Three-dimensional (3D) printing technologies have been developed for prototype purposes. However, it has become possible to manufacture various functional parts with improving mechanical properties of 3D printing materials. Although polylactic acid (PLA) is the most widely used 3D printing material, the mechanical properties required for functional parts are not sufficient. For this reason, carbon fibre reinforced PLA composites are preferred as 3D printing material to advance the mechanical properties of the fabricated parts. However, for 3D printed parts, it is known that the layer thickness and printing orientation angles affect the mechanical properties. In this study, unreinforced PLA and 15% carbon fibre reinforced PLA composite tensile specimens were 3D printed using fused deposition modeling (FDM) technique. The effects of printing orientation angle and layer thickness on modulus of elasticity and tensile strength are investigated. 3D printed unreinforced PLA samples exhibited better tensile performance as compared to carbon fibre reinforced PLA composite samples.
Keyword: 3d printing
The effect of the low-frequency vibration processing on the residual elastic stresses in the Ti-6Al-4V alloy manufactured by 3D printing (Selective laser melting) was investigated. The studied sample was manufactured horizontally in respect to the building platform. Different vibration oscillations modes (vertical, horizontal, and elliptical) were chosen for study. The oscillations were done with frequency of 16 Hz, and a processing time was 20 minutes. Studies shown that 3D printed sample had a high level of residual elastic stresses, which were changed after vibration treatment. The optimal parameters of vibration processing, which provide a minimum level of residual elastic stresses in 3D printed Ti-6Al-4V alloy are discussed.
The application of the selective laser melting (SLM) method requires knowledge of not only the properties of the material after manufacturing, but also after mechanical loading. The aim of this work is to investigate the strain-rate dependence and microstructure of Ti6Al4V samples manufactured by SLM method with different angles to the building platform. SLM Ti-6Al-4V samples were manufactured using the EOSINT M280 (EOS GmbH) at angles of 0°, 30°, 45°, 90° to the building platform. A medicine Ti6Al4V (ASTM grade 23) powder was used for the study. Tensile tests were performed with an Instron test machine using two strain rates 0.5 mm/min and 2 mm/min at room temperature. It was found the strain-rate dependence in the studied samples. The features of the mechanisms of hardening and softening in an investigated SLM Ti-6Al-V alloy are discussed.
Three-dimensional (3D) printing technologies are the most promising method in the production of functional parts. Although 3D printing technology includes various methods, fused deposition modelling (FDM) is the most widely used one. In FDM, generally polylactic acid (PLA) filaments are used to fabricate 3D geometry by stacking individual layers. In fact, FDM is a complicated process with numerous parameters that affect printing quality. Printing parameters such as printing orientation, layer thickness, printing orientation angle, filling ratio, filament feed rate, etc. have significant impact on the quality and performance of FDM printed parts. Since the mechanical properties are very important for functional parts, the effect of these parameters on the mechanical properties of the PLA specimens has been extensively studied. However, there is no sufficient data in the surface characterization literature of these parameters. In this study, the effect of layer thickness and printing temperature on the surface properties of PLA specimens printed using FDM was investigated.
DOMINANT TECHNOLOGIES IN “INDUSTRY 4.0”
MOLD DESIGN AND PRODUCTION BY USING ADDITIVE MANUFACTURING (AM) – PRESENT STATUS AND FUTURE PERSPECTIVES
This paper covers the advanced Additive Manufacturing (AM) techniques applied to injection mold design and production. Its aim is to do a comprehensive analysis on what AM is doing for the recent and future perspectives in the field of mold’s production.
Further analyses are done on the possible use of Rapid Tooling (RT) techniques based on AM technologies. These include plastic mold inserts made using high strength polymer resins and metal-based technologies for direct tooling work.
Moreover, the work also reviews conformal cooling channel design based on laser sintering AM technologies and its effect in improving mold cooling efficiency to reduce cycle times, which is an important issue in the injection molding process.
Finally, a brief techno-economical analysis is presented, as well as a comparison between the two different types of molds – the conventional ones, and molds produced by rapid tooling. The conclusions leads toward future usage of RT and AM in the mold design and
MATHEMATICAL MODELLING OF TECHNOLOGICAL PROCESSES AND SYSTEMS
3D printing also called Layer based technology, Freeform fabrication, Additive manufacturing or Rapid Prototyping technologies has undergone significant development over the last decades. The growth is related to the expansion of the range of materials used, application areas, and range of possible sizes from nanometer to tens of meters as well as increasing machine accessibility. There is a growing consensus that 3D printing technologies will be at the heart of the next major technological revolutions. At present there are some technological specifics and associated difficulties in 3D printing one of which is the accuracy of the manufactured product. Research in this area would allow modelling of 3D printing processes.
The article describes the possible types and sources of inaccuracies in 3D printing processes. The various types of test pieces used in practice are examined to quantify the errors in shape and sizes after building. Test pieces with predefined discrete points and methodology are provided to calculate inaccuracies. The results are presented in the terminology of “linear” and “shear” deformations. This gives opportunity to determine the variations in the shape and dimensions of the parts built by 3D printing. On the basis of the discreet results obtained, the possibility of 3D printing process modelling is discussed and presented.
The purpose of the present paper is to evaluate the geometric accuracy and surface roughness of polymeric samples manufactured by Digital Light Projection (DLP) Stereolithography. The standard cubic samples with dimensions 5 mm х 5 mm х 5 mm were printed of two polymers: NextDent C+B (white-yellowish color A3.5, VITA shade guide) and NextDent Cast (dark-red color), in two ways of placement to the base – horizontally and inclined at 45о. The samples were printed with two different layer’s thickness – 35 μm and 50μm. It was established that the samples of both polymers, manufactured in horizontal position with the lower layer’s thickness (35μm) possess highest dimensional accuracy and lowest interval of deviation. The most accurate are the dimesons parallel to the basis, while these, parallel or inclined to the print direction, have the highest deviations. The interval of the deviations of the dimensions of samples, manufactured inclined at 45o, is nearly 2-3 times higher, as the interval of the samples, made of NextDent Cast, is more than 50% higher than that of NextDent C+B. The horizontally printed samples have 1.5-2 times lower surface roughness compared to the samples, printed inclined at 45o. The surface roughness of the samples, made of NextDent Cast, is 30-50% higher than that of NextDent C+B independently of the layer’s thickness. The increase of the thickness from 35 μm to 50μm leads to 1.5-2 times higher surface roughness in the two samples’ positions. The optical properties of both polymers in the research strongly influence the geometric characteristics, dimensional accuracy and surface roughness of the objects, manufactured by DLP stereolithography.
Direct Metal Laser Sintering (DMLS) is a revolutionary technology that allows a production of fully functional metal parts directly from a 3D CAD data, eliminating the investment to production tools and technologies which brings considerable cost and time savings. Metal parts made by DMLS technology are fully comparable with casted or machined parts. A range of application of DMLS technologies is very wide – from prototypes, through short-run production to final products. Advantages of DMLS technology are arising along with complexity of parts – more complex geometry of parts (in terms of shape and occurrence of the detail) make DMLS technology even more economically effective.
Nowadays the field of Rapid Prototyping is rapidly changing and providing a clear overview is challenging. One of the biggest problems in this context is that different operations are often named similar. In the beginning of this paper the most important related terms are defined and classified. Afterwards the major Rapid Prototyping techniques, called generative manufacturing methods, are explained.
Alternatives to these generative methods as well as 3D-scanning methods are dealt with too. All in all these emerging technologies around 3D-printing and 3D-scanning are revolutionizing the way Rapid Prototyping laboratories look like. They offer new possibilities and reduce the complexity of prototyping. One of the future trends is so called Fab Labs which are currently stretching the boundaries of the common Rapid Prototyping laboratories. At Graz University of Technology the second Fab Lab in Austria has been established lately. Especially its implementation in University education as part of the Product Innovation Project is discussed in detail.
EFFECT OF OXYGEN AND NITROGEN CONTENTS ON THE STRUCTURE OF THE Ti-6Al-4V ALLOY MANUFACTURED BY SELECTIVE LASER MELTING
TiAl6V (ELI) has the low density, low elastic modulus and high strength. Biocompatibility of this material allows one to adapt it to human implant production and successfully use in the manufacture of surgical implants. Spherical argon-atomized Ti6Al4V (ELI) (45µm) powder from TLS Technik was used for study. The chemical composition complies with the ASTM F-136 (grade 5), ASTM B348 (grade 23) standard for surgical implant applications. Two machines from two scientific centers (Russia and South Africa) were used for the manufacturing of the alloys. Analysis of the oxygen and nitrogen contamination in SLM alloys was done with Van de Graaff accelerator with 2 Mega Volts. It is found that the oxygen concentration in both samples is about 0.2 wt. % and decreases with the increasing of the sample depth; the nitrogen concentration is about 0,02 wt%. X-Ray results show an absence of beta (BCC) phase in both samples. TEM studies found the metastable martensitic structure and silicon nitride Si3N4.