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For geometries exhibiting overhanging surfaces, support structures are needed to dissipate process heat and to minimize geometrical distortions attributed to internal…
For geometries exhibiting overhanging surfaces, support structures are needed to dissipate process heat and to minimize geometrical distortions attributed to internal stresses. The use of support structures is often time- and cost-consuming. For this reason, this study aims to propose an approach which minimizes the use of such structures.
For minimizing the use of support structures, process parameters in combination with a contour-like exposure strategy are developed to realize support-less overhanging structures of less than 35°. These parameters are implemented in a shell-core strategy, which follows the idea of applying different processing strategies to the critical (overhanging) shell and the uncritical core of the part. Thereby, the core is processed with standard parameters, aiming a dense material. On the critical shell, optimized processing parameters are applied, reaching good results in terms of surface quality, especially at extreme overhang situations.
The results show that the selective laser melting (SLM) technology is able to realize support-less overhanging surfaces by choosing suitable scan strategies and process parameters. Particularly good results are always obtained when the exposure direction of the shell is parallel to the contour of the sample.
The validity of the results is demonstrated through the successful reproduction of the build strategy on two commercial SLM machines, reaching support-free builds of surfaces with an angle to the horizontal of less than or equal to 30°.
Michael Holquist (1990), one of the commentators on Mikhail Bakhtin’s monumental work, stated flatly that “human existence is dialogue,” and Ivana Markova (2003) declared…
Michael Holquist (1990), one of the commentators on Mikhail Bakhtin’s monumental work, stated flatly that “human existence is dialogue,” and Ivana Markova (2003) declared that “dialogism is the ontology of humanity.” Bakhtin (1985;1986) himself said that such dialogues are conducted by using “speech genres.” From another angle Kenneth Burke asked, “What is involved when we say what people are doing and why they are doing it?” and claimed – and showed – that this question can be best answered by using what he called the “grammar of motives,” which consisted of a hexad of terms: act, attitude, scene, agent, agency, and purpose. In this chapter, I examine, by using various examples, how the Burkean grammar is used in the construction of one speech genre or the other to achieve rhetorically effective dialogic communication.