EXPERIMENTAL INVESTIGATION OF ADDING VARIOUS ADDITIVES AND BINDERS IN DRY SAND MOULDING BY TAGUCHI’S METHOD
Mr. Ayanesh Y. Joshi 1*, Mr. Vaishal J. Banker 2, Dr. Unnati A. Joshi 3 1 Research
Scholar, Mechanical Engineering, Gujarat Technological University Professor, ADIT, New V. V. Nagar, Gujarat, India 3 Associate Professor, ADIT, New V. V. Nagar, Gujarat, India 2 Assistant
*Corresponding author (e-mail:
[email protected]; Phone: +91 9925012591) Abstract
An optimization technique for process parameters of dry sand mould (core) based on the Taguchi orthogonal design approach is proposed. An attempt is made to optimize the process parameters level in order to yield the optimum quality characteristics of the castings. Taguchi method is used here for experimental investigation and to analyse the effect of selected process parameters and their levels on the casting defects. The effect of process parameters i.e. sand type, binder percentage and additive percentage is indicated by the measuring values of shear strength, permeability and mould hardness. The experimental runs confirm that the used method is efficient in optimizing the parameters and thereby the levels and its combinations. Keywords: Dry sand Mould; Additive; Binder; Permeability; Shear Strength; Hardness. 1. INTRODUCTION
The dry sand of mould making uses dry sand bonded with materials other than clay, using a fast curing adhesive. The latter may also be referred to as no bake mould casting. When these are used, they are collectively called "air set" sand castings to distinguish them from "green sand" castings (Bin,2007). Two different types of moulding sand are naturally bonded together ones is (bank sand) and another is synthetic (lake sand); it is generally preferred due to its more consistent composition in mixing. Base sand is the type used to make the mould or core in absence of any binder (Casalino et al., 2005). Binders are added to a base sand to bond the sand particles together (i.e. it is the glue that holds the mould together). It is the prime requirement’s where the higher strength is required in the mould (Szanda and Balinski, 2011). Additives are added to the moulding components to improve: surface finish, dry strength, refractoriness, and "cushioning properties"(Karl Kurple and Concetta Kurple, 2005) The literature study of additives and effects on various parameters of the casting process, hence ascertaining the influence of all operational variables causes to the final product, even a changing atmospheric condition shows the varying results on the final product of the casting (Kozlov et al.) Green sand moulding (wet) the oldest and most popular methods in the casting industries. The olivine sand having low expansion foundry sand produces the castings with closer dimensional control, better casting accuracy and smoother surface finish of the product (Wang et al., 1999). The moulding mixture is composed of sand, adhesive, water, clay (Wa et al., 2003). Since the availability factor closes certain ways of
modification. The quality of castings in a Dry sand mould is highly influenced by its properties such as compression strength, shear strength, permeability and hardness of the surface. The evaluation of dry sand mould properties has been carried out using different additives (Aggarwal and Siddique, 2013). Additives are plays very important role in the dry sand combination.
The properties such as compression strength, permeability and collapsibility have been studied, comparison have made with different additives. Hydrated sodium silicate is one of the most popular inorganic binders. Although sands with sodium silicate are of a versatile nature, being moreover relatively cheap and characterized by numerous advantages, their indisputable drawback is too high residual strength and hence poor knocking out properties and difficult reclamation of the used, ceramic sand grains (Xu et al., 2007). . The formation of sinters resulting from the tendency of a Na2O&SiO2 system to react with silica can be reduced by reducing the amount of binder in molding sand on condition, however, that its binding properties are improved (Casalino et al., 2005). So, from the literature study, it was found that there is a scope to study effect of various additives and binders on properties like permeability, shear strength and hardness in current investigation. 2. MATERIALS AND METHODS
2.1. Experimental Methodology
To study various types of sand additives w.r.t bonding power and moisture absorptivity
Sand & Additives mixing ratio analysis based on previous research works
Process Parameters Selection
Parameters Optimization
DOE using MINITAB
Result Analysis of sand mold
2.2. Materials
Mold Property Testing
Figure 1: Flow Chart for Methodology
The materials used for the current investigation were Industrial Oil, Molasses and Sodium Silicate. The various percentage of additives and binders are shown below in Table 1 (Major and Rady, 2000).
Table 1: Additives and Binder Composition Additives Specification
Industrial Oil
Molasses
Sodium Silicate
Specific Gravity
0.95
1.42
1.8
Weight of 1 litre
950 g
1420 g
1800
Sand Mixture prepared
550 g
550 g
550 g
3 % Weight/Volume
16.6 g (17.5 ml)
16.6 g (11.6 ml)
16.6 g (10 ml)
7 % Weight/Volume
38.5 g (40.5 ml)
38.5 g (27.11 ml)
38.5 g (21.3ml)
Binder (Wood flour) 1.5 % requires 8.25 g
2.5 % requires 13.75 g
2.3. Design of Experiment
Taguchi method is a tool for evaluating and implementing improvements in products, processes, materials, equipment, and facilities. Taguchi method is used whenever we have to reduce the total number of experiments in order to minimise the cost of production (Sushil Kumar et al., 2011). This method uses the Signal-to-Noise ratio concept where signal is a desirable effect while noise is referred to as an undesirable effect. For the current investigation, we have 3 input parameters each having 2 levels as shown in Table 2. The total number of experiments is 8 (Total Experiments = (Level) Factors) as shown in the Table 3 (Sanjeev Das et al., 2006) which was made using MINITAB 14 software. The concept of Larger – is – better is considered to obtain S/N Ratio to maximize the responses that are Permeability, Hardness and Shear Strength by using the following equation 2.4. Testing of Specimens
S/N = -10 * log (Σ(1/Y2)/n)
(1)
After performing the experiment (as per the guidelines given by IS : 1918 – 1966) the specimens are allowed to dry at the room temperature for 10 hours and then it is tested for permeability, hardness and shear strength (S. Guharaja et al., 2006). The equipment use are Permeability meter (Make : Versatile Equipments, Model : VP/020305 ), Mould hardness tester (Make : Versatile Eqyipments, Model : VMH (B)), Universal strength machine (Make : Versatile Equipments , Model : VUN/020602 ). Table 2: Coded values of Input Parameters and their levels Lower Level
Higher Level
1
2
Sand (Grade)
36
52
C2
Additive (%)
3
71.5
C3
Binder (%)
1.5
2.5
Coded Value
Input Parameter
C1
3. RESULTS AND DISCUSSIONS Table 3: Taguchi’s L8 array with output parameters
Binder (%)
Molasses
Oil
Na2CO3
1
36
3
1.5
173
253
275
1.5
7.6
1.5
40
36
18
2
36
3
2.5
173
253
275
1.7
7.7
1.7
42
40
20
3
36
7
1.5
119
178
467
1.7
25
1.1
45
57
25
4
36
7
2.5
119
178
467
2.1
28
1.3
48
60
27
5
52
3
1.5
178
193
226
1.7
6.2
1.8
36
40
7
6
52
3
2.5
178
193
226
1.8
6.5
2
38
42
9
7
52
7
1.5
156
212
376
0.7
22
1.6
38
47
45
8
52
7
2.5
156
212
376
0.8
25
1.8
40
50
48
Na2CO3
Additives (%)
Oil
Sand (Grade)
Molasses
Sr. No.
Na2CO3
Hardness (BHN)
Oil
Shear Strength (kg/cm2)
Molasses
Permeability (m2)
Figure 2: Main effects Plots for various output parameters.
3.1.Permeability
It can be seen from the main effects plot of Permeability Fig. 2 that the permeability increases with increase of Sand grade in case of Molasses whereas it decreases for Oil and Sodium Carbonate. 3.2.Shear Strength
It can be seen from the main effects plot of Shear Strength Fig. 2 that the Shear Strength decreases with increase of Sand grade in case of Molasses and oil whereas it increases for addition of Sodium Carbonate. 3.3. Hardness
It can be seen from the main effects plot of Hardness Fig. 2 that the hardness decreases with increase of Sand grade in case of Molasses and oil whereas it increases for addition of Sodium Carbonate. 4. CONCLUSIONS
By testing the sand mould for process parameters like hardness of mould, shear strength of mould and permeability of the mould for its variation in the sand grade, additives and binder proportions it can be observed that Sand of grade 36 mixed with 7 % additive and 2.5 % binder gives comparatively better properties than the other selected combinations. Na 2CO3 gives the best permeability for the same combination (As selected) whereas the Industrial oil delivers best shear strength and hardness values.
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