Design, built and test a bridge using a Protos 3D- Printer

Bibliography

Hamburg University of TechnologyInstitute of Laser Systems and Process TechnologiesProf. Dr.-Ing. Claus Emmelmann

Design, built and test a bridge using aProtos 3D - Printer

Advance Studies Module IPM

Editor: Team 1Student ID number: 21262702 - Alapati Chaitanya 21262317 - Hyacinth Mario Arvind Anand 21263859 - Nishok Angalamman Viswanathan Rajendran 47266 - Pooja Anilkumar21262871 - Rajeev Annigeri 21263624 - Tharun Kumar BalakrishnanCourse: International Production ManagementExaminer: Prof. Dr.-Ing. C. EmmelmannSupervisor: Dipl - Ing. Arne Neef

Hamburg, 03.03.2014DeclarationHamburg, 03.03.2014We, the students of International Production Management at the Hamburg University of Technology, certify that we have written this thesis independently and without assistance other than those specified sources and tools used. We swear that this document was never handed in to another department in this or any deviated manner. Every passage referring to or quoted from another source is identifiable as such.

Alapati Chaitanya 21262702 Hyacinth Mario Arvind Anand 21262317 Nishok Angalamman Viswanathan Rajendran 21263859 Pooja Anilkumar 47266Rajeev Annigeri 21262871Tharun Kumar Balakrishnan 21263624

______________________________________________________________________Place, date signature

Alapati Chaitanya 21262702 Hyacinth Mario Arvind Anand 21262317 Nishok Angalamman Viswanathan Rajendran 21263859 Pooja Anilkumar 47266Rajeev Annigeri 21262871 Tharun Kumar Balakrishnan 21263624

We, the students of International Production Management at the Hamburg University of Technology, certify that the information related to the findings and results, are maintained confidential The material will remain as the property of the Institute of Laser and System Technologies (iLAS) and hence will not be disclosed to third parties or used for commercial purposes in any form without permission.

______________________________________________________________________Place, date signature

AbstractIn the current scenario, 3D printing process is widely used for prototyping and manufacturing. The process focuses on additive manufacturing methodology. The major highlights of 3D printing are the ease of manufacturing complex parts using less raw materials at low cost and time. It enables industries to not only print parts but also print their own customized tools according to their specific requirements. 3D printing process is considered to revolutionize the industrial sector in the future by replacing conventional techniques. This project work aims to print an optimized bridge model by using a 3D printer considering the given specifications and testing it under a quantified load. The material used for production of the bridge is polylactic acid.

Table of contentsAbstractiTable of contentsiiList of figuresiiiList of tablesivList of abbreviationsvNomenclaturevi1Introduction71.1Objective71.2Work structure72Project management82.1Project definition82.2Division of roles and responsibilities92.3Project plan93Design and analysis113.1Bridge113.1.1 Force propagation in a beam bridge113.1.2 Force propagation in an arch bridge113.2Initial design113.3Structural optimization - Stage one123.4Structural optimization - Stage two133.5Structural optimization - Stage three133.6Final optimized design144Design of experiments (DOE)164.1Randomized block design164.1.1Variable parameters164.1.2Calculation174.2Design of experiments table175Production of bridge195.1Calibration195.2Problems encountered195.3Production of final bridge model206Conclusion227Bibliography22

List of figuresFigure 1 : Roles and responsibilities9Figure 2 : Activities performed10Figure 3 : Gantt chart10Figure 4 : Initial design12Figure 5 : Structural optimization - stage one12Figure 6 : Structural optimization - stage two13Figure 7 : Structural optimization - stage three14Figure 8 : Stress analysis for structural optimization - stage three14Figure 9 : Final optimized design15Figure 10 : I - section17Figure 11 : Material clamping19Figure 12 : Bridge model - final21

List of tablesTable 1 : Project specifications8Table 2 : Fixed parameters16Table 3 : Factor level17Table 4 : Design of experiments18Table 5 : Parameter combination - Final18Table 6 : Final parameters - Input20Table 7 : Final parameters - Output21

List of abbreviations3D - 3 DimensionalCAD - Computer Aided DesignDOE - Design of ExperimentsFDM - Fused Deposition ModelingRBD - Randomized Block Design

NomenclatureDescriptionUnit

Kilogram kg

Millimetermm

Millimeter per secondmm/s

Minutemin

SecondS

23IntroductionIn the recent years, 3D printing technology was driven forward by advancements in design software, new materials and innovation. The emergence of this technology is opening up new frontiers in manufacturing as common people are getting access to powerful tools of production and design (Lipson and Kurman, 2013).3D printing is based on Fused Deposition Modeling (FDM), which is a form of additive manufacturing technology based on laying down successive layers of material. In the FDM process, the filament is pushed through the chamber by means of a wheel arrangement mechanism. From the chamber the filament is then passed through a heated nozzle where it is melted and used for printing out the designs. The main advantages of 3D printing are the conversion of a digital file into a three dimensional model, the wide range of materials and the effective mechanical properties of the final products (Gibson, Rosen and Stucker, 2010). These unique abilities of 3D printing help to manufacture complex shapes that were difficult to be manufactured using conventional techniques. This technology aims to merge rapid prototyping techniques to meet the high volume conventional manufacturing processes. This provides product developers the ability to print parts according to specific requirements and also enable assembly of final products, made of different materials with different mechanical and physical properties. 3D printing is also faster, more affordable and easier to use compared to other additive manufacturing technologies (Roebuck, 2011).ObjectiveThe main objective of this project work is to design, build and test a bridge on a 3D printer of given specifications, which can withstand a weight of five kilograms (kg). The steps to achieve the target are mentioned as below:1. Project management to monitor on the progress2. Design and analysis of the bridge model3. Design of experiments4. Production of the bridge modelWork structureThe project structure is divided into six chapters, post the introductory part. These chapters depict the work flow in accomplishing the objective of this project work. Chapter two deals with project management to plan the execution of project work, monitor the ongoing activities and organize the final presentation and documentation. Chapter three is dedicated to design of the bridge model that focusses on developing an optimized design using CAD software, considering the given specifications.In chapter four efforts are put forth in conducting trials to identify the optimal parameter combination for production of the final bridge model. Chapter five constitutes the steps involved in production of the trials and the final optimized model. Finally in chapter six, the conclusion of this project work are enumerated.

Project managementProject management is an essential step to handle the projects effectively. Collection of tools and techniques, are used for planning, executing, monitoring and evaluating a project (Munns and Bjeirmi, 1996). In the current project work, the software Microsoft Project is deployed to support the ongoing status of the project. The functions that are used for managing the project include: Project definition Division of roles and responsibilities Monitoring the progress Resolving visible deviationsTo begin with any project, the first important step is to define the project. By defining a project, the final target to be accomplished is well realized among the members, to work towards this goal. Project definition This section determines the requirements and specifications to be considered for the project work. The time schedule for completion of the project work is defined in this stage and approximated to four months. The task work is done in an enclosed environment using a 3D printer. The Error! Reference source not found. shows the criteria to be taken into consideration and standards to be followed.Table 1 : Project specificationsCriteriaSpecification

Weight to carry5 Kg

Type of loadPoint load

Minimal weight of the bridge10 mm

Internal distance between the columns150 mm

Object to bridge width45 mm

Object to bridge height15 mm

Softwares and tools used: Microsoft Project Creo Sli3r Audrino PronterfaceDivision of roles and responsibilities

Figure 1 : Roles and responsibilitiesResponsibilities carried out in each division: 1. Project management Assigning suitable tasks to the members of the team Preparing project plan and charts to illustrate work progress Sharing information among the team and updating tasks2. Design and analysis Researching on available bridge models and designing using Creo Optimization of the bridge design based on analysis using Creo Discussion of the design with team members 3. Design of experiments Understanding the parameters that influence the production Generation of experimental solution based on logical thinking Derivation of optimized parameter combinations from trial experiments4. Production Getting accustomed with usage of Sli3r software and 3D printer Calibration and leveling of the 3D printer Checking the dimensional accuracy, time consumed and weight of the part produced Project plan The project plan was created based on the time schedule. The activities accomplished during the project are as listed below in the Figure 2. The activity starts with assigning the roles and responsibilities based on the division of the task work. The critical points in the task work and the progress of the project with respect to the time schedule is also depicted in the Figure 2 . The project plan helps the team members to view the overall progress and monitor the same. The Gantt chart represent the above mentioned activities that are used for viewing the project status based on the allotted time schedule as shown in Figure 3.

Figure 2 : Activities performed

Figure 3 : Gantt chartOnce the project plan is created, the work is proceeded by developing designs of models for production. The following chapter illustrates the tasks involved in designing the optimized bridge model.

Design and analysisThe bridge model design is initiated based on deriving the concepts from the literature study done on beam and arch bridge. The concepts of beam and arch design are described in the following section before proceeding into the development of design.Bridge A simple definition of a bridge is a structure that spans horizontally between supports whose function is to carry vertical loads (Melaragno, 1998).3.1.1 Force propagation in a beam bridgeThe downward force acting on the beam bridge results in bending movement. The top edge is pushed together, and its bottom edge is pulled apart (Melaragno, 1998). Compression forces acts on the top members of the beam Tensional forces acts on the bottom members of the beam3.1.2 Force propagation in an arch bridgeAs a structural unit, an arch is defined as a member shaped and supported in such a way that intermediate transverse loads are transmitted to the supports, primarily by axial compressive thrusts in the arch (Fu, 2005).The forces applied propagate concave downwards through the arch shape and the reaction components are (Fu, 2005): Normal reaction at the leg of the bridge Lateral reaction acting outwards of the bridgeInitial designThe first model is designed considering the advantages of beam and arch bridge design. The top half of the bridge model is a concept from the beam bridge design whereas the bottom part is adopted from the arc bridge design. At the point of load application, excess material was added to improve the load carrying capacity of the bridge. The bridge design is illustrated in Figure 4.

Figure 4 : Initial designAfter printing the bridge it was found to be over engineered. The bridge sustained more than the required amount of load. Considering the main parameters for evaluation i.e. the amount of material consumed and production time, a scope for reducing the weight of the bridge was identified in the subsequent design.Structural optimization - Stage oneThe second design focuses on reducing the weight of the bridge. The weight reduction is accomplished by placing holes at left and right corners that will relieve stress and in turn reduce weight. As planned, the weight of the bridge and the time taken for manufacturing was reduced. This design was also found to hold more than the required load and hence further scope for optimization were identified. The CAD model is as shown in Figure 5.

Figure 5 : Structural optimization - Stage oneStructural optimization - Stage twoThe third design is developed based on the core structure concept of beams. The core structure helps in supporting the load by utilizing the structural strength that leads to further possibility of weight reduction.

Figure 6 : Structural optimization - Stage twoThis design focuses on distribution of the load across the two columns connected by a central beam element and beam on the edges. With a considerable amount of weight reduction the columns were added to enhance the load bearing capability of the structure. Testing of this design clearly shows a further scope of optimization and the bridge model is as shown in Figure 6. The goal of design optimization is to obtain a final bridge model, which is capable to withstand the stresses induced by the point load acting, with the minimal weight.Structural optimization - Stage threeThe previous designs load bearing capacity exceeded the expectations because of the structural design of the bridge. Hence, the structural frame is retained and the beams are removed to reduce the thickness of the bridge.

Figure 7 : Structural optimization - Stage threeThe need for structural analysis is recognized to know the stresses induced in the members and stress propagation in the structure. The software Creo is used for structural analysis. Based on the output of this analysis the members subjected to lower stress indicated (Blue color) in the Figure 7 are to be removed. The stress analysis is depicted in Figure 8.

Figure 8 : Stress analysis for structural optimization - Stage threeFinal optimized designAs stated previously the less stressed members are removed. The design is loaded and the physical sign of slight bending is observed, which is clearly evident that further weight reduction will lead to failure of the bridge. Hence this design is considered to be the final optimized design. The final design meets the dimension requirements as per given specifications and has the load bearing capacity when subjected to a point load of 5kg. The same is shown in Figure 9.

Figure 9 : Final optimized designThe next chapter focuses on design of experiments that is used for finding out the optimal parameters in order to achieve the final target.

Design of experiments (DOE)Design of experiments (DOE) is a statistical approach that includes the total scope of experimentation considering the process parameters, procedure of experimentation and actual performance, in order to determine critical process parameters, reduce the number of experiments and also simultaneously improve the experimental output (Barrentine, 1999). Based on this approach, for obtaining the final bridge model with low production time and material consumption, the randomized block design is chosen.Randomized block designRandomized block design (RBD) reduces the sampling variance of the experimental units in each parameter, thereby optimizing the parameters by substantial error reduction (Gosling, 1995). To achieve the final output considering the given constraints (low production time and material usage) three parameters are varied and the remaining is fixed. The following is the table for fixed parameters:Table 2 : Fixed parametersFixed ParametersValues

Layer height0.5 mm

Perimeter2

Solid layerTop:2

Solid layerBottom:2

Perimeter speed30 mm/s

Travel speed130 mm/s

Nozzle diameter0.5

Variable parametersThe following are the variable parameters taken into account. The Sli3r software provides details of various parameters and based on the input obtained the optimal parameters are selected for 3D printing .1. Infill patternThe following pattern types line, rectilinear and Archimedean chords are selected based on object strength, production time and material usage. 2. Infill speedIn order to obtain a smooth finish and to avoid weak spots resulting in breakage, infill speed of 40 mm/s and 50 mm/s are chosen.3. Infill densityFill density is varied between a scale of 0 and 1, with 1 being the highest. High-density values led to solid structures, with additional material usage and time. Therefore, a density value of 0.3 and 0.4 is selected as it is sufficient to develop a bridge model with acceptable mechanical strength to hold 5 Kg. CalculationBased on the above-mentioned variable parameters the total number of experiments is calculated by using RBD. The following table shows the variable parameters and their corresponding levels considered for the calculation of RBD.Table 3 : Factor levelNo.Parameter (X)Level (L)

1Infill pattern3

2Infill speed2

3Infill density2

Total number of experiments= L1 x L2 x L3 = 3 x 2 x 2= 12 experimentsDesign of experiments tableBased on the total number of experiments from the RBD calculation the parameter combinations are obtained for proceeding with the production of the bridge model. To identify the filament usage and production time for each parameter combination, I sections are produced initially with the following specifications (length - 50 mm, width - 40 mm, thickness - 5mm).

Figure 10 : I - sectionThe following table provides detailed information about the filament usage and printing time for production of I sections.

Table 4 : Design of experiments Trial no.InfillOutput

PatternSpeed(mm/s)Density (%)Filament consumed (mm)Production time (min)

1Line400.3741.6611:33

20.4782.1712:08

3500.3741.6611:10

40.4782.1711:37

5Archimedean chords400.3728.6612:08

60.4767.6012:57

7500.3728.6611:36

80.4767.6012:16

9Rectilinear400.3744.7811:36

100.4785.3512:08

11500.3744.7811:12

120.4785.3511:38

By looking at DOE tables the line pattern is the one with least filament consumption and production time, but the cross linkage in the rectilinear provides additional stability to the bridge, which is beneficial. Hence, the following optimal parameters shown in Table 5 are selected for printing the final bridge model.Table 5 : Parameter combination - FinalTrial no.InfillOutput

PatternSpeed(mm/s)Density (%)Filament consumed (mm)Production time (min)

1Rectilinear500.3744.7811:12

The next chapter focuses on the production of the bridge using the 3D printer and then followed by testing it under a load of 5kg.

Production of bridgeThe required inputs for the production process are obtained from the design of experiments prepared in the previous chapter. The production process is initially carried out with the production of test models in order to generate the optimized inputs. The optimization process is based on series of trials conducted using the elements of DOE.Calibration Calibration of the instrument has to be done before the commencement of the production. This leads to setting up the instrument as per the standards. The below mentioned are the elements that needs to be calibrated in the equipment.1. Working temperature of the extruder to be maintained at 190 degree and that of the bed at 60 degrees.2. Alignment of X-axis is done by alignment of the printing bed using the spirit level3. Alignment of Y-axis is done by adjusting the guide rods parallel to the clamps4. Alignment of Z-axis is performed by maintaining the orthogonality of guide rods and printing bed.5. Distance between nozzle and printing bed should be 0.2 mm.6. Clamping the material into the extruder and adjusting of the compression springs for the proper flow of material. The same is shown in the Figure 11.

Figure 11 : Material clampingProblems encountered There were series of problems encountered with the 3D printers. These problems have to be tackled to have an effective functioning of the system. As described in the previous section the first major thing to be taken into consideration is the calibration of the equipment. Defective parts are one of the effects of improper alignment of axis. In this particular project the major problems faced were due to mechanical issues related to machine and minor problems due to the electronic equipment. Necessary steps were taken to sort out the issues and for proper functioning of the printer. The problems encountered were rectified during every lab session. These continuous improvement steps taken to handle the issues, resulted in reduction of defective parts.The overview of the problems encountered and the subsequent solutions that were taken in this project are mentioned below.1. Alignment of the bedThe following problem is rectified by adjusting the bed screws and checking the level of the bed using a spirit level. Additionally the overhang support also is adjusted using the motor screws to achieve a perfect leveling.2. Low voltage and Synchronization of the stepper motors By adjusting the voltage in the potentiometer screw in the electric circuit to the required voltage, leads to the adjustment of synchronization between the motors.3. Extruder malfunctionThe material that is melted before entering the extruder gets blocked at the point of entry and the material flow is obstructed causing the malfunctioning of the extruder. Opening up the filament feed wheel and cleaning it before inserting the filament material back into the correct position solves the problem.4. Ease of lead screw rotation constrainedThe guide rods that help in the movement of the extruder in the Z direction are connected to the screw that operates the stepper motors. The inefficient functioning of this screw is identified by noise generated from the stepper motors. The problem is solved by removing the guide screws and cleaning them from foreign particles.Production of final bridge modelThe final model is produced based on the optimal design and parameter combination described in the previous sections. The model is tested under a quantified load to prove the sustainability of the bridge. The model is depicted in the Figure 12. The parameters obtained for the same is shown in Table 5.Table 6 : Final parameters - InputInput parametersValue

PatternRectilinear

Infill density0.3

Infill speed50 mm/s

Figure 12 : Bridge model - FinalThe Table 6 shows the final output parameters and the respective values, which are the basis for evaluation of the task work. The values of production time and filament consumed are obtained from the Pronterface after the completion of the production. The weight is measured using the weighing scale.Table 7 : Final parameters - Output Output parametersValue

Production time35 min

Filament consumed2285 mm

Weight of the bridge15.5 g

ConclusionIn this project work, the initial activities include getting familiarized with the 3D printer and the softwares such as Sli3r and Pronterface that are required for the functioning of the 3D printer. The initial steps of the project work consists of distribution of the tasks among the team members and creating a project plan for completion of the project within the stipulated time. The design is carried out in optimization of the bridge. Simultaneously the DOE and the production are carried out to print sample parts. The critical production parameters of the 3D printer are identified to achieve the design target. After initial experiments with the printer the optimal production parameters are found.Using the optimal parameters the bridge designs are produced using the 3D parameter. The printed bridges are tested on the test rig and based on the results the design is optimized using the CAD software and subsequently printed again. In this manner optimized design and the optimum parameters for the printer are used to reach the desired target of printing the bridge. The target is to produce a bridge with least weight and manufacturing time that can sustain a point load of 5 kg. The problems relating to technical issues resulted in loss of work hours and shortened the time for project completion. On the contrary the project is completed with successful production of the bridge and testing it under a point load of 5kg.Word RepRap is a reference to the self-replicating properties of 3D printers and is a good example to see its advantages while printing small and complex geometries. The project is known with its evolutionary aspect; therefore it is possible to conclude that there will always be more upgrades and better build-ups to increase the performance of these 3D printers.

BibliographyComment by chaitanya alapati: All the citations have not come here tharun.Can u check the software that u used.Barrentine, L.B., 1999. An introduction to design of experiments: a simplified approach. ASQ Quality Press, Milwaukee.Fu, G., 2005. Inspection and Monitoring Techniques for Bridges and Civil Structures. Elsevier.Gosling, J., 1995. Introductory Statistics. Pascal Press.Lipson, H., Kurman, M., 2013. Fabricated the new world of 3D printing. John Wiley, Indianapolis, IN.Melaragno, 1998. Preliminary Design of Bridges for Architects and Engineers. CRC Press.Munns, A., Bjeirmi, B., 1996. The role of project management in achieving project success. Int. J. Proj. Manag. 14, 8187.Roebuck, K., 2011. 3d Printing: High-Impact Emerging Technology - What You Need to Know: Definitions, Adoptions, Impact, Benefits, Maturity, Vendors. Emereo Pty. Limited.