MODUL PRAKTIKUM
PROSES MANUFAKTUR II
LABORATORIUM PENGECORAN LOGAM
KEMENTRIAN RISET TEKNOLOGI DAN PENDIDIKAN TINGGI
UNIVERSITAS BRAWIJAYA
FAKULTAS TEKNIK
JURUSAN TEKNIK MESIN
MALANG
2018
Laboratorium Pengecoran Logam Jurusan Mesin Universitas Brawijaya
PL I
PENGUJIAN KOMPOSISI PASIR CETAK
1.1 Tujuan Pengujian Kadar Air
1. Praktikan mengetahui dan memahami persentase kadar air pasir cetak
2. Praktikan mengetahui penguapan rata-rata pasir cetak
3. Praktikan mengetahui laju penguapan pasir cetak
1.2 Pelaksanaan Pengujian Kadar Air
1.2.1 Alat dan Bahan yang Digunakan
A. Alat yang Digunakan
1. Moisture Analyzer
Alat ini digunakan untuk mengukur kandungan kadar air pasir cetak.
Spesifikasi alat :
Merk : Saitorius
Voltase : 115-230V (AC)
Model : MA 30
Frekuensi : 50-60 Hz
Arus : 3,3 A / 1,6 A
Sample Disk : Ø 90 mm
Housing Dimensions (WxDxH) : 217x283x165 (mm)
Net weight : approx. 5.5 (kg)
Sample weight : max. 30 g, typical 5–10
Temperature increments : 5 °C
Measuring Heating Method : by infrared rays, determination of weight loss
Readability (moisture content) : 0.01%
Temperature range : +40 – +160 °C
Laboratorium Pengecoran Logam Jurusan Mesin Universitas Brawijaya
Gambar 1.1 Moisture Analyzer
Sumber : Laboratorium Pengecoran Logam Jurusan Mesin Fakultas Teknik Universitas
Brawijaya
2. Timbangan Elektrik
Alat ini digunakan untuk menimbang berat pasir cetak sebelum dan sesudah
diukur kandungan kadar airnya.
Spesifikasi alat :
Merk : Melter
Frekuensi : 50-60 Hz
Type : PJ 3000
Voltase : 100-120V 80mA /200-240V 45mA
Beban maksimal : 2100 gram
Dimensi (PxLxT) : 31x29x6 (cm)
Gambar 1.2 Timbangan Elektrik
Sumber : Laboratorium Pengecoran Logam Jurusan Mesin Fakultas Teknik Universitas
Brawijaya
Laboratorium Pengecoran Logam Jurusan Mesin Universitas Brawijaya
3. Cawan
Alat ini digunakan untuk wadah spesimen yang akan di masukan pada
moisture analyzer.
Spesifikasi :
Tipe Produk : Weighing dish
Diameter : 90 mm
Kapasitas : 80 ml
Gambar 1.3 Cawan
Sumber : Laboratorium Pengecoran Logam Jurusan Mesin Fakultas Teknik Universitas
Brawijaya
B. Bahan yang Digunakan
Bahan yang digunakan adalah pasir cetak sebanyak ....... gr, dengan komposisi :
- pasir silika : ........... %
- pengikat : ........... %
- air : ........... %
1.2.2 Urutan Kerja Pengujian
Urutan kerja dalam pengujian kadar air adalah sebagai berikut :
1. Buat pasir cetak seberat 25 gram sebanyak 3 buah sebagai spesimen. Dengan
komposisi yang telah ditentukan.
2. Nyalakan Moisture Analyzer menekan tombol ON/OFF sampai terdengar bunyi alarm.
3. Masukan cawan pertama kedalam alat penentu kelembapan kemudian panaskan pada
suhu sampai 110o C selama 10 menit
4. Mengatur temperatur dengan menekan tombol F1 dan tekan F1 untuk menaikan suhu
sampai 110o C kemudian tekan ENTER.
5. Mengatur waktu pemanasan dengan menekan tombol F2 dan tekan F1 untuk menaikan
waktu sampai 10 menit kemudian tekan ENTER.
6. Tekan ENTER untuk menghilangkan TAR lalu letakkan spesimen di cawan.
7. Tutup penutup Moisture Analyzer kemudian tekan ENTER untuk eksekusi.
Laboratorium Pengecoran Logam Jurusan Mesin Universitas Brawijaya
8. Catat kandungan kadar air yang terbaca pada alat ukur tiap menitnya.
9. Setelah terdengar alarm ukurlah berat akhir pasir cetak setelah dikeringkan dengan
tombol CF.
10. Ulangi langkah 3 – 9 untuk cawan berikutnya.
Laboratorium Pengecoran Logam Jurusan Mesin Universitas Brawijaya
DIAGRAM ALIR PENGUJIAN KADAR AIR PASIR CETAK
Mulai
Tancapkan kabel power ke sumber
listrik
Nyalakan Moisture Analyzer
Siapkan pasir cetak seberat 25 gram
Atur temperatur
Atur waktu pemanasan
Buka penutup Moisture Analyzer
Masukkan sample pasir cetak ke dalam moisture analyzer untuk
dilakukan pengujian
Tutup penutup Moisture Analyzer
Catat kandungan air yang terbaca pada layar tiap menit
A B
A
Setelah terdengar bunyi alarm, ukur berat pasir setelah
dikeringkan dengan menekan tombol CF
Apakah sudah menguji 3 sample ?
B
Selesai
TIDAK
YA
Gambar 1.4 Diagram Alir Pengujian Kadar Air Pasir Cetak
Laboratorium Pengecoran Logam Jurusan Mesin Universitas Brawijaya
1.3 Pengolahan Data
1.3.1 Data Hasil Pengujian
Tabel 1.1
Data Hasil Pengujian Kadar Air
No. Berat Spesimen Awal
( gram )
Berat Spesimen Akhir
( gram ) Kadar Air ( % )
1.
2.
3.
4.
Σ
Sumber : Laboratorium Pengecoran Logam Jurusan Mesin Fakultas Teknik Universitas
Brawijaya
Tabel 1.2
Hasil Perhitungan
No. Berat Awal
( gram )
Berat Akhir
( gram )
Kadar Air
(%) ( X ) ( X - X ) ( X - X )2
1
2
3
4
5
Σ
Sumber : Laboratorium Pengecoran Logam Jurusan Mesin Fakultas Teknik Universitas
Brawijaya
1.3.2 Perhitungan Data Hasil Pengujian
Perhitungan Statistika :
- Kadar air rata – rata ( x )
X = n
x ............................................................................................................. 1-1
Laboratorium Pengecoran Logam Jurusan Mesin Universitas Brawijaya
- Simpangan baku ( )
= 1
)( 2
n
xx ................................................................................................ 1-2
- Simpangan baku rata – rata (
)
= n
............................................................................................................... 1-3
- Kesalahan relatif (Kr)
Kr = x
................................................................................................................. 1-4
%100 Kr .................................................................................................... 1-5
- Derajat kebebasan
(db) = n – 1 ......................................................................................................... 1-6
t.( /2;db) ........................................................................................................... 1-7
- Interval penduga kesalahan permeabilitas pasir cetak
1.3.2 Perhitungan Data Hasil Pengujian
Perhitungan Statistika
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Laboratorium Pengecoran Logam Jurusan Mesin Universitas Brawijaya
1.4 Tujuan Pengujian Kadar Pengikat
1. Praktikan mengetahui persentase kadar pengikat dalam pasir cetak
2. Praktikan mengetahui dan mampu menganalisis pengujian kadar pengikat
1.4.1 Pelaksanaan Pengujian Kadar Pengikat
1.4.2 Alat dan Bahan yang Digunakan
A. Alat – alat yang digunakan.
1. Kompor listrik
Alat ini digunakan untuk mengeringkan spesimen
Merk : Maspion (tipe 1)
Daya : 300-600 W
Berat : 3 Kg
Dimensi (PxLxT) : 24x22x4 (cm)
Sistem pemanasan dengan elemen koil
Bodi plat besi
Gambar 1.5 Kompor listrik
Sumber : Laboratorium Pengecoran Logam Jurusan Mesin Fakultas Teknik Universitas
Brawijaya
2. Timbangan Elektrik
Alat ini digunakan untuk menimbang spesimen sebelum dan sesudah
dikeringkan. (Untuk spesifikasi dan gambar dapat dilihat pada gambar 1.2 dan
penjelasannya).
Laboratorium Pengecoran Logam Jurusan Mesin Universitas Brawijaya
3. Panci
Digunakan sebagai wadah pasir cetak untuk menghilangkan pengikat dan
mengeringkan pasir pada kompor listrik Dengan spesifikasi :
Bahan : Aluminium
Berat : 400 g
Diameter : 25 cm
Tinggi : 14 cm
Tebal : 1 mm
Gambar 1.6 Panci
Sumber : Laboratorium Pengecoran Logam Jurusan Mesin Fakultas Teknik Universitas
Brawijaya
4. Gelas Ukur
Alat ini digunakan untuk mengukur volume larutan yang dipakai. Dengan
spesifikasi :
Kapasitas : 250 ml
Tinggi : 32 cm
Diameter : 4 cm
Tebal : 1,5 mm
Bahan : Glass
Laboratorium Pengecoran Logam Jurusan Mesin Universitas Brawijaya
Gambar 1.7 Gelas ukur
Sumber : Laboratorium Pengecoran Logam Jurusan Mesin Fakultas Teknik Universitas
Brawijaya
B. Bahan - bahan yang digunakan.
Bahan yang digunakan untuk pengujian kadar pengikat antara lain :
- Pasir cetak seberat 100 gr
- Larutan NaOH 2,5 %
- Air sebanyak 950 ml
1.4.3 Urutan Kerja Pengujian
Urutan kerja pengujian kadar pengikat pada pasir cetak adalah :
1. Timbang pasir cetak seberat 100 gr sebagai spesimen
2. Larutkan pasir di dalam 950 ml air pada panci
3. Tambahkan NaOH sebanyak 2,5 gr.
4. Aduk campuran tersebut dan biarkan pasir mengendap selama 5 menit
5. Buang airnya sebanyak 5/6 dari tinggi permukaan air. Ingat : Jangan Sampai Pasir Ikut
Terbuang.
6. Tambahkan airnya hingga seperti semula dan ulangi langkah kerja 4, 5, 6 dan diamkan
selama 5 menit hingga airnya jernih
7. Panaskan pasir cetak dalam panci dengan kompor listrik pada daya 600 watt.
8. Aduk pasir hingga kering
9. Timbang pasir cetak kering tersebut dan catat hasilnya
10. Hitung kadar lempung dengan rumus di bawah ini :
Kadar pengikat = %100 AwalBerat
AkhirBerat - AwalBerat x - Kadar Air .................................... 1-8
Laboratorium Pengecoran Logam Jurusan Mesin Universitas Brawijaya
1.5 Pengolahan Data
1.5.1 Data Hasil Pengujian
Tabel 1.3
Data Hasil Pengujian Pengikat
No Berat Spesimen Awal
(gr)
Berat Spesimen Akhir
(gr) Kadar Pengikat (%)
1
2
3
4
Σ
Sumber : Laboratorium Pengecoran Logam Jurusan Mesin Fakultas Teknik Universitas
Brawijaya
Tabel 1.4
Data Hasil Perhitungan
No Berat Awal
(gr)
Berat Akhir
(gr)
% Kadar Pengikat
)(X ( X - X ) ( X - X ) 2
1
2
3
4
5
Σ
Sumber : Laboratorium Pengecoran Logam Jurusan Mesin Fakultas Teknik Universitas
Brawijaya
1.5.2 Perhitungan Data Hasil Pengujian
Perhitungan Statistika :
- Persentase kadar pengikat pada spesimen :
Kadar pengikat = %100 AwalBerat
AkhirBerat - AwalBerat x - Kadar Air ................................. 1-9
- Kadar lempung rata – rata ( X )
X = n
X ........................................................................................................................ 1-10
.
Laboratorium Pengecoran Logam Jurusan Mesin Universitas Brawijaya
- Simpangan baku ( )
= 1
)( 2
n
XX ....................................................................................................... 1-11
- Simpangan baku rata –rata (
)
= n
.................................................................................................................... 1-12
- Kesalahan relatif (KR)
KR = X
.................................................................................................................... 1-13
%100 Kr ........................................................................................................... 1-14
- Derajat kebebasan
(db) = n – 1................................................................................................................. 1-15
t(α/2;db) ..................................................................................................................... 1-16
- Interval penduga kesalahan prosentase kadar lempung pasir cetak
}).;2.({}).;2.({ dbtxxdbtx .............................................................. 1-17
Laboratorium Pengecoran Logam Jurusan Mesin Universitas Brawijaya
1.5.3 Perhitungan Data Hasil Pengujian
Perhitungan Statistika
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Laboratorium Pengecoran Logam Jurusan Mesin Universitas Brawijaya
1.6 Tujuan Pengujian Distribusi Besar Butir Pasir Cetak
1 Praktikan mengetahui dan memahami besar butir pasir melalui nomor kehalusan
2 Praktikan mampu menganalisis dan melakukan pengujian distribusi besar butir pasir
cetak.
1.6.1 Pelaksanaan Pengujian Kadar Air
1.6.2 Alat dan Bahan yang Digunakan
A. Alat – alat yang digunakan.
1. Mesin Pengguncang Rotap
Alat ini berfungsi untuk menyaring pasir
Spesifikasi alat :
- Jenis : Rotap
- Tipe : VS 1
- Merk : Retsch
- Voltase : 220 V
- Daya : 430 Watt
- Buatan : Jerman Barat
- Artikel : 30 40 0010
- No. Serie : 01849038
- Frekuensi : 50 Hz
Laboratorium Pengecoran Logam Jurusan Mesin Universitas Brawijaya
Gambar 1.8 Mesin Pengguncang Rotap
Sumber : Laboratorium Pengecoran Logam Jurusan Mesin Fakultas Teknik Universitas
Brawijaya
2. Timbangan Pasir Elektrik
Alat ini digunakan untuk menimbang pasir yang akan diuji. (Untuk spesifikasi
dan gambar dapat dilihat pada gambar 1.2 dan penjelasannya).
3. Cawan
Alat ini digunakan untuk menampung pasir silika. (Untuk spesifikasi dan
gambar dapat dilihat pada gambar 1.3 dan penjelasannya).
1.6.3 Urutan kerja pengujian
Urutan kerja pengujian distribusi pasir cetak adalah:
1. Ambil pasir silika seberat 50 gr sebanyak 3 sampel
2. Susun ayakan dari bawah keatas dengan tingkat mesh semakin keatas semakin besar
bukaan meshnya, kemudian letakkan pada mesin penggunccang rotap.
3. Letakkan spesimen pasir pada ayakan paling atas lalu tutup.
4. Hidupkan Mesin pengguncang rotap selama 15 menit dengan frekuensi getar 50 Hz
5. Setelah selesai timbang berat pasir yang berada di masing-masing mesh
6. Cari harga Sn dari tiap-tiap mesh yang ada dari tabel-tabel yang terlampir
7. Hitung besar nomor kehalusan pasir dalam standar AFS
Laboratorium Pengecoran Logam Jurusan Mesin Universitas Brawijaya
DIAGRAM ALIR PENGUJIAN DISTRIBUSI BESAR BUTIR PASIR CETAK
Gambar 1.9 Diagram Alir Pengujian Distribusi Besar Butir Pasir Cetak
Y
T
Laboratorium Pengecoran Logam Jurusan Mesin Universitas Brawijaya
1.7 Pengolahan Data
1.7.1 Data hasil pengujian
Tabel 1.5
Data Hasil Pengujian
No Ukuran Mesh
(m) Berat 1 (gr) Berat 2 (gr) Berat 3 (gr)
1
2
3
4
5
6
7
8
Σ
Sumber : Laboratorium Pengecoran Logam Jurusan Mesin Fakultas Teknik Universitas
Brawijaya
Rumus yang digunakan untuk mencari nomor kehalusan pasir cetak adalah:
Wi
MiWiNumberAFS
).( ...................................................................... 1-18
Dimana :
AFS Number = Nomor kehalusan butir pasir standar AFS
W = Berat pasir pada ayakan ke – i
M = Faktor pelipat untuk ukuran butir ayakan ke – i
Laboratorium Pengecoran Logam Jurusan Mesin Universitas Brawijaya
Tabel 1.9
Data Perhitungan Spesimen 1
No Ukuran Mesh
(m) Us M Wn1 (Wn1 . Sn)
1
2
3
4
5
6
7
8
Σ
Sumber : Laboratorium Pengecoran Logam Jurusan Mesin Fakultas Teknik Universitas
Brawijaya
Contoh Perhitungan 1 :
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Laboratorium Pengecoran Logam Jurusan Mesin Universitas Brawijaya
Tabel 1.10
Data Perhitungan Spesimen 2
No Ukuran Mesh
(m) Us M Wn2 (Wn2 . Sn)
1
2
3
4
5
6
7
8
Σ
Sumber : Laboratorium Pengecoran Logam Jurusan Mesin Fakultas Teknik Universitas
Brawijaya
Contoh Perhitungan 2 :
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Laboratorium Pengecoran Logam Jurusan Mesin Universitas Brawijaya
Tabel 1.11
Data Perhitungan Spesimen 3
No Ukuran Mesh
(m) Us M Wn3 (Wn3 . Sn)
1
2
3
4
5
6
7
8
Σ
Sumber : Laboratorium Pengecoran Logam Jurusan Mesin Fakultas Teknik Universitas
Brawijaya
Contoh Perhitungan 3 :
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Laboratorium Pengecoran Logam Jurusan Mesin Universitas Brawijaya
1.7.2 Perhitungan Data Hasil Pengujian
Perhitungan Statistika
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Laboratorium Pengecoran Logam Jurusan Mesin Universitas Brawijaya
1.8 Pembahasan
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Laboratorium Pengecoran Logam Jurusan Mesin Universitas Brawijaya
PL II
PENGUJIAN KARAKTERISTIK PASIR CETAK
2.1 Tujuan Pengujian
1. Praktikan mengetahui dan memahami karakteristik pasir cetak.
2. Praktikan memahami faktor-faktor yang mempengaruhi karakteristik pasir cetak.
3. Praktikan mengetahui dan melakukan pengujian karakteristik pasir cetak..
4. Praktikan mampu menganalisis hasil karakteristik pasir cetak.
2.2.1 Pelaksanaan Pengujian Permeabilitas
2.2.2 Alat dan Bahan yang Digunakan
Alat-alat yang digunakan dalam pengujian ini adalah :
1. Stop Watch
Alat ini digunakan untuk mengukur waktu sampai 2000 cc udara.
Gambar 2.1 Stopwatch
Sumber : Laboratorium Pengecoran Logam Jurusan Mesin Fakultas Teknik Universitas
Brawijaya
2. Sand Rammer
Alat ini digunakan untuk menumbuk pasir cetak menjadi bentuk spesimen yang
dikehendaki yaitu panjang 5 cm dan diameter 5.08 cm.
Spesifikasi alat :
- Tipe : POU
- Merk : George Fisher
- Fabr : 2054
- Buatan : Jerman Barat
Laboratorium Pengecoran Logam Jurusan Mesin Universitas Brawijaya
Gambar 2.2 Sand Rammer
Sumber : Laboratorium Pengecoran Logam Jurusan Mesin Fakultas Teknik Universitas
Brawijaya
3. Permeabilitas Meter
Alat ini digunakan untuk mengetahui seberapa besar angka permeabilitas dari pasir
cetak yang diuji.
Spesifikasi alat :
- Tipe : POU
- Buatan : Jerman Barat
- Fabr : 1725
Laboratorium Pengecoran Logam Jurusan Mesin Universitas Brawijaya
Gambar 2.3 Permeabilitas Meter
Sumber : Laboratorium Pengecoran Logam Jurusan Mesin Fakultas Teknik Universitas
Brawijaya
4. Timbangan Elektrik
Alat ini digunakan untuk menimbang bahan dan berat spesimen yang akan
digunakan dalam pengujian. (Untuk spesifikasi dan gambar dapat dilihat pada gambar
1.2 dan penjelasannya).
2.2.3 Urutan Kerja Pengujian
1. Panaskan pasir cetak selama 60 menit dengan temperatur 110 °C
2. Siapkan 150 gr pasir cetak untuk pengujian ini dengan menggunakan sand rammer,
3. Buka pelindung orifice dan pilihlah salah satu posisi penunjuk skala yang akan
digunakan.
- Tanda biru untuk skala p (Permeabilitas) = 0-50 cm3/menit
- Tanda merah untuk skala p (Permeabilitas) = 0-500 cm3/menit
Skala p (Permeabilitas) dibaca dari skala merah bagian luar dari pengukuran
tekanan
Laboratorium Pengecoran Logam Jurusan Mesin Universitas Brawijaya
Skala paling dalam menunjukkan tekanan dinamis antara orifice dan spesimen
dalam mm kolom air (mm Wh).
4. Memutar keran pada posisi B dan angkat tabung udara ke atas secara perlahan-lahan
hingga angka Nol terlihat tepat pada batas tabung bawah lalu kunci pada posisi E,
5. Letakkan tabung spesimen berikut spesimen di dalamnya pada orifice,
6. Putar keran pada posisi A bersamaan mulai menghitung waktu dengan stop watch saat
udara dialirkan ke spesimen pasir cetak. Hal ini ditandai dengan tabung udara mulai
turun ke bawah,
7. Catat besar p (Permeabilitas) spesimen pasir cetak dengan tekanan yang terbaca pada
skala permeabilitas meter saat 1000 cc udara yang sudah terlewatkan,
8. Catat waktu yang dibutuhkan untuk mengalirkan udara sebanyak 2000 cc melalui
tabung spesimen pasir cetak yang diuji.
9. Ulangi langkah 1-8 sampai spesimen 3 serta catat data P (tekanan).
Laboratorium Pengecoran Logam Jurusan Mesin Universitas Brawijaya
DIAGRAM ALIR PEMBUATAN SPESIMEN UJI PERMEABILITAS
Gambar 2.4 Diagram Alir Pengujian Kadar Air Pasir Cetak
Laboratorium Pengecoran Logam Jurusan Mesin Universitas Brawijaya
DIAGRAM ALIR UJI PERMEABILITAS
Mulai
Isi tabung permeabilitas meter dengan air 2000 cc
Apakah spesimen sudah
sesuai ?
Buat spesimen 150 gr pasir cetak dengan sand
reammer
Panaskan spesimen dengan
suhu 110oC selama 60
menit
Apakah spesimen sudah
sesuai ?
Apakah spesimen sudah
sesuai ?
Buka pelindung orifice dan pilih skala PBiru = 0 – 50
Merah = 0 - 500
A B
Ya
Tidak
Tidak
Tidak
Ya
Ya`
Laboratorium Pengecoran Logam Jurusan Mesin Universitas Brawijaya
A B
Buka kran B angkat tabung udara sampai angka 0
Kunci kran posisi kran E
Letakkan tabung spesimen dan spesimen di dalamnya pada orifice
Buka kran A bersamaan hitung waktunya
Catat permeabilitas saat 1000 cc
Catat waktu saat 2000 cc
Hasil permeabilitas spesimen
Apakah sudah sampai pengujian ke 3 ?
A
Ya
Tidak
Gambar 2.5 Diagram Alir Pengujian Permeabilitas
Laboratorium Pengecoran Logam Jurusan Mesin Universitas Brawijaya
2.3 Pengolahan Data
2.3.1 Data hasil pengujian
Tabel 2.1
Tabel Hasil Pengujian
No Tekanan (p)
( mm ka )
Waktu (t)
( menit )
Panjang (l)
( mm )
Permeabilitas
( ml/menit )
1
2
3
4
Σ
Sumber : Laboratorium Pengecoran Logam Jurusan Mesin Fakultas Teknik Universitas
Brawijaya
Tabel 2.2
Tabel Perhitungan Permeabilitas
No P ( ml/menit ) ( P - P ) ( P - P )2
1
2
3
4
Σ
Sumber : Laboratorium Pengecoran Logam Jurusan Mesin Fakultas Teknik Universitas
Brawijaya
2.3.2 Perhitungan Data Hasil Pengujian
Perhitungan Permeabilitas
tAp
HVP
..
. ..................................................................................................... 2-1
di mana :
P = Permeabilitas ( cm3/menit = ml/menit )
V = Volume udara yang dialirkan ( 1 ml = cm3 )
H = Tinggi spesimen ( cm )
p = Tekanan fluida yang mengalir ( 10 gr/cm² = 10 cmKa )
Laboratorium Pengecoran Logam Jurusan Mesin Universitas Brawijaya
A = Luas penampang spesimen ( cm2 )
T = Waktu yang diperlukan untuk mengalirkan 1 liter udara (menit)
Perhitungan Statistika
- Permeabilitas Rata-rata ( P ) :
n
PP
Σ= ............................................................................................................ 2-2
- Simpangan Baku ( δ ) :
1
)( 2
n
PP .............................................................................................. 2-3
- Simpangan Baku Rata-rata ( δ ) :
n
δδ = ................................................................................................................ 2-4
- Kesalahan Relatif ( Kr ) :
P
Kr
............................................................................................................. 2-5
%100 Kr ................................................................................................. 2-6
- Interval Penduga Kesalahan :
P - { t ( α/2 ; db ) . δ } < P < P + { t ( α/2 ; db ) . δ } .......................................... 2-7
2.3.3 Perhitungan Data Hasil Pengujian
Perhitungan Permeabilitas
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Laboratorium Pengecoran Logam Jurusan Mesin Universitas Brawijaya
Perhitungan Statistika
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Laboratorium Pengecoran Logam Jurusan Mesin Universitas Brawijaya
2.4 Pembahasan
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Laboratorium Pengecoran Logam Jurusan Mesin Universitas Brawijaya
2.5 Pelaksanaan Pengujian Kekuatan
2.5.1 Alat dan Bahan yang Digunakan
A. Alat yang Digunakan
1. Universal Strength Machine
Alat ini digunakan untuk menguji kekuatan pasir cetak.
Spesifikasi alat :
- Merk : Georg Fischer
- Buatan : Jerman Barat
Gambar 2.6 Alat Penguji Kekuatan Pasir Cetak
Sumber : Laboratorium Pengecoran Logam Jurusan Mesin Fakultas Teknik Universitas
Brawijaya
Keterangan gambar :
01. Main Piston
02. Low Pressure Gauge
03. Pressure Piston Hydraulic Press Hand Operated
04. Handwheel
05. Throttle Reflux Valve
06. Plug In Coupling
07. Compression Insert
Laboratorium Pengecoran Logam Jurusan Mesin Universitas Brawijaya
2. Locking Plug Kepala penekan untuk uji kekuatan tekan
3. Kepala penekan untuk uji kekuatan geser
Gambar 2.7 (a) Kepala penekan untuk uji kekuatan tekan,
(b) Kepala penekan untuk uji kekuatan geser
Sumber : Laboratorium Pengecoran Logam Jurusan Mesin Fakultas Teknik Universitas
Brawijaya
4. Kepala penekan untuk uji kekuatan tarik
Gambar 2.8 Kepala penekan untuk uji kekuatan tarik
Sumber : Laboratorium Pengecoran Logam Jurusan Mesin Fakultas Teknik Universitas
Brawijaya
5. Sand rammer
Alat ini digunakan untuk memadatkan pasir cetak dalam tabung spesimen.
(Untuk spesifikasi dan gambar dapat dilihat pada gambar 2.2 dan penjelasannya).
6. Timbangan elektrik
Alat ini digunakan untuk menimbang pasir cetak sebelum dibuat spesimen.
(Untuk spesifikasi dan gambar dapat dilihat pada gambar 1.2 dan penjelasannya).
Laboratorium Pengecoran Logam Jurusan Mesin Universitas Brawijaya
7. Cetakan spesimen uji kekuatan geser
Gambar 2.9 Skala alat uji kekuatan pasir cetak
Sumber : Laboratorium Pengecoran Logam Jurusan Mesin Fakultas Teknik Universitas
Brawijaya
B. Bahan yang Digunakan
Bahan yang digunakan adalah pasir cetak sebanyak ....... gr, dengan komposisi :
- pasir silika : ........... %
- pengikat : ........... %
- air : ........... %
2.5.2 Urutan Kerja Pengujian
A. Urutan Kerja Pengujian Kekuatan Tekan
a. Langkah-langkah pengujian tanpa perlakuan panas
1. Ambil campuran pasir cetak seberat 150 gr, lalu buat spesimen uji tekan dengan
menggunakan sand rammer (spesimen sebanyak 5 buah).
2. Pasang kepala uji tekan pasir cetak pada alat uji kekuatan pasir cetak.
3. Letakkan spesimen pada kepala uji tekan pasir cetak secara hati-hati jangan
sampai rusak.
4. Putar handwheel secara terus menerus dengan putaran konstan dan perlahan-
lahan hingga spesimen hancur.
5. Baca dan catat besar kekuatan tekan pasir cetak tersebut (lengkap dengan
satuannya) pada skala paling luar yang terdapat pada alat uji tekan pasir cetak.
6. Lakukan langkah 1–5 untuk spesimen berikutnya.
Laboratorium Pengecoran Logam Jurusan Mesin Universitas Brawijaya
b. Langkah-langkah pengujian dengan perlakuan panas
Langkah pengujian sama dengan tanpa perlakuan, hanya setelah pasir cetak
dibentuk spesimen uji tekan lakukan pemanasan dalam dapur pemanas dengan suhu
110C selama 1 jam.
B. Urutan Kerja Pengujian Kekuatan Geser
a. Langkah-langkah pengujian tanpa perlakuan panas
1. Ambil campuran pasir cetak seberat 150 gr, kemudian buat spesimen uji geser
dengan menggunakan sand rammer (spesimen sebanyak 5 buah).
2. Pasang kepala uji geser pasir cetak pada alat uji kekuatan geser pasir cetak.
3. Letakkan spesimen pada kepala uji geser secara hati-hati jangan sampai spesimen
rusak.
4. Putar handwheel secara terus menerus dengan putaran konstan dan perlahan-lahan
hingga spesimen hancur.
5. Baca dan catat besar kekuatan tekan pasir cetak tersebut pada skala yang di tengah
pada alat uji geser tersebut.
b. Langkah pengujian dengan perlakuan panas
Langkah pengujian sama dengan tanpa perlakuan, hanya setelah pasir cetak
dibentuk spesimen uji geser lakukan pemanasan dalam dapur pemanas dengan suhu
110C selama 1 jam.
C. Urutan Kerja Pengujian Kekuatan Tarik
a. Langkah-langkah pengujian tanpa perlakuan panas
1. Ambil campuran pasir cetak seberat 125 gr, kemudian buat spesimen uji tarik
dengan menggunakan sand rammer (spesimen sebanyak 5 buah).
2. Pasang kepala uji tarik pasir cetak pada alat uji kekuatan pasir cetak.
3. Letakkan spesimen pada kepala uji tarik pasir cetak secara hati-hati jangan sampai
rusak.
4. Putar handwheel secara terus menerus dengan putaran konstan dan perlahan-lahan
hingga spesimen hancur.
5. Baca dan catat besar kekuatan tarik pasir cetak tersebut (lengkap dengan
satuannya) pada skala paling dalam yang terdapat pada alat uji tarik pasir cetak.
6. Lakukan langkah 1–5 untuk spesimen berikutnya.
Laboratorium Pengecoran Logam Jurusan Mesin Universitas Brawijaya
b. Langkah-langkah pengujian dengan perlakuan panas
Langkah pengujian sama dengan tanpa perlakuan, hanya setelah pasir cetak
dibentuk spesimen uji tarik lakukan pemanasan dalam dapur pemanas dengan suhu
110C selama 1 jam.
Laboratorium Pengecoran Logam Jurusan Mesin Universitas Brawijaya
DIAGRAM ALIR PEMBUATAN SPESIMEN UJI TEKAN DAN GESER
Gambar 2.10 Diagram Alir Pembuatan Spesimen Uji Tekan dan Geser
Y
T
Laboratorium Pengecoran Logam Jurusan Mesin Universitas Brawijaya
DIAGRAM ALIR PEMBUATAN SPESIMEN UJI TARIK
Gambar 2.11 Diagram Alir Pembuatan Spesimen Uji Tarik
T
Y
Laboratorium Pengecoran Logam Jurusan Mesin Universitas Brawijaya
DIAGRAM ALIR PENGUJIAN KEKUATAN TEKAN
Gambar 2.12 Diagram Alir Pengujian Kekuatan Tekan
Laboratorium Pengecoran Logam Jurusan Mesin Universitas Brawijaya
DIAGRAM ALIR PENGUJIAN KEKUATAN GESER
Gambar 2.13 Diagram Alir Pengujian Kekuatan Geser
Laboratorium Pengecoran Logam Jurusan Mesin Universitas Brawijaya
DIAGRAM ALIR PENGUJIAN KEKUATAN TARIK
Gambar 2.14 Diagram Alir Pengujian Kekuatan Tarik
Laboratorium Pengecoran Logam Jurusan Mesin Universitas Brawijaya
2.6 Pengolahan Data
2.6.1 Data hasil pengujian
A. Data Hasil Pengujian Kekuatan Tekan
Tabel 2.3
Data pengujian tanpa perlakuan
No Kekuatan Tekan
(N/cm2)
_
(X-X)
_
(X-X)2
1
2
3
4
5
Sumber : Laboratorium Pengecoran Logam Jurusan Mesin Fakultas Teknik Universitas
Brawijaya
Tabel 2.4
Data hasil pengujian dengan perlakuan panas
No Kekuatan Tekan
(N/cm2)
_
(X-X)
_
(X-X)2
1
2
3
4
5
Sumber : Laboratorium Pengecoran Logam Jurusan Mesin Fakultas Teknik Universitas
Brawijaya
Laboratorium Pengecoran Logam Jurusan Mesin Universitas Brawijaya
B. Data Hasil Pengujian Kekuatan Geser
Tabel 2.5
Data pengujian tanpa perlakuan
No Kekuatan Geser
(N/cm2)
_
(X-X)
_
(X-X)2
1
2
3
4
5
Sumber : Laboratorium Pengecoran Logam Jurusan Mesin Fakultas Teknik Universitas
Brawijaya
Tabel 2.6
Data pengujian dengan perlakuan panas
No Kekuatan Geser
(N/cm2)
_
(X-X)
_
(X-X)2
1
2
3
4
5
Sumber : Laboratorium Pengecoran Logam Jurusan Mesin Fakultas Teknik Universitas
Brawijaya
Laboratorium Pengecoran Logam Jurusan Mesin Universitas Brawijaya
C. Data Hasil Pengujian Kekuatan Tarik
Tabel 2.7
Data pengujian tanpa perlakuan panas
No Kekuatan Tarik
(N/cm2)
_
(X-X)
_
(X-X)2
1
2
3
4
5
Sumber : Laboratorium Pengecoran Logam Jurusan Mesin Fakultas Teknik Universitas
Brawijaya
Tabel 2.8
Data pengujian dengan perlakuan panas
No Kekuatan Tarik
(N/cm2)
_
(X-X)
_
(X-X)2
1
2
3
4
5
Sumber : Laboratorium Pengecoran Logam Jurusan Mesin Fakultas Teknik Universitas
Brawijaya
2.6.2 Perhitungan Data Hasil Pengujian
A. Perhitungan pengujian kekuatan tekan
Perhitungan statistika
- Perhitungan kekuatan rata-rata (
X )
X =n
X ............................................................................................................ 2-8
Laboratorium Pengecoran Logam Jurusan Mesin Universitas Brawijaya
- Simpangan baku ( )
= 1
)( 2
n
XX ................................................................................................ 2-9
- Simpangan baku rata –rata (
)
= n
.............................................................................................................. 2-10
- Kesalahan relatif (KR)
KR = X
............................................................................................................. 2-11
%100 Kr .................................................................................................... 2-12
- Derajat kebebasan
(db) = n – 1 ......................................................................................................... 2-13
t( /2;db) ............................................................................................................. 2-14
- Interval penduga kesalahan prosentase kadar lempung pasir cetak
}).;2.({}).;2.({ dbtxxdbtx ....................................................... 2-15
Uji T
- Tingkat kesalahan ( )
- Derajat bebas (db)
- Dari tabel t di dapat, t(( /2;db)
- Hipotesa :
1. Daerah terima, H0: μ1 = μ2
2. Daerah tolak, H1 : μ1 ≠ μ2
3. t hitung =
2
)/1/1}()1()1{(
)(
21
21
2
22
2
11
21
nn
nnnn
XX
........................................2-16
Laboratorium Pengecoran Logam Jurusan Mesin Universitas Brawijaya
2.6.2 Perhitungan Data Hasil Pengujian
A. Perhitungan pengujian kekuatan tekan
Perhitungan statistika
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Laboratorium Pengecoran Logam Jurusan Mesin Universitas Brawijaya
B. Perhitungan Pengujian Kekuatan Geser
Perhitungan statistika
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Laboratorium Pengecoran Logam Jurusan Mesin Universitas Brawijaya
C. Perhitungan Pengujian Kekuatan Tarik
Perhitungan statistika
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Laboratorium Pengecoran Logam Jurusan Mesin Universitas Brawijaya
2.7 Pembahasan
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Laboratorium Pengecoran Logam Jurusan Mesin Universitas Brawijaya
PL III
PERENCANAAN PENGECORAN
3.1 Tujuan Pengujian
1. Praktikan mengetahui dan memahami apa saja yang dibutuhkan dalam perencanaan
pengecoran
2. Praktikan mampu merencanakan dan membuat cetakan pasir, sistem saluran dan pola.
3. Praktikan mampu memecahkan masalah-masalah dalam perencanaan pengecoran
3.2 Pelaksanaan Pembuatan Cetakan Pasir
3.2.1 Alat dan bahan yang digunakan
Alat-alat yang digunakan dalam pengujian ini adalah :
1. Rangka Cetak (Cope dan Drag)
Alat ini digunakan sebagai tempat untuk membuat cetakan pasir.
2. Saluran Masuk dan Saluran Penambah
Alat ini digunakan sebagai tempat mengalirnya logam cair dalam cetakan.
3. Pola
Alat ini digunakan untuk membuat bentuk/rongga cetakan benda cor.
4. Papan Datar
Alat ini digunakan sebagai tempat landasan dalam membuat cetakan.
5. Kamera
Digunakan sebagai alat dokumentasi.
Bahan yang digunakan adalah pasir cetak dengan komposisi pasir silica, bentonit,
dan air serta :
1. Pasir silika halus
2. Grafit
Laboratorium Pengecoran Logam Jurusan Mesin Universitas Brawijaya
3.2.2 Urutan Kerja Pembuatan Cetakan Pasir
Langkah-langkah dalam pembuatan cetakan adalah :
1. Aduk pasir cetak dengan komposisi tertentu dengan tangan agar campurannya merata.
2. Letakkan pola cetakan pada papan datar berikut drag, kemudian masukkan pasir cetak
dan padatkan hingga rata dan padat memenuhi drag. Ratakan permukaan pasir cetak
bagian atas dengan papan kayu.
3. Balik drag, kemudian taburi pola dengan grafit. Sedangkan untuk pasir cetak taburi
dengan pasir silika halus agar pola dan pasir cetak tidak lengket, kemudian ratakan
dengan kuas secara hati-hati.
4. Letakkan cope di atas drag, kemudian letakkan saluran turun dan saluran penambah.
5. Isi cope dengan pasir cetak, padatkan dan selama pemadatan jangan sampai saluran
turun maupun saluran penambah berubah posisinya.
6. Ambil saluran turun, saluran penambah dengan hati-hati jangan sampai pasir ikut
terangkat.
7. Angkat cope dari drag secara hati-hati, kemudian ambil polanya. Apabila masih
terjadi kerusakan, maka tempatkan kembali pola ke posisi semula dan isi bagian-
bagian yang rusak tersebut dengan pasir cetak.
8. Taburi rongga bekas pola tersebut dengan grafit, kemudian ratakan dengan kuas secara
hati-hati.
9. Letakkan kembali kup di atas drag, kemudian cetakan yang sudah jadi tersebut
letakkan di tempat yang aman dan datar, di atas cetakan beri pemberat.
PERHATIAN !!!!!!
1. Sekali cavity rusak akan sulit untuk diperbaiki dan pembuatan cetakan pasir harus
diulang kembali. Oleh karena itu berhati-hatilah ketika menggerakkan rangka cetak.
2. Urutan kerja praktikum di atas dapat berubah sesuai dengan bentuk benda yang akan
dicor.
Laboratorium Pengecoran Logam Jurusan Mesin Universitas Brawijaya
Gambar 3.1 Rangka Cetak
Sumber : Tata Surdia (1996: 95)
Gambar 3.2 Prosedur Pembuatan Cetakan Pasir
Sumber : (Tata Surdia 1996 : 94)
Laboratorium Pengecoran Logam Jurusan Mesin Universitas Brawijaya
Contoh Pola :
1. Pola Plat Pasangan
Gambar 3.3 Pola Plat Pasangan
Sumber : Mechanical Inventions (2017)
2. Pola Cetakan Sapuan
Gambar 3.3 Pola Cetakan Sapuan
Sumber : Iron Foundry (2010)
3. Pola Cope dan Drag
Gambar 3.4 Pola Cope dan Drag
Sumber : Mechanical Inventions (2017)
Laboratorium Pengecoran Logam Jurusan Mesin Universitas Brawijaya
3.3 Rancangan Cetakan Pasir dan Pola
3.3.1 Sistem saluran
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Laboratorium Pengecoran Logam Jurusan Mesin Universitas Brawijaya
3.3.2 Gambar Cetakan Pasir dan Pola
(Terlampir)
3.4 Studi Kasus dan Pemecahannya
3.4.1 Kasus pada cetakan pasir yang dibuat
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Laboratorium Pengecoran Logam Jurusan Mesin Universitas Brawijaya
3.4.2 Pemecahan masalah
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Laboratorium Pengecoran Logam Jurusan Mesin Universitas Brawijaya
PL IV
PENUANGAN LOGAM DAN INSPEKSI
4.1 Tujuan Praktikum
1. Praktikan dapat mengetahui dan memahami definisi beserta macam pengecoran logam
2. Praktikan dapat mengetahui macam cacat coran beserta penyebab dan pencegahannya.
3. Praktikan mampu menganalisis hasil coran beserta solusi pada cacat coran
4.2 Pelaksanaan Penuangan
4.2.1 Alat dan Bahan yang Digunakan
Alat yang digunakan dalam praktikum ini adalah :
1. Stopwatch
Digunakan untuk menghitung waktu penuangan. (Untuk spesifikasi dan gambar
dapat dilihat pada gambar 2.1 dan penjelasannya).
2. Kamera
Digunakan sebagai alat dokumentasi.
4.2.2 Urutan Kerja Penuangan Logam
Praktikum ini dilakukan dengan urutan kerja sebagai berikut :
1. Panaskan dan cairkan aluminium di dalam dapur listrik di atas titik cairnya ( 900C).
2. Pakai pelindung tubuh, sarung tangan dan kaca mata sebelum mengambil logam cair
dari dalam dapur.
3. Siapkan cetakan pasir dan dekatkan pada dapur.
4. Sebelum mengambil logam cairnya, maka bersihkan dulu terak-terak di atasnya
dengan alat pengambil terak.
5. Setelah bersih dari terak, ambil logam cair dengan ladel secara hati-hati, kemudian
tuangkan logam cair kedalam cetakan pasir melalui saluran masuk.
6. Selama penuangan, jaga kecepatan tuangnya jangan sampai terlalu cepat atau terlalu
lambat. Gunakan stopwatch untuk mencacat waktu penuangan dan hentikan stopwatch
ketika logam cair sudah muncul dari saluran keluar.
7. Hentikan penuangan jika logam cair sudah muncul dari saluran keluar.
8. Kembalikan logam cair sisa ke dalam dapur.
9. Bongkar cetakan pasir jika logam sudah dingin. INGAT!!!! Pembongkaran jangan
Laboratorium Pengecoran Logam Jurusan Mesin Universitas Brawijaya
sampai merusak coran.
10. Amati hasil coran dan analisa permasalahan yang timbul pada hasil coran. Jangan lupa
mendokumentasikan hasil coran dengan kamera.
Laboratorium Pengecoran Logam Jurusan Mesin Universitas Brawijaya
DIAGRAM ALIR UJI PIKNOMETRI
Gambar 4.1 Diagram Alir Pengujian Piknometri
Laboratorium Pengecoran Logam Jurusan Mesin Universitas Brawijaya
4.3 Hasil Coran
A. Benda Cor I
Gambar 4.2______________________________________
Sumber : Dokumentasi Pribadi
B. Benda Cor Antar Kelompok
Gambar 4.3______________________________________
Sumber : Dokumentasi Pribadi
Laboratorium Pengecoran Logam Jurusan Mesin Universitas Brawijaya
4.4 Pembahasan
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