JAWAHARLAL NEHRU TECHNOLOGICAL UNIVERSITY HYDERABAD

Pre-requisites

Machine Tools, Metrology

Course Objectives:

• To give the basic precision engineering methodology and state-of-the-art concepts for designing high-precision CNC machines and products.
• The course is specifically tailored to teach the novel design principles leading to improved machine performance and reliability.
• To apply the acquired knowledge to other design efforts and fields as well

Course Outcomes

At the end of the course, the student will be able to:

• Apply fits and tolerances for parts and assemblies according to ISO standards.
• Apply selective assembly concept for quality and economic production.
• Assign tolerances using principles of dimensional chains for individual features of a part or assembly.
• Evaluate the part and machine tool accuracies.
• Analyze the causes for dimensional and geometrical errors prior to and during machining and suggest remedies

UNIT - I

Concepts of Accuracy: Introduction – Concept of Accuracy of Machine Tools – Spindle and Displacement Accuracies – Accuracy of numerical Control Systems – Errors due to Numerical Interpolation Displacement Measurement System and Velocity Lags. Geometric Dimensioning and Tolerance: Tolerance Zone Conversions – Surfaces, Features, Features of Size, Datum Features – Datum Oddly Configured and Curved Surfaces as Datum Features, Equalizing Datum –Datum Feature of Representation – Form Controls, Orientation Controls – Logical Approach to Tolerance.

UNIT - II

Datum Systems: Design of freedom, Grouped Datum Systems – different types, two and three mutually perpendicular grouped datum planes; Grouped datum system with spigot and recess, pin and hole; Grouped Datum system with spigot and recess pair and tongue – slot pair – Computation of Transnational and rotational accuracy, Geometric analysis and application.

UNIT - III

Tolerance Analysis: Process Capability, Mean, Variance, Skewness, Kurtosis, Process Capability Metrics, Cp, Cpk, Cost aspects, Feature Tolerances, Geometric Tolerances. Tolerance Charting Techniques: Operation Sequence for typical shaft type of components, Preparation of Process drawings for different operations, Tolerance worksheets and central analysis, Examples. Design features to facilitate machining; Datum Features – functional and manufacturing. Components design – Machining considerations, Redesign for manufactured parts examples

UNIT - IV

Surface finish, Review of relationship between attainable tolerance grades and different machining process. Cumulative effect of tolerances sure fit law, normal law and truncated normal law.

UNIT - V

Measuring Systems Processing: In process or in-situ measurement of position of processing point- Post process and on-machine measurement of dimensional features and surface-mechanical and optical measuring systems.

TEXT BOOKS:

• 1. Precision Engineering in Manufacturing by Murthy R. L., New Age International (P) limited, 1996.
• 2. Geometric Dimensioning and Tolerancing by James D. Meadows, Marcel Dekker Inc. 1995.

REFERENCE BOOK:

• 1. Engineering Design – A systematic Approach by Matousek, Blackie & Son Ltd, London. M. TECH. I Year I Sem. (AMS)