Why this topic is important for ECET?
The Foundry Process is one of the most important manufacturing methods to produce complex shapes of metals. Many ECET questions are asked on pattern types, allowances, sand properties, defects, and solidification concepts. Mastering this ensures you can easily score 2–3 direct questions in ECET 2026.
📘 Concept Notes
🔹 What is Foundry?
A foundry is a place where metal casting is carried out. Casting is the process of pouring molten metal into a mould cavity (formed by a pattern), allowing it to solidify, and then removing the final casting.
🔹 Basic Steps of Foundry Process
- Pattern Making
- Patterns are replicas of the object to be cast.
- Materials: wood, plastics, metals.
- Types: single piece, split pattern, match plate, sweep pattern.
- Moulding
- Mould is prepared using moulding sand around the pattern.
- Moulding materials must have properties: strength, permeability, refractoriness, cohesiveness, collapsibility.
- Melting and Pouring
- Metals are melted in furnaces (cupola, electric arc furnace, crucible furnace).
- Molten metal poured into mould cavity through gating system.
- Solidification & Cooling
- After pouring, molten metal cools and solidifies in the mould.
- Solidification time depends on casting volume & surface area.
- Shakeout & Fettling
- Mould broken → casting removed.
- Fettling = cleaning, removing excess metal, finishing operations.
🔹 Pattern Allowances
To ensure correct size of casting, allowances are given:
- Shrinkage allowance – compensates metal contraction.
- Draft allowance – taper to remove pattern easily.
- Machining allowance – extra metal for machining.
- Distortion allowance – prevents bending/warping.
🔹 Casting Defects
- Blow holes, pin holes (gas defects)
- Shrinkage cavity
- Misrun (incomplete filling)
- Cold shut (improper fusion of streams)
- Inclusion (slag, dirt inside)
🔹 Applications of Foundry
- Engine blocks, pump casings, pipes, rail components, machine parts.
⚙️ Formulas
- Chvorinov’s Rule (Solidification Time):
where
- tst_sts = solidification time
- VVV = volume of casting
- AAA = surface area of casting
- CCC = mould constant
- nnn ≈ 2 (for most cases)
- Shrinkage Allowance:
where
- LLL = length
- α\alphaα = coefficient of thermal expansion
- ΔT\Delta TΔT = temperature change
- Pouring Time (approx):
where
- WWW = weight of metal
- ρ\rhoρ = density
- QQQ = volumetric flow rate
🔟 10 MCQs
Q1. The main purpose of a pattern in foundry is:
a) To provide strength to mould
b) To form cavity for casting
c) To act as a gating system
d) To cool the molten metal
Q2. Which property of moulding sand allows hot gases to escape?
a) Strength
b) Cohesiveness
c) Permeability
d) Refractoriness
Q3. Which furnace is commonly used in foundries for melting cast iron?
a) Cupola furnace
b) Bessemer converter
c) Induction furnace
d) Blast furnace
Q4. The draft allowance is given to:
a) Compensate shrinkage
b) Allow easy removal of pattern
c) Avoid distortion
d) Provide machining stock
Q5. According to Chvorinov’s rule, solidification time is proportional to:
a) AV\frac{A}{V}VA
b) VA\frac{V}{A}AV
c) VVV
d) AAA
Q6. A cube casting of 5 cm side solidifies in 2 minutes. For a cube of 10 cm side, approximate solidification time will be:
a) 4 min
b) 8 min
c) 16 min
d) 32 min
Q7. Which of the following is NOT a casting defect?
a) Blow holes
b) Shrinkage cavity
c) Machining allowance
d) Misrun
Q8. In sand moulding, collapsibility of sand helps in:
a) Easy pattern removal
b) Avoiding hot tearing
c) Increasing permeability
d) Providing strength
Q9. If the volume of casting is 125 cm³ and surface area is 150 cm², find (V/A) ratio.
a) 0.25 cm
b) 0.5 cm
c) 0.75 cm
d) 1 cm
Q10. Which one is an example of expendable mould casting?
a) Die casting
b) Shell moulding
c) Permanent mould casting
d) Centrifugal casting
✅ Answer Key
| Q | Ans |
|---|---|
| 1 | b |
| 2 | c |
| 3 | a |
| 4 | b |
| 5 | b |
| 6 | c |
| 7 | c |
| 8 | b |
| 9 | b |
| 10 | b |
🧠 Explanations
- Q1: Pattern creates mould cavity → (b).
- Q2: Permeability allows gas escape → (c).
- Q3: Cupola is standard for CI → (a).
- Q4: Draft helps pattern removal → (b).
- Q5: Chvorinov’s rule → (V/A)n(V/A)^n(V/A)n → (b).
- Q6: Solidification ∝ (side)² → doubling side = 4× time → 2×4=16 → (c).
- Q7: Machining allowance is not a defect → (c).
- Q8: Collapsibility avoids hot tearing during cooling → (b).
- Q9: V/A=125/150=0.833≈0.5V/A = 125/150 = 0.833 ≈ 0.5V/A=125/150=0.833≈0.5 → (b).
- Q10: Shell moulding uses expendable moulds → (b).
🎯 Motivation / Why Practice Matters
Foundry process questions in ECET are usually direct and scoring. Many students lose marks in simple areas like pattern allowances or casting defects because of confusion. Regular practice helps you:
- Answer faster (no second guessing).
- Reduce silly mistakes in formula applications.
- Gain an edge in competitive ranking.
👉 Practicing foundry makes your Manufacturing Tech section a high-scoring unit in ECET 2026.
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