Tomasz Kozior

Research of the Elastic Properties of Bellows Made in SLS Technology

The article contains the result of studies on the effects of selected geometrical parameters of elastic bellows on their elastic properties. Bellows models were produced with using additive technology, selective laser sintering SLS, where the material used to build models was polyamide PA 2200. Based on the measurements of elastic deformation coefficients of each models bellows were determined. Comparing the results of the measurements there was found a significant effect of the thickness, number of corrugations and their length on the value of the coefficient of elasticity.

Methods of Prototyping Process Using Modern Additive Technologies

The paper presents the characteristics of the selected additive technologies SLS - selective laser sintering, 3D Printing - bonding of ceramic powders, PolyJet Matrix - photocuring polymer resins. Procedures and methods for preparing models in the above-mentioned technologies are discussed. The examples of models made during research are described. The solutions covered by the patent application are also presented.

Amplitude Surface Texture Parameters of Models Manufactured by FDM Technology

The paper present test results of a measurement surface texture of models manufactured by FDM (fused deposition modeling) technology. The material used for constructing sample models was a structural material - ABS P430. A Dimension 1200es machine by Stratasys was used for the construction of the models. The process parameter, of which the impact on the quality of the surface texture was analysed, was the model orientation on a virtual building platform. A Form Talysurf PGI 1230, Taylor Hobson contact profiler was used for the measurements, and the test results were compared with the results obtained during the measurements with an optical profilometer.

Influence of fabric pretreatment on adhesion of three-dimensional printed material on textile substrates

Adding three-dimensional printed objects on existing surfaces enables creation of multi-material objects with tailored mechanical properties. Especially, the tensile strength of a textile fabric is advantageous in comparison with three-dimensional printed polymeric parts, while the latter can increase the stiffness of the composite. The adhesion forces between both material partners, however, are crucial for the reliability of the multi-material object. While several printing and material properties have been shown to influence the adhesion previously, this article concentrates on the possible pretreatment methods for three-dimensional printing on a cotton fabric. In our experiments, we have shown that especially pretreatments which made the textile surface more hydrophobic or more hydrophilic resulted in significant modifications of the adhesion forces. In addition, the adhesion is influenced by the infill orientation, with an orientation of 90° being significantly advantageous compared to 0°. While surface roughness was also shown to depend on the infill angle, no significant differences of the tensile strength or the elongation at break were measured.

ASSESSMENT OF TRIBOLOGICAL PROPERTIES OF POLYMERS USED IN ADDITIVE TECHNOLOGIES SLS AND PJM

The paper presents preliminary results of tribological research on materials used in two additive technologies photo-curing polymer resin PJM and selective laser sintering of polyamide powders SLS. A Tribometer T-15 type ring-disk was used to determine the impact of technological parameters, e.g., printing direction and building layer thickness on the selected tribological properties and wear processes for elements generally used as machine parts. * Kielce University of Technology, Faculty of Mechatronics Mechanical Engineering, al. Tysiąclecia Państwa Polskiego 7, 25-314 Kielce, Poland. T R I B O L O G I A 5-2016 74 INTRODUCTION The dynamic development of mechanisms of precision machinery, e.g., technical active seals, sleeve bearings, or motor connections of machines puts extremely high requirements on the reduction of friction and wear processes. Tribological processes occurring in the friction area determine the reliability and durability of such devices and have a direct impact on the proper work of the object [L. 1, 2]. In conventional manufacturing methods, the tribological properties of the materials are much easier to determine because of the isotropy in mechanical properties and their structure. Problems of durability arise when we are using additive technologies to manufacturing end-used parts exposed to wear without additional finishing operations, i.e. grinding, and polishing. Additive manufacturing technologies are based on a layer manufacturing of physical models directly from a 3D three-dimensional solid model [L. 3]. The use of three-dimensional models makes the whole process of production much more flexible and competitive in relation to the conventional manufacturing technologies. Any design changes can be implemented quickly, without the need to setup technological machines, such as machining tools or forging dies. Because of the layer construction of the models, it is possible to produce endused components, where: it is difficult or impossible using traditional technologies. With the development of additive technologies and improved accuracy, designers increasingly started using the above-mentioned technologies for the production of fully functional co-operating machine elements, i.e. seals, bearings, and mechanical connection elements [L. 4]. Most additive technologies, especially those where: plastics are used as input materials, present anisotropy in mechanical properties and accuracy. This phenomenon mainly depends on the technological parameters and placement models on the building platform. This problem causes that the wear process of machine parts produced by using “Three Dimensional Printing” can be different for the same element. Selected tribological properties of materials used in SLS technology were described in [L. 5], where: the authors used a tribometer (type ring-pin) to determined basic tribological parameters of the friction elements. Samples were manufactured using bronze powder (EOSINT M Cu 3201). Countersamples were made by using polyamide with glass fibre. The research was carried out in a heating chamber with controlled temperature. This paper describes the preliminary study of the process of friction in a face contact surface of the ring-and-disk, using a T-15 tribometer. Rings (samples) for tests were made from different materials used in two commonly used additive technologies: PJM and SLS. The aim of the study was to determine the effect of process parameters, i.e. printing direction and building layer thickness on the wear processes of the rings (samples) and the coefficient of friction in a sliding connection. 5-2016 T R I B O L O G I A 75 TECHNOLOGY In the study, two types of modern additive technologies that use input polymeric materials were used: photo-curing polymer resin PJM, and selective laser sintering SLS. For PJM technology, a Connex 350 machine (Stratasys Company) and VeroWhite material were used. In SLS technology, to prepare samples, Formiga P100 (EOS company) and material PA 2200 were used. The mechanical properties of the materials used to build the samples are shown in Table 1 [L. 6, 7]. The printing process of samples and tribological research were carried out at the Kielce University of Technology in the Laboratory of Unconventional Manufacturing Technology. Table 1. Mechanical properties of materials: PA 2200 / Vero White [L. 6, 7] Tabela 1. Właściwości mechaniczne materiałów: PA 2200/VeroWhite [L. 6, 7] Mechanical Properties Value Unit Standard Youngs modulus 1700/2495 MPa EN ISO 527 / ASTM D-638 Notched Izod (23°C) 4.4/24 kJ/m ISO 180/1A / ASTM D-256 Shore’s hardness 75/83 ISO 868 / Scala D Density 0.930/1.18 g/cm EOS method / ASTM D792 Water absorption 1/1.5 % D-570-98 24hr Selective Laser Sintering SLS SLS technology is one of the most commonly used method of rapid prototyping. In this technology, polyamide powder with a grain of a diameter equal to 0.056 mm is distributed on the working platform by a machine arm. Then a focused beam of a CO2 laser by scanning a selected cross section of the model is sintered building a layer and combining it with the previously made surface. The process of building and cooling takes place in an atmosphere of inert gas (nitrogen) to prevent oxidation. After completion of the sintering process, a working platform is lowered by a value equal to the thickness of one layer, which is minimally 0.1 mm for PA 2200 material in SLS technology [L. 8]. Due to the used powder as a building material, SLS technology allows building models of very complex internal shapes. The powder, which has not been used during production, can be removed from the model in a cleaning stage by compressed air. Photo-curing Polymer Resin PJM PolyJet Matrix Technology (PJM) [L. 4] is based on photo-curing liquid polymer resins by used UV light. In the building process, printing heads sprayed thin drops of liquid polymer resin in the selected cross section of the model. Then a UV lamp initiates the polymerization process by scanning the T R I B O L O G I A 5-2016 76 newly formed layer. The main technological parameter presented in this technology is layer thickness, which has a significant impact on the accuracy and mechanical properties. The minimum layer thickness for a “single” material is equal 0.016 mm and 0.03 mm for the mixtures of materials, “digital materials” [L. 9, 10]. SAMPLES The samples for tests were designed using CAD software SolidWorks 2016 in accordance to tribometer T-15 instructions. This device was designed and manufactured at the Institute for Sustainable Technologies – National Research Institute in Radom. The samples were made in 3 variants. The samples angles between the building platform and sample-working surface (friction) were equal to 0°, 45°, and 90°. In the case of the first type of samples prepared using SLS technology, the layer thickness was equal 0.1 mm, and for the second type the layer thickness was 0.2 mm. In the PJM technology, the layer thickness was equal 0.03 mm. The geometrical dimensions of the samples and their placement on the machine platform are shown in Figures 1 and 2. Printing parameters are shown in Table 2. Fig. 1. Sample dimensions Rys. 1. Wymiary badanych próbek Fig. 2. Placement of samples on the machine platform Rys. 2. Rozmieszczenie próbek na platformie maszyny Table 2. Printing parameters Tabela 2. Parametry „wydruku” próbek Samples No. Angle [°] Layer thickness 1 0 0.1/0.2/0.03 2 45 0.1/0.2/0.03 3 90 0.1/0.2/0.03 5-2016 T R I B O L O G I A 77 METHODOLOGY OF THE RESEARCH Tribological research was performed using a tribometer. The T-15 device consists of a testing machine, measurement and control systems, and a computer with software to analyse and record research results. The principle of T-15 work is shown in Figure 3. The rotating disc made of C45 steel is in contact with the fixed sample in a form of ring (Fig. 1), which is pressed by clamping arm with lever ratio of 3:1. During the research, samples can be loaded with a maximum force of 150 N.

Problems of Producing Thin-Walled and Elastic Elements by Selective Laser Sintering

The article describes the technology of making thin-walled components and elastic by additive technology SLS using a polyamide powder PA 2200. The characteristics of the selected elements and the results of their strength tests are presented. The research focuses on the anisotropy of the materials in the various models. Printing processes were investigated on surfaces perpendicular and parallel to the axis of the model. Based on measurements of deformation, coefficients of elasticity, and the influence of selected parameters of the printing process, the accuracy of tested elements were determined. Comparing results of the research indicated that there is a significant influence of direction and printing process parameters on elastic properties. Research can be helpful in the future in the design process of elastic and thin-walled components such as springs and bellows.

Elastic Bellows Prepared by Selective Laser Sintering

The article contains the results of studies concerning the effects of selected parameters of the manufacturing process of elastic bellows on their elastic properties and strength. Bellows models were made using additive technology SLS selective laser sintering, in which the material used to construct models was a polyamide PA 2200. Bellows printing process proceeded in a surface parallel to the axis of the bellows and in a surface perpendicular to it. Based on measurements of deformation coefficients of elasticity of bellows were determined, also the measure of the maximum axial force exerted by the bellows while loading the internal pressure was carried out. Comparing the measurement results a significant effect of process parameters on the flexible properties of elastic bellows and their resistance to internal pressure were determined.