extruded rims.



Fig 2.2 Contour Crafting Process

2.1. CONTOUR CRAFTING TECHNOLOGY
            Extensive experiments have been conducted to configure the CC process to produce a variety of small and full scale object. Small 2.5D and 3D parts with square, convex and concave features have been fabricated from a variety of thermoplastic and ceramics materials. A limited axis but larger machine was then developed to demonstrate the possibility of fabricating full scale concrete structures. Standard houses can be built by integrating the CC machine with a support beam picking and positioning arm to place beams for roofs. The structure can be built without external support elements using shape features such as domes and vaults. The operation of CC machine for building a house can be light weight and easy to transport and quickly assemble and disassemble by small crew. The operation may be fully automated requiring minimum supervision.
            In CC, computer control is used to take advantage of the superior surface forming capability of troweling to create smooth and accurate planar and free-form surfaces. The layering approach enables the creation of various surface shapes using fewer different troweling tools than in traditional plaster handwork and sculpting. It is a hybrid method that combines an extrusion process for forming the object surfaces and a filling process to build the object core.

Fig 2.3 Application of CC in House Construction


Fig 2.4 Structures Built By Contour Crafting
Some interesting aspects of this automated construction concept include:
·         Maximum flexibility for architectural design allowing custom designs to be fabricated directly from computer model of the building.
·         Possibility for automatic imbedding of plumbing, electrical and communication networks.
·         Dramatic impact on cost and speed (a 200 m2, two- story house may be built within two days).
·         Simplicity of construction logistics and management.
·         Friendliness to the environment due to low emissions and waste less operation.
·         Significantly reduced energy usage compared to manual construction.

2.2 Integrated Contour Crafting System
An integrated CC system includes a control module, a geometry analysis module, a planning and optimization module and a presentation module. The control module is a digital control of the Contour Crafting machine. The geometry analysis having structure feasibility analysis and support structure generation to annotate the original geometry. The planning and optimization module includes tool path planning, multi-nozzle coordination and other operational issues. 3D presentation and real time simulation functions are included in the presentation module. The machine task sequences are fed to the Contour Crafting machine for construction execution after process planning, optimization and simulation.

3. CONTOUR CRAFTING PROCESS
The CC process is based on an extrusion and filling process The extrusion process forms the smooth object surface by constraining the extruded flow in the vertical and horizontal directions by trowels. The orientation of the side-trowel is dynamically changed for better surface fit.
The side-trowel allow thicker material deposition while maintaining high surface finish. Thicker material deposition cuts down manufacturing time. It is essential for building large- scale parts using the additive process. The maximum deposition of layer thickness is limited to the trowel height.
As the extrusion nozzle moves according to the predefined material deposition path of each layer (rims) are first created. The troweled outer surface of each layer determines the surface finish quality of the object. The top surface of each layer is also important for building a strong bond with the next layer. The boundaries of each layer are created the filling process begins and material is injected to fill the internal volume.


Fig 3.1 Multiple Nozzle and Single Nozzle Assemblies

The basic idea is that the extruder goes around the building’s margins to construct the walls. When one layer is over it automatically moves up to build the next layer. It will be done slice by slice until it reaches the desired height. Other materials like roofs, pipes and window frames will be placed by another robot on the gantry. It will simply pick up the materials and place them on the right time. In the case of glass windowsstill need human labor because of its fragility.
            There are two key parts that make Contour Crafting superior to any otherlayered fabrication technology. The two trowel create buildings with remarkable smooth surfaces while eliminating any trace of the layers. Depending on the shape and the angle between the trowels, various designs can be built. The quality of construction is much superior and flexible in making any kind of building.
To create a building with Contour Crafting, engineers or architects must design the buildings in CAD. Then the design are analyzed and verified by civil engineers, and should pass all the governmental regulations. The materials for construction may differ according to the characteristics of the terrain, cost-effective supplies of the materials and type of the structure.

4. APPLICATIONS OF CONTOUR CRAFTING
Contour Crafting technology is relatively straight forward and simple. The significant benefits of Contour Crafting are short construction times, no human workers, cheaper cost and flexible of materials. These characteristics gave researches several brilliant applications.
·         Application in construction
·         Commercial applications
·         Low-income housing
·         Emergency housing
·         Space colonies

4.1 APPLICATIONS IN CONSTRUCTION
A single house or a colony of houses, each with possibly a different design can be automatically constructed in a single run using Contour Crating technology. Conventional structures can be built by integrating the CC machine with a support beam picking and positioning arm and adobe structures. It may be built without external support elements using shape features.
Design flexibility: The process allows architects to design structures with functional and exotic architect geometries that are difficult to realize using the current manual construction practice.
Multiple materials: Various materials for outside surfaces and as fillers between surfaces may be used in CC. The quantity of each material may be controlled by computer and correlated to various regions of the geometry of the structure being built.

Fig 4.1 Construction of Conventional Buildings Using CC
Utility conduits: Utility conduits are built into the walls of a building structure precisely as dictated by the CAD data.

Fig 4.2 Complex Wall Section

Fig 4.3 Construction of Adobe Buildings Using CC
Paint ready surfaces: The quality of surface finish in Contour Crafting is independent of the size of the nozzle orifice. Sand, gravel, reinforcement fiber and other applicable materials available locally are mixed and extruded through the CC nozzle. The surface quality in CC is such that no further surface preparation would be needed for painting surfaces.
Smart materials: The deposition in CC is controlled by computer, accurate amount of selected construction materials such as smart concrete may be deposited precisely in the intended locations. Elements such as strain sensors, floor and wall heaters can be built into the structure in an integrated manner.

4.1.1 AUTOMATED REINFORCEMENT
Robotic modular embedding of steel mesh reinforcement into each layer may be devised. The three simple modular components may be delivered by an automated feeding system that deposits and assembles them between the two rims of each layer of walls built by Contour Crafting. A 3D mesh can be built for columns. The mesh will follow the geometry of the structure. It is possible to feed glass or carbon fiber tows through the CC nozzle to form continuous reinforcement consolidated with the matrix materials to be deposited. Reinforcement can also be provided using the post-tensioning system.

(a)

(b)

Fig 4.4(a, b, c) Reinforcement Components and Assembly Procedure for Walls and Columns

4.1.2 AUTOMATED TILING OF FLOORS AND WALLS
Automated tiling can be integrated by robotically delivering and spreading the material for adhesion of tiles to floor or walls. Another arm can then pick the tiles from a sack and place it over the area treated with the adhesive material.

(a)

(b)
Fig 4.5(a, b) Automated Tiling and Flooring

4.1.3 AUTOMATED PLUMBING
Contour Crafting based construction system has the potential to build utility conduits within the wall. The automated construction of plumbing and electrical works are possible. For plumbing after fabrication of several wall layers a segment of any type material pipe is attached through the constructed conduits into the lower segment already installed. The robotic system delivers the new pipe segment and in case of copper pipes has heater element in the form of ring. The inside or outside rim of each pipe segment is pretreated with a layer of solder. The heater ring heats the connection area, melts the solder and once the alignment is made bonds the two pipe segments.
The needed components may be pre-arranged in a tray or magazine for easy pick up by the robotic assembly system. Using this components various plumbing networks may be automatically imbedded in the structure.


(a)


(b)Fig 4.6(a, b) Plumbing Modules and Grippers

4.1.4 AUTOMATED ELECTRICAL AND COMMUNICATION LINE WIRING
A modular approach similar to industrial bus-bars may be used for automating electrical and communication line wiring used in Contour Crafting. The modules have conductive segments of power and communication lines imbedded in electrically non-conductive materials. All modules are capable of being robotically fed and connected. The automated construction system could properly position the outside access modules behind the corresponding openings on the wall.

(a)

(b)
Fig 4.7(a, b) Electrical Modules and Assembly Process

4.1.5 AUTOMATED PAINTING
During layer wise construction of wall a spray painting robotic manipulator attached to the CC main structure will paint each wall according to the specification. The painting mechanism may be a spray nozzle or inject printer head.
4.2 COMMERCIAL APPLICATION
The cost of construction includes huge amounts of material waste, labor problems and uneconomical building design. Conventional construction is not eco-friendly, it produce air, water and noise pollution. Hundreds of thousands of people injured or killed annually at construction field. Contour Crafting make robots do the risky work preventing any kind of human injuries. It has lessen the harmful impacts. Since materials will be precisely measured prior to construction, there will be no material waste. It will produce less pollution than the conventional method. In the end when the people use CC, the commercial industry will not be restricted by inefficient costs and human labor.
4.3 LOW-INCOME HOUSING
The population is growing faster than ever. Population in developing countries re growing five times faster than those of developed countries. They do not have residence or money to afford such population boom. Slums form because the country’s rate of urbanization is too accommodate all of poor citizens. The cheap and rapid characteristics of CC provides a solution since a fully functional house can be made in less than one day. By using this technology developing countries will be able to solve housing problems of the current and future population.

Fig 4.8 Slum in India

4.4 EMERGENCY HOUSING
The people are prone to some kind of emergency due to war, natural disasters or economic crisis. So many peoples are suffering from these problems. So the best option for them is a home. The house should be cost effective, good quality and proper facilities are there. The CC creates a fully functional house including pumping and heating within a day.

4.5 SPACE COLONIES
Contour Crafting is the best solution for any extraterrestrial construction that NASA approved. Peoples are already using tremendous amounts of money on shipping research machines from earth to another planet, they need to minimize the cost on the actual construction. Astronauts do not have much labor power and time to construct building by themselves. Sending construction materials from earth is too expensive and inefficient to carryout. By using lunar Contour Crafting, there is no need for human labor.
Once solar power is available, it should be possible to adapt the current contour crafting technology to the lunar and other environments to use this power to build various forms of infrastructure. The lunar regolith can be sintered using microwave to produce construction materials. The CC system that uses microwave power to turn the lunar regolith into lava paste and extrude it through the nozzle to create various structures.
Understanding of the following is crucial for successful planetary construction
v  The fluid dynamics and heat transfer characteristics of the extrudate under partial gravity level
v  Process such as curing of the material under lunar environmental conditions
v  Structural properties of the end products as a function of gravity level
v  Effects of extrudate material composition on the mechanical properties of the constructed structure.
One of the ultimate goals of the Human Exploration and Development of Space (HEDS) program of NASA in colonization, building habitats for long term occupancy by humans. The proposed approach has direct application to NASA’s mission of exploration, with the ultimate goal of in- situ resource utilization for automated construction of habitats in non-terrestrial environments.
The ability to construct support-less structures is an ideal feature for building structures using in-situ materials. To explore the applicability of the CC technology for building habitats on the Moon and Mars. In the recent years there has been growing interest in the idea of using these planets as platforms for solar power generation, science, industrialization, exploration of our solar system and beyond and for human colonization. The moon has been suggested as the ideal location for solar power generation and subsequent microwave transmission to earth via satellite relay stations.

Fig 4.9 Lunar Contour Crafting

4.5.1 ROBOTIC OPERATIONS FOR LUNAR CONSTRUCTION
CC technology requires accurate, variable speed motion control of the nozzle over the entire construction work volume. It is best to make the gantry frame mobile in order to eliminate on-site human assembly and disassembly. The mobile gantry robot should be capable or retractable for launch and deployment at the lunar construction site.
OPERATION
v  Launch the mobile gantry robot with gantry collapsed or retracted.
v  After landing traverse to the construction site with the gantry still retracted.
v  Upon arrival to the construction site deploy the gantry
v  Perform self- alignment and leveling of the gantry
v  Ensure that the nozzle,hopper, and material delivery system operate properly.
v  Perform contour crafting construction
v  After the completion of the construction, retract the gantry into transport configuration
v  Traverse to a new construction site for the next construction
A lunar mobile gantry robot can be viewed as a two rower platform connected by a cross beam. Passive complaint joints and position sensors can be utilized for safe and reliable mobility control. The mobile platform having 4 wheels with steering and drive motors each wheel. The mobile gantry robot requires as many as seven retractable beams for lunar launch and deployment- four horizontal beams, two vertical posts, and one top crossbeam. The mobile gantry robot will have passive compliant joints during the traverse, deployment and retraction operations to allow flexing of the structure to reduce stress on the components. These joints will have to be locked after the alignment, levelling and calibration operation.


(a)   Launched


(b)Unfolding Horizontal Rails and Extending Cross Beam
Fig 4.10(a, b ) Mobile Gantry CC Sequences

5. STATE OF DEVELOPMENT IN CONTOUR CRAFTING
Several Contour Crafting machines are developed by USC for research on fabrication with various materials including thermoplastics, thermosets and various types of ceramics. The machine having a XYZ gantry system. The motional assembly with three motion control components (extrusion, rotation, trowel deflection) and a six coordinated motion control system. The machine developed for ceramic processing and is capable of extruding variety of materials like clay and concreting.
5.1 CERAMIC MATERIALS
Clay is a ceramic material which is abundant in nature and hence it has been used for creating various objects with or without thermal treatment. Clay has been used in uncured form as clay bricks in construction. More recently, ceramic material are finding advanced applications in manufacturing. Ceramics processing usually starts with ceramic paste the property of which is influenced by its mineral and structural composition, and by the amount of water that it contains.

Mechanical properties of ceramic paste primarily depend on the water content. With sufficient water the paste softens and forms slurry that behaves as a viscous and formable liquid. When the water content is gradually reduced by drying, the ceramic paste loses its plastic state property and holds together resisting deformations. Ceramic paste shrinks and its stiffness increases until it becomes brittle with further loss of water and enters the semisolid state. By drying continuously, the clay reaches a constant minimum volume at its solid state.

5.2 CC MACHINE STRUCTURE FOR CERAMICS PROCESSING

The machine consisting of an extrusion unit and the trowel control mechanism. The extrusion unit carries uncured ceramic paste into material carrying tank and a linear ball screw driven piston pushes the paste through a CC extrusion nozzle. By the controlled rotational speed of feeding motor stabilized extrusion flow can be achieved.

Fig 5.1 System Configuration for Ceramic Part Fabrication (a) CC Extruder Sits on XYZ Gantry Robot and (b) CC Nozzle Assembly

6. APPLICABILITY CONTOUR CRAFTING CONSTRUCTION OF LOW INCOME HOUSES IN SELECTED COUNTRIES
The evaluation of applicability of CC in different countries include:

1.      Identify target markets that have resources capable of mass 3D printing construction and proven demand based on affordable housing fundamentals.
2.      Evaluate primary research data (qualitative factors) to identify countries most likely to benefit from social impact investing.
3.      Expose deal structuring and partnership options that will facilitate the implementation of Contour Crafting technologies.
4.      Highlight a case study demonstrating macro-demand criteria that justify enteringChina or Saudi Arabia.
Quantitative analysis was the first step in narrowing target markets of interest. To lend insight into product attractiveness in developing and developed countries, secondary data was collected from various sources and organized according to four key variables: wealth, size, likelihood to consume, and accessibility of the resources critical to the product. Each variable was assigned a specified weight from one to five; a higher weight means that a variable has a relatively greater influence in determining product likelihood to succeed.
To account for discrepancies and to be able to compare data among all four variables, data was normalized. For each country, the normalized data for each variable with applied weight was then summed.


Fig 6.1 Market Segmentation According To The Top 10 Countries Applicable for CC

Entry Strategy by Selected Country
Quantitative analysis dictates that China and Saudi Arabia would be ideal countries for market entry and will be the subject of further investigation for how Contour Crafting can be implemented internationally.
These sample countries demonstrate the capital and political characteristics as well as social demand drivers that would determine the feasibility of success of our international marketing plans.
Entry Strategy: China
Though China represents an ideal market for Contour Crafting – based on theirquantitative research and anticipated demand from the end-users – political risks and regulation pose too much of a threat.
The End-Users
Contour Crafting’s success in China hinges on the country’s government housing subsidies. The end users targeted are those who would typically seek one of the following types of affordable housing options offered by the government:

• Cheap rental housing (CRH) - These are rental-housing subsidies to provide provisions for rent control rent subsidies (monetary subsidies), and rent reduction to households who already live in public rental housing. These are provided by municipal government, developers, or work units and are subsidized by housing provisions with controlled rents, rent subsidies, and rent reduction. The target customers are those requiring low-income housing or have housing difficulty.
• Economic and comfortable housing (ECH) - Refers to ownership-oriented housing provided by developers on free land allocated by local municipalities, and sold to qualified households at government-controlled prices. These are provided by developers and subsidized by the municipal government. The target customers are low and middle-income households.
• Public Rental Housing (PRH) - Rental housing provided by the municipal government, work units or developers. The land can be free and rents are regulated. This targets lower-middle income households, new employees, and qualified migrants with difficult housing.

The government has been constantly adjusting its low-income housing policies to try to get all citizens to qualify for a type of affordable housing should they need it. However, a significant portion of the population are still considered “sandwich households,” those that cannot afford to purchase ECH but do not qualify for CRH. 3D concrete printing affordable houses would be fit for the sandwich households, those on the margin, but this would mean that the government would have to expand their subsidizing program.
Secondly, for those who were displaced from their houses, Contour Crafting can be used to build replacement homes efficiently.

To better define the customer segment ofdevelopment-induced displacement, it is important to note some of the process’ causes.
• Urban infrastructure
• Water supply (Dams, reservoirs, irrigation)
• Transportation
• Energy (power plants, mining areas etc.)
• Agricultural expansion
• Parks and forest reserves
• Population redistribution scheme

Purchasing habits among the Chinese for affordable housing is utilized on a needs basis for those displaced. Displaced people tend not to have much choice about where to live, upon being evicted from their homes. A purchase by the end user tends to be made near or onsite

Construction of low-income housing has been the key project vigorously promoted by the central government.China Development Bank would be an appropriate and particularly useful JV partner for the construction of affordable housing by means of Contour Crafting.
.
Entry Strategy: Saudi Arabia
To understand Saudi Arabia’s motivation to a more progressive and humanitariana biding position in the global sphere, we need to take a look at the drivers of this change.As Saudi Arabia has joined NATO and the U.N., it is actively seeking to make progress to conform to the values and practices mandated by the respective organizations.There are existing products that house these migrantworkers, but unfortunately they are criticized as the equivalent of Gulags and slave camps18. Given the availability of low cost labour for construction in Saudi Arabia, it is counterintuitive for the government to use these transients as labours when they are trying to reduce the frequency of human rights violations. Due to the prevailing circumstances, Contour Crafting may be the solution to the inhumane housing conditions these transients reside in.Contour Crafting likely will not be threatened by prefabricated housing techniques made in a factory, since the costs to distribute those materials around the country would most likely be higher than using isolated land to “roll out” housing units generated by the technology.
Saudi Arabia could be an ideal environment to apply contour crafting partly because of its accessibility to concrete and its existing human rights violations related to the labour pool. The country is already the highest consumer of concrete per capita and this building aggregate is highly adaptable, sustainable, and suitable to the environment.

7. FUTURE RESEARCH PLAN
The research planning for CC is on progress

7.1 PROCESS PLANNING AND OPTIMIZATION IN CC

Process planning and optimization play important role in realizing the automation of the technology and improving the overall efficiency by generating optimal nozzle paths for the given structure design.The research presents a systematic methodology for process planning and optimization to handle complicated large-scale structures for Contour Crafting systems with single or multiple machines through the following steps:

1.      Describe system characteristics and define tool path elements of Contour Crafting.
2.      Develop practical tool path planning and an optimization method for the single nozzle CC system.
3.      Develop practical tool path planning and optimization methods for multi-nozzle system based on the optimization method for single nozzle.
4.      Define performance factors and critical design parameters for the multi-machine system to improve efficiency.

The research activities for Contour Crafting tool path planning and optimization can be categorizedinto three groups: Preliminary Research, Developmental Research and Analytical Research.
Under preliminary research the specific characteristics of the Contour Crafting process are identifiesand proper assumptions are made to simplify the problem so that the Contour Crafting tool path model can be constructed. Once these assumptions are stated the Contour Crafting tool path elements can be defined systematically. Physical constraints and utility functions are then structured according to these assumptions.Approaches for tool path planning and optimization for the single nozzle Contour Crafting system are proposed in the development research. Three approaches that follow the two-step procedure are developed and illustrated in detail. A machine behaviour model is incorporated into one of the approaches to make the system more robust. Under analytical research experimental and numerical investigations are performed to analyse the feasibility and efficiency of tool path planning and optimization for both single and multiple nozzle systems. A simulation test bed is implemented for the purpose of simulation.

7.2 ALTERNATIVE ROBOTICS APPROACH

The process was carried out using a gantry robot that has to be large enough to build an entire house within itsoperating envelope and laysone continuous bead for eachlayer. Such an approach is notwithout its attractions, but itrequires a large amount of site preparation and a large robot structure. An approach involving thecoordinated action of multiple mobile robots is to be preferred. The mobile robotics approach has several advantages including ease of transportation and setup, the possibility of concurrent construction where multiple robots work on various sections of the structure to be constructed, the possibility of scalable deployment (in number) of equipment, and the possibility of construction of structures with unlimited foot print.

A construction mobile robot may use a conventional joint structure and be equipped with material tanks as well as material delivery pump and pipes. The end effector of the robot could carry a CC nozzle that can reach from ground level all the way to the top of a wall. If the mobile robot arm could be made of a rigid structure, position sensing at the end effector may not be necessary. Instead, a position sensor may be mounted at a fixed location, and the related retro reflectors may be installed on each mobile robot base. In this configuration, the robot does not engage in fabrication while moving. Once it reaches pre-defined post (called mobile platform post), it anchors itself by extending some solid rods from its bottom. Then it starts the fabrication from the last point fabricated while at the previous post. This arrangement is routinely practiced in some industrial applications such as robotic welding of large parts, such as in ship building.


Fig 7.1 Construction By Mobile

Roof construction may or may not need support beams. Support-less structures such as domes and vaults may be built by mobile robots. Under each beam a thin sheet may be attached. The beams may be picked and positioned on the structure by two robots working collaboratively, each being positioned on the opposite sides outside of the structure. Delivery of roof material becomes challenging with mobile robots and may be done by a robot inside the structure. This robot may progressively deliver the material over the beam panels as each beam is placed on the roof. For the last few beams this robot could exit the structure and perform the delivery from outside. An alternative approach is to use the NIST Robo-Crane system which may be installed on a conventional crane.


Fig 7.2 Robo-Crane for Roof Construction

7.3 RELATED INFORMATION TECHNOLOGY RESEARCH

The IT components in our future researchdirected at mobile robotics application in construction by CC. The diagram depicts a planning system, the output of which, we plan to feed into a virtual system and eventually to a real system, once the required hardware becomes available.

Analysis of CC Feasibility: Afterpossible refinements specific analysis is conducted for conformance to fabrication by the CC process. This activity is supported by various engineering models and simulation programs. The design requirements and these process specifications are then passed to the planning system. Infeasible features are reported to the architect.

City Inspection requirements generation: Design specifications are compared against local construction codes and an inspection plan is generated in accordance with the city inspection process, specifying various inspection types at various stages of construction. The inspection requirements are integrated with other construction requirements and are submitted to the planning system. Due to variations in local construction codes, the effort on this module will be minimal in the proposed research.

High level partial plan: This is are presentation of possible meaningful sequences of high level activities (e.g., build living room, build roof of kitchen, etc.). A centralized planning system may generate the plan in whole, or generate it partially upon demand. The plan includes alternative sequences of activities which may be fetched if downstream high level planning runs into undesirable high level schedules.

High level plan: These are generated by a central planner the output of which includes items such as specification of platform posts (various stationary points at which robots anchor and it perform their assigned operations) for various progressive stages of construction, without specific allocation of robots to posts. These high level plans, which specify what needs to be done at which post, are also sent to the Multiple Robot Coordination module.

Multi-Robot Coordination: This module performs a decentralized allocation of tasks to the available robots based on various factors such as: extent of suitability of robot for the task closeness to the task post point, amount of concrete left in the robot tank, amount of batter charge left, etc. This module performs decentralized planning for maximum plan efficiency and agility.


Fig 7.3 IT Components of Future Automated Construction

Logistics Planner: Details of the layout for resources (main concrete tanks, reinforcement, plumbing, and electrical modules, and charging station) and possible palletizing schemes, as well as dispatching and delivery schedules, are generated by this module, which operates in harmony with modules identifying the platform posts and schedule of operation at each post.

Dynamics and Control: This module is in charge of actual delivery of tasks and assurance of successful performance. The module uses robot dynamics modelling and devises control schemes that incorporate objectives beyond mere task performance.

8. CONCLUSION
Contour Crafting is the only layered fabrication technology which is suitable for large scale fabrication. It has the potential for immediate application in low income housing and emergency shelter construction.The CC approach has direct application to extra-terrestrial construction. Construction of luxury structures with exotic architectural designs involving complex curves and other geometries is another candidate application domain for CC.Lunar Contour Crafting appears to be a viable methodology for construction of Lunar and Martian habitats.The CC technology has the potential to revolutionize the industry, changing it from conventional ‘beam and post’ paradigm to a layer by layer approach.In terms of the country-specific case studies, Saudi-Arabia would be better suited than China adopt CC for use in affordable housing projects. Construction machines built for CC may be fully electric and hence emission free. Because of its accurate additive fabrication approach Contour Crafting could result in little or no material waste. The CC method will be capable of completing the construction of an entire house in a matter of few hours instead of several months as commonly practiced. This speed of operation results in efficiency of construction and management and hence favourable impacts the transportation system and environment. CC is a huge step towards the future. It is cheaper, faster, safer, and easier than any other method. It is a powerful potential construction method of the future.

9. REFERENCE
1.      Behrokh Khoshnevis (2002), “ Automated construction by Contour Crafting –Related Robotics and Information Technologies”, Journal of Automation in construction: The best of ISAR 2002, Volume 13, Issue 1, January 2004, page no.5-19
2.      Behrokh Khoshnevis et al. (2006),”Mega-scale fabrication by Contour Crafting”, International Journal of Industrial and Systems Engineering, Volume 1.
3.     David Weinstein et al. (2015), “Determining the applicability of 3D concrete construction (Contour Crafting ) of low income houses in selected countries”, Cornell Real Estate Review, Article 11, volume 13
4.      Dong Min Kim (2013), “Contour Crafting; a future method of building”, Illumin Article, writing 340
5.     Dooil Hwag et al. (2005),”An innovative construction process-Contour Crafting “; 22nd International Symposium and Robotics in construction.
6.    Jing Zhang et al (2010),”Contour Crafting process plan optimization part 1: Single-Nozzle case”, journal of Industrial and Systems Engineering, Volume 4, page no.33-46.

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