NC Programming
-
Upload
vishnuvardhan-reddy-sirigireddy -
Category
Automotive
-
view
164 -
download
0
Transcript of NC Programming
©2008 Pearson Education, Inc., Upper Saddle River, NJ. All rights reserved. This material is protected under all copyright laws as they currently exist. No portion of this material may be reproduced, in any form or by any means, without permission in writing from the publisher. For the exclusive use of adopters of the book
Automation, Production Systems, and Computer-Integrated Manufacturing, Third Edition, by Mikell P. Groover.
Numerical Control
Sections:1. Fundamentals of NC Technology2. Computer Numerical Control3. DNC4. Applications of NC5. Engineering Analysis of NC Positioning Systems6. NC Part Programming
©2008 Pearson Education, Inc., Upper Saddle River, NJ. All rights reserved. This material is protected under all copyright laws as they currently exist. No portion of this material may be reproduced, in any form or by any means, without permission in writing from the publisher. For the exclusive use of adopters of the book
Automation, Production Systems, and Computer-Integrated Manufacturing, Third Edition, by Mikell P. Groover.
Numerical Control (NC) Defined
Form of programmable automation in which the mechanical actions of a machine tool or other equipment are controlled by a program(through punched tape) containing coded alphanumeric data.
The alphanumeric data represent relative positions between a work-head (e.g., cutting tool) and a work-part.
When the current job is completed, a new program can be entered for the next job.
Punched tape
©2008 Pearson Education, Inc., Upper Saddle River, NJ. All rights reserved. This material is protected under all copyright laws as they currently exist. No portion of this material may be reproduced, in any form or by any means, without permission in writing from the publisher. For the exclusive use of adopters of the book
Automation, Production Systems, and Computer-Integrated Manufacturing, Third Edition, by Mikell P. Groover.
Basic Components of an NC System
1. Program of instructions Part program in machining
2. Machine control unit Controls the process
3. Processing equipment Performs the process
©2008 Pearson Education, Inc., Upper Saddle River, NJ. All rights reserved. This material is protected under all copyright laws as they currently exist. No portion of this material may be reproduced, in any form or by any means, without permission in writing from the publisher. For the exclusive use of adopters of the book
Automation, Production Systems, and Computer-Integrated Manufacturing, Third Edition, by Mikell P. Groover.
Basic Components of an NC System
1.Program:
•Is a set of detailed step by step command that direct the action of the
processing equipment.
•A person who prepare the program is called part programmer.
•Individual commandrefer position of cutting tool relative to w/p.
•Older days the part program was punched in 1 inch wide punched
tape.
•But now, magnetic tape, diskettes and electronic transfer .
2.Machine control unit:Is a micro computer and related control hardware that stores the program of instruction and execute it by converting each command into mechanical action.
•The term CNC is used that all MCU are based on computer technology.
•MCU includes control system software, calculation algorithm, and translation
software.
3.Processing equipment:
•That perform the actual productive work(e.g.machining).
•Its operation directed by MCU.
•The processing equipment consist of worktable, and spindle as well as motor
and controls to drive them.
•NC coordinate system:
•First define standard axis system(x,y,z), three rotational axis(a,b,c).
•In most m/c application x,y axis are used to move and position the work table.
And z axis for controlling the tool movement.
©2008 Pearson Education, Inc., Upper Saddle River, NJ. All rights reserved. This material is protected under all copyright laws as they currently exist. No portion of this material may be reproduced, in any form or by any means, without permission in writing from the publisher. For the exclusive use of adopters of the book
Automation, Production Systems, and Computer-Integrated Manufacturing, Third Edition, by Mikell P. Groover.
NC Coordinate Systems
For flat and prismatic (block-like) parts Milling and drilling operations Conventional Cartesian coordinate system Rotational axes about each linear axis Right hand rule
©2008 Pearson Education, Inc., Upper Saddle River, NJ. All rights reserved. This material is protected under all copyright laws as they currently exist. No portion of this material may be reproduced, in any form or by any means, without permission in writing from the publisher. For the exclusive use of adopters of the book
Automation, Production Systems, and Computer-Integrated Manufacturing, Third Edition, by Mikell P. Groover.
Coordinate Axis System for Flat and Prismatic Parts
©2008 Pearson Education, Inc., Upper Saddle River, NJ. All rights reserved. This material is protected under all copyright laws as they currently exist. No portion of this material may be reproduced, in any form or by any means, without permission in writing from the publisher. For the exclusive use of adopters of the book
Automation, Production Systems, and Computer-Integrated Manufacturing, Third Edition, by Mikell P. Groover.
NC Coordinate Systems
For rotational parts: Turning operations Conventional Cartesian coordinate system, but only x- and
z-axes y-axis not needed in turning
©2008 Pearson Education, Inc., Upper Saddle River, NJ. All rights reserved. This material is protected under all copyright laws as they currently exist. No portion of this material may be reproduced, in any form or by any means, without permission in writing from the publisher. For the exclusive use of adopters of the book
Automation, Production Systems, and Computer-Integrated Manufacturing, Third Edition, by Mikell P. Groover.
Coordinate Axis System for Rotational Parts
©2008 Pearson Education, Inc., Upper Saddle River, NJ. All rights reserved. This material is protected under all copyright laws as they currently exist. No portion of this material may be reproduced, in any form or by any means, without permission in writing from the publisher. For the exclusive use of adopters of the book
Automation, Production Systems, and Computer-Integrated Manufacturing, Third Edition, by Mikell P. Groover.
Motion Control Systems
Point-to-Point systems Also called position systems System moves to a location and performs an operation at
that location (e.g., drilling) Also applicable in roboticsContinuous path systems Also called contouring(when continuous path control is used
for simultaneous control of two or more axes) systems in machining
System performs an operation during movement (e.g., milling and turning)
©2008 Pearson Education, Inc., Upper Saddle River, NJ. All rights reserved. This material is protected under all copyright laws as they currently exist. No portion of this material may be reproduced, in any form or by any means, without permission in writing from the publisher. For the exclusive use of adopters of the book
Automation, Production Systems, and Computer-Integrated Manufacturing, Third Edition, by Mikell P. Groover.
Point-To-Point Control in NCDrilling of Three Holes in Flat Plate
©2008 Pearson Education, Inc., Upper Saddle River, NJ. All rights reserved. This material is protected under all copyright laws as they currently exist. No portion of this material may be reproduced, in any form or by any means, without permission in writing from the publisher. For the exclusive use of adopters of the book
Automation, Production Systems, and Computer-Integrated Manufacturing, Third Edition, by Mikell P. Groover.
Continuous Path Control in NCProfile Milling of Part Outline
©2008 Pearson Education, Inc., Upper Saddle River, NJ. All rights reserved. This material is protected under all copyright laws as they currently exist. No portion of this material may be reproduced, in any form or by any means, without permission in writing from the publisher. For the exclusive use of adopters of the book
Automation, Production Systems, and Computer-Integrated Manufacturing, Third Edition, by Mikell P. Groover.
Interpolation Methods
1. Linear interpolation Straight line between two points in space
2. Circular interpolation Circular arc defined by starting point, end point, center
or radius, and direction3. Helical interpolation
Circular plus linear motion4. Parabolic and cubic interpolation
Free form curves using higher order equations
©2008 Pearson Education, Inc., Upper Saddle River, NJ. All rights reserved. This material is protected under all copyright laws as they currently exist. No portion of this material may be reproduced, in any form or by any means, without permission in writing from the publisher. For the exclusive use of adopters of the book
Automation, Production Systems, and Computer-Integrated Manufacturing, Third Edition, by Mikell P. Groover.
Circular Interpolation
Approximation of a curved path in NC by a series of straight line segments, where tolerance is defined on only the inside of the nominal curve
©2008 Pearson Education, Inc., Upper Saddle River, NJ. All rights reserved. This material is protected under all copyright laws as they currently exist. No portion of this material may be reproduced, in any form or by any means, without permission in writing from the publisher. For the exclusive use of adopters of the book
Automation, Production Systems, and Computer-Integrated Manufacturing, Third Edition, by Mikell P. Groover.
Circular Interpolation
Approximation of a curved path in NC by a series of straight line segments, where tolerance is defined on only the outside of the nominal curve
©2008 Pearson Education, Inc., Upper Saddle River, NJ. All rights reserved. This material is protected under all copyright laws as they currently exist. No portion of this material may be reproduced, in any form or by any means, without permission in writing from the publisher. For the exclusive use of adopters of the book
Automation, Production Systems, and Computer-Integrated Manufacturing, Third Edition, by Mikell P. Groover.
Circular Interpolation
Approximation of a curved path in NC by a series of straight line segments, where tolerance is defined on both the inside and outside of the nominal curve
©2008 Pearson Education, Inc., Upper Saddle River, NJ. All rights reserved. This material is protected under all copyright laws as they currently exist. No portion of this material may be reproduced, in any form or by any means, without permission in writing from the publisher. For the exclusive use of adopters of the book
Automation, Production Systems, and Computer-Integrated Manufacturing, Third Edition, by Mikell P. Groover.
Absolute and Incremental Positioning
Another aspect of motion control is concern with whether position are defined relative to the origin or relative to previous location of the tool.
Absolute positioning Locations defined relative to origin of axis systemIncremental positioning Locations defined relative to previous position Example: drilling
©2008 Pearson Education, Inc., Upper Saddle River, NJ. All rights reserved. This material is protected under all copyright laws as they currently exist. No portion of this material may be reproduced, in any form or by any means, without permission in writing from the publisher. For the exclusive use of adopters of the book
Automation, Production Systems, and Computer-Integrated Manufacturing, Third Edition, by Mikell P. Groover.
Absolute vs. Incremental Positioning
The workhead is presently at point (20, 20) and is to be moved to point (40, 50) In absolute positioning, the move is specified by x = 40, y = 50 In incremental positioning, the move is specified by x = 20, y = 30.
©2008 Pearson Education, Inc., Upper Saddle River, NJ. All rights reserved. This material is protected under all copyright laws as they currently exist. No portion of this material may be reproduced, in any form or by any means, without permission in writing from the publisher. For the exclusive use of adopters of the book
Automation, Production Systems, and Computer-Integrated Manufacturing, Third Edition, by Mikell P. Groover.
Computer Numerical Control (CNC) – Additional Features
CNC is defined as an NC system whose MCU is based on micro computer rather than on a hard wired controller.
Features of CNC: Storage of more than one part program Various forms of program input(punched,magnetic,floppy
diskettes,RS 232 communication) Program editing at the machine tool Fixed cycles and programming subroutines Interpolation Acceleration and deceleration computations Communications interface Diagnosticsmalfunction sign
Machine control unit for CNC
The MCU consists of the following components and subsystems:
(I) central processing unit(2) memory(3) l/O interface(4) controls for machine tool axes and spindle speed. And(5)sequence controls for other machine tool functions.
These subsystems are interconnected by means of a system bus. which communicates data and signals among the components of network. indicated in the figure,
©2008 Pearson Education, Inc., Upper Saddle River, NJ. All rights reserved. This material is protected under all copyright laws as they currently exist. No portion of this material may be reproduced, in any form or by any means, without permission in writing from the publisher. For the exclusive use of adopters of the book
Automation, Production Systems, and Computer-Integrated Manufacturing, Third Edition, by Mikell P. Groover.
Central Processing Unit
The central processing unit (CPU) is the brain of the MCU. It manages the other components in the MCU based on
software contained in main memory. The CPU can be divided into three sections: (1) control section, (2) arithmetic-logic unit, and (3) immediate access memory. control section retrieves commands and data from memory
and generates signals to activate other components in the MCU. In short, it sequences. coordinates. and regulates all of the activities of the MCU computer.
©2008 Pearson Education, Inc., Upper Saddle River, NJ. All rights reserved. This material is protected under all copyright laws as they currently exist. No portion of this material may be reproduced, in any form or by any means, without permission in writing from the publisher. For the exclusive use of adopters of the book
Automation, Production Systems, and Computer-Integrated Manufacturing, Third Edition, by Mikell P. Groover.
Arithmetic logic unit (ALU) consists of the circuitry to perform various calculations (addition, subtraction, multiplication), counting. and logical functions required by software residing in memory.
Immediate access memory provides a temporary storage for data being processed by the CPU. It is connected to main memory by means of the system data bus.
©2008 Pearson Education, Inc., Upper Saddle River, NJ. All rights reserved. This material is protected under all copyright laws as they currently exist. No portion of this material may be reproduced, in any form or by any means, without permission in writing from the publisher. For the exclusive use of adopters of the book
Automation, Production Systems, and Computer-Integrated Manufacturing, Third Edition, by Mikell P. Groover.
©2008 Pearson Education, Inc., Upper Saddle River, NJ. All rights reserved. This material is protected under all copyright laws as they currently exist. No portion of this material may be reproduced, in any form or by any means, without permission in writing from the publisher. For the exclusive use of adopters of the book
Automation, Production Systems, and Computer-Integrated Manufacturing, Third Edition, by Mikell P. Groover.
Configuration of CNC Machine Control Unit
©2008 Pearson Education, Inc., Upper Saddle River, NJ. All rights reserved. This material is protected under all copyright laws as they currently exist. No portion of this material may be reproduced, in any form or by any means, without permission in writing from the publisher. For the exclusive use of adopters of the book
Automation, Production Systems, and Computer-Integrated Manufacturing, Third Edition, by Mikell P. Groover.
DNC
Direct numerical control (DNC) – control of multiple machine tools by a single (mainframe) computer through direct connection and in real time 1960s technology Two way communication
Distributed numerical control (DNC) – network consisting of central computer connected to machine tool MCUs, which are CNC Present technology Two way communication
©2008 Pearson Education, Inc., Upper Saddle River, NJ. All rights reserved. This material is protected under all copyright laws as they currently exist. No portion of this material may be reproduced, in any form or by any means, without permission in writing from the publisher. For the exclusive use of adopters of the book
Automation, Production Systems, and Computer-Integrated Manufacturing, Third Edition, by Mikell P. Groover.
General Configuration of a Direct Numerical Control System
Connection to MCU is behind the tape reader (BTR). In distributed NC, entire programs are downloaded to each MCU, which is CNC rather than conventional NC
©2008 Pearson Education, Inc., Upper Saddle River, NJ. All rights reserved. This material is protected under all copyright laws as they currently exist. No portion of this material may be reproduced, in any form or by any means, without permission in writing from the publisher. For the exclusive use of adopters of the book
Automation, Production Systems, and Computer-Integrated Manufacturing, Third Edition, by Mikell P. Groover.
Distributed Numerical Control Configurations
Switching network
©2008 Pearson Education, Inc., Upper Saddle River, NJ. All rights reserved. This material is protected under all copyright laws as they currently exist. No portion of this material may be reproduced, in any form or by any means, without permission in writing from the publisher. For the exclusive use of adopters of the book
Automation, Production Systems, and Computer-Integrated Manufacturing, Third Edition, by Mikell P. Groover.
Distributed Numerical Control Configurations
Local area network (LAN)
©2008 Pearson Education, Inc., Upper Saddle River, NJ. All rights reserved. This material is protected under all copyright laws as they currently exist. No portion of this material may be reproduced, in any form or by any means, without permission in writing from the publisher. For the exclusive use of adopters of the book
Automation, Production Systems, and Computer-Integrated Manufacturing, Third Edition, by Mikell P. Groover.
Applications of NC
Machine tool applications: Milling, drilling, turning, boring, grinding Machining centers(almost any CNC milling and drilling machine
that includes an automatic tool changer and a table that clamps the workpiece in place), turning centers, mill-turn centers
Punch presses, thermal cutting machines, etc. Other NC applications:
Component insertion machines in electronics Drafting machines (x-y plotters) Coordinate measuring machines Tape laying machines for polymer composites Filament winding machines for polymer composites
Automatic insertion m/c
Coordinate measuring m/c
©2008 Pearson Education, Inc., Upper Saddle River, NJ. All rights reserved. This material is protected under all copyright laws as they currently exist. No portion of this material may be reproduced, in any form or by any means, without permission in writing from the publisher. For the exclusive use of adopters of the book
Automation, Production Systems, and Computer-Integrated Manufacturing, Third Edition, by Mikell P. Groover.
Common NC Machining Operations
Turning
©2008 Pearson Education, Inc., Upper Saddle River, NJ. All rights reserved. This material is protected under all copyright laws as they currently exist. No portion of this material may be reproduced, in any form or by any means, without permission in writing from the publisher. For the exclusive use of adopters of the book
Automation, Production Systems, and Computer-Integrated Manufacturing, Third Edition, by Mikell P. Groover.
Common NC Machining Operations
Milling Drilling
©2008 Pearson Education, Inc., Upper Saddle River, NJ. All rights reserved. This material is protected under all copyright laws as they currently exist. No portion of this material may be reproduced, in any form or by any means, without permission in writing from the publisher. For the exclusive use of adopters of the book
Automation, Production Systems, and Computer-Integrated Manufacturing, Third Edition, by Mikell P. Groover.
CNC Horizontal Milling Machine
©2008 Pearson Education, Inc., Upper Saddle River, NJ. All rights reserved. This material is protected under all copyright laws as they currently exist. No portion of this material may be reproduced, in any form or by any means, without permission in writing from the publisher. For the exclusive use of adopters of the book
Automation, Production Systems, and Computer-Integrated Manufacturing, Third Edition, by Mikell P. Groover.
NC Application Characteristics (Machining)
Where NC is most appropriate:1. Batch production2. Repeat orders3. Complex part geometries4. Much metal needs to be removed from the starting
workpart5. Many separate machining operations on the part6. The part is expensive
©2008 Pearson Education, Inc., Upper Saddle River, NJ. All rights reserved. This material is protected under all copyright laws as they currently exist. No portion of this material may be reproduced, in any form or by any means, without permission in writing from the publisher. For the exclusive use of adopters of the book
Automation, Production Systems, and Computer-Integrated Manufacturing, Third Edition, by Mikell P. Groover.
Advantages of NC
Nonproductive time is reduced(e.g.set up time) Greater accuracy and repeatability Lower scrap rates Inspection requirements are reduced More complex part geometries are possible Engineering changes are easier to make Simpler fixtures Shorter lead times Reduce parts inventory and less floor space Operator skill-level requirements are reduced
©2008 Pearson Education, Inc., Upper Saddle River, NJ. All rights reserved. This material is protected under all copyright laws as they currently exist. No portion of this material may be reproduced, in any form or by any means, without permission in writing from the publisher. For the exclusive use of adopters of the book
Automation, Production Systems, and Computer-Integrated Manufacturing, Third Edition, by Mikell P. Groover.
Disadvantages of NC
Higher investment cost CNC machines are more expensive
Higher maintenance effort CNC machines are more technologically sophisticated
Part programming issues Need for skilled programmers Time investment for each new part
Higher utilization is required
©2008 Pearson Education, Inc., Upper Saddle River, NJ. All rights reserved. This material is protected under all copyright laws as they currently exist. No portion of this material may be reproduced, in any form or by any means, without permission in writing from the publisher. For the exclusive use of adopters of the book
Automation, Production Systems, and Computer-Integrated Manufacturing, Third Edition, by Mikell P. Groover.
NC Positioning System
Typical motor and leadscrew arrangement in an NC positioning system for one linear axis
For x-y capability, the apparatus would be piggybacked on top of a second perpendicular axis
©2008 Pearson Education, Inc., Upper Saddle River, NJ. All rights reserved. This material is protected under all copyright laws as they currently exist. No portion of this material may be reproduced, in any form or by any means, without permission in writing from the publisher. For the exclusive use of adopters of the book
Automation, Production Systems, and Computer-Integrated Manufacturing, Third Edition, by Mikell P. Groover.
Analysis of Positioning NC Systems
Two types of NC positioning systems:1. Open-loop - no feedback to verify that the actual
position achieved is the desired position2. Closed-loop - uses feedback measurements to
confirm that the final position is the specified position Precision in NC positioning - three measures:
1. Control resolution2. Accuracy3. Repeatability
©2008 Pearson Education, Inc., Upper Saddle River, NJ. All rights reserved. This material is protected under all copyright laws as they currently exist. No portion of this material may be reproduced, in any form or by any means, without permission in writing from the publisher. For the exclusive use of adopters of the book
Automation, Production Systems, and Computer-Integrated Manufacturing, Third Edition, by Mikell P. Groover.
Open-Loop Motion Control System
Operates without verifying that the actual position achieved in the move is the desired position
©2008 Pearson Education, Inc., Upper Saddle River, NJ. All rights reserved. This material is protected under all copyright laws as they currently exist. No portion of this material may be reproduced, in any form or by any means, without permission in writing from the publisher. For the exclusive use of adopters of the book
Automation, Production Systems, and Computer-Integrated Manufacturing, Third Edition, by Mikell P. Groover.
Where α-step angle (degrees), and n = the number of step angles for the motor, which must be an integer.
An open-loop positioning system typically uses a stepping motor to rotate the leadscrew.A stepping motor is driven by a series of electrical pulses, which are generated by the MCUin an NC system. Each pulse causes the motor to rotate a fraction of one revolution. calledthe step angle. The possible step angles must be consistent with the following relationship:
The angle through which the motor shaft rotates is given by
©2008 Pearson Education, Inc., Upper Saddle River, NJ. All rights reserved. This material is protected under all copyright laws as they currently exist. No portion of this material may be reproduced, in any form or by any means, without permission in writing from the publisher. For the exclusive use of adopters of the book
Automation, Production Systems, and Computer-Integrated Manufacturing, Third Edition, by Mikell P. Groover.
©2008 Pearson Education, Inc., Upper Saddle River, NJ. All rights reserved. This material is protected under all copyright laws as they currently exist. No portion of this material may be reproduced, in any form or by any means, without permission in writing from the publisher. For the exclusive use of adopters of the book
Automation, Production Systems, and Computer-Integrated Manufacturing, Third Edition, by Mikell P. Groover.
©2008 Pearson Education, Inc., Upper Saddle River, NJ. All rights reserved. This material is protected under all copyright laws as they currently exist. No portion of this material may be reproduced, in any form or by any means, without permission in writing from the publisher. For the exclusive use of adopters of the book
Automation, Production Systems, and Computer-Integrated Manufacturing, Third Edition, by Mikell P. Groover.
Closed-Loop Motion Control System
Uses feedback measurements to confirm that the final position of the worktable is the location specified in the program
©2008 Pearson Education, Inc., Upper Saddle River, NJ. All rights reserved. This material is protected under all copyright laws as they currently exist. No portion of this material may be reproduced, in any form or by any means, without permission in writing from the publisher. For the exclusive use of adopters of the book
Automation, Production Systems, and Computer-Integrated Manufacturing, Third Edition, by Mikell P. Groover.
Optical Encoder
Device for measuring rotational position and speed Common feedback sensor for closed-loop NC control
©2008 Pearson Education, Inc., Upper Saddle River, NJ. All rights reserved. This material is protected under all copyright laws as they currently exist. No portion of this material may be reproduced, in any form or by any means, without permission in writing from the publisher. For the exclusive use of adopters of the book
Automation, Production Systems, and Computer-Integrated Manufacturing, Third Edition, by Mikell P. Groover.
©2008 Pearson Education, Inc., Upper Saddle River, NJ. All rights reserved. This material is protected under all copyright laws as they currently exist. No portion of this material may be reproduced, in any form or by any means, without permission in writing from the publisher. For the exclusive use of adopters of the book
Automation, Production Systems, and Computer-Integrated Manufacturing, Third Edition, by Mikell P. Groover.
Precision in NC Positioning
Three measures of precision:1. Control resolution - distance separating two adjacent
addressable points in the axis movement2. Accuracy - maximum possible error that can occur
between the desired target point and the actual position taken by the system
3. Repeatability - defined as 3 of the mechanical error distribution associated with the axis
©2008 Pearson Education, Inc., Upper Saddle River, NJ. All rights reserved. This material is protected under all copyright laws as they currently exist. No portion of this material may be reproduced, in any form or by any means, without permission in writing from the publisher. For the exclusive use of adopters of the book
Automation, Production Systems, and Computer-Integrated Manufacturing, Third Edition, by Mikell P. Groover.
Definitions of Control Resolution, Accuracy, and Repeatability
©2008 Pearson Education, Inc., Upper Saddle River, NJ. All rights reserved. This material is protected under all copyright laws as they currently exist. No portion of this material may be reproduced, in any form or by any means, without permission in writing from the publisher. For the exclusive use of adopters of the book
Automation, Production Systems, and Computer-Integrated Manufacturing, Third Edition, by Mikell P. Groover.
NC Part Programming
NC part programming consists of planning and documenting the sequence of processing steps to be performed on an NC machine.
The part programmer must have a knowledge of machining (or other processing technology for which the NC machine is designed) as well as geometry and trigonometry.
The documentation portion of par! programming involves the input medium used to transmit the program of instructions to the NC machine control unit (MCU).
The traditional input medium dating back to the first NC machines in the 1950s is l-inch wide punched rape.
More recently the use of magnetic tape and floppy disks have been used for NC due to their much higher data density.
Part programming can he accomplished using a variety of procedures ranging from highly manual to highly automated methods.
1. Manual part programming2. Computer-assisted part programming3. Part programming using CAD/CAM4. Manual data input
1.Manual Part Programming
In manual part programming, the programmer prepares the NC code using the low-level machine language previously described.
The coding system is based on binary numbers This coding is the low level machine language that can be understood by the MCU. Whenever higher level languages are used , such as APT, the statements in the program are
converted to this basic code NC uses a combination of the binary and decimal number system, called BCD system.
In this coding scheme , each of the ten digits (0-9) in the decimal system is coded as a four digit binary number, and these binary number are added in sequence as in the decimal number system.
Conversion of the ten digits in the decimal system into binary numbers Exe: decimal value 1250 would be coded in BCD Number sequence binary number decimal value First 0001 1000 Second 0010 200 Third 0101 50 Fourth 0000 0 Sum 1250
©2008 Pearson Education, Inc., Upper Saddle River, NJ. All rights reserved. This material is protected under all copyright laws as they currently exist. No portion of this material may be reproduced, in any form or by any means, without permission in writing from the publisher. For the exclusive use of adopters of the book
Automation, Production Systems, and Computer-Integrated Manufacturing, Third Edition, by Mikell P. Groover.
Binary Coded Decimal System
Each of the ten digits in decimal system is coded with four-digit binary number
The binary numbers are added to give the value BCD is compatible with 8 bits across tape format, the
original storage medium for NC part programs Eight bits can also be used for letters and symbols
©2008 Pearson Education, Inc., Upper Saddle River, NJ. All rights reserved. This material is protected under all copyright laws as they currently exist. No portion of this material may be reproduced, in any form or by any means, without permission in writing from the publisher. For the exclusive use of adopters of the book
Automation, Production Systems, and Computer-Integrated Manufacturing, Third Edition, by Mikell P. Groover.
Creating Instructions for NC
Bit - 0 or 1 = absence or presence of hole in the tape Character - row of bits across the tape Word - sequence of characters (e.g., y-axis position) Block - collection of words to form one complete
instruction Part program - sequence of instructions (blocks)
©2008 Pearson Education, Inc., Upper Saddle River, NJ. All rights reserved. This material is protected under all copyright laws as they currently exist. No portion of this material may be reproduced, in any form or by any means, without permission in writing from the publisher. For the exclusive use of adopters of the book
Automation, Production Systems, and Computer-Integrated Manufacturing, Third Edition, by Mikell P. Groover.
Block Format
Organization of words within a block in NC part program Also known as tape format because the original
formats were designed for punched tape Word address format - used on all modern CNC
controllers Uses a letter prefix to identify each type of word Spaces to separate words within the block Allows any order of words in a block Words can be omitted if their values do not
change from the previous block
©2008 Pearson Education, Inc., Upper Saddle River, NJ. All rights reserved. This material is protected under all copyright laws as they currently exist. No portion of this material may be reproduced, in any form or by any means, without permission in writing from the publisher. For the exclusive use of adopters of the book
Automation, Production Systems, and Computer-Integrated Manufacturing, Third Edition, by Mikell P. Groover.
Types of Words
N - sequence number prefixG - preparatory words
Example: G00 = PTP rapid traverse moveX, Y, Z - prefixes for x, y, and z-axesF - feed rate prefixS - spindle speedT - tool selectionM - miscellaneous command
Example: M07 = turn cutting fluid on
©2008 Pearson Education, Inc., Upper Saddle River, NJ. All rights reserved. This material is protected under all copyright laws as they currently exist. No portion of this material may be reproduced, in any form or by any means, without permission in writing from the publisher. For the exclusive use of adopters of the book
Automation, Production Systems, and Computer-Integrated Manufacturing, Third Edition, by Mikell P. Groover.
Example: Word Address Format
N001 G00 X07000 Y03000 M03N002 Y06000
©2008 Pearson Education, Inc., Upper Saddle River, NJ. All rights reserved. This material is protected under all copyright laws as they currently exist. No portion of this material may be reproduced, in any form or by any means, without permission in writing from the publisher. For the exclusive use of adopters of the book
Automation, Production Systems, and Computer-Integrated Manufacturing, Third Edition, by Mikell P. Groover.
Issues in Manual Part Programming
Adequate for simple jobs, e.g., PTP drilling Linear interpolation
G01 G94 X050.0 Y086.5 Z100.0 F40 S800 Circular interpolation
G02 G17 X088.0 Y040.0 R028.0 F30 Cutter offset
G42 G01 X100.0 Y040.0 D05
Common Format of a BlockSequen
ce #Preparat
ory Function
Dimension
Words
Feed
Rate
Spindle
Function
Tool Functi
on
Misc. Functio
n
N50 G90 G01
X1.40Y2.25 F10 S1500 T01 M03
Individual Words
Word Address 1N – Sequence or line number
A tag that identifies the beginning of a block of code. It is used by operators to locate specific lines of a program when entering data or verifying the program operation.
G – Preparatory functionG words specify the mode in which the milling machine is to move along its programmed axes.
Reserved Code Words WorksheetN – Sequence or line number
G – Preparatory function
Dimension Words:X –
Y –
Z –
Word Address 2
Dimension WordsX – Distance or position in X directionY – Distance or position in Y directionZ – Distance or position in Z direction
M – Miscellaneous functionsM words specify CNC machine functions not related to dimensions or axial movements.
Word Address 3
F – Feed rate (inches per minute or millimeters per minute)Rate at which cutting tool moves along an axis.
S – Spindle speed (rpm – revolutions per minute)Controls spindle rotation speed.
T – Tool numberSpecifies tool to be selected.
Word Address 4
I – Circular cutting reference for x axis
J – Circular cutting reference for y axis
K – Circular cutting reference for z axis
G Word
G words or codes tell the machine to perform certain functions. Most G words are modal which means they remain in effect until replaced by another modal G code.
Common G CodesG00 – Rapid positioning mode
Tool is moved along the shortest route to programmed X,Y,Z position. Usually NOT used for cutting.
G01 – Linear Interpolation mode Tool is moved along a straight-line path at
programmed rate of speed.
G02 – Circular motion clockwise (cw)G03 – Circular motion counter clockwise (ccw)
Common G Codes, con.,
G17 – XY planeG18 – XZ planeG19 – YZ planeG20 – Inch ModeG21 – Metric ModeG28 – Return to axis machine Zero (Home)
G Codes: G90, G91G90 – Absolute Coordinate ReferenceReferences the next position from an absolute
zero point which is set once for the entire program.
G91 – Incremental Coordinate ReferenceReferences the next position from the previous
position.
G Codes: Canned Cycles
G80 – Cancel canned cycleG81 – Drilling cycleG83 – Peck drilling cycleG84 – Tapping cycleG85 – Boring cycleG86 – Boring cycle
NOTE: A canned cycle stays in effect until cancelled by a G80.
Canned Cycles: G81G81 – Drilling Cycle
Feed to depth, rapid return
Example of program code:N35 G81 X.500Y.500Z-1.000 R.100 F1.50N36 X1.000Y1.500N37 X1.500Y2.000N38 G80
Canned Cycles: G83, G84
G83 – Peck Drilling Cycle Feed to an intermediate depth, rapid out, rapid back to just above previous depth, feed to next depth, rapid out, repeat until reaching full depth.
G84 – Tapping CycleThis cycle creates internal threads in an existing hole. NOTE: One cannot over-ride the feed rate.
Canned Cycles: G85, G86
G85 - Boring Cycle
Feed to depth, feed back out.
G86 – Boring Cycle
Feed to depth, rapid out.
G Codes: Cutter CompensationG40 – Cancel cutter diameter compensation.
G41 – Cutter compensation left.
G42 – Cutter compensation right.
M Word
M words tell the machine to perform certain machine related functions, such as: turn spindle on/off, coolant on/off, or stop/end program.
Common M words
M00 – Programmed pauseAutomatically stops machine until operator pushes a button to resume program.
M01 – Optional stopA stop acted upon by the machine when operator has signaled this command by pushing a button.
M02 – End of programStops program when all lines of code are completed. Must be last command in program.
Common M wordsM03 – Turn spindle on
In clockwise direction
M04 – Turn spindle on In counter clockwise direction
M05 – Stop spindleUsually used prior to tool change or at end of program.
M06 – Tool changeStops program and calls for a tool change, either automatically or manually.
Common M words
M08 – Turns Accessory 1 on. M09 – Turns Accessory 1 off.
M10 – Turns Accessory 2 on. M11 – Turns Accessory 2 off.
M30 – End of program Similar to M02 but M30 will also “rewind” the program. Must be last statement in program. If used, DO NOT use M02.
Example of CNC Programming What Must Be Done To Drill A Hole On A CNC
Machine
Top View
Front View
Tool Home
1.) X & Y Rapid To Hole Position
Top View
Front View
2.) Z Axis Rapid Move Just Above Hole
3.) Turn On Coolant4.) Turn On Spindle
.100”
Top View
Front View
5.) Z Axis Feed Move to Drill Hole
Top View
Front View
6.) Rapid Z Axis Move Out Of Hole
Top View
Front View
9.) X&Y Axis Rapid Move Home
7.) Turn Off Spindle8.) Turn Off Coolant
Top View
Front View
Tool At Home
O0001N01 G20 G90 S600 M03N02 G00 X1.0 Y1.0N03 T01 H01 Z.1 M08N04 G01 Z-.75 F3.5
N06 G92 X0 Y0 Z0N07 M30
N05 G00 Z.1 M09
Here’s The CNC Program!
Top View
Front View
Tool At Home
O0001O0001
Number Assigned to this program
Top View
Front View
Tool At Home
O0001N005 G20 G90 S600 M03
N005 Sequence NumberG90 Absolute Programming ModeS600 Spindle Speed set to 600 RPM
M03 Spindle on in a Clockwise DirectionG20 Dimensions in inch
Top View
Front View
O0001N005 G20 G90 S600 M03N010 G00 X1.0 Y1.0
G00 Rapid MotionX1.0 X Coordinate 1.0 in. from ZeroY1.0 Y Coordinate 1.0 in. from Zero
Top View
Front View
O0001N005 G20 G90 S600 M03N010 G00 X1.0 Y1.0N015 G43 H01 Z.1 M08
G43 Tool Length CompensationH01 Specifies Tool length compensation
Z.1 Z Coordinate .1 in. from ZeroM08 Flood Coolant On
Top View
Front View
O0001N005 G20 G90 S600 M03N010 G00 X1.0 Y1.0N015 G43 H01 Z.1 M08N020 G01 Z-.75 F3.5
G01 Straight Line Cutting MotionZ-.75 Z Coordinate -.75 in. from Zero
F3.5 Feed Rate set to 3.5 in./min.
Top View
Front View
O0001N005 G20 G90 S600 M03N010 G00 X1.0 Y1.0N015 G43 H01 Z.1 M08N020 G01 Z-.75 F3.5
G00 Rapid MotionZ.1 Z Coordinate .1 in. from Zero
M09 Coolant Off
N025 G00 Z.1 M09
Top View
Front View
O0001N005 G20 G90 S600 M03N010 G00 X1.0 Y1.0N015 G43 H01 Z.1 M08N020 G01 Z-.75 F3.5
N030 G92 X0 Y0 Z0G92 Zero Return Command
X0, Y0, Z0 X,Y,& Z Coordinates at Zero
N025 G00 Z.1 M09
Top View
Front View
O0001N005 G20 G90 S600 M03N010 G00 X1.0 Y1.0N015 G43 H01 Z.1 M08N020 G01 Z-.75 F3.5
N035 M30N030 G92 X0 Y0 Z0
N025 G00 Z.1 M09
M30 End of Program
Output: NC Code - Canned Cycles
©2008 Pearson Education, Inc., Upper Saddle River, NJ. All rights reserved. This material is protected under all copyright laws as they currently exist. No portion of this material may be reproduced, in any form or by any means, without permission in writing from the publisher. For the exclusive use of adopters of the book
Automation, Production Systems, and Computer-Integrated Manufacturing, Third Edition, by Mikell P. Groover.
2.Computer-Assisted Part Programming
Manual part programming is time-consuming, tedious, and subject to human errors for complex jobs
Machining instructions are written in English-like statements that are translated by the computer into the low-level machine code of the MCU
APT (Automatically Programmed Tool) The various tasks in computer-assisted part
programming are divided between The human part programmer The computer
©2008 Pearson Education, Inc., Upper Saddle River, NJ. All rights reserved. This material is protected under all copyright laws as they currently exist. No portion of this material may be reproduced, in any form or by any means, without permission in writing from the publisher. For the exclusive use of adopters of the book
Automation, Production Systems, and Computer-Integrated Manufacturing, Third Edition, by Mikell P. Groover.
Computer-Assisted Part Programming
Sequence of activities in computer-assisted part programming
©2008 Pearson Education, Inc., Upper Saddle River, NJ. All rights reserved. This material is protected under all copyright laws as they currently exist. No portion of this material may be reproduced, in any form or by any means, without permission in writing from the publisher. For the exclusive use of adopters of the book
Automation, Production Systems, and Computer-Integrated Manufacturing, Third Edition, by Mikell P. Groover.
Part Programmer's Job
Two main tasks of the programmer:1.Define the part geometry2.Specify the tool path
©2008 Pearson Education, Inc., Upper Saddle River, NJ. All rights reserved. This material is protected under all copyright laws as they currently exist. No portion of this material may be reproduced, in any form or by any means, without permission in writing from the publisher. For the exclusive use of adopters of the book
Automation, Production Systems, and Computer-Integrated Manufacturing, Third Edition, by Mikell P. Groover.
Defining Part Geometry
Underlying assumption: no matter how complex the part geometry, it is composed of basic geometric elements and mathematically defined surfaces
Geometry elements are sometimes defined only for use in specifying tool path
Examples of part geometry definitions:P4 = POINT/35,90,0L1 = LINE/P1,P2C1 = CIRCLE/CENTER,P8,RADIUS,30
©2008 Pearson Education, Inc., Upper Saddle River, NJ. All rights reserved. This material is protected under all copyright laws as they currently exist. No portion of this material may be reproduced, in any form or by any means, without permission in writing from the publisher. For the exclusive use of adopters of the book
Automation, Production Systems, and Computer-Integrated Manufacturing, Third Edition, by Mikell P. Groover.
Specifying Tool Path and Operation Sequence
Tool path consists of a sequence of points or connected line and arc segments, using previously defined geometry elements
Point-to-Point command:GOTO/P0
Continuous path commandGOLFT/L2,TANTO,C1
©2008 Pearson Education, Inc., Upper Saddle River, NJ. All rights reserved. This material is protected under all copyright laws as they currently exist. No portion of this material may be reproduced, in any form or by any means, without permission in writing from the publisher. For the exclusive use of adopters of the book
Automation, Production Systems, and Computer-Integrated Manufacturing, Third Edition, by Mikell P. Groover.
Other Functions in Computer-Assisted Part Programming
Specifying cutting speeds and feed rates Designating cutter size (for tool offset calculations) Specifying tolerances in circular interpolation Naming the program Identifying the machine tool
©2008 Pearson Education, Inc., Upper Saddle River, NJ. All rights reserved. This material is protected under all copyright laws as they currently exist. No portion of this material may be reproduced, in any form or by any means, without permission in writing from the publisher. For the exclusive use of adopters of the book
Automation, Production Systems, and Computer-Integrated Manufacturing, Third Edition, by Mikell P. Groover.
Cutter Offset
Cutter path must be offset from actual part outline by a distance equal to the cutter radius
©2008 Pearson Education, Inc., Upper Saddle River, NJ. All rights reserved. This material is protected under all copyright laws as they currently exist. No portion of this material may be reproduced, in any form or by any means, without permission in writing from the publisher. For the exclusive use of adopters of the book
Automation, Production Systems, and Computer-Integrated Manufacturing, Third Edition, by Mikell P. Groover.
Computer Tasks in Computer-Assisted Part Programming
1. Input translation – converts the coded instructions in the part program into computer-usable form
2. Arithmetic and cutter offset computations – performs the mathematical computations to define the part surface and generate the tool path, including cutter offset compensation (CLFILE)
3. Editing – provides readable data on cutter locations and machine tool operating commands (CLDATA)
4. Postprocessing – converts CLDATA into low-level code that can be interpreted by the MCU
©2008 Pearson Education, Inc., Upper Saddle River, NJ. All rights reserved. This material is protected under all copyright laws as they currently exist. No portion of this material may be reproduced, in any form or by any means, without permission in writing from the publisher. For the exclusive use of adopters of the book
Automation, Production Systems, and Computer-Integrated Manufacturing, Third Edition, by Mikell P. Groover.
3.NC Part Programming Using CAD/CAM
Geometry definition If the CAD/CAM system was used to define the original
part geometry, no need to recreate that geometry as in APT Automatic labeling of geometry elements
If the CAD part data are not available, geometry must be created, as in APT, but user gets immediate visual feedback about the created geometry
©2008 Pearson Education, Inc., Upper Saddle River, NJ. All rights reserved. This material is protected under all copyright laws as they currently exist. No portion of this material may be reproduced, in any form or by any means, without permission in writing from the publisher. For the exclusive use of adopters of the book
Automation, Production Systems, and Computer-Integrated Manufacturing, Third Edition, by Mikell P. Groover.
Tool Path Generation Using CAD/CAM
Basic approach: enter the commands one by one (similar to APT) CAD/CAM system provides immediate graphical
verification of the command Automatic software modules for common machining cycles
Profile milling Pocket milling Drilling bolt circles
©2008 Pearson Education, Inc., Upper Saddle River, NJ. All rights reserved. This material is protected under all copyright laws as they currently exist. No portion of this material may be reproduced, in any form or by any means, without permission in writing from the publisher. For the exclusive use of adopters of the book
Automation, Production Systems, and Computer-Integrated Manufacturing, Third Edition, by Mikell P. Groover.
Examples of Machining Cycles in Automated NC Programming Modules
Pocket milling
Contour turning
©2008 Pearson Education, Inc., Upper Saddle River, NJ. All rights reserved. This material is protected under all copyright laws as they currently exist. No portion of this material may be reproduced, in any form or by any means, without permission in writing from the publisher. For the exclusive use of adopters of the book
Automation, Production Systems, and Computer-Integrated Manufacturing, Third Edition, by Mikell P. Groover.
Examples of Machining Cycles in Automated NC Programming Modules
Facing and shoulder facing
Threading (external)
©2008 Pearson Education, Inc., Upper Saddle River, NJ. All rights reserved. This material is protected under all copyright laws as they currently exist. No portion of this material may be reproduced, in any form or by any means, without permission in writing from the publisher. For the exclusive use of adopters of the book
Automation, Production Systems, and Computer-Integrated Manufacturing, Third Edition, by Mikell P. Groover.
4.Manual Data Input
Machine operator does part programming at machine Operator enters program by responding to prompts and
questions by system Monitor with graphics verifies tool path Usually for relatively simple parts
Ideal for small shop that cannot afford a part programming staff
To minimize changeover time, system should allow programming of next job while current job is running