Foundry Technology II
Dr. Emmanuel Kwesi Arthur
Department of Materials Engineering,
Kwame Nkrumah University of Science and Technology, Kumasi
February 7, 2019
Course Code: MSE 358
Email: [email protected]
Phone #: +233 (0) 541710532
Course ObjectivesThis course aims to introduce students to the foundry industry and provide
clear understanding to the students of the technology processes, design flow
and the techniques that can be employed to realize effective casting designs
using concept from Foundry Technology I
The students will learn engineering/pattern drawing, design calculations,
moulding techniques, gating system design, materials used, melting and pouring
and cast metal techniques and so on.
The course aims to develop appropriate technical knowledge as well as the professional skills of the students, so that they are equipped to take gainful employment in the said vocation
Casting of Brake Disk
Actual Component
3-D Engineering Drawing
Students at Suame to Pose for PicturesHow can you ramp with fan yoghurt in one hand?
Still Posing
Who is Preparing the Mould?
Where is the Riser?
Creating the pouring Cup
Mould Cavity
Melting
Melting and Pouring
Final Cast Component
Case Study
Casting of thin Aluminium Alloy (Al-Si) Plates
Gating System Design for Casting thin AluminiumAlloy (Al-Si) Plates
This study describes the design of a gating system to produce thin Aluminiumcast alloy plates
The plates are of different sizes and thicknesses of 4mm, 6mm, 8mm, and 10mm
A non-pressurized gating with ratio of 1:4:4 and green sand mouldingtechnique was used
The gating design was based on the laws of fluid mechanics and empirical rules of gating for non ferrous metals.
Why Gating System Design
It has been shown that an optimum gating system design could reduce the turbulence in the melt flow; minimize air entrapment, minimize sand inclusion, minimize oxide film and dross
Also, relatively slower filling might generate cold shuts
Furthermore, porosity which is a common defect in casting also could result from improper design of gating system
Mould Making
Materials used include; silica sand, clay, wood, glue and Aluminium alloy scraps.
The table below present the composition of melt.
Aim and Objectives
The aim of this project is to improve the quality of Aluminium alloy thin plates castings produced in green sand moulding process.
The specific objectives are toDevelop engineering and pattern drawings Develop proper gating system designIdentify the furnace and amount of heat neededCalculate the mould filling time and solidification time
Materials and Methods
The experimental procedure involved: the gating design calculations, construction of wooden pattern and gating; using the wooden pattern and gating to produce the mould
cavities and gating; melting, melt treatment and pouring of melt in the sand mould to produce the casting.
Engineering and Pattern Drawing
• Pattern Allowances
• Shrinkage allowance for Aluminium alloys is 16mm/m.
• These allowances shall be added to the pattern parts in the mould cavity.
• Pattern Dimension = Actual Dimension + Shrinkage allowance
• For PART A
• Pattern thickness = 4 + (0.004×16) = 4.064 mm
• Pattern length = 80 + (0.08×16) = 81.28 mm
• Pattern breath = 40 + (0.04×16) = 40.64 mm
SN Actual Dimension [mm]
Part Length Breath Thickness
1 A 80 40 4
2 B 120 60 6
3 C 160 80 8
4 D 200 100 10
Don’t forget machining allowance where it is needed
Dimensions of the pattern plates
Table below shows the dimensions of the pattern plates used in the design of a gating for four thin Aluminium alloy plates.
Step 1: Calculate the total weight of castings
W = ρ×V
where: W = total weight of casting, ρ = density, V = total volume of casting.
V = 13411.07 + 45335.68 + 107420.69 + 209754.42 = 375921.86 mm3
W = 2500×375921.86×(10-3)3 = 0.9399Kg
Step 2: Calculate the pouring rate and pouring time
Pouring rate formula for non-ferrous gating:
where: R=pouring rate, b=constant, depends on wall thickness; typical values of b are shown on Table 2.
Table 2. Values of constant (b) for different Casting thickness [14]
where: Ra = adjusted pouring rate, K = metal fluidity, C = the effect of friction with values of 0.85-0.90 for tapered sprues in the gating system.
Pouring Time
where: t = pouring time [14].
Step 3: Calculate the effective sprue height
Sprue height H sprue = 100mm [15]
Height of casting in the cope H1 = 5 mm
Total height of casting H2 = 10mm, then using equation below from [14]:
where: Hp = effective sprue height.
Step 4: Calculate the choke cross sectional area
• The flow rate equation:
• H p = effective sprue height (mm), C = discharge coefficient (0.8), g = acceleration due to gravity (9.81m/s 2 ), R a = adjusted pouring rate (Kg/s) and t = pouring time (s) [16].
where: Ac = choke area (mm2 ), W = casting weight (Kg), ρ = density of molten metal (kg/m3 ),
Gating Design Calculations
For this study on aluminium alloys, we shall be using the non-pressurized gating system with a gating ratio of:
As:Ar:Ag=1:4:4 (Non pressurized gating ratio)
where As = the cross sectional area of the sprue exit, Ar = the cross sectional area of the Runner(s) and A g = the cross sectional area of the ingate(s).
The choke (the smallest cross sectional area) is at the sprue base exit therefore.
As =Ac
where Ac = the cross sectional area of the choke.
Pattern Allowances
Shrinkage allowance for alluminium alloys is 16 mm/m.
These allowances shall be added to the pattern parts in the mould cavity
Pattern Dimension =Actual Dimension + Shrinkage allowance
For 4 mm thickness plate, actual length = 80 mm and breath = 40 mm
Pattern thickness = 4 +[0.004x16] = 4.064 mm
Pattern length = 80 +[0.08x16] = 81.28
Final Cast Component
Production Steps in Sand-Casting
Figure 11.2 Outline of production steps in a typical sand-casting operation.
Sand Mold
Figure 11.3 Schematic illustration of a sand mold, showing various features.
Pattern Plate
Figure 11.4 A typical metal match-plate pattern used in sand casting.
Sand Cores
Figure 11.6 Examples of sand cores showing core prints and chaplets to support cores.
Thank You
