Publication: Sfero dökme demir süspansiyon kolu bileşeninin frezeleme operasyonu için işleme fikstür tasarımının optimizasyonu
Abstract
Grafit, sfero (küresel grafitli) dökme demirlerde lameler yapıdan küresel yapıya dönüştürülür. Karbonun küre yapıya dönüşmesini sağlamak için dökme demire ergimiş halde iken seryum ve magnezyum (Ce ve Mg) gibi nadir toprak elementleri eklenir. Grafit şeklinin lameler yapı yerine küresel yapıda oluşu, dökme demire süneklik ve mukavemet kazandırır. Yüksek mukavemet ve uzama kabiliyeti sayesinde küresel grafitli dökme demirler birçok sektörde kendine yer bulmuştur. Bu çalışma kapsamında, sfero dökme demirden imal edilmiş bir otobüs arka süspansiyon kolunun işleme fikstürü tasarımı ve optimizasyon çalışmaları CAD (bilgisayar destekli tasarım) ve CAE (bilgisayar destekli mühendislik) programları kullanılarak gerçekleştirilmiştir. Süspansiyon kolu; havalı körüklerin, darbe sönümleyicilerin ve aksın bağlandığı otobüs arka süspansiyonunu daha konforlu hale getiren emniyet parçasıdır. İşleme fikstürü, parçanın talaşlı şekillendirilebilirliği üzerinde önemli rol oynamaktadır. Süspansiyon kolu parçasının fikstürü, topoloji optimizasyonu kullanılarak şekillendirilmiştir. Oluşturulan ve üzerinde DFM (üretilebilirlik için tasarım) çalışması gerçekleştirilen fikstür tasarımı, kesme kuvvetleri ve sıkma kuvvetleri dikkate alınarak, nihai yapısal analiz çalışmalarıyla sonuçlandırılmıştır. Yapısal analizlerde kullanılan kesme ve sıkma kuvvetleri, ampirik olarak hesaplanmış, elde edilen değerler DOE (Deney Tasarımı) metodları ile optimize edilmiştir. Sonuç olarak, gerçekleştirilen bu çalışma ile topoloji optimizasyonuna dayalı, mühendislik temelli bir fikstür tasarımı ortaya konmuştur. Elde edilen tasarım, geleneksel yöntemlerle belirlenen fikstürlere kıyasla yaklaşık %45 daha hafif olmasına rağmen daha yüksek rijitlik sergilemiştir. Yapısal analizler sonucunda, işleme sırasında oluşan kesme ve sıkma kuvvetlerine karşı yeterli dayanımı sağladığı tespit edilmiştir. İş parçasının talaşlı şekillendirme sonrası yapılan ölçümlerinde, teknik resim toleranslarına uygunluk başarıyla sağlanmıştır. Bu yönüyle, optimize edilmiş fikstür tasarımı, hem üretim doğruluğunu hem de yapısal verimliliği artıran bir çözüm sunmaktadır.
Graphite is transformed from a lamellar structure to a spherical structure in spheroidal (spheroidal graphite) cast irons. In order to ensure that carbon transforms into a spherical structure, rare earth elements such as cerium and magnesium (Ce and Mg) are added to the cast iron while it is molten. The fact that the graphite shape is spherical instead of lamellar provides ductility and strength to the cast iron. Thanks to its high strength and elongation ability, spheroidal graphite cast irons have found a place in many sectors. Within the scope of this study, the machining fixture design and optimization studies of a bus rear suspension arm made of spheroidal cast iron were carried out using CAD (computer aided design) and CAE (computer aided engineering) programs. The suspension arm is the safety part that turns the bus rear suspension more comfortable, to which the air bellows, shock absorbers and axle are connected. The machining fixture plays an important role in the machinability of the part. The fixture of the suspension arm part was shaped using topology optimization. The fixture design, which was created and subjected to a DFM (Design for Manufacturability) study, was finalized through structural analysis, taking into account the cutting and clamping forces. The cutting and clamping forces used in the structural analyses were calculated empirically, and the resulting values were optimized using DOE (Design of Experiments) methods. As a result, a fixture design based on engineering-oriented topology optimization was successfully developed in this study. The resulting fixture was found to be approximately 45% lighter than those designed using conventional methods, yet it exhibited higher rigidity. Structural analyses confirmed that the fixture provided sufficient resistance to the cutting and clamping forces encountered during machining. Dimensional measurements conducted after the machining process demonstrated that the workpiece met the technical drawing tolerances. In this respect, the optimized fixture design offers an effective solution that enhances both manufacturing accuracy and structural efficiency.
Graphite is transformed from a lamellar structure to a spherical structure in spheroidal (spheroidal graphite) cast irons. In order to ensure that carbon transforms into a spherical structure, rare earth elements such as cerium and magnesium (Ce and Mg) are added to the cast iron while it is molten. The fact that the graphite shape is spherical instead of lamellar provides ductility and strength to the cast iron. Thanks to its high strength and elongation ability, spheroidal graphite cast irons have found a place in many sectors. Within the scope of this study, the machining fixture design and optimization studies of a bus rear suspension arm made of spheroidal cast iron were carried out using CAD (computer aided design) and CAE (computer aided engineering) programs. The suspension arm is the safety part that turns the bus rear suspension more comfortable, to which the air bellows, shock absorbers and axle are connected. The machining fixture plays an important role in the machinability of the part. The fixture of the suspension arm part was shaped using topology optimization. The fixture design, which was created and subjected to a DFM (Design for Manufacturability) study, was finalized through structural analysis, taking into account the cutting and clamping forces. The cutting and clamping forces used in the structural analyses were calculated empirically, and the resulting values were optimized using DOE (Design of Experiments) methods. As a result, a fixture design based on engineering-oriented topology optimization was successfully developed in this study. The resulting fixture was found to be approximately 45% lighter than those designed using conventional methods, yet it exhibited higher rigidity. Structural analyses confirmed that the fixture provided sufficient resistance to the cutting and clamping forces encountered during machining. Dimensional measurements conducted after the machining process demonstrated that the workpiece met the technical drawing tolerances. In this respect, the optimized fixture design offers an effective solution that enhances both manufacturing accuracy and structural efficiency.