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A Study on Development of Die Design System for Diecasting
J.C. Choi*, T.H. Kwon**, J.H. Park**, J.H. Kim**, C.H. Kim***
* Dept. of Mechanical Design Engineering, ERC for NSDM at Pusan Nat'l University
** Graduate School, Dept. of Precision Mechanical Engineering at Pusan Nat'l University
*** Dept. of Mechanical Engineering, Dong-eui University
Abstract
Diecasting is one of the forming methods to manufacture large number of products with short period time
and clean surface by high injection pressure of cast alloy. Die design is composed of selection of cast alloy,
design of product, runner and gate design etc. In reality, however, die design of diecasting has been performed by
trial and error method, which cause economic and time loss. This paper describes a research work of developing
computer-aided design of product and die design. Approach to the CAD system has been written in Auto LISP
on the AutoCAD with personal computer.
In this study, die design system of die casting process has been developed to present flow chart for
automation of die design, especially runner-gate system. As generation process and die design system using 3-D
geometry handling are integrated with technology of process planning, die design is possible to be automated. In
addition, specific rules and equations for the runner-gate system have been presented to avoid too many trials
and errors with expensive equipment. It is possible for engineers to make automatic and efficient die design of
diecasting and it will result in reduction of required expenses and time. An example is applied to cap-shaped
product, motor pulley product using proposed flow chart.
Key words : Die casting, Die design system, Rule base, Runner, Gate
Nomenclature
Qa volume of cavity to be filled, cm3
Vg main gate velocity, m/sec
tg filling time, sec
K heat capacity per unit volume, cal
q' the rate heat evolved per unit time during solidification, cal/sec
L latent heat during solidification, cal/g
Cp specific heat of molten metal, cal/g
Tm temperature of molten metal,
Ts solidus temperature,
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Td die temperature,
density of alloy, g/cm3
S radiation area, cm
2
X a half thickness of cast, cm
thermal conductivity of alloy, cal/cm sec
1. Introduction
Die-cast components are being used increasingly in the automobile, aerospace, electronic and other
industries after Doehler manufactured diecasting product by using Al alloys in 1915[1]. Diecasting is not
suitable for a small quantity production because of the high cost. But it has various advantages such as
manufacturing products of complex geometry and thin-wall sections, high productivity, smooth surface of cast
and excellent dimensional accuracy. Therefore diecasting process is developing sharply with establish thousands
of diecasting machines.
Diecasting die design consists of the selection of materials for diecasting alloys, the application of shrinkage, and
the casting plan including designs of cast, gate, runner and overflow. While manufacturing die design is highly
demanded for high precision and shorts the date of delivery, in most of the case, it is designed by determining
product geometry. So it is needed experienced know-how and experts who have a skill for manufacturing die.
In result, such diecasting die design has much economical losses and wastes of time by trial and error method.
Therefore it constructs DB from know-how, designs automatic shape of die and makes a 3D modeling for
diecasting die design & manufacturing by introducing CAD/CAM system.
Diecasting die design includes a process of determining geometrical figure of the product and die and
selecting condition for forming products. Mechanical and external quality of the ultimate diecasting product is
determined by interaction of each variables of the design. Therefore the die designer has to design after due
consideration of the problems that can be caused at the time of production. The traditional die design has been
carried out a designer who experienced for many years and followed a process of trial and error that happens in
the time from designing product and die to producing the ultimate product. Such processes cause the term of
production to extend and have the prime cost rise. As a result, there have been attempts to reduce them in various
ways.
One of them is construction of system that assists initial step developing diecasting product and die
design CAD system. The other is finding formability of product and mechanical defects before manufacturing
process and considering the countermeasure in advance by simulating diecasting process. In the latter study of
diecasting process, C.C Thai used runner-optimization design method and the abdicative network in modeling
the diecasting process according to the experimental data [2,3]. Generally speaking, die design still depends on
experience, due to lack of analytical ability in die and melting metal flow and heat transfer. Current shop floor
practice uses the trial-and-error method to determine die design, when new molds are used. This method is costly
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and results in a lot of wasted casting. To solve this problem a study was done on the runner and gating system to
simulate the molten metal flow and to analyze the pressure and metal movement during the casting process [4].
Although some finite element analysis software is capable of analyzing the melting process and flow conditions
of the products (workpiece) under various injection conditions, they are only giving some limited suggestions
and information to die design.
This research is the former and study on such die design system. W. Zhang et. al. [5] built the applicable
concept of CAD/CAE system for diecasting using by CAD package. J. P. Kruth et. al. [6] applied CAD/CAM
system to mold design. Yuh-Min Chen et. al. [7] developed CAD system using feature-based geometry design
for net shape manufacturing, diecasting and injection mold process. Kishinami T. et. al. [8] developed
CAD/CAM system for modeling of mold cavity and machine manufacturing. Walsham P. A. et. al. [9] developed
the geometry modeling system of CAM for die or mold. These researches are limited to CAD/CAM system for
injection molding. Therefore, so far, the cases applied CAD/CAM system for diecasting die design is scarce. In
this research, we apply CAD system for diecasting die design.
Diecasters usually carry out the diecasting experiments before producing new casts. At the diecasting
stages, the runner-gate part is always repeatedly corrected, which leads to a lengthened processing time and
increased processing cost. The diecasting die design should consider component system factors, such as runner,
gate, biscuit, over flow and airvent. A large amount of experience is essential in manual assessment and if the
design is defective, much time and a great deal of efforts will be wasted in the modification of the die. Thus
human negligence should be minimized.
In this study, die design system for diecasting process has been developed to present algorithm for
automation of die design, especially runner-gate system. In addition, specific rules and equations for runner-gate
system have been presented to avoid too many trials and errors with expensive equipment. It is possible for
engineers to make automatic and efficient die design of diecasting and it will result in reduction of expense and
time to be required. And we developed CAD system for diecasting die design by AutoLISP language under
AutoCAD using proposed algorithm and the database. The detailed contents of the research are described in the
following.
2. Algorithm for die design of diecasting
As shown in Fig. 1, die design is roughly composed of cast design, die layout design and die generation.
At first, 3D geometry of the cast is input and the design of the cast is begun. Each parts such as gate, runner,
overflow and airvent are determined using rule base. After the parts assembled with the cast, the final dies can be
generated.
First of all, the cast must be designed because the dies can be generated from the cast in diecasting die
design. The cast design consists of three parts; cast input, material selection and application shrinkage. In cast
input part, the cast modeling in commercial modeler as IGES file format is input. The input cast is located fitting
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viewpoint from desirable direction. And the parting surface should be determined for detailed die design for
diecasting. But the algorithm that determines the parting surface is not constructed, and in this system it is
supposed that user recognizes the location of parting surface in advance. After inputting the cast in this system,
the material of the cast should be selected. Next, the cast should be applied to shrinkage. The flowchart of cast
design is shown in Fig. 2.
When the cast design is completed, the die layout design for constructing master mold is accomplished.
In the process of die layout design, the gate, runner and overflow are designed for constructing dies. In this
system, the die layout design is divided four parts; gate design, runner design, runner-gate design and overflow
design. In gate design part, the properties are input for gate design and the gate sectional area is determined by
filling speed and time. The runner sectional area is determined by gate its in runner design. The part of
connecting gate and runner can be designed and assembled with cast in runner-gate system. And the overflow
can be designed with an algorithm that is similar with runner-gate system. Fig. 3 shows the flowchart of this
system.
As shown in Fig. 4, the diecasting dies can be generated. The cavity block should be generated first by
using the cast for generating diecasting dies. Hence, it is needed that the cast should be recognized. That is, the
minimum and maximum values of cast geometry should be recognized.
The following is the technique of the geometry recognition. The geometry of cast consists of the line, arc,
circle and spline. The geometry recognition of cast can be made from the understanding this entity information.
The minimum and maximum values of cast can be calculated by changing the current WCS values of this entity
from these of UCS. Here, this transformation is carried out by trans function from AutoLISP. The following is
the detailed content of this function.
But the other entity except line can be generated after defining the essential plan. Specifies the 3D
normal unit vector for this entity. This normal vector is the Z coordinate of OCS of the given entity. Therefore,
the OCS values of this entity should be diverted to WCS values using this function after diverting to UCS values.
Here, the changing UCS values from OCS values are carried out by Z-axis of UCS option. In this process, the
OCS values of this entity are converted into UCS values. And the technique of changing WCS values from UCS
values is equal to line entity. The cast is recognized by this process. Also, the algorithm of geometry recognition
is used for the die generation. That is, this algorithm is used for die splitting.
The cavity block can be generated by geometry recognition and rule base. After generating the cavity
block, the type of dies is determined according to the geometry of the cast. In this system, the types of dies are
set up in two types. Thus, One of them is the case that the cast is located at one side of dies and the other is the
case that the product is divided by parting surface. Here, because of difficulty of detailed geometry recognition
user can determine the selection of die. Consequently, the cavity block is generated and the type of dies is
selected, and ultimately the dies can be generated.
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3. Data Base for die design of diecasting
3.1 Material and Shrinkage DB
Most of the diecasting processes are used to shape or form parts made from both ferrous and nonferrous
metals, principally aluminum, magnesium, and zinc. In this research, it used aluminum alloys. The physical and
mechanical properties of Al alloys are illustrated Table 1.
In establishing dimensions for cavities, an allowance must be added to the dimensions specified for the part
to be cast, for shrinkage of the casting metal. The shrinkage allowances normally used are: 0.005in. per inch for
zinc alloys, 0.006in. per inch for aluminum alloys, and 0.007in. per inch for magnesium alloys. Shrinkage
allowances for copper alloys vary from 0.008 to 0.018 in. per inch, the allowance used depending largely on
foundry experience with the type of alloy being cast. The above values are influenced by several variables,
primarily size and shape of the casting. For castings that have irregular surface contours, die sections and cores
are designed to prevent free shrinkage in specific areas. Die sections or cores so designed are often called shrink
resistors.
For close-tolerance castings, it may be necessary to make an allowance for the expansion of the die cavity
caused by the difference in the temperature at which it was made and the operating temperature. In general, the
calculation of shrinkage allowances at room temperature is illustrated below equation.
)20()20( = tTL (1)
3.2 Gate and Runner DB
The main function of the runner and gating system is to deliver molten metal passed into the mold into
all section of the molten cavity. First, casting material is selected and cavity volume is calculated. Once
mechanical properties of cast are input and filling speed is selected, the gate area is generated.
Table 2 shows the Filling speed according to minimum thickness of cast. The cross-sectional area of the
gate Ag is shown by equation (2).
gg
a
gtV
QA
= (2)
The filling time of die cavity tg is assigned to be that a fraction of solidus comes up to 70 %.
Heat capacity per unit volume, K is given by
XSTTCLKsmp
+= )]([ (3)
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The flow rate heat per unit time, q'is given by
XTTSqdm
/)( = (4)
From the equation (3) and (4), filling time, tg can be obtained.
7.0
=
q
Ktg
(5)
Generally, the gate thickness, t is selected properly, which is between 0.5 and 3.0mm, considering
trimming etc. The width of gateL is determined by following equation from gate area calculated by equation (2).
t
AL
g= (6)
Standards proportions for runner configurations, as established within reasonable limits, are shown in
Fig. 5. To obtain gate-controlled fill of the die cavity, the cross-sectional area of a runner must be larger than
of the gate. However, for minimum heat loss, metal velocity in the runner feeding a gate must be as high as
possible. For these reasons, a runner-to-gate area ratio of 1.15:1 to 1.5:1 is generally used. Oversize runners will
increase metal losses and remelting costs.
Runners should be designed with a stepped increase in cross-sectional area from the gate via branch
runners to main runners, and on to sprue or biscuit, to promote uniform metal velocities and uniform ratios of
cross section to perimeter. The cross-sectional area of a feed runner is equal to, or less than, the sum of the cross-
sectional areas of the branch runners.
On runners of different lengths feeding identical parts, the longest runner should be given a slightly
larger cross section. A runner that converges into a long gate should increase in cross section toward the feed
runner, to keep metal velocities as uniform as possible. Theoretically, these runners should taper out at the ends
to the thickness of the gate, but practical considerations require a compromise. Turns and leading edges should
have generous radii and should be smoothly blended where thickness or width changes occur. Runners should
have a reasonably smooth surface finish.
A thick runner will not solidify fast enough for the cycling rates generally used. A thin, flat runner will
cause the metal to lose too much heat before it enters the gate. As a compromise, a standard width-to-depth ratio
of 1.6:1 to 1.8:1 , side angle is 10~20 and corner radius is over 6mm. has been adopted. This ratio provides for
reasonably fast cooling without excessive heat loss during cavity filling. And then the shape of runner is selected
from database. The width and depth of runner varies with the volume of metal to be injected into the cavity.
Various shapes of a runner are illustrated in Fig. 6.
3.3 Overflow, Airvent and Cavity block DB
The placing of overflows is generally predictable, and their location and size are designed into the gating
system of a die. However, the addition or relocation of overflows is the most frequent cause of failure in the 15%
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of dies for which first-shot success is not achieved. The weight of metal in overflows should be added to the part
weight in calculating the total weight of metal flowing through the gate. Details the shape of overflow are
illustrated in Fig. 7.
Airvent on the die faces usually lead out of overflows. The total of the cross-sectional areas of vents
should be at least 50% of the gate area. Self-cleaning of vents can be ensured by making vents 20 30mm thick,
0.1 0.15mm length. Venting may also be provided by small grooves cut across the parting plane of the die, or
by the clearance around the ejector pins or movable cores and slides.
The shape of the finished component determines the design of a diecasting die. But there are a number of
aspects involved in the design and sizing of a die, which can have an influence and important bearing on die life.
Details the shape of cavity block are illustrated in Fig. 8 [10].
4. Application of system and consideration
4.1 Application of cap-shaped product
The constructed system is applied to some examples as the type of dies in this research. At first, this
system is applied to the cap-shaped product that has one side dies type. As shown in Fig. 9(a), this product is
modeled using by commercial modeler, Pro/Engineer 2000i for diecasting die design.
The geometrical feature of the cap-shaped product is that the parts assembled runner-gate is the plane. In
this case it is simple to apply. And the inner geometry of the cast should be the geometry of die because the type
of dies is one side type. But the recognition of the inner geometry is not accomplished. Therefore, the user
should recognize it.
The geometry that designed the cast and die layout is shown in Fig. 9(b). Here, the ultimate dies are
generated as shown in Fig. 9(c) through the geometry recognition of cast, runner-gate and overflow. In this
system the other parts of dies are not considered.
4.2 Application of motor pulley product
Next, this system is applied to the motor pulley product that has both side dies type. As shown in Fig.
10(a), this product is modeled using by commercial modeler, Pro/Engineer 2000i for diecasting die design.
The geometrical feature of the cap-shaped product is that the parts assembled runner-gate is the cylindrical
plane. In this case, the shape of gate should be modified fitting the cylindrical plane. And the product should be
split the parting surface for generating the dies.
The geometry that designed the cast and die layout is shown in Fig. 10(b). Here, the ultimate dies are
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generated as shown in Fig. 10(c) through the geometry recognition of cast, runner-gate and overflow.
5. Conclusions
The study developed an automated CAD system for die design of diecasting. The primary conclusions of
this study are as follows.
1. This study suggested an algorithm for easy and effective die design system that the die
designer can design diecasting die, especially runner-gating system.
2. This system is constructed using proposed die design algorithm and database in the
circumstance AutoCAD.
3. The constructed system was applied to some examples as the type of dies in this research.
At first, this system was applied to the cap-shaped product that has one side dies type. Next,
this system was applied to the motor pulley product that has both side dies type.
4. A novice who may not have any experience of die design can perform die design only if he
has a little knowledge about diecasting. This system quantifies practical knowledge and
experiences in die designing of diecasting as formulating procedure of design.
Henceforth, the research assignment needs the supplementation of various details that are not considered in this
system. That is, the system that the product having the undercut can be applied should be constructed. And in
this system, the part of user selection should be replaced with accomplishment by an algorithm. Moreover, this
system should be applied to not only the single-impression dies but also multiple impression dies.
6. References
[1] H.H. Doehler, "Diecasting", McGraw-Hill Book Company, 1951.
[2] C. C Tai, J. C Lin, "A runner-optimization design study of a die-casting die", Journal of Materials
Processing Technology, Vol. 84, pp. 1-12, 1998.
[3] C. C Tai, J. C Lin, "The optimal position for the injection gate of a die-casting die, Journal of Materials
Processing Technology, Vol. 86, pp. 87-100, 1998.
[4] Shamsuddin Sulaiman and Tham Chee Keen, "Flow analysis along and gating system of a casting
process", Journal of Materials Processing Technology, Vol. 63, pp. 690-695, 1997.
[5] W. Zhang, S. Xiong, B. Liu, "Study on a CAD/CAM System of Diecasting", Journal of Materials
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Processing Technology, Vol. 63, pp. 707-711, 1997.
[6] J.P. Kruth, "Steps Toward an Integrated CAD/CAM System for Mold Design and Manufacture:
Anisotropic Shrinkage, Component Library and Link to NC Machining and EDM", Annals of the CIRP,
Vol. 35, 1986.
[7] Yuh-Min Chen and Ching-Ling Wei, Compu ter-aided feature-based design for net shape manufacturing,
Computer Integrated Manufacturing System, Vol. 10, No. 2, pp. 147-164, 1997.
[8] KISHINAMI T., et. al., "Development of Interactive Mold Cavity CAD/CAM System", CIRP Annals, Vol.
32, No. 1, pp. 345-349, 1983.
[9] WALSHAM P.A., et. al.., Further Developments of a Geometric Modeling System for the Computer
Aided Manufacture of Dies and Molds , CIRP Annals, Vol. 32, No. 1, pp. 339-342, 1983.
[10] John Worbye, "New Information Points the way to Longer Diecasting Die Life", Diecasting Engineer, pp.
42-54
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ADC1 ADC3 ADC5 ADC6 ADC10 ADC12 ADC14
Density
(Mg/m
3
)
2.65 2.63 2.57 2.65 2.71 2.68 2.73
Specific heat
(KJ/kg/K)
0.96 0.96 0.96 - 0.96 0.96 -
Melting range
(K)
847-855 830-869 808-894 871-913 810-866 788-855 780-921
Coefficient of
thermal
expansion
(10/K)
21.4 22.0 25.0 25.0 21.8 21.0 27.0
Thermal
conductivity
(J/cm/s/K)
1.21 1.13 0.96 1.38 0.96 0.96 1.34
Latent heat
(KJ/kg)
- - - - 394.8 394.8 -
Tensile
strength
(N/mm2)
290 320 310 280 320 310 320
0.2% offset
strength
(N/mm2)
130 170 190 - 160 150 250
Elongation
(%)
3.5 3.5 5.0 10.0 3.5 3.5 -
Table 1 Physical and mechanical properties of aluminum diecasting alloys
Filling speed (m/s )
Minimum thickness (mm)
ADC1 ADC12
1.270 45 46.2
1.905 42 43.5
2.540 40.5 42
3.175 39 40.5
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3.810 37.5 39
4.572 36 37.5
5.080 34.5 36
6.350 31.5 33
Die Temp. 260 C 260 C
Table 2 Filling speed according to minimum thickness of cast
Cast des ign Die Generation
Rule Bas e for dieca sting die
des ign
Die Layout
Design
Cast Input
(3D Wire-
frame )
Material
Selection
Apply
Shrinkage
Gate
Design
Runner
Design
Runner-
Gate
s y s t e m
Overflow
Design
Cavity
Block
Design
Die type
- One side
- Both side
Die
Generation
Fig. 1 Flowchart of die design system for diecasting
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Cast Input Apply ShrinkageMaterial
Selection
IGES file input
( by commercial
modeler)
Aluminum alloy
Zinc alloy
Mag nes ium alloy
Change View
point
Determination of
Parting Surface
( use r )
Mechanical ,
Physical
Propert ies
Calculate
shrinkage (s)
Apply Shrinkage
- Sca ling fac tor
(1+s)
Fig. 2 Flowchart for cast design
Gate
D e s ig nR u n n e r -G a te
S y s t e m
Runner
D e s ig n
Calculate Filling
S p e e d
( by min imum
th ickness )
Ca lcu la t ion o f
runner a rea
( b y g a t e a r e a )
Calculate Filling
Time
Dete rmina tion o f
g a t e a r e a
Se lec t ion
ru n n e r- g a t e t y p e
Dete rmina tion o f
spec if icd im e n s io n
( use r )
Overflow
D e s ig n
Input Value for
g a t e d e s ig n
Se lec t ion o f
g a t e t h i c kn e s s
Dete rmina tion o f
ga te wid th
Se lec t ion
normal line of
pa rt ing surface
Se lec t ion
overflow type
Dete rmina tion o f
spec if icd im e n s io n
( ru le base )
Se lec t ion
normal line of
pa rt ing surface
Se lec t ion
part ing surface
Se lec t ion
part ing surface
Fig. 3 Flowchart for die layout design
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Cavity Block
Design
Die
Generat ionDie Type
Recog ni tion of
c a s t
Determination
die type
- O ne s id e typ e
- Bo th s id e t yp e
Calculate
maximum,
minimum value
Determination of
Cavity Block
Recog nit ion of
s h a p e
Die Generation
Fig. 4 Flowchart for die generation
Width(W)
Radius(R)
Depth(D)
Side Angle
Fig. 5 Schematic drawing of general section shape for runner
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Fig. 6 Schematic drawing of runner type
Cavity
Overf low0.5-0.8mm
3 - 8m m
30 - 45
Fig. 7 Schematic drawing of general shape for overflow
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AB
C
Cavity B lo ck
CastRunner-gate
C : A = 2 : 1
B : A = 3 : 1
Fig. 8 Schematic drawing of general shape for cavity block
(a)
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(b)
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(c)
Fig. 9 Application the developed system for cap-shaped product
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(a)
(b)
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(c)
Fig. 10 Application the developed system for motor pulley product
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