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"In producing Thin Wall Ductile Iron (TWDI) plate, special notice should be taken on the skin effect formation. Skin effect is a rim of flake interdendritic graphite formed in the surface. In a normal ductile iron casting, skin effect can be removed with machining process. Unfortunately this procedure cannot be applied in TWDI due to the thickness. This paper discusses the effect of casting design to the skin effect formation. Vertical casting design is used in this work. Variations are made in the thicknesses of the plate. The T1 model is equipped with 5 plates with thicknesses of 1, 2, 3, 4, and 5 millimeters; while the T1-Mod is equipped also with 5 plates, but with the same thickness, which is 1 mm. Skin thicknesses, nodule count, and nodularity are measured by NIS Element software. The result showed that skin effect formation is determined by magnesium content and cooling rate. Skin effect thicknesses are determined by cooling rate and the interaction area of molten metal with the mould. The presence of the skin effect in similar thickness and position of plate improved nodule count. In the same thickness, without the presence of the skin effect, the nodule count tends to increase as the positions of the plates increase. In the design ranging from 1 to 5 mm plate thickness, the highest nodule count is 1284 nodule/mm2 gained by 1 mm plate thickness in 1st position and the lowest one is 512 nodule/mm2 gained by 5 mm plate thickness in 5th position. As for the design of all 1 mm thickness where skin effect is not formed the highest nodule count is 1689 nodule/mm2 gained by 1 mm plate thickness in the 5th position and the lowest is 1113 nodule/mm2 gained by 1 mm plate thickness in the 1st position (near the in gate). The highest nodule count is 90 and the smallest is 85."

"Upaya yang dilakukan dari industri otomotif untuk mengurangi konsumsi energi mendorong para peneliti melakukan berbagai penelitian. Salah satunya adalah dengan metode untuk membuat komponen lebih ringan dengan pengecoran besi ulet dinding tipis (TWADI). Pengurangan berat komponen seperti connecting rod (conrod) akan menyebabkan konsumsi energi menjadi lebih sedikit, tetapi dengan syarat komponen ini tetap memenuhi standar berupa sifat mekanik dan struktur mikro atau bahkan melebihinya. Pada penelitian ini diterapkan optimasi desain conrod pada area I-beam dengan membuat ketebalannya menjadi 0 mm (kosong), yang diharapkan dapat menggantikan conrod Vespa PX-150. Proses pembuatan tersebut terbagi atas beberapa tahapan. Namun, fokus penelitian ini hanya membahas pada tahap proses pembuatan desain sampai penentuan desain optimal dengan bantuan simulasi menggunakan komputer. Perbedaan yang ditemukan adalah jumlah cacat yang terbentuk. Hasil pengamatan cacat penyusutan pada Model A dan juga Model B sama-sama terletak pada rodbig end. Perbandingan cacat penyusutan yang terbentuk, pada Model A terdapat 3 cacat penyusutan lebih banyak daripada Model B hanya terdapat 2 cacat. Hasil analisa makroskopi menunjukkan bahwa semua hasil coran tidak terdapat cacat secara makro struktur dan perlu adanya analisa lebih lanjut untuk memvalidasi hasil pada desain hollow conrod yang dioptimasi.

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Efforts made from the automotive industry to reduce energy consumption encourage researchers to conduct various studies. One of them is a method to make components lighter by casting thin-wall ductile iron (TWADI). Reducing the weight of components such as connecting rod (conrod) will lead to less energy consumption, but with the condition that these components still meet the standards in the form of mechanical properties and microstructure or even exceed them. In this research, the design optimization of the conrod in the I-beam area is applied by making its thickness 0 mm (hollow), which is expected to replace the Vespa PX-150 conrod. The manufacturing process is divided into several stages. The focus of this research is prioritized on discussing the design process until the determination of the optimal design with the help of simulation using Z-CastPro software on a computer. The difference found is the number of defects formed. The observation shows that the shrinkage defects in Model A and Model B are both located on the big end rod. Comparing the shrinkage defects formed, Model A has 3 more shrinkage defects than Model B with only 2 defects. The results of macroscopic analysis show that all castings have no macro structural defects and further analysis is needed to validate the results of the optimized hollow conrod design."