Manufacturing Practices (BT-106) - Important Questions

Describe the following casting processes with typical applications, advantages and disadvantages: sand casting, die casting, investment casting and centrifugal casting.

Explain the purpose of gating and riser systems in casting. Draw labelled sketches of a typical gating system and a blind riser. Explain the principles of riser design and calculate the minimum riser volume required to feed a casting of volume $V_{casting}$ assuming a solidification shrinkage of $s$ (express your final relation).

Classify forging processes. Explain the difference between open die forging and closed die forging with suitable sketches and typical applications.

Compare the following welding processes with respect to heat input, typical applications, advantages and limitations: Shielded Metal Arc Welding (SMAW), Gas Metal Arc Welding (GMAW/MIG), Gas Tungsten Arc Welding (GTAW/TIG) and Submerged Arc Welding (SAW).

Explain the following heat treatment processes applied to carbon steels: full annealing, normalizing, hardening (quenching) and tempering. For each process state the typical temperature ranges, microstructural changes and the effects on mechanical properties.

A turning operation is to be performed on a cylindrical job of diameter $D=50\,\text{mm}$. If the recommended cutting speed is $V=120\,\text{m/min}$ and feed per revolution is $f=0.25\,\text{mm/rev}$ with depth of cut $d=2\,\text{mm}$, calculate:

1. The spindle speed $N$ in rpm using the relation $N = \frac{1000\,V}{\pi\,\left(D\right)}$.

2. The material removal rate (MRR) in $\text{mm}^3/\text{min}$ using the relation $\text{MRR} = \pi\,\left(\frac{D}{2}\right)\times 2\times f\times N$ and simplify to an expression using $D$, $f$, $d$ and $N$ if necessary.

(Show calculations and final numerical answers.)

Describe the properties, advantages and typical applications of the following cutting tool materials: High Speed Steel (HSS), cemented carbide (tungsten carbide), ceramics and cubic boron nitride (CBN). Mention common coatings used on cutting tools and their benefits.

Describe the principles, typical applications and limitations of the following non-destructive testing (NDT) methods: dye penetrant testing, magnetic particle testing, radiographic testing and ultrasonic testing.

Explain the meaning of the following metrology terms: nominal size, tolerance, allowance, limit dimensions. Describe the system of limits and fits and explain the difference between clearance fit, interference fit and transition fit. Give examples of applications for each fit type.

Describe the working principle, typical applications and surface finish achievable for the following processes: grinding, honing, lapping and polishing.

Explain the powder metallurgy process route. List and briefly describe the main steps involved and mention advantages, limitations and typical applications of powder metallurgy.

Explain the concept of process capability. Define $C_p$ and $C_{pk}$ and write the formulae. For $C_p$ use the relation $$C_p = \frac{\left(USL - LSL\right)}{6\,\sigma}$$ and explain each term. Describe what values of $C_p$ indicate about a process.

What are the basic components of a CNC part program? Explain the roles of G-codes and M-codes. Write a short example program (pseudocode) to face off a component on a CNC lathe mentioning required preparatory codes, spindle start/stop and dwell if necessary.

List common defects encountered in casting (e.g., blow holes, porosity, cold shuts, cracks, shrinkage) and welding (e.g., porosity, lack of fusion, slag inclusion, undercut, cracks). For each defect give the possible causes and remedial measures.