Question

please answer all the questions

11. Write five M codes and their use 12. List the hardware components of CNC Machine tools? 13. Explain briefly the function of at least two hardware component with one example. 14. List the three fundamental components of automated system in manufacturing 15. Explain briefly at least two components with at least one example. 16. Explain the function of a NC positioning System 17. List two types of NC positioning system 18. Explain briefly at least one NC positioning system 19. Draw a diagram of any one NC positing system 20. Explain the function of a NC positioning System 7 Dane 9nf4.

Answer 1

11)

1. G00 – Rapid move: Rapid moves are used to move from point to point in free space, not cutting material
2. G17/G18/G19 – Plane Selection: Arcs, circles and drill cycles require the selection of a plane. The three axes X, Y and Z
3. G28 – Zero Return: This function is used to send one or more axes to the home position via an intermediate point
4. G32 – Threading: It is possible to cut threads using a spindle to rotate the work piece and a non rotating threading tool
5. G81 – Drilling: This is a straight drilling cycle. The tool simply moves to position, feeds to the bottom of the hole then rapid retracts to either the R point or the initial point

12) HARDWARE OF CNC MACHINE : The drive units of the carriages in NC machine tools are generally the screw & the nut mechanism. There are different types of screws and nuts used on NC machine tools

• Recirculating Ball Screw
• Roller Screw
• Planetary Roller Screw
• Recirculating Roller Screw
• Tool changer
• Automatic Guided Vehicle (AGV)

13) a) Recirculating Ball Screw : The recirculating ball screw assembly has the flanged nut attached to the moving chamber and the screw to the fixed casting. Thus the moving member will move during rotational movement of the screw. In these types of screws, balls rotate between the screw and nut and convert the sliding friction (as in conventional nut & screw) to the rolling friction. As a consequence wear will be reduced and reliability of the system will be increased. .

b) The term "automated guided vehicle" (AGV) is a general one that encompasses all transport systems capable of functioning without driver operation. The term "driverless" is often used in the context of automatic guided vehicles to describe industrial trucks, used primarily in manufacturing and distribution settings, that would conventionally have been driver-operated

ex: Masted vehicles forked, clamp, single-double Unit Load – lift deck, conveyor Tow or Tuggers,Carts etc..

14) An automated system consists of three basic elements:

(1) power to accomplish the process and operate the system.

(2) a program of instructions to direct the process, and

(3) a control system to actuate the instructions

15) Program of Instructions

The actions performed b) an automated process arc defined by a program of instructions Whether the manufacturing operation involves low, medium, or high production (Section 1.1), each part or product style made in the operation requires one or more processing steps that are unique to that style, These processing steps are performed during a work cycle. A new part is completed during each work cycle (in some manufacturing operations, more than one part is produced during the work cycle; e.g., a plastic injection molding operation may produce multiple parts each cyde using a multiple cavity mold). The particular processing steps for the work cycle are specified in a work cycle program. Work cycle programs are called part programs in numerical control (Chapter 6). Other process control applications use different names for this type of program.

EXAMPLE  :     An Automated Turning Operation

Control System

The controls in an automated system can be either closed loop or open loop. A closed loup control system, also known as a feedback control system. is one in which the output variable is compared with an input parameter, and any difference between the two is used to drive the output into agreement with the input.As shown in Figure 3.3. a closed loop control system consists of six basic elements: (I) input parameter, (2) process, (3) output van. able, (4) feedback sensor. (5) controller. and (0) actuator.

16) Positioning Control System

Function : In order to accomplish the machining process, the cutting tool and workpiece must be moved relative to each other

17)

1) Point-to-point Positioning Control:

2) Straight-cut Positioning Control

18) Point-to-point Positioning Control: - Point-to-point (PTP) is also sometimes called a positioning system. In PTP, the objective of the machine tool control system is to move the cutting tool to a predefined location. The principle function of the PTP is to position the tool form one point to another within coordinate system. The positioning may be linear in the x-y plane or linear and rotary if the machine has a rotary table. Each tool axis is controlled independently, therefore; the programmed motion always in rapid travers. Once the tool reaches the desired location, the machining operation is performed at that position (machining can only take place after positioning is completed). NC drill presses are a good example of PTP systems. The spindle must first be positioned at a particular location on the workpiece. This is done under PTP control. Then the drilling of the hole is performed at the location, and so forth. Since no cutting is performed between holes, there is no need for controlling the relative motion of the tool and workpiece between hole locations. Figure (1) illustrates the point-to-point type of control.

19) Point-to-point Positioning Control

Tool path Starting point Operation performed at each point location Fig(1): Point-to-point (positioning) NC system