ARCHIVES
ISSN (1897-3310)
Volume 11
Issue 2/2011
85–88
Of
FOUNDRY ENGINEERING
17/2
Published quarterly as the organ of the Foundry Commission of the Polish Academy of Sciences
Evaluation of wax pattern properties
in the lost-wax process
H. Matysiak a , R. Haratym b , R. Biernacki c*
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Warsaw University of Technology, UCB Functional Materials, Woloska 141, 02-507 Warsaw
b
University of Ecology and Management, Wawelska 14, 02-061 Warsaw
c
Warsaw University of Technology, Institute of Manufacturing Technologies, Narbutta 85, 02-524 Warsaw
*
Contact: e-mail: [email protected]
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Received 11.04.2011; accepted in revised form 26.04.2011
Abstract
This article present achieved results of examination of wax pattern properties (wax compounds) which are used in lost wax process.
Evaluation of those results was made with approach as it is taken in foundry. Evaluation included: evaluation of wax compound shrinkage,
bending strength test, hardness test using penetration method, and resistance to creep of wax patterns in precision foundry environment.
Keywords: Quality of models, Technological properties of models
1. Introduction
solved by comparison analysis of technological properties of both
masses.
In lost wax process three technological phases have the major
influence on surface quality (surface micro geometry) and
dimensional accuracy of precision casts.
One of those technological phases is manufacturing of precise
wax patterns.
Main properties that need to be investigated are:
1) shrinkage of the wax pattern compound
2) bending strength of wax patterns
3) hardness of wax patterns
4) creep resistance in temperature function
During making of precision casts there are usually two main
problems: first, when there is an introduction of new materials
and wax patterns to the manufacturing process, there need to be
solution for chemical composition problem and previously
mentioned investigation. Second major problem, occur when
there is known sample wax pattern mass and there is a need to use
another wax pattern mass with known composition, this can be
Moreover for lowering production costs purposes recycled
wax pattern compound is used with the addition of new material
and in this case examination of only few technological properties
is needed.
In production process desired is to use comparison analysis of
those wax pattern masses with already wax pattern masses which
already proved there reliability in practice.
Most of the time this inspection methods need to be chosen,
which has appropriate strength and is resistant to the temperatures
which usually occurs in foundry.
Inspection method should be simple, low cost equipment
should be used and examination condition should be as similar as
possible to those in foundry in which patterns and molds are
made.
ARCHIVES of FOUNDRY ENGINEERING Volume 11, Issue 2/2011, 85–88
85
2. Methodology and results of
technological properties examination
2.1. Evaluation of wax pattern compound
shrinkage
Fig. 2. Research array of wax patterns for examination of wax patterns
shrinkage (during examination in exchange of dial indicator
displacement transducer Ptx 100- Peltron was used)
1,4
Shrinkage, %
1,2
1
0,8
0,6
0,4
0,2
0
20
Sample shape is shown in fig. 2. Results of already examined
samples are shown is graph (fig. 3 and fig. 4).
86
30
35
40
Temperature, ºC
45
50
1,8
1,6
1,4
1,2
1
0,8
0,6
0,4
0,2
0
20
Fig. 1. Examination station for shrinkage testing of wax compounds [6]
25
Fig. 3. Shrinkage of Blayson wax (A7-FR60) for 6 groups of samples
(shape of samples consistent with fig. 2; injection pressure 2 MPa;
injection temperature 60–70 °C; cooling water temperature 20–22 °C)
Shrinkage, %
Important issues which decide about precision of wax patterns are
the shrinkage properties of wax pattern compounds used to produce
those patterns.
According to [1], [2], [3], [4] literature sources, precision of wax
patterns is mostly determined by injection of wax pattern compound in
to the die, injection pressure, individual time of injection, intensity of
wax pattern compound flow in die. All of those parameters have major
influence on shrinkage of wax patterns.
Quality of precision cast highly depends on their dimensional
accuracy. Important phase of technological process which determines
dimensional accuracy of casts is quality of wax patterns.
Factor which decides about dimensional accuracy of wax patterns
is shrinkage of wax compounds used to produce them.
In this research paper examination of shrinkage properties of wax
pattern compounds based on hard wax will be presented in comparison
with wax based on paraffin and stearin. In the same time value of
recycled hard wax was determined.
Examination station (fig. 1) was build from certain components:
1. Injection molding cylinder with wound heater
2. Actuator control valve
3, 4 Rotameter
5. Strenghten unit “Peltron” do Ptx100
5.a Displacement transducer Ptx100 “Peltron”
6. Measurement of temperature inside of sample (sensor 12)
7. Displacement measurement
8. Computer
9. Multimeter – temperature measurement inside of cylinder
10. Multimeter – temp. measurement of water in the exit of die (14)
11. Autotransformer to power cylinder heater
12. Temperature sensor in injection mold
13. Entrance of cooling water
14. Exit of cooling water
15. Die (for injection of wax pattern compounds)
25
30
35
40
Temperature, ºC
45
50
Fig. 4. Shrinkage of Castylene wax (B405) for 4 groups of samples
(shape of samples consistent with fig. 2; injection pressure 2 MPa;
injection temperature 60–70 °C; cooling water temperature 20–22 °C)
Shrinkage examination methodology require specialized equipment
including die, measurement devices and require ability to withstand
high pleasure of injection even up to 20 MPa.
ARCHIVES of FOUNDRY ENGINEERING Volume 11, Issue 2/2011, 85–88
English Wax
5,5
4,4 +−00,,78
French Wax
4,4 +−00,,78
5,9 +−00,,88
+0 , 4
−0, 4
3,8+−00,,67
PSW compound (3 times recycle)
Wax compound (recycle, 1time)
3,2
+1, 6
−1,1
5,1
6,3
+0 , 5
− 0,5
2.3. Hardness evaluation of wax patterns based
on penetration method
Hardness test was made using penetration method [7], and the
standardized penetration needle was used [5]. Evaluation methodology
and research station is presented in fig. 5.
2.3.1. Preparing the research station for displacement
measurement
Devices that were used in research station include
displacement sensor, amplifier from Peltron Company, and signal
translator from Labor Aster Company and multimeter from Sanwa
Company.
50
45
40
35
30
25
20
15
10
5
0
o
o
18 C
o
23 C
27 C
PSCP
7,0 +−00,,78
+0 , 5
−0, 6
KC-4017
7,4 +−11,,66
B-405
American Wax
PSCP
7,5+−00,,23
A7-FR60
6,5
B-405
Blayson
KC-4017
6,7 +−11,,00
+0 , 7
− 0 ,8
PSCP
6,4 +−22,,57
Castylene
A7-FR60
Average bending strength Rgavg.[MPa]
Temp. 21oC
Temp. 26oC
B-405
Type of sample
KC-4017
Table 1. Results of bending strength test
Hardness of wax pattern mass was tested using penetration
method which use standardized penetration steel needle which is
described in PN-EN 1426 2001r. Needle is put in to the wax
pattern mass in 90 degrees angle, and with 160 G force which
take from one up to 5 minutes. Measurement of depression of
needle in to the wax pattern mass is described in penetration units
(penetration unit – described by needle depression of 0,1 mm in to
the mass) and this was made with usage of penetrometer [6]. and
devices shown in fig. 5.
One of the first conclusions was realizing that time has low
influence on hardness results of “hard” wax compounds (fig. 6).
Moreover “hard” wax is significantly harder then compounds
made from paraffin a stearin (PSCP) with 5% addition of ceresin
and 1% of polyethylene.
A7-FR60
Banding of roller samples with ø 7,8 mm diameter was made, those
samples were placed between two knife-edge support points and
initiating a load at the midpoint of the sample. Distance between
supports is 50 mm.
Results of those tests are presented in table 1.
2.3.2. Methodology of hardness test using penetration
method
Penetration units .
2.2. Bending strength test
Fig. 6. Hardness graph for different wax compounds –
measurement time 5 minutes
2.4. Model Resistance to creep in temperature
function
Examination device is presented in fig. 7. Simple device was used
in the form of arm with holes (1) in those holes roller samples of
ø 7,8 mm diameter were installed (2) and measurement of changing
shape in function of time in different temperatures was made.
(1)
Fig. 5. Scheme of research station for displacement measurement
(penetrometer with induction displacement sensor). 1 – Holed for
displacement sensor; 2 – Tested sample; 3 – Displacement sensor
Ptx100; 4 – Penetration needle; 5 – Transducer, Amplifier; 6 –
Multimeter Sanwa PC5000; 7 – Laptop with installed PC-link
plus program
Description of research station for displacement measurement
which was used for hardness test and resistance to creep
deformation (fig. 5).
(2)
Fig. 7. Research station for measurement of deflection (creep)
of wax pattern masses [6]
Results of those measurements were gathered with usage of
computer based device or altimeter (device accuracy is 0,02mm).
ARCHIVES of FOUNDRY ENGINEERING Volume 11, Issue 2/2011, 85–88
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Examination was made to determine deflection of roller samples,
which were under constant load of 30 G on 150 mm arm. Examination
was done in 18 °C and 25 °C. Examination took around 10 to 20
minutes for each sample.
On presented graphs, fig. 8 and fig. 9, small influence of
pressure on deflection was seen. PSCP mass is a compound which
has the lowest creep resistance under constant small load which
equal to 30 G. The highest creep resistance has hard waxes, which
is most visible for 25 °C temperature (fig. 9).
Deflection, mm a
14
PSCP
12
10
B-405
8
6
A7-FR60
4
KC-4017
2
0
0
2
4
Time, min
6
8
10
Deflection, mm a
Fig. 8. Comparison of creep resistance of different masses
in 18 °C (Blayson mass A7-FR60; american mass KC-4017;
Castylene mass B-405; PSCP mass)
40
35
30
25
20
15
10
5
0
B-405
A7-FR60
KC-4017
2
4
6
Time, min
8
4. Conclusions
1. Taking in consideration possibility of making those tests
and evaluation in precision foundry, the most optimal option of
testing wax patterns is evaluation of wax pattern resistance to
creep in temperature from 16 to 25 °C.
2. If there is a need for quick evaluation of wax pattern
properties hardness test using penetration method in temperature
function directly on production wax pattern is recommended.
Acknowledgements
Part of the research was granted from European Social Found,
as a part of “Development Program of Warsaw University of
Technology”
References
PSCP
0
wax compound in case of hard mass. To conduct this test special
research station is needed (fig. 5).
Wax pattern resistance to creep in temperature function.
Results of this test are repeatable. Methodology of this evaluation
include influence of temperature and allow choose optimal pattern
compound. Research station necessary to do this kind of
evaluation is relatively simple, and it’s possible to implement it in
precision foundry.
10
Fig. 9. Comparison of creep resistance of different masses
in 25 °C
3. Analysis of achieved results
Achieved results of wax pattern (fig. 2) compound shrinkage
which are very repeatable were further analyzed by following
rules from literature [10]. Because of the amount of parameters
that need to be considered during this evaluation, none of the
pattern shape will be optimal.
Strength test of wax patterns needs special equipment, but
achieved results have quite high measurement uncertainty [10].
Results of hardness test were repeatable, but it was realized
that influence of temperature not always allow choose optimal
[1] W. Bonilla, S.H. Masood and P. Jovenitti, An Investigation of
Wax Patterns for Accuracy Improvement in Investment Cast,
Part 5, Advanced Manufacturing Technology, Londyn,
2001/18.
[2] M. Horacek, Accuracy of casting manufactured by lost wax
process, Foundry Trade Journal, October 1997.
[3] R. Wiliams, D. Morson, D. Bond, M. Horacek, Latest
Developments in Waxes and Aucilliary Equipment for Wax
room, Precast 98, Praga September 1998.
[4] W.N Iwanow, S.A. Kazenow, B.S. Kurczmem, Litje po
Wypłajaemym Modeljam, Maszynostrojenie, 1984.
[5] Standard PN_EN 1426, 2001.
[6] P. Terlecki, Bachelor thesis, Warsaw University of
Technology, Institute of Manufacturing Technologies, 2009,
(in Polish).
[7] J. Doskar, Wyroba presnych odlitku, Praha 1976, SNTL.
[8] Materials from firm Blayson Olefines Ltd, Cambridge UK.
[9] Materials from firm The Kindt-Collins, Cleveland, Ohio.
[10] J. Arendarski, Uncertainty of measurements, Warsaw
University of Technology, Publishing House, Warsaw 2003,
(in Polish).
Ocena właściwości modeli w procesie wytapianych modeli
Streszczenie
W artykule przedstawiono dane dotyczące badań własności modeli (mieszanek modelowych) stosowanych w procesie wytapianych
modeli. Dokonano oceny badań w aspekcie prowadzenia ich bezpośrednio w odlewni precyzyjnej. Badania obejmowały: ocenę skurczu
mieszanek modelowych, badania wytrzymałości na zginanie, ocenę twardości mieszanek metodą penetracyjną oraz ocenę odporności na
pełzanie modeli wytapianych w warunkach każdej odlewni precyzyjnej.
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ARCHIVES of FOUNDRY ENGINEERING Volume 11, Issue 2/2011, 85–88