Mehdi Kazemi and Abdolreza Rahimi
Additive manufacturing technology significantly simplifies the production of complex three-dimensional (3 D) parts directly from the computer-aided design (CAD) model. Although…
Abstract
Purpose
Additive manufacturing technology significantly simplifies the production of complex three-dimensional (3 D) parts directly from the computer-aided design (CAD) model. Although additive manufacturing (AM) processes have unexampled flexibility, they still have restrictions inhibiting engineers to easily generate some specific geometric shapes, easily. Some of these problems pertain to the consumption of materials as supports, the inferior surface finish of some surfaces with certain angles, etc. One of the approaches to overcome these problems is designing by segmentation.
Design/methodology/approach
The proposed methodology consists of two steps: (1) segmentation of the 3 D model and (2) exploring the best orientation for each segment. In the first step, engineers consider the possible number of segments and the connection method of segments. In this paper, a series of segments, called a segmentation pattern (SP), is obtained by the recognition of features and separating them automatically (or manually when needed) with one or more appropriate planes. In the second step, the best fabrication orientation should be chosen. The criteria for choosing the best SP and OPs are minimizing the support volume, building time (directly affected by segments’ height in layer-wise AM processes) and surface roughness. Both steps are performed automatically (or manually when needed) by the algorithm created based on principles of particle swarm optimization (PSO) algorithm using Visual C#.
Findings
Experimental tests show that the segmentation design improves AM processes from the aspects of building time, material consumption and the surface quality. Segmentation design empowers users of AM technologies to reduce consumption of material by decreasing the support structures, to decrease the time of building by lowering the segments height and to decrease the surface roughness.
Originality/value
This paper presents an original approach in efficiency improvement of AM technologies, thus bringing the AM one step closer to maturity.
Details
Keywords
Mehdi Kazemi and Abdolreza Rahimi
Stereolithography (SLA) is a broadly used technology in the field of rapid prototyping. One of the disadvantages of SLA is poor mechanical properties of its products. To approach…
Abstract
Purpose
Stereolithography (SLA) is a broadly used technology in the field of rapid prototyping. One of the disadvantages of SLA is poor mechanical properties of its products. To approach the mechanical properties of original part, the mechanical properties of SLA part, such as tensile strength, should be optimized. In this process, there are many parameters that affect the tensile strength of parts. However, the “layer thickness”, “fabrication orientation” and “post curing time” are the most significant ones. Hence, the purpose of this study is to investigate the influence of these parameters on tensile strength of SLA parts.
Design/methodology/approach
According to the obtained results from experiments based on the “full factorial” method, an empirical equation was developed for the tensile strength in terms of the effective parameters by using regression analysis. Considering this empirical equation, the process parameters were optimized to maximize the tensile strength by using genetic algorithm. Finally, the tensile tests of the specimens were simulated via the general-purpose finite element package of ABAQUS.
Findings
The outputs of the numerical simulations were in good agreement with experimental results. Both experimental and numerical results show that the increase of layer thickness and the decrease in post curing time increase the tensile strength. Furthermore, the tensile strength of parts produced in vertical orientation is higher than that of parts produced in horizontal orientation.
Originality/value
This is a complete study about the tensile strength of the SLA parts from experimental and analytical viewpoints.
Details
Keywords
Morteza Vatani, Farshad Barazandeh, AbdolReza Rahimi and Amir Sanati Nezhad
In stereolithography (SL), the total exposure absorbed by photopolymer is variable and is a function of height. This phenomenon causes heterogeneous properties and develops…
Abstract
Purpose
In stereolithography (SL), the total exposure absorbed by photopolymer is variable and is a function of height. This phenomenon causes heterogeneous properties and develops residual stresses during process. Consequently, a pronounced deformation occurs especially when small and more intricate objects are fabricated. The purpose of this paper is to predict this deformation when miniature and complicated parts are fabricated.
Design/methodology/approach
In this paper classical lamination theory is employed to model mechanical properties of layers, layers shrinkage and residual stress growth during SL process. Distortion is predicted based on the developed model.
Findings
Results show that final distortion is proportional to part thickness and it increases exponentially as parts thickness or layers thickness decrease.
Practical implications
To verify the results, several test pieces were built with SLA 5000 machine and SOMOS 11120 resins. Their distortions were measured with video measuring machine (VMM‐3020D machine). The estimation agrees very well with the experimental results (less than 10 per cent error).
Originality/value
The paper considers the heterogeneous properties of SL parts during fabrication process; an item which was ignored in previous researches. This theoretical and experimental study provides useful information about estimation of deformation of SL parts after building. This information helps the SL machine user to select the best parameters when fabricating miniature and intricate features, especially for biomechanics parts.