Selective laser sintering (SLS) system is an additive manufacturing technique used in a variety of different applications, such as tool industries, medicine, aerospace, automotive, and electronics. A prototype SLS system was designed, built, and validated to improve SLS-manufactured part quality in terms of porosity and surface roughness. The prototype SLS system was designed for laboratory use only. Critical process parameters were identified to optimize the manufacturing process: forward step, side step, speed, platform temperature, and layer depth. The most essential defects associated with the SLS manufacturing process are porosity, shrinkage, surface roughness, and reduced hardness. The goals of this work were to design and build the prototype SLS system, then to quantify the effects of the selected process parameters on manufacturing defects and minimize manufacturing defects. Validation data from each SLS subsystem was compared to manufacturing simulation program parameters. Validation data included laser power, laser beam diameter, gantry motion in two axes, gantry vibration, and CAD/CAM interface program. Revisions of the prototype SLS system are proposed to maintain the resolution of 0.003 m and cost of less than $10,000.
Selective laser sintering is an additive manufacturing technique that uses a high power laser to sinter or melt powder layer by layer to build 3D shapes. This paper focuses on creating a mathematical model of the crack width and surface roughness that occur during the selective laser sintering process. Response surface methodology is used to build and determine a mathematical model. Five variables at five levels are selected: forward step, side step, speed, platform temperature and layer depth. Based on response surface methodology, 32 experiments are used to determine the mathematical model of two selective laser sintering defects: crack width and surface roughness. Next, a genetic algorithm is used to determine the optimal solution to minimize crack width and surface roughness of the part. Results show that the five selected parameters have an effect on the target defects as confirmed by the resulting main effects plots, interaction plots, and contour plots. An optimal set of parameters is determined for future use.
The producer focuses on producing parts that match the customer's requirements during manufacturing the automotive engine parts. One of the essential automotive engine parts is a crankshaft used to translate movement from the pistons to the car axle. The crankshaft is a complex shape and diffi cult to produce accurate dimensions during the machining processes. Many machines are used to create the crankshaft. Therefore, many defects happen during the machining process, reducing reliability and increasing the manufacturing process's production cost. This paper focuses on analyzing failure data and reliability of the crankshaft production line that occurs during the manufacturing process of one year. The common failure associated with the manufacturing process were ring screw, unbalanced crankshaft, broken drill screw, hub machining error, mains part machining error, and setup error. The paper aimed to determine and analyze the best failure fi t between the distribution methods, such as Weibull, normal, lognormal, and exponential. Also, the reliability, hazard rate, surviving quantity, and failure density were calculated to evaluate the current situation and predict the reliability of the production line. Results proved the skewness of the data was positive equal to 3.33; the last months had the highest production failure rate, which is 53.8%, the normal method had a proper distribution of data depending on the Anderson-Darling (adj) values which is 1.367 when it compared with other methods, the normal method had the best fi tting result depended on failure percentage, from 1% to 95% of the crankshafts production are expected to fail between 47.2676 and 1149.85 months respectively. The reliability of the production line decreased with manufacturing time increased. To reduce the failure and increase reliability, the maintenance system must be supported, analyze the sources that cause failure and downtime of the production line, continue the employee training system on an ongoing basis, and support the production line with modern technology. All analytical results and suggestions could be valuable to the production line to improve reliability and reduce the manufacturing process's failure.
Three-dimensional printing has recently come into the spotlight due to its promising potential to create physically three-dimensional parts or structures through computer-aided design. While there are many options for 3D printing methods, photopolymerization 3D printing has garnered much attention because of its high resolution. However, the mechanical properties of photopolymerized 3D printed parts can vary widely depending on the manufacturing parameters and post-processing settings used. This research focuses on studying the effect of printing variables on the mechanical properties of samples printed using a Stereolithography machine (Formlabs, Form+3). Three variables are used: layer thickness (25 and 50 ?m), part orientation (X and Z directions), and post-curing. Also, eight groups of 3D-printed photopolymer specimens for twenty-four specimens are used for the tensile test results. The results showed the printing variables affected the mechanical properties of samples, which were proven by Young's modulus, ultimate stress, and ultimate strain. ABSTRAK: Pencetakan tiga dimensi baru-baru ini menjadi perhatian kerana potensinya yang menjanjikan bagi mencipta bahagian atau struktur tiga dimensi secara fizikal melalui reka bentuk bantuan komputer. Walaupun terdapat banyak pilihan bagi kaedah percetakan 3D, pencetakan 3D fotopolimerisasi telah mendapat banyak perhatian kerana resolusinya yang tinggi. Walau bagaimanapun, sifat mekanikal bahagian bercetak 3D fotopolimer adalah pelbagai bergantung pada parameter pembuatan dan tetapan pasca pemprosesan yang digunakan. Kajian ini memberi tumpuan kepada kesan pembolehubah cetakan terhadap sifat mekanikal sampel yang dicetak menggunakan mesin Stereolitografi (Formlabs, Form+3). Tiga pembolehubah digunakan: ketebalan lapisan (25 dan 50 ?m), orientasi bahagian (arah X dan Z), dan pasca pengawetan. Juga, lapan kumpulan spesimen fotopolimer cetakan 3D untuk dua puluh empat spesimen digunakan bagi mendapatkan keputusan ujian tegangan. Dapatan kajian menunjukkan pembolehubah cetakan mempengaruhi sifat mekanikal sampel, dibuktikan oleh modulus Young, tegangan utama, dan tarikan utama.
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