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oughness value (Ra), which describes surface quality. A software was developed which does the slicing of the CAD model created by sweeping a Bezier curve around an axis. The software for direct slicing of axis symmetric parts takes the control points of Bezier curve, maximum and minimum fabrication thickness available in the FDM machine and maximum Ra value desired on the part surface as input. The software gives the variable slice thickness list, overall part surface roughness and the graphics of the slices formed. It was observed that the number of slices were reduced and hence the build time. The major advantage being the part quality expressed in terms of Ra value which is used in design and manufacturing which is being quite realistic. Part quality can also be improved by modifying the pattern of deposition. To improve the scanning efficiency in FDM, Yang et al [21] developed an equidistant path generation algorithm. To evaluate the path generation algorithm, simulated and experimental analyses were carried out and it was proven that this deposition can improve the rapid prototyping process by increasing part quality and processing efficiency. To determine the most crucial elements affecting the quality of prototypes in fused deposition modeling, a work study using Taguchi methods was undertaken by Anitha et al [22]. It was found that without pooling, only the layer thickness is effective to 49.37% at ninety five percent level of significance. On pooling it was found that the layer thickness is effective to 51.57% at ninety nine percent level of significance. The significance of layer thickness is further strengthened by correlation analysis, which indicates a strong inverse relationship with surface roughness. In an experimental work done by L.M.Galantucci et al [23], have studied the influence of FDM machining parameters on acrylonitrile butadiene styrene (ABS) prototype‟s surface finish. The surface finish of products after the modification of extrusion parameters has been measured and processed through designed experiments. The roughness of FDM prototypes is analyzed. Process parameters have been shown to affect the Ra. In particular the slice height and the raster width are important parameters while the tip diameter has little importance for surfaces running either parallel or perpendicular to the build direction. A chemical post- 34
processing treatment was analyzed which yields a significant improvement of the Ra of the treated specimens. The proposed chemical treatment is economic, fast and easy to use. Despite all the research and development done in this field which have been discussed above and more in the industries R & D labs, accuracy of the part and surface quality are key criteria for this form of rapid prototyping. Printing of curved surfaces with high precision and eliminating stair case effect has been a area of repeated problem occurrence where many have tried to provide solution in their own literature review‟s but they still have their shortcomings – mainly associated with curved surfaces. Even though there has been a continuous development of these rapid prototyping processes, improvisation in its application, product development and other areas have quite significantly improved, there is a downside in getting a balanced result in the material front. Materials, which can be rapid prototyped and engineered to be used as end solutions right to the customer or as a part of a component are still yet to come in a big way in the consumer market. The processes which currently use low or poor quality material for most of the part and are only good for testing of limited properties as those materials may not be deemed fit. Only with continuous machine and material improvements the dream of building products with true engineering value can be realized. Stair case effect, as discussed earlier is a common defect in FDM methods is a major reason for poor surface quality of parts produced. Due to this the number of layers to make up the part is high which results in increased build time and poor strength in some cases. In case of thin shell type and curved parts these problems are severe, critical and undesirably high in most cases. FDM has been used to recreate parts such as skull bone replacements, turbine blades, etc. Using conventional FDM parts to manufacture curved shell type parts results in poor quality parts with discontinuous filaments. The main obstacle for the application of new materials with specific properties for FDM often comes from the use of intermediate precursors such as a filament. Also during the extrusion phase, frequent buckling causes the interruption of the process. 35
Page 1 and 2: An Investigation into curved layer
Page 3 and 4: Contents Abstract..................
Page 5 and 6: 3.5.2 Fabepoxy.....................
Page 7 and 8: methodology to print simple curved
Page 9 and 10: List of Figures 1.1 The Rapid proto
Page 11 and 12: 4.3 Parts being tested with Hounsfi
Page 13 and 14: List of Abbreviations 3D: Three dim
Page 15 and 16: Fig 1.1 The Rapid prototyping Cycle
Page 17 and 18: 1.1.1 Stereolithography Stereolitho
Page 19 and 20: The object to be made is first mode
Page 21 and 22: 1.1.5 Laser Engineered Net Shaping
Page 23 and 24: 1.2 Fused Deposition Modeling A det
Page 25 and 26: Fig 1.8 Deposition Head Different t
Page 27 and 28: 900mc is capable of producing parts
Page 29 and 30: noted that the parts built in this
Page 31 and 32: structure. Honeycomb scaffold archi
Page 33: optimal direction to build a part t
Page 37 and 38: The actual influence of the curved
Page 39 and 40: Separating the Main part with its s
Page 41 and 42: limited to simple models. It could
Page 43 and 44: Fig 2.2 Faces, Edges and Vertices o
Page 45 and 46: 2.1.5 Constructive Solid Geometry C
Page 47 and 48: A STL file is a triangular represen
Page 49 and 50: Fig 2.8 A sample Binary STL File Sl
Page 51 and 52: Different processes may either vary
Page 53 and 54: At the very outset of generating th
Page 55 and 56: and correction of each point to sat
Page 57 and 58: apid prototyping machine are remove
Page 59 and 60: Fig 2.13 Main Part Fig 2.14 Support
Page 61 and 62: As this text file is to be used wit
Page 63 and 64: mounted to the axes carriage. Timin
Page 65 and 66: Fig 3.1 The deposition head At the
Page 67 and 68: 3.2.3 Assembling Electronics and ca
Page 69 and 70: microcontroller is now disconnected
Page 71 and 72: The relationship between test point
Page 73 and 74: on the mechanical properties and po
Page 75 and 76: 3.5.1 Silicone with other materials
Page 77 and 78: Fab@home machine. Since our require
Page 79 and 80: are printed using the two suitable
Page 81 and 82: The support structure‟s dimension
Page 83 and 84: machine Fig 3.13 Flat and curved la
Page 85 and 86:
4.1 Experimental conditions Chapter
Page 87 and 88:
have many factors from contention a
Page 89 and 90:
4.3 Taguchi methods There are two t
Page 91 and 92:
Such steps usually identify the nee
Page 93 and 94:
Nominal is best Larger is better S
Page 95 and 96:
Control of material flow - The lead
Page 97 and 98:
Fig 4.3 Parts being tested with Hou
Page 99 and 100:
values in all cases are almost doub
Page 101 and 102:
level. The other parameters were in
Page 103 and 104:
The finite element method has had a
Page 105 and 106:
performance of finished FDM parts [
Page 107 and 108:
ehaviour with failure occurring at
Page 109 and 110:
Fig. 2 (a) is the thin curved part
Page 111 and 112:
Table 5.1 Property data: Fabepoxy M
Page 113 and 114:
optimum number. The final finite el
Page 115 and 116:
Fig. 5.11 Load and boundary conditi
Page 117 and 118:
overall deflection pattern of two s
Page 119 and 120:
Fig. 5.13 Variation of compressive
Page 121 and 122:
Fig. 5.15 shows the overall deforma
Page 123 and 124:
The effectiveness of the deposition
Page 125 and 126:
[11] M. Greul, T. Pintat, M. Greuli
Page 127 and 128:
[32] Philip J. Ross, 1988, “Taguc
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