Recent Approaches for the Manufacturing of Polymeric Cranial Prostheses by Incremental Sheet Forming

This paper presents recent research experiences developed with the aim of manufacturing cranial prostheses in polymeric sheet using Incremental Sheet Forming (ISF) technologies. With this purpose, different approaches have been carried out in Single-Point Incremental Forming (SPIF) and Two-Point Incremental Forming (TPIF) in order to produce customized cranial implants using different polymeric materials. In this context, this research work provides a methodology to design and manufacture polymer customized cranial prostheses using the ISF technologies starting from a patient’s computerized tomography (CT). The results demonstrate the potential of manufacturing polymeric cranial prostheses by ISF in terms of the high formability achievable and show the appropriate geometrical accuracy at affordable manufacturing costs provided by these processes.Ministerio de Economía y Competitividad DPI2015-64047-

On the manufacturing of highly-customized near net-shape medical implants using magnesium alloy sheet

Incluída en Procedia Manufacturing 50The purpose of this work is defining a global methodology framework for the manufacturing of medical implants using Mg alloys by Incremental Forming process from the results attained by the authors in this field. The methodology proposed considers two main steps, an indispensable related to material characterization that includes from the classical and mechanical to spifability testing and it includes numerical simulations. And another one related mainly to implant forming taking into account the best process parameters from the analysis carried out in the previous step. As newness, two variants of the incremental forming process, Single (SPIF) and Two-Point (TPIF) Incremental Forming, are used for the same magnesium implant geometry. Different outputs variables, mainly: Ra, Shape accuracy and Thicknesses, besides Force and Temperature were analysed for comparison purposes.Universidad de Girona MPCUdG2016 / 036Ministerio de Educación, Universidad e Investigación (Italia) CUP - D94I18000260001Ministerio de Educación (España) DPI2016-77156-

Revisiting Formability and Failure of AISI304 Sheets in SPIF: Experimental Approach and Numerical Validation

Single Point Incremental Forming (SPIF) is a flexible and economic manufacturing process with a strong potential for manufacturing small and medium batches of highly customized parts. Formability and failure in SPIF have been intensively discussed in recent years, especially because this process allows stable plastic deformation well above the conventional forming limits, as this enhanced formability is only achievable within a certain range of process parameters depending on the material type. This paper analyzes formability and failure of AISI304-H111 sheets deformed by SPIF compared to conventional testing conditions (including Nakazima and stretch-bending tests). With this purpose, experimental tests in SPIF and stretch-bending were carried out and a numerical model of SPIF is performed. The results allow the authors to establish the following contributions regarding SPIF: (i) the setting of the limits of the formability enhancement when small tool diameters are used, (ii) the evolution of the crack when failure is attained and (iii) the determination of the conditions upon which necking is suppressed, leading directly to ductile fracture in SPIF.Universidad de Girona DPI2016-77156-RMinisterio de Educación DPI2015-64047-

Statistical Evaluation of Metaproteomics and 16S rRNA Amplicon Sequencing Techniques for Study of Gut Microbiota Establishment in Infants with Cystic Fibrosis

Newborn screening for cystic fibrosis (CF) can identify affected but asymptomatic infants. The selection of omic technique for gut microbiota study is crucial due to both the small amount of feces available and the low microorganism load. Our aims were to compare the agreement between 16S rRNA amplicon sequencing and metaproteomics by a robust statistical analysis, including both presence and abundance of taxa, to describe the sequential establishment of the gut microbiota during the first year of life in a small size sample (8 infants and 28 fecal samples). The taxonomic assignations by the two techniques were similar, whereas certain discrepancies were observed in the abundance detection, mostly the lower predicted relative abundance of Bifidobacterium and the higher predicted relative abundance of certain Firmicutes and Proteobacteria by amplicon sequencing. During the first months of life, the CF gut microbiota is characterized by a significant enrichment of Ruminococcus gnavus, the expression of certain virulent bacterial traits, and the detection of human inflammation-related proteins. Metaproteomics provides information on composition and functionality, as well as data on host-microbiome interactions. Its strength is the identification and quantification of Actinobacteria and certain classes of Firmicutes, but alpha diversity indices are not comparable to those of amplicon sequencing. Both techniques detected an aberrant microbiota in our small cohort of infants with CF during their first year of life, dominated by the enrichment of R. gnavus within a human inflammatory environment. IMPORTANCE In recent years, some techniques have been incorporated for the study of microbial ecosystems, being 16S rRNA gene sequencing being the most widely used. Metaproteomics provides the advantage of identifying the interaction between microorganisms and human cells, but the available databases are less extensive as well as imprecise. Few studies compare the statistical differences between the two techniques to define the composition of an ecosystem. Our work shows that the two methods are comparable in terms of microorganism identification but provide different results in alpha diversity analysis. On the other hand, we have studied newborns with cystic fibrosis, for whom we have described the establishment of an intestinal ecosystem marked by the inflammatory response of the host and the enrichment of Ruminococcus gnavus

On the effective peek application for customized cranio-maxillofacial prostheses: An experimental formability analysis

This is an open access article under the CC BY license (http://creativecommons.org/licenses/by/4.0/)Single Point Incremental Forming (SPIF) is a dieless and flexible forming technology that allows performing complex shapes and presents a high economic payoff for low production series. In this context, this research presents an experimental investigation of Polyether ether ketone (PEEK) sheets deformed by SPIF at room temperature, determining the influence of the process parameters on the material formability. The research is performed in terms of principal strains that are evaluated within the material Forming Limit Diagram (FLD) obtained by means of Nakajima tests allowing to establish the forming limits of PEEK sheet material. On the other hand, the results of the SPIF tests performed gave rise to an analysis in terms of formability, modes of failure, temperature, forming force, and geometry accuracy. These experiments allow assessing the optimal parameters and forming methodologies/procedures for the manufacturing of cranio-maxillofacial prostheses. In this sense, it was performed a global study in terms of the formability of the manufactured prostheses, as well as the shape accuracy, temperature and roughness analysis, among others. This research showed that the maximum strains attainable by the two prostheses were still found far away from the Fracture Forming Limit (FFL) of the material, showing the feasibility to obtain extra formability within the forming safe zone. In conclusion, this work proved the high potential of manufacturing prostheses in the biomedical field using Incremental Sheet Forming (ISF) processes in combination with advanced biocompatible polymers such as PEEK

Critical analysis of necking and fracture limit strains and forming forces in single-point incremental forming

Single-Point Incremental Forming (SPIF) is an emerging manufacturing process especially suitable to pro-duce small batches of metal parts. Moreover, the enhanced formability of metal sheets deformed by SPIFmakes this technology useful to those industrial applications requiring high deformation levels. In thissense, the precise setting of limit strains in SPIF in relation to the conventional formability limits ofthe material, as well as the influence of the process parameters on these strains, are essential variablesto understand how and how much can be deformed the metal sheets in real production. On the otherhand, the forming force in SPIF is an essential variable, especially for the design of dedicated equipmentor for the safe use of adapted machinery. This paper revisits failure in SPIF by means of an experimentalanalysis of the influence of process parameters, such as the tool diameter, the spindle speed and the stepdown, on the formability in SPIF (spifability) of AISI 304 metal sheets, studied in the light of circle gridanalysis. The work also involves the independent determination of conventional formability limits bynecking and fracture under laboratory conditions by using stretching tests (Nakazima tests), in conjunc-tion with stretch-bending tests performed in order to quantify the influence of the bending induced bythe tool radius. Failure strains are experimentally obtained and compared in stretch-bending and SPIFtests, being the failure mode discussed in each case. Finally, the axial forming force evolution wasrecorded with the aim of analyzing the range of process parameters that would guarantee the safely uti-lization of the non-dedicated process equipment.Gobierno de España DPI2012-32913Gobierno de España DPI2012-36042Ministerio de Educación, Cultura y Deporte FPU12 / 0540

Preliminary study on the use of 3D printed biodegradable polymeric sheet for the manufacturing of medical prostheses by SPIF

This is an open access article under the CC BY-NC-ND license (https://creativecommons.org/licenses/by-nc-nd/4.0)Incremental Sheet Forming (ISF) and Fused Deposition Modelling (FDM) of polymers have both an edge over conventional manufacturing by their ability to directly get complex structures without the need of a mold or a die. Obtaining biocompatible polymer blanks for ISF is not always as easy as it could be expected. Concerning nowadays FDM offers a good opportunity to print biocompatible polymer sheets as blanks to next be formed by ISF. Exploring the combination of FDM and ISF for two biodegradable polymers (Polylactic acid (PLA) and Polycaprolactone (PCL)) is the objective of this work. An analysis of the initial printed sheets in terms of thickness uniformity and surface roughness was carried out. Truncated cone shape with fixed slope angle geometries in a CNC machine were formed. The ISF process parameters modified were the traditional: step down, feed rate and spindle speed. As saved outputs there are: Forming Forces, Maximum Temperature, Surface Integrity, Surface Roughness and Shape Accuracy. After this first approach, a good feasibility process window was established for being used on prosthesis manufacturing of PCL. On the contrary, the feasibility window for PLA is limited because of its low formability. The first results of the combination of both additive manufacturing processes are interesting and deserve further studies to evaluate more in depth the behaviors and the forming mechanism of these materials

Germoplasma extranjero de melocotonero para aumentar la diversidad genética en la mejora: abstract

Publishe

A peach germplasm collection for increasing the genetic diversity in European breeding programs: abstract

Publishe