(SEM VII) THEORY EXAMINATION 2018-19 COMPUTER AIDED MANUFACTURING

COMPUTER AIDED MANUFACTURING (CAM)

B.Tech – Semester VII

SECTION A

(Attempt all questions)

(a) Basic elements of automation

Automation in manufacturing consists of several interrelated elements that work together to perform production operations with minimal human intervention. The basic elements include power, which provides the energy required for operation; a program of instructions that defines the sequence of operations; and a control system that executes these instructions. Sensors and feedback devices are also essential elements, as they monitor process variables and ensure accurate and reliable operation. Together, these elements enable consistent quality, higher productivity, and reduced human effort.

(b) Open loop and closed loop control system

An open loop control system operates without feedback, meaning the output is not measured or compared with the desired result. Such systems are simple and economical but lack accuracy and adaptability. In contrast, a closed loop control system continuously monitors the output through feedback devices and compares it with the desired value. Any deviation is corrected automatically, resulting in improved accuracy, reliability, and performance. CNC machines typically use closed loop control systems.

(c) Difference between CNC and DNC machines

A CNC machine operates independently using a part program stored in its local memory. It is suitable for individual machine operation. Direct Numerical Control (DNC), on the other hand, uses a central computer to control and supply programs to multiple CNC machines. DNC improves program management, reduces storage limitations, and allows centralized control of manufacturing operations, making it suitable for large-scale production environments.

(d) Basic components of NC system

An NC system consists of an input device, machine control unit, drive system, machine tool, and feedback devices. The input device reads the part program, which is processed by the control unit to generate control signals. These signals drive the machine tool axes and spindle. Feedback devices ensure that actual movements match the programmed commands, resulting in precise machining.

(e) Working of Automatic Tool Changer (ATC)

An Automatic Tool Changer is used in CNC machines to change cutting tools automatically during machining. The control unit selects the required tool from the tool magazine based on the part program. The ATC mechanism removes the used tool from the spindle and replaces it with the selected tool accurately and quickly. This reduces non-productive time, increases machining efficiency, and allows complex machining operations to be performed in a single setup.

(f) Feedback devices

Feedback devices are used to measure the actual position, speed, or displacement of machine components. Common feedback devices include encoders, resolvers, and tachometers. These devices send signals back to the control unit, enabling error detection and correction. Feedback ensures high accuracy and repeatability in NC and CNC machining operations.

(g) G-codes for canned cycles in CNC programming

Canned cycles are predefined machining cycles that simplify programming for repetitive operations such as drilling, tapping, and boring. G-codes such as G81 for drilling, G82 for counterboring, G83 for peck drilling, and G84 for tapping are commonly used. These codes reduce program length, minimize errors, and improve programming efficiency.

(h) Types of statements in APT language

APT (Automatically Programmed Tool) language consists of geometry statements, motion statements, and auxiliary statements. Geometry statements define points, lines, and surfaces. Motion statements specify tool movement relative to geometry, while auxiliary statements control machine functions such as spindle speed, feed rate, and tool changes. Together, these statements enable precise tool path generation.

(i) Advantages of Group Technology

Group Technology is a manufacturing philosophy that identifies and groups similar parts to take advantage of their similarities in design and production. It reduces setup time, improves machine utilization, simplifies production planning, and enhances quality control. GT leads to reduced manufacturing lead time and lower production costs.

(j) Laws of robots

The laws of robots, proposed by Isaac Asimov, define ethical guidelines for robotic behavior. According to these laws, a robot must not harm humans, must obey human commands unless they conflict with the first law, and must protect its own existence as long as it does not violate the first two laws. These laws highlight the importance of safety and responsibility in robotic systems.

SECTION B

(Attempt any three)

Automated manufacturing systems

Automated manufacturing systems are classified into fixed automation, programmable automation, and flexible automation. Fixed automation is used for high-volume production with dedicated equipment. Programmable automation allows production of different products in batches using reprogrammable machines such as CNC machines. Flexible automation enables rapid changeover between products with minimal setup time and is widely used in modern manufacturing environments to meet varying customer demands.

Numerical control and its applications

Numerical Control is a system in which machine tool operations are controlled by coded numerical instructions. NC technology improves accuracy, repeatability, and productivity. It is widely used in milling, turning, drilling, grinding, and sheet metal operations. NC machines reduce human error and enable complex machining operations.

Role of computers in manufacturing

Computers play a vital role in manufacturing by integrating design, planning, and production activities. Computer Aided Design, Computer Aided Process Planning, and Computer Aided Manufacturing systems enable seamless data flow, improved efficiency, and reduced product development time. Computer integration leads to higher productivity and better quality control.

SECTION C

(Attempt any one)

Automation in manufacturing industry

Automation in manufacturing refers to the use of control systems, computers, and machinery to perform production processes with minimal human intervention. The need for automation arises from the demand for high productivity, consistent quality, reduced labor cost, and improved safety. Automation enhances production efficiency, reduces human fatigue, and enables mass customization. It is essential for modern competitive manufacturing industries.

Automated flow lines and AGVs

Automated flow lines consist of a sequence of machines connected by material handling systems, designed for continuous production. They are widely used in mass production industries. Automated Guided Vehicles are driverless vehicles used to transport materials within manufacturing facilities. AGVs improve material handling efficiency, reduce labor dependency, and increase operational flexibility.