Michal Ackermann

Impact Testing of H13 Tool Steel Processed with Use of Selective Laser Melting Technology

This paper deals with experimental determination of toughness, hardness and impact properties of AISI H13 (DIN 1.2344) tool steel which was manufactured using Selective Laser Melting (SLM) technology. The H13 is a chromium-based tool steel which is primarily used for hot working applications such as pressure casting moulds for automotive industry. Evaluation of toughness and impact properties are vital for reliable use of SLM-processed material, especially in the case of highly loaded structures. Mechanical tests were carried out on printed specimens, subjected to thermal treatment and proper data were evaluated. For better understanding of differences between conventionally produced and SLM-processed material, same mechanical tests were done even for hot-rolled H13 tool steel. SLM-printed material shows more brittle behaviour than conventionally made material. This is most probably caused by combination of H13 thermal properties and fast melting and solidification due to SLM processing.

How does the surface treatment change the cytocompatibility of implants made by selective laser melting

ABSTRACT Introduction: The study investigates the potential for producing medical components via Selective Laser Melting technology (SLM). The material tested consisted of the biocompatible titanium alloy Ti6Al4V. The research involved the testing of laboratory specimens produced using SLM technology both in vitro and for surface roughness. The aim of the research was to clarify whether SLM technology affects the cytocompatibility of implants and, thus, whether SLM implants provide suitable candidates for medical use following zero or minimum post-fabrication treatment. Areas covered: The specimens were tested with an osteoblast cell line and, subsequently, two post-treatment processes were compared: non-treated (as-fabricated) and glass-blasted. Interactions with MG-63 cells were evaluated by means of metabolic MTT assay and microscope techniques (scanning electron microscopy, fluorescence microscopy). Surface roughness was observed on both the non-treated and glass-blasted SLM specimens. Expert Commentary: The research concluded that the glass-blasting of SLM Ti6Al4V significantly reduces surface roughness. The arithmetic mean roughness Ra was calculated at 3.4 µm for the glass-blasted and 13.3 µm for the non-treated surfaces. However, the results of in vitro testing revealed that the non-treated surface was better suited to cell growth.

Use of Composite Materials for FDM 3D Print Technology

This article deals with specific polymer composites modified for the Fused Deposition Modelling (FDM) which is a 3D print technology. These two phase systems involve thermoplastic matrix filled with natural fibres. The crucial demand of this progressive technology is put on the accuracy of the semi-product formed into the filament shape. To reach the smooth production of 3D prototypes the filament should have a constant diameter. In the article, individual steps of the polymer composite pelletization and following pre-processing and processing activities are described. Among these steps the extrusion of the filaments belongs and subsequent print test on “RepRap” device accompanied by optimization of building parameters. Tensile specimens were chosen for print with regard to maps mechanical properties of this newly developed material which was the final stage of this work. Tensile test curves were then compared with those graphs which can be found for the material produced by conventional technologies such as injection moulding.

EVALUATION OF THE IMPACT OF PRODUCTION PARAMETERS ON THE FINAL PROPERTIES OF THE PART MADE OF NYLON 12 WITH RAPID PROTOTYPING TECHNOLOGY (FDM)

e-mail: jiri.safka@tul.cz Nylon is a widespread polymer material employed primarily for engineering applications. Its rheological behavior is suitable for a wide range of manufacturing techniques which produce parts with very specific properties. Representatives of prototype systems are included among these production technologies and this article is focused especially on 3D printing. FDM technology, that allows processing of nylon filaments, was selected to analyze the effect of various processing parameters on the final properties of the product and the overall production procedure. The effect of orientation of the components in the production machine work space on the final strength and structural compactness was analyzed. The product quality and overall economic aspects, based on production time and the total amount of material, including the supporting materials were other evaluating criteria.

Properties of Models Produced by Direct Selective Laser Melting Technology

The paper deals with evaluation of selected mechanical properties of tensile test specimens which were made from AlSi12 material by Direct Selective Laser Melting (DSLM) technology. Specimens were built in three various set-ups such as different angles towards building platform and various types of supporting structures in order to prove the influence of these parameters to mechanical properties of resulting product. The specimens were also subjected to material tests to reveal its inner structure, quality of a grain and chemical composition of the material. As a conclusion, the selection of the most suitable supporting structure and alignment of a model towards building platform are discussed. Mechanical parameters evaluated from tensile tests such as Young’s modulus (E), 0.2% proof stress (Re0,2) and tensile strength (Rm) are compared with values typical for the selected material AlSi12.

The effect of ethylene oxide sterilization on electrospun vascular grafts made from biodegradable polyesters

The study describes the detailed examination of the effect of ethylene oxide sterilization on electrospun scaffolds constructed from biodegradable polyesters. Different fibrous layers fabricated from polycaprolactone (PCL) and a copolymer consisting of polylactide and polycaprolactone (PLCL) were investigated for the determination of their mechanical properties, degradation rates and interaction with fibroblasts. It was discovered that the sterilization procedure influenced the mechanical properties of the electrospun PLCL copolymer scaffold to the greatest extent. No effect of ethylene oxide sterilization on degradation behavior was observed. However, a delayed fibroblast proliferation rate was noticed with concern to the ethylene oxide sterilized samples compared to the ethanol sterilization of the materials.

Rapid Prototyping Technology for Special Pressure Vessels

The article deals with the topic of 3D printing of pressure vessels and their testing. The main focus of the research was on a 3D model of the pressure vessel, which was originally designed for a student formula racing car project. The described virtual 3D model was designed with regard to 3D printing. The physical model was manufactured using several additive manufacturing technologies. The first technology was FDM using ULTEM 1010 material. The next technology was SLS (Selective Laser Sintering) using polyamide materials (PA3200GF and PA2220). The last technology was SLA (Stereolithography) using a polypropylene material (Durable). Experimental evaluation of the vessels was carried out by a pressure test, which verified the compactness of the 3D printed parts and their possible porosity. At the end of the article, a comparison of each printed model is made in terms of their final price and weight, together with pressure and thermal resistance.

Using of 3D Printing Technology in Low Cost Prosthetics

The 3D printing technology used for final production of upper limb prostheses is the topicof this article. It focuses on different 3D printing technologies and testing of different thermoplasticmaterials. As the testing object an index finger of HACKberry open source myoelectric bionic handwas used. This part was 3D printed by using of different printing technologies (FFF/FDM, SLA, SLS,PolyJet), and different materials (PLA, ABS, PC-ABS, Though, etc.), and different strategies (heightof layers). The fingers were mechanically tested to simulate flexion in a tip pinch grip. At the endof this paper results of this research and testing is summarized, and optimal material, technology andstrategies of parts production is highlighted.

Selective Laser Melting Technology and Manufacturing of Accurate Thin Structures

This paper deals with finding the building parameters for manufacturing of fine structures with regard to their size precision and structural consistency. Practical use of these structures can be found in areas such as microelectronics, fine mechanics and automotive. Very fine structures with thickness lower than 0.3 mm are very hard to be manufactured due to the limitations of Selective Laser Melting (SLM) technology. These limitations lie in building parameters including mean size and shape of the powder particles, diameter of laser spot and scanning speed. Practical part of the work consists of printing the testing matrices from AlSi12 material with different building parameters for each element. Final products are then evaluated using scanning electron microscope in order to verify final size and structural properties of the specimens. Thanks to these tests, it was possible to find actual border of the technology for given type of powder. Structure with minimal thickness and sufficient strength was found to be 0.21 mm. Moreover, the method for finding parameters for manufacturing of fine structures is applicable for other types of materials.

Influence of Different Coupling Agent Type on Processibility and Applicability of Polymer Composites

The contribution deals with the processibility and applicability of polymer composite systems based on polypropylene matrix. The composites were filled with vegetable fibres (particularly the cotton fibres, coir fibres, hemp fibres and jute fibres) and the interface between the polymeric matrix and the natural fibres was modified using two types of coupling agents (the organosilane coupling agent and maleic anhydride grafted polypropylene). For evaluation of the final impact of all three phases presence on the processibility of the polymer composite the melt flow behaviour was analyzed (MFI analysis according to ISO 1133) for the filler concentration of 10, 20 and 30 wt. %. This study involves also the natural fibre surface profile analyses (based on SEM observation) and the applicability of created composite materials was determined using the heat deflection temperature (HDT analysis according to ISO 75).