Pengembangan proses multi material deposition indirect sintering (MMS-Is)

WIDYANTO, Susilo Adi, Promotor Ir. Alva Edy Tontowi, M.Sc., Ph.D

2008 | Disertasi |

Penelitian ini bertujuan mengembangkan proses multi-material deposition indirect sintering (MMD-Is) untuk pembuatan produk-produk multi-material dalam vertikal maupun horisontal. Didasarkan prosedur prosesnya, MMD-Is digolongkan dalam proses layer manufacturing (LM). Berbeda dengan mesinmesin LM umumnya, pelaksanaan proses deposisi dilakukan dua tahap meliputi deposisi serbuk produk dan supporting powder. Proses deposisi dilakukan secara kontinyu hingga membentuk geometri objek tiga dimensi tanpa diselingi proses sintering maupun stabilisasi geometri. Tahap berikutnya, proses indirect sintering dilakukan dengan sumber panas yang dipasangkan pada dinding build part. Pelaksanaan penelitian diawali dengan pengembangan metode deposisi serbuk produk getaran berfrekuensi rendah, metode gesekan dan metode screw feeder. Metode deposisi terbaik (diukur dari konsistensi aliran serbuk dan metode pengaturan kapasitas aliran) diaplikasikan dalam proses MMD-Is. Pengujian lintasan deposisi dilakukan untuk memperoleh lebar lintasan deposisi minimum. Bahan uji deposisi berupa serbuk stainless steel ukuran 35-150 μm, duraform polyamide ukuran 35-150 μm, silika ukuran 75-150 μm, besi cor ukuran 35-150 μm dan campuran silika-PE maupun besi cor-PE ukuran 100-150 μm. Penelitian dilanjutkan dengan Optimasi proses sintering dan pengamatan mekanisme ikatan antar partikel. Bahan-bahan penelitian meliputi serbuk PE, PP dan silika. Penelitian untuk peningkatan sifat mekanik produk MMD-Is (karena proses sintering dilakukan tanpa tekanan/kompaksi) dilakukan dengan proses infiltrasi yang menggunakan lem cyanoacrylate sebagai infiltran. Parameter penelitian meliputi temperatur curing (500C, 750C, 1000C) dan porositas (dengan/tanpa proses burn out). Spesimen diuji tarik dan mikrografi dengan SEM. Dengan mesin MMD-Is hasil rancang-bangun, optimasi akurasi dimensi dan sifat mekanik produk MMD-Is dilakukan dengan memvariasikan parameter deposisi, parameter sintering dan ukuran partikel serbuk. Berdasarkan kurva-kurva hasil pengujian, hubungan antar parameter ditentukan yang dinyatakan dalam bentuk formulasi empiris akurasi dimensi produk MMD-Is. Pada bagian akhir, percobaan pembuatan produk multi material dilakukan berbahan besi cor-PE dan silika-PE. Hasil penelitian menunjukkan bahwa metode screw feeder menghasilkan konsistensi aliran terbaik dibandingkan dua metode deposisi lainnya. Metode infiltrasi dapat meningkatkan kekuatan tarik produk hingga 1250 % untuk bahan besi cor-PE dan sekitar 1100 % untuk bahan silika-PE. Pergeseran dimensi produk secara dominan terjadi pada arah pengerolan. Akurasi dimensi produk optimal arah pengerolan maupun tegak lurus pengerolan dicapai pada harga rasio pengerolan sama dengan 1. Pergeseran dimensi produk arah ketebalan merupakan fungsi temperatur sintering di bawah 1600C dan ukuran partikel supporting powder. Masalah utama akurasi dimensi produk multi material berupa perbedaan penyusutan bahan penyusun, dengan penyusutan bahan besi cor-PE lebih besar dari bahan silika-PE.

This research is aimed to develop multi material deposition indirect sintering (MMD-Is) process which is classified in rapid prototyping (RP) process. Compared to the commercial RP machines, the MMD-Is process has a capability to produce a multi material part in block formation. This was achieved with modifying powder deposition sub system and the sintering process. Research implementations were initiated with developing product powder deposition methods which included low frequency vibration method, friction method and screw feeder deposition. By these methods, the best method (measured with the flow consistency and the effectiveness of controlling flow capacity) was applied in developing the MMD-Is process. Testing deposition methods included testing flow ability and line deposition. Materials of the test were the powder of stainless steel (with particle size of 35-150 μm), duraform polyamide (35-150 μm), silica (75-150 μm), cast iron (35-150 μm) and a blend of silica-PE as well as cast iron-PE (100-150 μm). The optimal of the sintering parameters and binding mechanism among particles is obtained with running experiments to optimize the sintering process. The materials used in these experiments were including the powder of PE, PP and silica. Because the MMDIs process was executed in pressure-less condition, so the experiments which was aimed to strengthen the mechanical properties was needed, it was the infiltration process which used a cyanoacrylate glue. The test of infiltration product included tensile strength and micrograph. To optimize the product mechanical strength, infiltration was run with varying curing temperature (500C, 750C, 1000C) and porosity (with/without burn out process). Optimization of product dimension accuracy and mechanical properties of MMD-Is process was conducted with varying deposition parameters, sintering parameters and powder particle size. After the experiments, an empirical formulation was determined. In the last, the experiments of producing multi material parts were run which used a blend of cast iron-PE and silica-PE as product materials. The experimental results show that the screw feeder deposition method was produce the best of powder flow consistence compared the others. Infiltration method increases the tensile strength of MMD-Is product, for cast iron-PE and silica-PE material, the tensile strength increases around of 1250 % and 1100 %, respectively. Product dimension error dominantly occurs in rolling direction. To produce optimal product dimension accuracy in parallel as well as perpendicular to rolling direction, the deposition parameters could be represented by rolling ratio which was achieved equals of 1. Product dimension error in thickness direction is a function of sintering temperature up to 1600C and the particle size of supporting powder. The primary dimension problem of the multi material product is a difference of material shrinkage. Shrinkage of cast iron-PE material is bigger than that of silica-PE.

Kata Kunci : Deposisi,Infiltrasi,Multi-material deposition indirect sintering,Sintering, deposition, infiltration, multi material deposition indirect sintering, sintering