(SEM VI) THEORY EXAMINATION 2023-24 TOOL DESIGN

TOOL DESIGN – KME604

Section-wise Important Questions & Ready Answers

SECTION A

(Attempt all – 2 marks each)

(a) Rake Angle

Rake angle is the angle between the rake face of a cutting tool and a plane perpendicular to the direction of cutting. It influences chip flow, cutting force, and tool life. Positive rake angles reduce cutting force, while negative rake angles provide tool strength.

(b) Milling Cutters

Common milling cutters include plain milling cutter, face milling cutter, end mill, side and face cutter, slotting cutter, angular cutter, and form cutter. Each is designed for specific machining operations.

(c) Applications of Jigs and Fixtures

Jigs and fixtures are used to locate, support, and hold workpieces during machining. They improve accuracy, reduce setup time, ensure interchangeability, and enhance productivity in mass production.

(d) Clamping Devices

Clamping devices are used to hold the workpiece firmly against locating surfaces during machining. They prevent movement under cutting forces and ensure dimensional accuracy.

(e) Punching and Blanking

Punching is a sheet metal operation in which the punched-out portion is scrap, whereas blanking is an operation where the punched-out portion is the useful product.

(f) Spring Back Effect

Spring back is the elastic recovery of metal after removal of forming forces in bending operations. It causes dimensional inaccuracies if not compensated in die design.

(g) Core and Core Print

A core is a sand insert used to create internal cavities in castings. A core print is a projection on the pattern that supports and positions the core inside the mould.

(h) Function of Riser

A riser supplies molten metal to the casting during solidification to compensate for shrinkage and prevent defects.

(i) Control System Requirements of Machine Tool

A machine tool control system must ensure accuracy, repeatability, quick response, stability, and ease of operation to achieve precise machining.

(j) Components of CNC Machine

Major components of a CNC machine include input device, machine control unit (MCU), drive system, machine tool, feedback system, and display unit.

SECTION B

(Attempt any three – 10 marks each)

1. Single Point Cutting Tool Nomenclature

The nomenclature of a single-point cutting tool includes rake angles, clearance angles, cutting edge angles, nose radius, and tool signature. Using the machine reference system, these angles are defined relative to tool motion and work surface.

2. Drill Jig Bush and Types of Jigs

A drill jig bush guides the drill accurately and prevents wear of the jig. Types of jigs include plate jig, channel jig, box jig, angle plate jig, and leaf jig, each suited for different workpiece shapes.

3. Types of Bending Dies

Bending dies include V-die, U-die, wipe bending die, offset bending die, and rotary bending die. These dies are selected based on bend angle, material thickness, and production volume.

4. Compression, Transfer, Blow Moulding and Extrusion Dies

Compression dies shape materials under pressure, transfer dies move workpieces between stations, blow moulding dies form hollow plastic products, and extrusion dies shape material by forcing it through a die opening.

5. Speed and Feed Changing System

Speed and feed changing systems regulate spindle speed and feed rate. Centralized control systems allow quick selection of speeds and feeds, improving machining efficiency.

SECTION C

Q3(a) Twist Drill Geometry

A twist drill consists of body, shank, flutes, cutting edges, web, and point angle. Proper geometry ensures efficient cutting, chip evacuation, and long tool life.

Q3(b) Types of Chips in Metal Cutting

Metal cutting produces continuous chips, discontinuous chips, and built-up edge chips. Chip type depends on material properties, cutting speed, and tool geometry.

Q4(a) Clamps Used in Jigs and Fixtures

Common clamps include strap clamps, cam clamps, toggle clamps, screw clamps, and hydraulic clamps. Each provides secure holding under machining forces.

Q4(b) Concept of Location and 1-2-3 Principle

Location restricts the degrees of freedom of a workpiece. The 1-2-3 principle uses one locator on one surface, two on another, and three on a third surface to fully locate a workpiece.

Q5(a) Sheet Metal Dies and Progressive Dies

Sheet metal dies include simple, compound, progressive, and combination dies. Progressive dies perform multiple operations at different stations in a single stroke, increasing productivity.

Q5(b) Die and Punch Design (Numerical)

Die and punch sizes are calculated using clearance values based on material thickness. Punching and stripping forces are determined using shear strength and perimeter of the blank.

Q6(a) Hot Chamber vs Cold Chamber Die Casting

Hot chamber die casting is used for low-melting alloys like zinc, while cold chamber die casting is suitable for high-melting alloys such as aluminium. Cold chamber systems offer better durability.

Q6(b) Gating System Elements

A gating system includes pouring basin, sprue, runner, ingate, and riser. It controls the flow of molten metal into the mould cavity.

Q7(a) Guideways in Machine Tools

Guideways support and guide machine tool components. Hydrodynamic guideways use a lubricant film, while antifriction guideways use rolling elements for reduced friction.

Q7(b) Reduction of Vibration in Machine Tools

Vibration is reduced by increasing rigidity, proper damping, balanced rotating parts, optimized cutting parameters, and vibration-isolating foundations.