Permanent Mold Casting (Gravity Die Casting)

02/03/2018
PE 5662 Teknologi Manufaktur Lanjut

(Advanced Manufacturing Technology)
Permanent Mold Casting
TEKNIK DAN SISTEM PRODUKSI

PE5662 – Teknologi Manufaktur
Permanent mold casting (gravity die casting)
Permanent mold casting (gravity die casting) adalah

proses pengecoran dengan cara menuang logam cair ke
dalam cetakan baja (atau besi cor) memanfaatkan gaya
gravitasi
Pengecoran cetakan permanen mirip dengan proses

pengecoran pasir. Dalam perbedaan dari cetakan pasir
yang rusak setelah setiap pengecoran, cetakan permanen
dapat digunakan untuk menuangkan setidaknya seribu
sampai dengan 120.000 siklus casting dan dengan tingkat
5-100 tuang / jam.

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Specification
Typical Feasible
Shape Thin-walled: Complex Flat
Solid: Cylindrical Thin-walled:
Solid: Cubic Cylindrical
Solid: Complex Thin-walled: Cubic
Weight 50 gr - 300 kg
Materials Aluminum Metals
Copper Alloy Steel
Magnesium Carbon Steel
Cast Iron
Stainless Steel
Lead
Nickel
Tin
Titanium
Zinc
Surface Finish - Ra 3.2 - 6.3μm (N8-N9) 0.8 - 12μm (N6-N10)
Tolerance ± 0.35 mm ± 0.25 mm
Max wall thickness 2 – 50 mm
Quantity 1000 - 100000 500 - 1000000

Material
Materials best suited for gravity die castings are materials with
relatively low melting points in order to be fluid in the mold.
Aluminum alloys,
Magnesium alloys,
Copper alloys, tend to be insufficiently fluid
zinc alloys,
steels require special molds
Cast irons.
Magnesium use in automotive applications
4 Kg
12,4 Kg 100 Kg
per Vehicle
(2020)

02/03/2018
Typical applications are:

o Automotive component :
• pistons/cylinders/rods
• gears
• rocker arm
o Kitchenware
o Power Electric component
o Ornamental Work

Al-Mg alloy 535

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Advantages:
o Better mechanical properties
o the mold can be chilled to speed cooling
o Homogeneous grain structure and chemical composition.
o Low shrinkage and gas porosity.
o Little scrap process
o Reduced machining for a total lower cost
Disadvantages:
o mold production is time consuming and costly
o mold sizes are limited
o Limitations in casting of high melting point metals into metallic
molds.
o Intrinsic and complex shapes can not be cast.
o Large parts can not be cast.
Molten aluminum is Aluminum is allowed

Mold is opened
poured into the mold. to solidify
Casting is removed
100% final visual
inspection prior to
packaging Hot inspection is
Gates and risers performed to ensure
are trimmed defectcastings.

02/03/2018
Slush Casting

Permanent Mold Casting Process

02/03/2018
Design aspects of permanent mold casting
Material Cetakan :
o Molds for casting iron or steel are made of graphite
or other refractories.
o Molds for casting aluminum, magnesium or copper
alloy castings are made of iron or die-steel.
Desain allowance penyusutan cetakan permanen lebih

kecil dibandingkan casting pasir.

 Produk dengan berat 0.1 kg hingga 10 Kg. Berat produk

70 kg memungkinkan untuk menggunakan metoda ini
 The section thickness of permanent mold casting may

vary in the range 2.5-50 mm
 The dimensional tolerances are 0.4-1.5 mm depending

on the casting section thickness.
 Allowances of 0.25-0.75 mm are taken for the dimensions

crossing the parting line of the mold.
 The draft angle is commonly 1-3o.

02/03/2018
Molds incorporate the necessary sprues and risers,

and also typically have pins for ejecting the castings.

Mold Design (untuk alumunium)

 Pada Permanent mold casting, pembekuan lebih cepat dari
sand casting
 Menuangkan miring, pengisian cetakan dengan turbulensi
minimum dan gradien termal dapat dikendalikan untuk
menghasilkan solidifikasi kearah riser
 Casting dan sistem salurannya harus mudah lepas dari
cetakannya (gaya dan abrasi)
 Bagian berat biasanya ditempatkan pada parting line untuk
memudahkan pengisian
 Sprues, runner, gate dan riser ditempatkan pada parting line,
memudahkan pelepasan

02/03/2018
 Sistem coran dan salurannya harus diatur agar arah

pembekuan mulai di daerah terpencil maju ke arah riser
 Untuk luas penampang besar gunakan pendingin baik

dari luar maupun memanfaatkan bentuk produk
 Daerah datar untuk mencegah kebocoran cetakan

dengan luas 250 mm2 adalah 50 mm dari bawah dan 25
sampai 35 mm dari sisi.
 Akibat panas maka cetakan akan warping, ketebalan

harus sesuai dan tidak menggunakan rib.

Sebaran Temperatur
• The parting line is the hottest portion of a mold,
• Different heating of the mold will cause the mold to open at

the parting line.
02/03/2018
Pertimbangan Disain
o Venting – semua udara dalam cetakan harus

keluar saat diisi
o Gating and risering – untuk ventilasi bisa
menggunakan mesin pengisian miring saat
mengisi cetakan melalui gate
o Chills

Gating / risering
Alumunium cair memasuki cetakan permanen akan kehilangan panas
dengan cepat dibandingkan dengan cetakan pasir  Pengisian lebih cepat
Bentuk Gating dan Riser
Riser harus berukuran cukup besar untuk menanggulangi efek penyusutan.

02/03/2018
Simulation by MagmaSoft
Mold 1. Mold 2. Mold 3.

Mold 4. Mold 5.
Conclusion:
1. A sprue-well, as designed in these experiments, does

not eliminate the vena contracta.
2. In order for a runner extension to operate efficiently, it
must have a small, squared cross-section
3. In bottom-feeding gating systems, a filter can
significantly improve the filling of the casting
4. In top-feeding gating systems, a filter can initially slow
the metal flow rate
5. Side-feeding gating systems provide less turbulent
flow into the mold cavity
6. Rough coatings promote better fill than smooth
coatings
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Draft Requirements
Gambar 1
Gambar 2 Gambar 3
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The actual dimensions of the mold and gating system will

depend on the weight and dimensions of the casting to be
produced.
Figure is given as a guideline. All the dimensions are based on

the thickness of the casting which is referred to as “T”.
Walls and Ribs

Recommended Design
Good Design

02/03/2018
Flatness and Straightness
Greatest Dimension Casting Tolerance

0 – 75 mm 1.27 mm
Each additional mm 0.07 mm

Dalam beberapa kasus, ventilasi tambahan harus

ditambahkan.
Umumnya metode yang digunakan meliputi:
1. Slot ventilasi biasanya 0,1-0,25 mm, potong sepanjang

parting line menuju ke luar cetakan
2. Lubang sangatkecil dibor melalui cetakan di daerah yang
tidak akan mempengaruhi permukaan casting
3. Plug ventilasi, lubang yang dibor dalam cetakan dan diisi
dengan plug

02/03/2018
Chills
Menanggulangi daerah pendinginan yang tidak seragam pada produk
akibat perbedaan ukuran cetakan
Jenis :
o adding ribs but casting may not be modifiable.
o An oversize riser and installing copper inserts
o Air chills are holes drilled into the mold and a blast of air is blown into to
the relief.
Mold Materials
Materials must include the following properties:
• The mold material must have adequate machinability. Gray cast
iron die blocks can usually be machined for less cost than tool
steels.
• The mold must have good dimensional stability, high
temperature strength, and thermal shock and fatigue resistance.
• The mold material must be resistant to reduce dimensional
changes caused by sand blasting, hand cleaning, liquid metal
erosion, abrasion from moving mold components and abrasion
from casting removal.
• Molds must display good thermal conductivity properties.
Thermal conductivity is the rate heat flows through a unit area
of material under a given temperature gradient.

02/03/2018
hot work tool steel should have the following properties:
• Low thermal expansion coefficient

• High yield strength
• High temper resistance
• Good resistance to erosion
• High thermal conductivity

Mold maintenance and repair
• Heat checking: thermo-mechanical fatigue process

caused by thermal cycling
• Erosion: complex phenomenon, which includes both
chemical and mechanical wear processes
• Gross cracking : the catastrophic cracking of the die,
due to mechanical or thermal overload.
• Plastic deformation : a matter of insufficient hot
strength in the mold in relation to actual mechanical
strain

02/03/2018
The following factors influence thermal fatigue
• Preheating temperature - minimum of 150°C, fracture

toughness is almost twice as high as room temperature
• Surface temperature - 600°C
• Holding time at peak temperature, implies an
increased risk of over tempering a mold
• Cooling rate - More rapid cooling results in greater
stresses and will lead to premature cracking

During casting the metal enters the mold as a liquid.

Under certain conditions it can lead to a reaction
between the molten metal and the mold steel and
can dissolve the steel. This phenomenon is known as
erosion or corrosion of the mold.
Most aluminum alloys, the critical temperature is

720°C

02/03/2018
Factors that influence erosion are

• Temperature of the casting metal
• Composition of the casting metal - Pure aluminum attacks the
mold material at a greater rate than commercial alloys
• Design of the mold
o Gating and mold design is critical in preventing erosion
o A thin directed jet of molten metal from a gate can cause hot spots and
erosion problems
o Care should be taken to avoid designs where jetting gates are near a
core or cavity wall
• Heat treatment of the mold
• Surface treatment of the mold - Mold coating touch up must be
performed during the work day to ensure that the risk of
erosion is minimized
Design of Tilt Permanent Mold Casting for Alumunium

02/03/2018
Design of Tilt Permanent Mold Casting for Alumunium

Mold Coating
Permanent mold coatings basic reasons :
• Coatings provide a protective barrier between the

mold and the casting to prevent mold erosion and
wear.
• Coatings provide some degree of control over the
solidification rate and direction.
• Coatings provide a barrier between the mold and the
casting so that the casting will release from the mold.

02/03/2018
Typical refractory materials found in mold coatings

include:
• Vermiculite
• Bentonite
• Talc
• Titanium dioxide
• Alumina
• Olivine
• Graphite

Contoh Pemanfaatan Gravity Die casting /

Permanent Mold Casting


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02/03/2018

PE 5662 Teknologi Manufaktur Lanjut

Permanent Mold Casting

TEKNIK DAN SISTEM PRODUKSI

Permanent mold casting (gravity die casting)

Permanent mold casting (gravity die casting) adalah

Pengecoran cetakan permanen mirip dengan proses

TEKNIK DAN SISTEM PRODUKSI

TEKNIK DAN SISTEM PRODUKSI

Magnesium use in automotive applications

TEKNIK DAN SISTEM PRODUKSI

Typical applications are:

TEKNIK DAN SISTEM PRODUKSI

Al-Mg alloy 535

TEKNIK DAN SISTEM PRODUKSI

Molten aluminum is Aluminum is allowed

TEKNIK DAN SISTEM PRODUKSI

TEKNIK DAN SISTEM PRODUKSI

Permanent Mold Casting Process

TEKNIK DAN SISTEM PRODUKSI

Design aspects of permanent mold casting

Desain allowance penyusutan cetakan permanen lebih

TEKNIK DAN SISTEM PRODUKSI

 Produk dengan berat 0.1 kg hingga 10 Kg. Berat produk

 The section thickness of permanent mold casting may

 The dimensional tolerances are 0.4-1.5 mm depending

 Allowances of 0.25-0.75 mm are taken for the dimensions

 The draft angle is commonly 1-3o.

TEKNIK DAN SISTEM PRODUKSI

Molds incorporate the necessary sprues and risers,

TEKNIK DAN SISTEM PRODUKSI

Mold Design (untuk alumunium)

TEKNIK DAN SISTEM PRODUKSI

 Sistem coran dan salurannya harus diatur agar arah

 Untuk luas penampang besar gunakan pendingin baik

 Daerah datar untuk mencegah kebocoran cetakan

 Akibat panas maka cetakan akan warping, ketebalan

TEKNIK DAN SISTEM PRODUKSI

• The parting line is the hottest portion of a mold,

• Different heating of the mold will cause the mold to open at

o Venting – semua udara dalam cetakan harus

TEKNIK DAN SISTEM PRODUKSI

Bentuk Gating dan Riser

Riser harus berukuran cukup besar untuk menanggulangi efek penyusutan.

Mold 1. Mold 2. Mold 3.

TEKNIK DAN SISTEM PRODUKSI

1. A sprue-well, as designed in these experiments, does

TEKNIK DAN SISTEM PRODUKSI

The actual dimensions of the mold and gating system will

Figure is given as a guideline. All the dimensions are based on

Walls and Ribs

TEKNIK DAN SISTEM PRODUKSI

Flatness and Straightness

Greatest Dimension Casting Tolerance

TEKNIK DAN SISTEM PRODUKSI

Dalam beberapa kasus, ventilasi tambahan harus

1. Slot ventilasi biasanya 0,1-0,25 mm, potong sepanjang

TEKNIK DAN SISTEM PRODUKSI