122,356 research outputs found
Identification of Microtopographic Surface Features and Form Error Assessment
No full textThis work is concerned with quality inspection of microtopographic surface features, such as those that may be commonly found in semiconductor products, microelectromechanical systems, and other microcomponents. Surface microtopography data are assumed to be available as a height map, acquired through raster scanning over the region of interest, by means of a 3D profilometer or a 3D scanning microscope. An algorithmic procedure is proposed for form error assessment, which comprises several steps: first the feature of interest is localized and identified within the height map; then it is extracted and aligned with a reference (i.e., nominal) geometry modeled by means of a CAD system; finally, form error is evaluated from the volume enclosed between the two aligned geometries. Feature identification is implemented through a modified version of the ring projection transform, adapted to operate on topography height maps; alignment comprises two steps (coarse alignment, consisting in an exhaustive search over discrete angular positions; and fine alignment, done with the iterative closest point technique). The final form error assessment procedure is applied to aligned geometries. The approach is illustrated and validated first through its application to an artificially generated case study, then to a real-life case of industrial relevance
“On Three-dimensional Surface Topography Analysis Process Planning and Documenting for Engineering Applications”,
No full textA contribution to the development of three-dimensional nano and micro-topography measurement and analysis techniques and systems
No full textInformation-rich surface metrology
No full textInformation-rich metrology refers to the incorporation of any type of available information in the data acquisition and processing pipeline of a measurement process, in order to improve the efficiency and quality of the measurement. In this work, the information-rich metrology paradigm is explored as it is applied to the measurement and characterisation of surface topography. The advantages and challenges of introducing heterogeneous information sources in the surface characterisation pipeline are illustrated. Examples are provided about the incorporation of structured knowledge about a part nominal geometry, the manufacturing processes with their signature topographic features and set-up parameters, and the measurement instruments with their performance characteristics and behaviour in relation to the specific properties of the surfaces being measured. A wide array of surface metrology applications, ranging from product inspection, to surface classification, to defect identification and to the investigation of advanced manufacturing processes, is used to illustrate the information-rich paradigm
A contribution to concurrent assembly design and assembly process planning based on distributed object technology
No full textOn the application of segmentation techniques to three-dimensional surface topography analysis
No full textAutomated identification and extraction of dale-like features from the three-dimensional topography of manufactured surfaces: an application to scratch testing
No full textBioceramic Materials Surface Topography Measurement and Analysis for Biomedical Applications
No full textMaterial extrusion additive manufacturing of metal parts: analysis of the performance and behaviour of parts according to process parameters
No full textThe Additive Manufacturing (AM) technology is one of the enabling technologies of the
Industry 4.0.
According to standard ASTM/ISO 52900, Additive Manufacturing compared to the conventional
manufacturing (CM) based on subtractive (machining) or formative (casting) methods, enables to
realize parts layer by layer starting from 3D model data and usin g different kinds of materials as
metals, polymers or ceramics. There are seven different technologies that belong to the AM class, but
one of the main commons is the Material Extrusion Additive Manufacturing (MEX). MEX
technology born to process polymeric materials in form of filament or pellets. In the last years,
however, its material portfolio expanded considering other materials as ceramics and metals. When
metal alloys are processed with MEX it takes the name of Metal MEX . The growing interest in the
Metal MEX field thanks to the simple processing equipment, the low investment costs and the low
hazards for the worker and environment allowed to consider this ne w technique a potential alternative
to the main Metal AM technologies as the Powder Bed Fusion or Direct Energy Deposition. In fact,
these well known techniques require the use of laser or electron beam, the exposure at metal powder
and high cost of investment and maintenance.
Metal MEX technology is
a multistep process composed by three stages , the printing, the debinding
and the sintering. After each phase, the part is in a different condition: once printed the part is called
“green part”, where the metal powder is dispersed in the polymeric matrix deposited during the
printing stage. O nce debound , the part is called “brown part and a remaining part of the polymeric
matrix is present to give strength to the part before the sintering. In this phase all polymers are
removed, and the metal particles start to grow creating necking between the par ticle and the part
become denser due to the fill of the voids. After sintering, the result is a “metal part” or “white part”.
In each stage , the process parameters defined play a fundamental role to modify the properties of the
different parts. The entire process is referred as Printing Debinding Sintering (PDS).
In this context, this thesis has the aim to provide
a deep study about th e performance and the behavior
of the parts realized with this emerging technology. T he response of the parts in the green and sintered
condition will be analysed considering the influence of the main process parameters those act during
the entire PDS chain. The materials investigated are two different stainless steel: t he martensitic
precipitation hardened stainless steel 17 4 PH and the austenitic stainless steel 316L . An analysis of
the response of the parts realized with these two materials cover a major part of the current work of
thesis. However, it is reported a preliminary study about a novel material processed trough MEX as
the pure copper. In this way, a strong optimization of the printing parameters to densify the part is the
main target reported in this work. In detail the thesis is
structured in the following way: a brief introduction about the Additive
Manufacturing and its technologies with a focus on the Metal AM technologies. I n the second chapter ,
the focus is on the MEX Debinding Sintering chain . The different methods to process the feedstock
and the different materials processable . A focus on the debinding and sintering about the different
methods, the main parameters and the effects on the part are reported. In the third chapter is a review
of the state of art about 316L, 17 4 PH and copper processed via MEX. The main properties are
explained and investigated are reported . In the fourth chapter the research question of the current
work f thesis is reported. From the fifth chapter to the eighth chapter the experiments performed on
the 316L and 17 4 PH . In the ninth chapter, a preliminary study about the feasibility to print and sinter
copper parts performed at Politecnico di Bari, instead in the tenth chapter the activities performed in
collaboration with the AML group of the KU Leuven during the abroad period. The last chapter
repo rts the general conclusions of the c urrent work and the possible future activities
Quality Inspection of Microtopographic Surface Features with Profilometers and Microscopes
No full textWith the increasingly widespread adoption of micromanufacturing solutions and with the production of a growing number of artifacts defined at the microscopic and submicroscopic scales, increasingly smaller geometries need to be verified for quality assurance. The study of precision at micro and submicro scales is gaining considerable interest: relevant issues pertain to how to define allowable geometric error on parts of such small sizes (e.g., semiconductor products, microelectromechanical systems, other microcomponents) with proper dimensional and geometric tolerances, and how to measure them. This work addresses the specific problem of assessing geometric error associated with micromanufactured surface features. Three-dimensional digital microscopes and profilometers for microtopography analysis are increasingly being adopted for such a task, owing to their suitability to operate at very small scales. However, this raises several challenges, as three-dimensional microscopes and profilometers have traditionally been used in different application domains, and are mainly aimed at the inspection of surface finish; new modes of operation must be identified which take into consideration such peculiarities. Both families of instruments need to be closely investigated, and their main constraints and benefits dissected and analyzed to assess their adaptability to the new task of assessing geometric error on micromanufactured parts or surface features. © 2010 Springer-Verlag London
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