laboratorium pengecoran logam -...

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


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


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


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.


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.


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


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


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


Brawijaya

1.3.2 Perhitungan Data Hasil Pengujian

Perhitungan Statistika :

- Kadar air rata – rata ( x )

X = n

x ............................................................................................................. 1-1


- 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


Perhitungan Statistika

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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


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


Brawijaya


Alat ini digunakan untuk menimbang spesimen sebelum dan sesudah

dikeringkan. (Untuk spesifikasi dan gambar dapat dilihat pada gambar 1.2 dan

penjelasannya).


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


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


Gambar 1.7 Gelas ukur


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


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


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


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


Brawijaya


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

.



= 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




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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


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


Gambar 1.8 Mesin Pengguncang Rotap


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


DIAGRAM ALIR PENGUJIAN DISTRIBUSI BESAR BUTIR PASIR CETAK

Gambar 1.9 Diagram Alir Pengujian Distribusi Besar Butir Pasir Cetak

Y

T


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


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


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


Brawijaya

Contoh Perhitungan 1 :

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Tabel 1.10


No Ukuran Mesh


1

2

3

4

5

6

7

8

Σ


Brawijaya


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Tabel 1.11


No Ukuran Mesh


1

2

3

4

5

6

7

8

Σ


Brawijaya


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1.8 Pembahasan

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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


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


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



Gambar 2.2 Sand Rammer


Brawijaya

3. Permeabilitas Meter

Alat ini digunakan untuk mengetahui seberapa besar angka permeabilitas dari pasir

cetak yang diuji.

Spesifikasi alat :

- Tipe : POU


- Fabr : 1725


Gambar 2.3 Permeabilitas Meter


Brawijaya


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).


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


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).


DIAGRAM ALIR PEMBUATAN SPESIMEN UJI PERMEABILITAS

Gambar 2.4 Diagram Alir Pengujian Kadar Air Pasir Cetak


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


sesuai ?


sesuai ?

Buka pelindung orifice dan pilih skala PBiru = 0 – 50

Merah = 0 - 500

A B

Ya

Tidak

Tidak

Tidak

Ya

Ya`


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


2.3 Pengolahan Data


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


Brawijaya

Tabel 2.2

Tabel Perhitungan Permeabilitas

No P ( ml/menit ) ( P - P ) ( P - P )2

1

2

3

4

Σ


Brawijaya


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 )


A = Luas penampang spesimen ( cm2 )

T = Waktu yang diperlukan untuk mengalirkan 1 liter udara (menit)


- 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


Perhitungan Permeabilitas

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2.4 Pembahasan

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2.5 Pelaksanaan Pengujian Kekuatan


A. Alat yang Digunakan

1. Universal Strength Machine

Alat ini digunakan untuk menguji kekuatan pasir cetak.

Spesifikasi alat :

- Merk : Georg Fischer


Gambar 2.6 Alat Penguji Kekuatan Pasir Cetak


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


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


Brawijaya

4. Kepala penekan untuk uji kekuatan tarik

Gambar 2.8 Kepala penekan untuk uji kekuatan tarik


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).


7. Cetakan spesimen uji kekuatan geser

Gambar 2.9 Skala alat uji kekuatan pasir cetak


Brawijaya

B. Bahan yang Digunakan

Bahan yang digunakan adalah pasir cetak sebanyak ....... gr, dengan komposisi :

- pasir silika : ........... %

- pengikat : ........... %

- air : ........... %


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.


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


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


dibentuk spesimen uji geser lakukan pemanasan dalam dapur pemanas dengan suhu

110C selama 1 jam.

C. Urutan Kerja Pengujian Kekuatan Tarik


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.


b. Langkah-langkah pengujian dengan perlakuan panas


dibentuk spesimen uji tarik lakukan pemanasan dalam dapur pemanas dengan suhu

110C selama 1 jam.


DIAGRAM ALIR PEMBUATAN SPESIMEN UJI TEKAN DAN GESER

Gambar 2.10 Diagram Alir Pembuatan Spesimen Uji Tekan dan Geser

Y

T


DIAGRAM ALIR PEMBUATAN SPESIMEN UJI TARIK

Gambar 2.11 Diagram Alir Pembuatan Spesimen Uji Tarik

T

Y


DIAGRAM ALIR PENGUJIAN KEKUATAN TEKAN

Gambar 2.12 Diagram Alir Pengujian Kekuatan Tekan


DIAGRAM ALIR PENGUJIAN KEKUATAN GESER

Gambar 2.13 Diagram Alir Pengujian Kekuatan Geser


DIAGRAM ALIR PENGUJIAN KEKUATAN TARIK

Gambar 2.14 Diagram Alir Pengujian Kekuatan Tarik


2.6 Pengolahan Data


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


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


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


Brawijaya

Tabel 2.6

Data pengujian dengan perlakuan panas

No Kekuatan Geser

(N/cm2)

_

(X-X)

_

(X-X)2

1

2

3

4

5


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


Brawijaya

Tabel 2.8

Data pengujian dengan perlakuan panas

No Kekuatan Tarik

(N/cm2)

_

(X-X)

_

(X-X)2

1

2

3

4

5


Brawijaya


A. Perhitungan pengujian kekuatan tekan

Perhitungan statistika

- Perhitungan kekuatan rata-rata (

X )

X =n

X ............................................................................................................ 2-8



= 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



A. Perhitungan pengujian kekuatan tekan


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B. Perhitungan Pengujian Kekuatan Geser


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C. Perhitungan Pengujian Kekuatan Tarik


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2.7 Pembahasan

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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


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.


Gambar 3.1 Rangka Cetak

Sumber : Tata Surdia (1996: 95)

Gambar 3.2 Prosedur Pembuatan Cetakan Pasir

Sumber : (Tata Surdia 1996 : 94)


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)


3.3 Rancangan Cetakan Pasir dan Pola

3.3.1 Sistem saluran

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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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3.4.2 Pemecahan masalah

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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


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


sampai merusak coran.

10. Amati hasil coran dan analisa permasalahan yang timbul pada hasil coran. Jangan lupa

mendokumentasikan hasil coran dengan kamera.


DIAGRAM ALIR UJI PIKNOMETRI

Gambar 4.1 Diagram Alir Pengujian Piknometri


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


4.4 Pembahasan

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laboratorium pengecoran logam -...

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