UNIT-4

Computer-Aided Manufacturing & Part Programming: 

Computer-Aided Manufacturing, Computer Applications in a Manufacturing Plant, Key Aspects of CAM in a Manufacturing System and Manufacturing Control, G Code & M Code generation through CAD CAM software,  Feature Technology , NC, DNC, CNC, Programmed Automations, Machine control unit, Part program, NC tooling. NC machine tools: Nomenclature of NC machine axes, Types of NC machine tools, Machining centers, Automatic tool changes (ATC), Turning centers. ISO codes for turning tools and holders; ATC, modular work holding and pallets; time and power estimation in milling, drilling and turning; adaptive control, sequence control and PLC; simple part programming examples.

CAM:

Computer-aided manufacturing (CAM) is an application technology that uses computer software and machinery to facilitate and automate manufacturing processes. CAM is the successor of computer-aided engineering (CAE) and is often used in tandem with computer-aided design (CAD).
In addition to materials requirements, modern CAM systems include real-time controls and robotics.

Siemens says: “Computer aided manufacturing (CAM) commonly refers to the use of numerical control (NC) computer software applications to create detailed instructions (G-code) that drive computer numerical control (CNC) machine tools for manufacturing parts. Manufacturers in a variety of industries depend on the capabilities of CAM to produce high-quality parts.”

A broader and simpler definition would be: any manufacturing process that uses computer software to facilitate, assist or automate parts of the manufacturing process.

The benefits of CAM

Using CAM has a number of benefits when it comes to creating components used in building construction. Compared to manually operated machines, CAM generally offers:

  • Greater speed in producing components
  • Greater accuracy and consistency, with each component or finished product exactly the same
  • Greater efficiency as computer controlled machines do not need to take breaks
  • High sophistication in terms of following complex patterns like tracks on circuit boards

There are some limitations. CAM-enabled machines are generally designed for a particular task and are not incredibly versatile, although new systems and designs are emerging all the time.

They also need an upfront investment and skilled operators and programmers. Once in place, however, they could potentially bring large savings in time and efficiency, thereby reducing costs and saving companies thousands.

Standard G & M codes:

  • G00 Rapid positioning (point to point)
  • G01 Linear interpolation
  • G02 Circular/helical interpolation CW
  • G03 Circular/helical interpolation CCW
  • G04 Dwell
  • G06 Spline interpolation
  • G07 Hypothetical axis interpolation
  • G09 Exact Stop
  • G11 Mirror image cancel
  • G12 Mirror X Axis values
  • G13 Mirror Y Axis values
  • G14 Mirror XY Axis values
  • G17 X-Y plane select
  • G18 Z-X plane select
  • G19 Y-Z plane select
  • G20 Inch input (equivalent to G70)
  • G21 Metric input (equivalent to G71 )
  • G28 Return to machine coordinate origin
  • G29 Return from machine coordinate origin
  • G40 Cutter radius compensation cancel
  • G41 Cutter radius compensation left
  • G42 Cutter radius compensation right
  • G43 Tool length compensation +
  • G44 Tool length compensation –
  • G49 Tool length compensation cancel
  • G50 Scaling cancel
  • G51 Scaling
  • G53 Machine coordinate system selected
  • G54 Work coordinate frame 1 selection
  • G55 Work coordinate frame 2 selection
  • G56 Work coordinate frame 3 selection
  • G57 Work coordinate frame 4 selection
  • G58 Work coordinate frame 5 selection
  • G59 Work coordinate frame 6 selection
  • G61 Exact stop mode (block by block)
  • G64 Continuous mode (look-ahead)
  • G70 Inch input
  • G71 Metric Input
  • G73 Peck drilling cycle
  • G74 Counter tapping cycle
  • G76 Fine boring cycle
  • G80 Canned cycle cancel
  • G81 Drilling cycle, spot boring
  • G82 Drilling cycle, counter boring
  • G83 Peck drilling cycle
  • G84 Tapping cycle
  • G85 Boring cycle
  • G86 Boring cycle
  • G87 Back boring cycle
  • G88 Boring cycle
  • G89 Boring cycle
  • G90 Absolute command
  • G91 Incremental command
  • G92 Work coordinates change
  • G93 Inverse time feed
  • G94 Feed rate per minute
  • G95 Feed rate per revolution
  • G98 Canned cycle initial level return
  • G99 Canned cycle R point level return
  • M00 Program stop
  • M01 Optional program stop
  • M02 Program end
  • M03 Spindle on CW
  • M04 Spindle on CCW
  • M05 Spindle off
  • M06 Program stop for tool change
  • M08 Coolant on
  • M09 Coolant off
  • M10 Brake/Misc. on
  • M11 Brake/Misc. off
  • M12 Clamp/Misc. on
  • M13 Clamp/Misc. off
  • M19 Oriented spindle stop
  • M47 Return to program start
  • M48 Bypass feed rate override cancel
  • M49 Bypass feed rate override
  • M90 User defined DOS call 1
  • M91 User defined DOS call 2
  • M92 User defined DOS call 3
  • M93 User defined DOS call 4
  • M94 User defined DOS call 5
  • M95 User defined DOS call 6
  • M98 Call sub-program
  • M99 Return from sub-program

G-and-M-Code-Reference

NC, DNC and CNC:

NC:

Numerical control can be defined as a form of programmable automation in which process is controlled by numbers,letters and symbols. In NC,the numbers form a programme of instructions designed for a particular workpart or job. When job changes the program of instruction changes. This capability to change a program for each new job gives NC its flexibilty.

 

1. Program of instructions.
2. Controller unit, also called machine tool unit.
3. Machine tool or other controlled process.
The program of instructions serves as input to the controller unit, which in turn commands the machine tool or other process to be controlled.

Program of Instructions.
The program of instructions is the detailed step by step set of instructions which tell the machine what to do. It is coded in numerical or symbolic form on some type of input medium that can be interpreted by the controller unit. The most common one is the 1-inch-wide punched tape. Over the years,other forms of input media has been used,including punched cards, magnetic tape, and even 35mm motion picturefilm.
There are two other methods of input to the NC system which should be mentioned. The first is by manual entry of instructional data to the controller unit. This is time consuming and is rarely used
except as an auxillary means of control or when one or a very limited no. of parts to be made. The second method of input is by means of a direct ling with the computer. This is called direct numerical
control, or DNC.

Controller Unit
The second basic component of NC system is the controller unit. This consists of electronics and hardware that read and interpret the program of instructionsand convert it to mechanical actions of the machine tool. The typical elements of the controller unit include the tape reader, a data buffer, signal output channels to the machine tool,and the sequencecontrols to coodinate the overall operation
of the foregoing elements.
The tape reader is an electrical-mechanical device for the winding and reading the punched tape containing the program of instructions. The signal output channels are connected to the servomotores
and other controls in machine tools. Most N.C. tools today are provided with positive feedback controls for this purposeand are referred as closed loop systems. However there has been growth in the open loop systems which do not make use of feedback signals to the controller unit. The advocates of the open loop concept claim that the realiblity of the system is great enough that the feedback controls are not needed.

Machine Tool
The third basic component of an NC system is the machine tool or other controlled process. It is part of the NC system which performs useful work. In the most common example of an NC system,one designed to perform machining operations, The machine tool consists of the worktable and spindle as well as the motorsand controls necessary to drive them. It also includes  the cutting tools,work fixtures and other auxillary equipment needed in machining operation.

Application of NC:

NC has been used in a variety of applications. Acomplete list of application is probably not possible but such a list would have to include the following:

  • Metal cutting machine tools
  • Pressworking machine tools
  • Welding machines
  • Inspection machines
  • Automatics drafting
  • Assembly machines
  • Tube bending
  • Flame cutting
  • Industrial Robots
  • Automated knitted machines
  • Cloth cutting
  • Automatics riveting

By far the most common application of the numerical control is for metal cutting machine tools. Within the category alone,NC equipment  has been built to perform virtually the entire range of material removal processes including:

  • Milling
  • Drilling and related operation
  • Boring
  • Turning
  • Grinding

PPT of  Unit 4:

 

 

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