Ahmet İpekçi
@duzce.edu.tr
Dr. Engin PAK Cumayeri Vocational High School
Duzce University
RESEARCH INTERESTS
Additive Manufacturing, Composite Materials, Robotic manufacturing, Machine Design, Machine Elements, Finite Element Analysis.
Scopus Publications
Scopus Publications
Menderes Kam, Hamit Saruhan, and Ahmet İpekçi
SAGE Publications
Additive Manufacturing (AM) method enables to produce products easily, cheaply and quickly with more complex geometry compared to traditional production methods. In this context; Fused Deposition Modeling (FDM) is a widely used for AM method that requires a large number of process parameters. In this study, it is aimed to experimentally investigate the damping capabilities of the metal/polymer composite sleeve bearings printed using FDM. A total of 54 pieces (27 pairs) were printed from composite filaments such as nine pairs for each of PLA, PLA + 20% Bronze, and PLA + 20% Copper metal/polymer with different filling structures (Octogram spiral, Archimedian chords, and 3D Honey comb) and different occupancy rates (10, 30, and 50%), respectively. The experiments were carried out using the shaft-bearing system under the same operating conditions at a rotational speed of 900 revolution per minute (rpm), and vibration data was collected from the rotating shaft with proxy probes. Rotating shaft position is very important to determine journal position in bearing for understanding deterioration in the bearing. Bode and Orbit plots are used to detect the level of deterioration in the bearing. The value of bearing to shaft clearence can vary widely depending on application. Since the bearings were heavily loaded, they were compressed by radial load caused large clearence. The results showed that compressed bearing had significant influence on the stability of rotating shaft system and significant differences in damping capabilities of composite sleeve bearings with different filling structures and occupancy rate. Increasing occupancy rate decreases the vibration amplitude values in copper-reinforced sleeve bearing but increases in bronze-reinforced sleeve bearing. From the microstructure analysis, it has been observed that the vibration absorbation capability is better due to the more homogeneous distribution of the copper reinforced bearings than the bronze reinforced bearings. Also, vibration absorption capability of sleeve bearings with 3D Honeycomb filling structureis increased significantly proportion to the occupancy rate.
Menderes Kam, Ahmet İpekçi, and Ömer Şengül
SAGE Publications
This study investigated the effects of FDM (Fused Deposition Modeling) process parameters on mechanical properties (tensile strength, elongation, and impact strength) of 3D (three-dimensional) printed PA12 (Polyamide12) samples using Taguchi method. In the experimental design (L8), four different layer thickness (0.1, 0.15, 0.2, 0.25 mm), extruder temperature (250 and 260°C), filling structure (Rectilinear and Full Honeycomb), and occupancy rate (25 and 50%) were determined. The tensile and impact strength test samples were printed with the FDM method. Tensile and impact strength of the test samples were carried out according to ISO 527 and ISO 180 test standards. The findings obtained from tests were analyzed and compared. As a result, the layer thickness is most effective factor for enhance the mechanical properties instead extruder temperature, occupancy rate, and filling structure. The optimum tensile strength of determined for process parameters (layer thickness, occupancy rates, filling structures and extruder temperature) were 0.25 mm, 50%, Rectilinear, and 250°C, respectively. The optimum impact strength of determined for process parameters (layer thickness, occupancy rates, extruder temperature, and filling structures) were 0.25 mm, 50%, 250°C, and Rectilinear, respectively. PA12 filament material can be used to printing for sleeve bearing due to their mechanical properties. It can be used in the production of many machine parts and components due to its tensile strength, impact strength resistance and damping properties.
Menderes Kam, Ahmet İpekçi, and Kudbeddin Argun
SAGE Publications
Electrical Discharge Machining (EDM) is commonly used as non-traditional manufacturing methods for geometrically complex shaped or hardened materials that are extremely difficult-to-machine with traditional machining processes. In this experimental study, investigations were carried out on the machining of Conventional Heat Treated three different deep cryogenically treated and tempering processes (DCT&T) of AISI 4140 steels in EDM process. The process parameter such as discharge current (9, 16, 23, and 30 A), pulse on time (120, 180, 240, 300 µs) and pulse off time (12, 18, 24, and 30 µs) were investigated and the output responses like surface roughness, electrode wear ratio, material removal rate, and machining time were explored. Experiments were conducted using L16 orthogonal array in EDM machining process. The data obtained from experiments were analyzed. As a result, determination of discharge current (30 Amps), pulse off time (12 to 18 µs), pulse on time (180 to 240 µs) and deep cryogenically treatment with 24 h and 48 h holding time as the optimum machining processing parameters for tempered steels to be subjected to DCT&T process. As a result of multi-criteria optimization, it is suitable for best surface quality and fast material removal rate.
Ahmet İpekçi and Bülent Ekici
SAGE Publications
Filament winding method is the most commonly used method to produce profiles with different cross sections as composite product manufacturing. In this method, fiber material is wound with resin at different angles on a mold that has a suitable cross section shape. As a winding strategy, angled and helical winding can be done. Motion planning for this process is done with geodesic and nongeodesic theories. Requirement to use mold in the filament winding method increases the cost. Also, there is an obligation to helical windings. In winding of different layers, 90° angle cannot be given between the layers. To overcome all these constraints, UV curing can be achieved using photopolymer resin and continuous fiber glass fiber with the help of robotic additive manufacturing technology. Toolpath strategies for production has a key role in this work. As a tool path strategy, nonplanar slicing can be done and manufactured composite elbow in angular layers without mold. Then, under favour of 6-axis mobility of the industrial robot arm, layers can be obtained at exactly 90° angle. In addition, in this method, unlike other winding methods, internal voids, i.e. a filling rate, can be given within the cylindrical encircled layers. In order to verify whether the elbows produced with this method meet the requirements of the desired applications in the industry in terms of mechanical properties, at different filling rates (50%, 75%, 100%), winding turns (0 and 1/8), and different fiber densities (45%, 55% and 65%) 90° curved composite elbows were produced and their internal pressure strength tests were tested. Afterwards, an optimization study was carried out with the Taguchi method for the production parameters that will maximize the internal pressure strength. According to the results of the optimization study, it is seen that it is appropriate to choose the printing parameters that will obtain the highest internal pressure strength values for production with this method, 100% fill rate, 65% fiber density and 0° winding angle. The products made of this process have the advantage of easy-shaping, reasonable ratio of axial strength and encircled strength, specification easy-unifying, stable product quality.
Menderes Kam, Ahmet Ipekci, and Omer Sengul
SciTech Solutions
This study was realized to determine effects of Fused Deposition Modeling (FDM) process parameters on mechanical characteristics with Taguchi optimization method. Three different FDM process parameters used for modified Polylactic Acid (PLA+) filament material; filling structures (Rectilinear, Triangular, and Full Honeycomb), occupancy rates (10, 30, and 50 %) and table orientation (0, 60, and - 45°) was specified as variable parameters for experiments. Other parameters kept fixed for each tensile and izod impact test samples were printed according to the ISO 527 – Type IV and ISO 180-Type I standards. The results found tensile strength values and izod impact values directly proportionate with occupancy rate. The difference between the estimation model and the results of experiments did not exceed the maximum value of 1.8 %. Thus, using the equations derived from this optimization, printing parameters can be determined for the desired tensile strength and izod impact values. By improving the material properties using modified PLA+ filament material as observed in the results, it will be possible to provide support for researchers, design engineers and manufacturer to optimize raw-material usage and margin.
Ahmet İpekçi and Bülent Ekici
Thomas Telford Ltd.
The further development of composite manufacturing methods is characterized by the progress of their mechanical properties which are widely used in many applications as automotive, aerospace, and marine industries. The automated composite production techniques are as follows: automatic tape layering, automatic fiber placement, and filament winding methods used in many industries. Photopolymerized composites and their additive manufacturing methods are promising with new advances in technology. This method for printing continuous fiber-reinforced plastic composite parts by a six-axis industrial robotic arm is based on fused deposition modeling technology. The objective of this work is to obtain a better understanding of the mechanical properties of robotic three-dimensional printed photopolymer resin continuous fiberglass–reinforced composites (CFGRCs) as a function of different printing speeds (10, 20 and 30 mm/s), fiber densities (45, 55 and 65%), and fiber orientations (0, 0/90 and ±45°). This work infers that mechanical properties are significantly affected by the fiber density and fiber orientation of CFGRC. With this method, approximately 300 MPa tensile strength can be obtained and structurally preferred instead of ferrous materials in many areas.
Ahmet İpekçi and Bülent Ekici
SAGE Publications
3D printing technology has gradually taken its place in many sectors. However, expected performance cannot be obtained from the structural parts with this method due to the raw material properties and constraints of Cartesian motion systems. This technology cannot replace structural parts produced by traditional manufacturing methods. In order to avoid these constraints, it is preferred to use continuous fiber reinforced polymer composites in many areas such as automotive and aerospace industries due to their low weight and high specific strength properties. These automated composite manufacturing methods currently have limited production of geometric shapes due to the need for additional molds and production as flat surfaces. To overcome all these constraints, fiberglass reinforced ultraviolet ray-curing polymer matrix composite material are selected for robotic 3 D printing process and various parameters are examined. Fiber-polymer combination and layer structure formation was examined. Scanning Electron Microscopy (SEM) images of sections of 3 D printed test samples were taken and fiber resin curing was examined. The nozzle diameter, printing speed, fiber density and Ultra Violet (UV) light intensity parameters, which will provide effective 3 D printing process, are optimized with the Taguchi method. Tensile strength, flexural strength and izod impact values are considered as result parameters for optimization. It was found that it would be appropriate for 3D printing with a 1.0 mm nozzle diameter, 600 tex fiber density, 4 UV light, 600 mm/min printing speed. With these 3D printing process parameters, approximately 125 MPa tensile strength and 450 MPa flexural strength can be obtained. With this study, support and contribution was provided to researchers, composite producers, tool manufacturer and literature who want to use and develop this 3D printing process.
G. Nilay Yücenur and Ahmet Ipekçi
Elsevier BV