(SEM VI) THEORY EXAMINATION 2021-22 TOOL DESIGN

TOOL DESIGN (KME604)

Section-Wise Exam Answers & Notes
 

SECTION A – Short Answer Type (2 Marks Each)
 

a) Define lubrication
 

Lubrication is the process of introducing a lubricant between two moving surfaces to reduce friction, wear, heat generation, and to ensure smooth operation of machine parts.
 

b) Define rigidity in machine tools
 

Rigidity of a machine tool refers to its ability to resist deformation under applied cutting forces so that dimensional accuracy and surface finish of the workpiece are maintained.
 

c) Define reliability in machine tools
 

Reliability is the probability that a machine tool will perform its intended function without failure for a specified period under given operating conditions.
 

d) What do you understand by adaptive control systems?
 

Adaptive control systems are automatic systems used in machine tools that continuously monitor machining conditions and adjust cutting parameters like speed and feed to improve performance and tool life.
 

e) What is tool?
 

A tool is a device used to remove material from a workpiece or to give it the desired shape, size, and finish during a manufacturing process.
 

f) List the advantages of jig and fixture
 

Jigs and fixtures improve accuracy, reduce production time, ensure interchangeability, minimize operator skill requirements, and increase productivity in mass production.
 

g) Explain importance of die allowance in bending die design
 

Die allowance compensates for elastic recovery (spring back) of material after bending so that the final product achieves the desired shape and dimensions.
 

h) Differentiate between jig and fixture
 

A jig guides the cutting tool and holds the workpiece, whereas a fixture only holds and locates the workpiece but does not guide the tool.
 

i) Briefly explain modern trends in die-casting dies
 

Modern die-casting dies focus on automation, use of advanced alloys, thermal control systems, CAD/CAM integration, and improved surface coatings for longer die life.
 

j) Explain phenomenon of spring back effect
 

Spring back is the tendency of a bent metal sheet to partially return to its original shape after removal of bending force due to elastic recovery.
 

SECTION B – Long Answer Type (Attempt Any Three – 10 Marks)
 

a) Drill jig bushes and their types
 

Drill jig bushes are hardened steel sleeves used in jigs to guide drill bits accurately.
They prevent wear of the jig body and ensure precise hole location.

Types include:

Fixed bushes – permanently fixed                          Renewable bushes – replaceable after wear

Slip bushes – removable for different tools           Liner bushes – used with renewable bushes

b) Effect of die casting on material properties

Die casting improves surface finish and dimensional accuracy.
Rapid cooling refines grain structure, increasing strength.
However, trapped gases may reduce ductility and cause porosity.

c) Main elements of injection molding

Injection molding consists of:

Injection unit (hopper, screw, barrel)                      Clamping unit (mold, platens)

Mold cavity and core                                              Cooling and ejection system
These elements work together to produce plastic components with high accuracy.

d) Adaptive control systems (Detailed)

Adaptive control systems monitor cutting forces, temperature, vibration, and tool wear.
They automatically adjust machining parameters to optimize tool life, surface finish, and productivity.
Types include adaptive control with constraints and adaptive control with optimization.

e) Speed gear box and feed box

Speed gear box provides different spindle speeds, while feed box controls feed rates of cutting tools.
Both improve flexibility and efficiency of machine tools.

SECTION C – Descriptive / Diagram-Based Questions

3(a) Progressive die

A progressive die performs multiple operations like cutting, bending, and punching in a single press stroke as the strip moves through successive stations.
It is widely used for mass production due to high accuracy and productivity.

3(b) Causes of spring back and methods to reduce it

Spring back occurs due to elastic recovery of material after bending.
Methods to reduce spring back include over-bending, applying higher bending force, using bottoming dies, and selecting proper material.

4(a) Milling fixture design procedure

The procedure includes:

Analysis of workpiece                                  Selection of locating surfaces

Clamping arrangement                               Fixture body design

Provision for chip clearance                        Proper design ensures rigidity and accuracy.

4(b) Steps in die casting die design

Steps include material selection, cavity design, gating system design, cooling arrangement, ejection mechanism, and final die assembly.

5(a) General design procedure for cutting tools

It involves tool material selection, tool geometry design, strength analysis, heat treatment, and testing to ensure efficient cutting performance.

5(b) Steps involved in tool design

Tool design includes studying the job, selecting tool type, designing geometry, selecting materials, and evaluating performance.

6(a) Types of single point cutting tools

Single point cutting tools are classified based on shape, application, method of holding, and material.
They are used in turning, facing, and shaping operations.

6(b) Tool design objectives

Tool design aims to achieve high productivity, accuracy, minimum cost, ease of handling, long tool life, and safety.

7(a) Nomenclature and angles of single point cutting tool

Tool nomenclature includes rake angle, clearance angle, cutting edge angle, nose radius, etc.
These angles affect cutting force, tool life, and surface finish.

7(b) Methods of ejection in injection molding

Common methods include:

Pin ejection                                             Sleeve ejection

Stripper plate ejection                            Air ejection
They help in safe removal of molded components.