Computer Numerical Control of Machine Tools Computer
COMPUTER NUMERICAL CONTROL OF MACHINE TOOLS
Laboratory for Manufacturing Systems and Automation Department of Mechanical Engineering and Aeronautics University of Patras, Greece
Dr. Dimitris Mourtzis Associate professor
Patras, 2016
Laboratory for Manufacturing Systems and Automation Dr. Dimitris Mourtzis 2.1 Chapter 2: Numerical Control Systems
Laboratory for Manufacturing Systems and Automation Dr. Dimitris Mourtzis 2.2 Table of Contents
Chapter 2: Numerical Control Systems….…………………………………………………………...... 2
2.1 Types of Control Systems in use on NC Equipment………………………………..…………….10
2.2 Drive systems used on CNC machinery………………………………………………………..18
2.3 The Cartesian Coordinate System………………………………………..……...... 29
2.4 Motion Directions of a CNC Milling Machine……..……………………………………...37
2.5 Absolute & Incremental Positioning..…………………………….……..……………..42
2.6 Setting the Machine Origin………………………………….…...... 46
2.7 Dimensioning Methods…………………………………………………...... 54
Laboratory for Manufacturing Systems and Automation Dr. Dimitris Mourtzis 2.3 Objectives of Chapter 2
Describe the two types of control systems in use on NC equipment
Name the four types of drive motors used on NC machinery
Describe the two types of loop systems used
Describe the Cartesian coordinate system
Define a machine axis
Describe the motion directions on a three-axis milling machine
Describe the difference between absolute and incremental positioning
Describe the difference between datum and delta dimensioning
Laboratory for Manufacturing Systems and Automation Dr. Dimitris Mourtzis 2.4 CNC Components
A CNC machine consists of two major components: CNC components
The Machine-Tool Controller – Machine Control Unit (MCU)
MCU is an on-board computer MCU and Machine Tool may be manufactured by the same company
(W. S. Seames Computer Numerical Control: Concepts and Programming) Laboratory for Manufacturing Systems and Automation Dr. Dimitris Mourtzis 2.5 Controllers
CNC controllers manufacturers
Fanuc
Bridgeport
Haas
Cincinnati Milacron
Mitsubishi
Siemens
Figure 2-1(a): A Fanuc CNC Controller (Source: http://www.fanuc.co.jp/)
Laboratory for Manufacturing Systems and Automation Dr. Dimitris Mourtzis 2.6 Controllers
CNC controllers manufacturers market share
Haas 14%
Figure 2-1(b): CNC controllers manufacturers market share survey, FANUC owns the largest share 26% (Source: cnccookbook.com)
Laboratory for Manufacturing Systems and Automation Dr. Dimitris Mourtzis 2.7 Controllers
Each MCU is manufactured with a standard set of build in codes
Other codes are added by the machine tool builders
Program codes vary somewhat from machine to machine
Every CNC machine is a collection of systems coordinated by the controller
Laboratory for Manufacturing Systems and Automation Dr. Dimitris Mourtzis 2.8 Types of Control Systems
There are two types of control systems used on CNC machines:
Control Systems
Point – to – Point Continuous – Path Systems Systems
Laboratory for Manufacturing Systems and Automation Dr. Dimitris Mourtzis 2.9 Types of Control Systems Point – to – Point machines: I. Move in straight lines II. They are limited in practical sense to hole operations:
Drilling
Reaming
Boring etc III. Straight milling cuts parallel to a machine axis IV. When making an axis move all affected drive motors run at the same speed
Cutting of 45o angles is possible BUT not angles or arcs other than 45o angles
(W. S. Seames Computer Numerical Control: Concepts and Programming) Laboratory for Manufacturing Systems and Automation Dr. Dimitris Mourtzis 2.10 Types of Control Systems Point – to – Point machines example Move to (X1, Y1) Move to (X2, Y1) Move to (X3’, Y3) where X3’ < X3 Move to (X3, Y3) Move to (X4, Y4’) and move to (X4, Y4)
(W. S. Seames Computer Numerical Control: Concepts and Programming) Laboratory for Manufacturing Systems and Automation Dr. Dimitris Mourtzis 2.11 Types of Control Systems
Point – to – Point machines:
Angle and arc segments must be programmed as a series of straight line cuts
Figure 2-2:Point – to – point angles and arcs (W. S. Seames Computer Numerical Control: Concepts and Programming)
Laboratory for Manufacturing Systems and Automation Dr. Dimitris Mourtzis 2.12 Types of Control Systems Movement of Tools example
● Point-to-point: The drill bit drills a hole at position 1, then is retracted and moved to position 2 and so on
Figure 2-4: Point – to – Point tool movement (Source: Manufacturing, Engineering & Technology, Fifth Edition,S. Kalpakjian and S. R. Schmid)
Laboratory for Manufacturing Systems and Automation Dr. Dimitris Mourtzis 2.13 Types of Control Systems
Continuous - Path machines:
Have the ability to move the drive motors at varying rates of speed while positioning the machine
The cutting of arc segments and any angle canbeeasily accomplished
Figure 2-3: Continuous – path angles and arcs (W. S. Seames Computer Numerical Control: Concepts and Programming)
Laboratory for Manufacturing Systems and Automation Dr. Dimitris Mourtzis 2.14 Types of Control Systems Movement of Tools example
● Continuous path by a milling cutter
Figure 2-5:Continuous – Path tool movement (Source: Manufacturing, Engineering & Technology, Fifth Edition,S. Kalpakjian and S. R. Schmid)
Laboratory for Manufacturing Systems and Automation Dr. Dimitris Mourtzis 2.15 Types of Control Systems
Point – to – Point Machines where common Their electronics where less expensive to produce The machine tools where less expensive to acquire Technological advancements have narrowed the cost difference between point – to point and continuous – path machines
Most CNC machines now manufactured are of continuous – path type
Laboratory for Manufacturing Systems and Automation Dr. Dimitris Mourtzis 2.16 Servomechanisms
The drive systems used on NC machinery:
STEPPER motors
DC (Direct Current) servos
AC (Alternating Current) servos
Hydraulic servos
Figure: The machine control sends a motion signal, to a servomotor attached to each machine axis. This causes the servomotor to rotate a ball screw attached to the table or column, causing it to move.
(http://www.hsmworks.com)
Laboratory for Manufacturing Systems and Automation Dr. Dimitris Mourtzis 2.17 Servomechanisms STEPPER Motors Move a set amount of rotation (a step) every time the motor receives an electronic pulse DC and AC servos Widely used variable-speed motors on small & medium continuous path machines Aservodoes not move a set distance When current is applied the motor starts to turn and when the current is removed the motor stops turning The AC motor can create more power than a DC motor – used on CNC Machining Centers HYDRAULIC servos Are variable-speed motors Produce much more power than an electric motor They are used on large CNC machinery with electronic or pneumatic system attached
Laboratory for Manufacturing Systems and Automation Dr. Dimitris Mourtzis 2.18 Controllers
Virtual Model of Trajectory Generation and Axes Control
CL :"Cutter Location“ file
"Jerk" is the time rate of change of acceleration. Jerk ramps the acceleration to smooth the velocity Article From: 9/9/2005 Modern Machine Shop, Norman Bleier, Siemens engineering manager (Moriwaki T., “Multi-Functional Machine Tool”,2008) Laboratory for Manufacturing Systems and Automation Dr. Dimitris Mourtzis 2.19 Loop Systems
Loop systems are electronic feedback systems that send and receive electronic information from the drive motors
Loop Systems
Open Closed Loop Loop
The type of system used affects the overall accuracy of the machine Open Loop use Stepper Motors Closed Loop usually use Hydraulic, AC and DC Servos
Laboratory for Manufacturing Systems and Automation Dr. Dimitris Mourtzis 2.20 Loop Systems For Controlling Tool Movement
Open – Loop System: Input Media The machine receives its information from the reader and stores it in the storage device Machine Control Unit When the information is needed it is Storage Reader sent to the drive motor (s) Memory
After the motor has completed its move a signal is sent back to the storage device telling it that the move has been completed and the next Drive Motor instruction may be received Motor Controller
There is no process to correct for error induced by the drive system Figure 2-7: An Open – Loop system
Laboratory for Manufacturing Systems and Automation Dr. Dimitris Mourtzis 2.21 Loop Systems For Controlling Tool Movement Open – Loop System
MCU
Figure 2-6: An open-loop control system for a numerical-control machine (Source: Manufacturing, Engineering & Technology, Fifth Edition,S. Kalpakjian and S. R. Schmid)
Laboratory for Manufacturing Systems and Automation Dr. Dimitris Mourtzis 2.22 Loop Systems For Controlling Tool Movement Open – Loop System
An open loop system utilizes stepping motors to create machine movements. These motors rotate a fixed amount, usually 1.8°, for each pulse received.
Stepping motors are driven by electrical signals coming from the MCU. The motors are connected to the machine table ball-nut lead screw and spindle
Upon receiving a signal, they move the table and/or spindle a fixed amount. The motor controller sends signals back indicating the motors have completed the motion
The feedback, however, is not used to check how close the actual machine movement comes to the exact movement programmed
Laboratory for Manufacturing Systems and Automation Dr. Dimitris Mourtzis 2.23 Loop Systems For Controlling Tool Movement
Closed – Loop System: The machine receives its information from the reader and stores it in the storage device When the information is sent to drive motor the motor’s position is monitored by the system and compared to what was sent If an error is detected the necessary correction is sent to the drive system If the error is large the machine may stop executing the program for correcting the inaccuracy Most errors produced by the drive motors are eliminated Advanced Stepper Motors make possible extremely accurate Open Figure 2-9: A Closed – Loop system – Loop Systems and less HW
Laboratory for Manufacturing Systems and Automation Dr. Dimitris Mourtzis 2.24 Loop Systems For Controlling Tool Movement Closed – Loop System
DAC : “digital-to-analog converter”
MCU
Figure 2-8: A closed-loop control system for a numerical-control machine (Source: Manufacturing, Engineering & Technology, Fifth Edition,S. Kalpakjian and S. R. Schmid)
Laboratory for Manufacturing Systems and Automation Dr. Dimitris Mourtzis 2.25 Loop Systems For Controlling Tool Movement Closed – Loop System
Special motors called servos areusedforexecuting machine movements in closed loop systems
Motor types include AC servos, DC servos,andhydraulic servos. Hydraulic servos, being the most powerful, are used on large CNC machines. AC servos are next in strength and are found on many machining centers
A servo does not operate like a pulse counting stepping motor. The speed of an AC or DC servo is variable and depends upon the amount of current passing through it
The speed of a hydraulic servo depends upon the amount of fluid passing through it. The strength of current coming from the MCU determines the speed at which a servo rotates (W. S. Seames Computer Numerical Control: Concepts and Programming) Laboratory for Manufacturing Systems and Automation Dr. Dimitris Mourtzis 2.26 Coordinate Systems
Geometrical means of communication between the operator and digitally driven machine-tool
Univocal characterization of a point in the plane or in space relative to a fixed point
Absolute coordinates
Relative coordinates
Figure 2-10:The simplest example of a coordinate system (en.wikipedia.org/)
Laboratory for Manufacturing Systems and Automation Dr. Dimitris Mourtzis 2.27 The Cartesian Coordinate System
The Cartesian Coordinate System is defined by two orthogonal axes which intersect at a point X Axis: Abscissa axis Y Axis: Ordinate axis
Figure 2-11 : The Cartesian Coordinate System definition, X&Y axis (Modern methods of material processing and programming with PC , D. Mourtzis et al.)
Laboratory for Manufacturing Systems and Automation Dr. Dimitris Mourtzis 2.28 The Cartesian Coordinate System
Z Axis: Applicate axis
Figure 2-12 : The Cartesian Coordinate System definition, Z axis (Modern methods of material processing and programming with PC , D. Mourtzis et al.)
Laboratory for Manufacturing Systems and Automation Dr. Dimitris Mourtzis 2.29 The Cartesian Coordinate System
Cartesian Coordinate System:
Is divided into quarters (quadrants): I, II, III, IV in counter-clockwise direction
This is the universal way of labelling axis quadrants
The signs of X and Y change when moving from quadrant to quadrant
Figure 2-13: Cartesian coordinate quadrants (W. S. Seames Computer Numerical Control: Concepts and Programming) Laboratory for Manufacturing Systems and Automation Dr. Dimitris Mourtzis 2.30 The Cartesian Coordinate System
Cartesian Coordinate System:
Points on a two-axis Cartesian system: Each of the points can be defined as a set of coordinates (X, Y) In mathematics this set of points is called an ordered pair In NC programming the points are referred as coordinates Cartesian coordinates will be used in writing NC programs
Figure 2-14: Cartesian coordinates
Laboratory for Manufacturing Systems and Automation Dr. Dimitris Mourtzis 2.31 The Cartesian Coordinate System Quadrants Quadrants in the plane Quadrants in the space
Figure 2-15:Positive and negative quadrants on a plane and in the space (Modern methods of material processing and programming with PC, D. Mourtzis et al.)
Laboratory for Manufacturing Systems and Automation Dr. Dimitris Mourtzis 2.32 The Cartesian Coordinate System Rule of right hand rotation
Figure 2-16: The Electronic Industries Association & Aerospace Industries of America established the right hand rule of coordinates. The right hand rule determines positive direction of each axis from the base of the finger to the tip
Laboratory for Manufacturing Systems and Automation Dr. Dimitris Mourtzis 2.33 The Cartesian Coordinate System Transferring coordinates Scheduling cutting, based on the coordinate system with axes starting at the zero point of the piece W Transfer coordinates in the coordinate system of the machine-tool axes beginning from the zero point of the machine M Need to define the coordinate system of the user in connection with the zero point or the reference point of the machine
Figure 2-17:Coordinate Systems Transfer (Modern methods of material processing and programming with PC , D. Mourtzis et al.)
Laboratory for Manufacturing Systems and Automation Dr. Dimitris Mourtzis 2.34 The Cartesian Coordinate System Rotation of a Coordinate System
Rotation can be made on any axis If the rotation is made on more than one axis, or with different angles of the 90o, 180o and 270o using functions transformation of coordinates is required
Scheme 1 Scheme 2
Figure 2-18: Rotation around the Z axis by -90o (Modern methods of material processing and programming with PC , D. Mourtzis et al.)
Laboratory for Manufacturing Systems and Automation Dr. Dimitris Mourtzis 2.35 The Cartesian Coordinate System The Cartesian Coordinate System in machines
The basis for all machine movement is the Cartesian Coordinate system
On a machine tool an axis is a direction of movement
In a Two – Axis Milling Machine:
X is the direction of the Table travel
Y is the direction of the Cross travel
Figure 2-19: Directions of movement on a machine (W. S. Seames Computer Numerical Control: Concepts and Programming) (http://www.hsmworks.com/)
Laboratory for Manufacturing Systems and Automation Dr. Dimitris Mourtzis 2.36 The Cartesian Coordinate System The Cartesian Coordinate System in machines
Three – Axis Milling machine: In a Three – Axis Vertical Milling Machine:
X is the direction of the Table travel
Y is the direction of the Cross travel
Z the Spindle travel up – down
Figure 2-20: Three – Axis vertical mill
Laboratory for Manufacturing Systems and Automation Dr. Dimitris Mourtzis 2.37 The Cartesian Coordinate System The Cartesian Coordinate System in machines
Six – Axis Milling machine: In a Six – Axis Vertical Milling Machine:
X is the direction of the Table travel
Y is the direction of the Cross travel
Z the Spindle travel up – down
A is the rotation around X – axis
B is the rotation around Y – axis
C is the rotation Z –axis (spindle)
Figure 2-21: Six – Axis machine layout
Laboratory for Manufacturing Systems and Automation Dr. Dimitris Mourtzis 2.38 Positive and Negative Movement
Machine axis direction is defined in terms of spindle movement On some axes the machine slides actually move; on other axes the spindle travels For standardization the positive and negative direction for each axis is always defined as if the spindle did the travelling The arrows saw the positive and negative direction of spindle movement along axes
Example To make a move in the +X direction (spindle right) the table would move to the left Tomakeamoveinthe+Y direction (spindle toward the column) the saddle would move away the column The Z-axis movement is always positive (+Z) when the spindle moves towards the machine head and negative (–Z) when it moves toward the workpiece
Laboratory for Manufacturing Systems and Automation Dr. Dimitris Mourtzis 2.39 The Polar Coordinate System
The polar coordinate system is a two-dimensional coordinate system in which each point on a plane is determined by a distance from a fixed point and an angle from a fixed direction
sin
cos Arc tan
Figure 2-23 :The Polar coordinate system (Modern methods of material processing and programming with PC , D. Mourtzis et al.)
Laboratory for Manufacturing Systems and Automation Dr. Dimitris Mourtzis 2.40 Positioning Systems
There are two ways that machines position themselves with respect to their coordinate systems :
Positioning Systems
Absolute Incremental Positioning Positioning
Laboratory for Manufacturing Systems and Automation Dr. Dimitris Mourtzis 2.41 Positioning Systems
Absolute Positioning:
All machine locations are taken from one fixed zero point
All positions on the part are taken from the (X0, Y0) point at the lower left corner of the part
The 1st hole will have coordinates of (X1.000, Y1.000)
The 2nd hole will have coordinates of (X2.000, Y1.000)
The 3rd hole will have coordinates of (X3.000, Y1.000)
ZERO REFERENCE POINT Every time the machine moves the FOR A MOVE TO ANY LOCATION controller references the lower left corner of the part Figure 2-24: Absolute positioning (W. S. Seames Computer Numerical Control: Concepts and Programming) Laboratory for Manufacturing Systems and Automation Dr. Dimitris Mourtzis 2.42 Positioning Systems
ZERO LOCATION FOR A MOVE ZERO LOCATION FOR A MOVE FROM HOLE #2 TO Incremental Positioning: FROM HOLE #1 TO HOLE #2 HOLE #3 The (X0, Y0) point moves with the machine spindle Each position is specified in relation to the previous one The 1st hole coordinates are: (X1.000, Y1.000) The 2nd hole coordinates are (X1.000, Y0) The 3rd hole coordinates are (X1.000, Y0) After each machine move the current location is reset to (X0, Y0) for the next move ZERO LOCATION FOR A MOVE The coordinate system moves with FROM HERE TO HOLE #1 the location and the machine controller does not reference any Figure 2-25: Incremental positioning common zero point
Laboratory for Manufacturing Systems and Automation Dr. Dimitris Mourtzis 2.43 Positioning Systems
THIS POINT IS ZERO THIS POINT IS ZERO FOR A MOVE FROM FOR A MOVE FROM HOLE #2 TO #3 HOLE #1 TO #2
INITIAL ZERO POINT, ZERO POINT FOR A MOVE (THIS POINT IS ZERO FOR A MOVE FROM HERE TO TO ANY LOCATION HOLE #1)
Figure 2-26(a):Relationship of the Cartesian Figure 2-26(b):Relationship of the Cartesian Coordinate system to the part coordinate system to the part when using absolute positioning when using incremental positioning
Laboratory for Manufacturing Systems and Automation Dr. Dimitris Mourtzis 2.44 Dimensioning Methods
In conjunction with NC machinery there are two types of dimensioning practices used on blueprints :
Dimensioning Methods
Datum Delta Dimensioning Dimensioning
These two dimensioning methods are related to absolute and incremental positioning
Laboratory for Manufacturing Systems and Automation Dr. Dimitris Mourtzis 2.45 Dimensioning Methods Datum Dimensioning
All dimensions on a drawing are placed in reference to one fixed zero point
Is ideally suited to absolute positioning equipment
All dimensions are taken from the corner of the part
Figure 2-28: A datum dimensioned drawing
Laboratory for Manufacturing Systems and Automation Dr. Dimitris Mourtzis 2.46 Dimensioning Methods Delta Dimensioning
Dimensions placed on a Delta Dimensioned drawing are “chain- linked”
Each location is dimensioned from the previous one
Delta drawings aresuitedfor programming incremental positioning machines
It is not uncommon to find the two methods mixed on one drawing
Figure 2-29: A delta dimensioned drawing
Laboratory for Manufacturing Systems and Automation Dr. Dimitris Mourtzis 2.47 Dimensioning Methods Example of the two methods mixed on one drawing
Delta Dimensioning
Datum Dimensioning
Figure 2-30: I-phone drawing (osxdaily.com)
Laboratory for Manufacturing Systems and Automation Dr. Dimitris Mourtzis 2.48 Setting the Machine Origin Machine Coordinate System
Most CNC machinery have a default coordinate system assumed during power-up the Machine Coordinate System
The origin of this system is called the Machine Origin
or Home Zero Location
Home Zero is usually located at
the Tool Change position of a Machining Center
(http://www.hsmworks.com/) Laboratory for Manufacturing Systems and Automation Dr. Dimitris Mourtzis 2.49 Setting the Machine Origin Programmer Coordinate System
A part is programmed independently of the Machine Coordinate System
The programmer can pick a location on the part or fixture becoming the origin of the coordinate system for that part
The programmer’s coordinate system is called the Local or Part Coordinate System
The Machine and Part Coordinate System will almost never coincide
Prior running the part program the coordinate system must be transferred from the machine system to part system, known as setting ZERO POINT
(http://content.heidenhain.de) Laboratory for Manufacturing Systems and Automation Dr. Dimitris Mourtzis 2.50 Setting the Machine Origin
There are three ways a ZERO POINT can be set on CNC machines
ZERO POINT Setting
Manual Setting Work Coordinates
Absolute Zero Shift
Laboratory for Manufacturing Systems and Automation Dr. Dimitris Mourtzis 2.51 Setting the Machine Origin Manual Setting
The set-up person (technician) positions the spindle over the desired part zero
Zero out the coordinate system on the Machine Control Unit (MCU) console
The actual coding for accomplishing zero out varies depending on the Machine Control Unit (MCU)
Laboratory for Manufacturing Systems and Automation Dr. Dimitris Mourtzis 2.52 Setting the Machine Origin Absolute Zero Shift
An Absolute Zero Shift is a transfer of the coordinate system inside the NC program
First: the programmer commands the spindle to the Home Zero Location
Next: a command is given that tells the MCU how far from the Home Zero Location the Coordinate System Origin is to be located An Absolute Zero Shift is given as follows: Line 0N10: Spindle moves to Home Zero (Send the spindle to home zero) Line 0N20: The location of the spindle became N010 G28X0Y0Z0 X5.0, Y6.0, Z7.0, for MCU (Set the current spindle position) The machine will now reference the Part (To X5.000 Y6.000 Z7.000) Coordinate System N020 G92 X5.000 Y6.000 Z7.000 G28 - Return to reference point G92 – Program absolute zero point
If more than a fixture is to be used on a machine, the programmer will use more than one part coordinate system – send spindle back to home zero G28 X0, Y0, Z0 – then G92 Line (W. S. Seames Computer Numerical Control: Concepts and Programming)
Laboratory for Manufacturing Systems and Automation Dr. Dimitris Mourtzis 2.53 Setting the Machine Origin
Work Coordinates
A work coordinate is a modification of the absolute zero shift Work coordinates are registers in which the distance from home zero to the part zero can be stored The part coordinate system does not take effect until the work coordinate is commanded in the NC program When using G92 zero shifts, the coordinate system changes to the part coordinate system When using work coordinates a register can be set at one place in the program and called at another If more than one fixture is used – a second part zero can be entered in a second work coordinate and called up when needed The work coordinate registers can be set manually by the operator or by the NC programmer without having to send the spindle to the home zero location This saves program cycle time by eliminating the moves to home zero
Laboratory for Manufacturing Systems and Automation Dr. Dimitris Mourtzis 2.54 Setting the Machine Origin
Work Coordinates Example
Figure 2-27 shows a part gripped in avise
The outside dimensions of the part have already been milled to size on a manual machine before being set on the CNC machine
The CNC is used to make the holes, pockets, and slot in this part
The Work Coordinates are located in the upper-left corner of the block
Figure 2-27 :A part gripped in a vise (Adapted by http://www.hsmworks.com/)
Laboratory for Manufacturing Systems and Automation Dr. Dimitris Mourtzis 2.55 Setting the Machine Origin Work Coordinates Are set and called in a program by commands called G-codes: G54, G55 and G56 G10 L2 offsets the origin of the axes (Set Coordinate System Command) An example of using the Work Coordinate System (WCS):
Line N010: the G54 WCS is set to X5.0, Y6.0, Z7.0,fromthezero home location (Set work coordinate P1-which is G54) (and work coordinate P2-which is G55) Line N20: the G55 WCS is set to X10.0, Y3.0, Z15.0 from home zero N010 G10 L2 P1 X5.000 Y6.000 Z7.000 N020 G10 L2 P2 X10.000 Y3.000 Z15.000 Line N100: the G54 WCS is called activating the part coordinate system moving the spindle to X1.0, Y1.0, Z0.5 as referenced from the part (Call work coordinate G54 and move) activated part coordinate system (To X1.000 Y1.000 Z0.500) N100 G54 X1.000 Y1.000 Z.500 Line N110: the G55 WCS is called activating the second part coordinate system moving the (Call work coordinate G55 and move) spindle to X2.0, Y2.0, Z3.0 as referenced from (To X2.000 Y2.000 Z3.000) the part activated part coordinate system N110 G55 X2.000 Y2.000 Z3.000 Work coordinates remain active until cancelled by another work coordinate
Laboratory for Manufacturing Systems and Automation Dr. Dimitris Mourtzis 2.56 Summary 1/2
The two types of NC control systems are point-to-point and continuous path The four types of drive motors used on NC equipment are stepper motors, AC servos, and hydraulic servos Loop systems are electronic feedback systems used to help control machine positioning. There are two types of loop systems: open and closed. Closed-loop systems can correct errors induced by the drive system; open loop system cannot The basic of machine movement is the Cartesian Coordinate system. Any point on the Cartesian coordinate system may be defined by X/Y or X/Y/Z coordinates An absolute positioning system locates machine coordinates relative to a fixed datum reference point In an incremental positioning system, each coordinate location is referenced to the previous one
Laboratory for Manufacturing Systems and Automation Dr. Dimitris Mourtzis 2.57 Summary 2/2
The machine coordinate system can be transferred to the part coordinate system manually, by an absolute zero shift, or by use of work coordinates
The positive or negative direction of an axis movement is always thought of as spindle movement
Machine movements occur along axes that correspond to the direction of travel of the various machine slides.
On a vertical mill, the Z axis of a machine is always the spindle axis.The X and Y axes of a machine are perpendicular to the Z axis, with X being the axis of longer travel
There are two dimensioning systems used on part drawings intended for numerical control: datum and delta. Datum dimensioning references each dimension to a fixed set of reference points; delta dimensioning references each dimension to the previous one
Laboratory for Manufacturing Systems and Automation Dr. Dimitris Mourtzis 2.58 Vocabulary Introduced in this Chapter
Absolute positioning Absolute zero shift Cartesian coordinate system Closed-loop system Continuous-path systems Datum dimensioning Delta dimensioning Incremental positioning Machine Control Unit (MCU) Point-to-point systems Open-loop system Work coordinates
Laboratory for Manufacturing Systems and Automation Dr. Dimitris Mourtzis 2.59 References
1. Ann Mazakas, Manager of Technical Communications, DP Technology, ‘’The Art of Automation’’, courses materials of ESPTRIT World Conference on CNC
2. Chryssolouris G., «Manufacturing Systems: Theory and Practice», 2nd Edition, 2006, Springer-Verlag
3. http://blog.cnccookbook.com
4. http://www.dptechnology.com/
5. http://www.hsmworks.com
6. http://content.heidenhain.de
7. http://www.fanuc.co.jp
8. www.osxdaily.com
9. Kalpakjian S., «Manufacturing Engineering and Technology», 2nd Edition, 1992, Addison-Wesley Publishing company
10. Manufacturing, Engineering & Technology, Fifth Edition,S. Kalpakjian and S. R. Schmid
11. Mattson M., “CNC Programming, Principles and Applications”, Delmar, 2002
12. Moriwaki T., “Multi-Functional Machine Tool”, CIRP Annals Manufacturing Technology, Vol. 57/2, 2008, pp. 736-749
Laboratory for Manufacturing Systems and Automation Dr. Dimitris Mourtzis 2.60 References
13. Seams W., “Computer Numerical Control, Concepts & Programming”, 4th Edition, Delmar, 2002
14. Norman Bleier, Siemens engineering manager Article From: 9/9/2005 Modern Machine Shop,
15. Γ. Χρυσολούρης, «Συστήματα Παραγωγής Θεωρία και Πράξη» Μέρος Ι και ΙΙ, Εκπαιδευτικές Σημειώσεις, Πανεπιστήμιο Πατρών, 2001,
16. Γ. Χρυσολούρης, Δ. Μούρτζης, Κ. Τσίρμπας, Σ. Καραγιάννης, “Ορθογωνική Κοπή”, Εκπαιδευτικές Σημειώσεις, Πανεπιστήμιο Πατρών, 2000
17. Γ. Χρυσολούρης, Δ. Μούρτζης, και άλλοι, “Εργαστήρια Μηχανουργικής Τεχνολογίας Ι και ΙI”», Εκπαιδευτικές Σημειώσεις για το εργαστήριο του αντιστοίχου μαθήματος, Πανεπιστήμιο Πατρών, 2008 (4η Έκδοση)
18. Δ. Μούρτζης, “Αριθμητικός Έλεγχος Εργαλειομηχανών” Εκπαιδευτικές Σημειώσεις, Πανεπιστήμιο Πατρών, 2011 (3η Έκδοση)
19. Πετρόπουλου Π.Γ., «Μηχανουργική Τεχνολογία – ΙΙ. Τεχνολογία κατεργασιών κοπής των μετάλλων», 1998, Εκδόσεις Ζήτη
20. Σύγχρονες μέθοδοι κατεργασίας υλικών και προγραμματισμός με ΗλεκτρονικόΥπολογιστή(Η/Υ),Δ. Μούρτζης ,Κ. Σαλωνίτης
Laboratory for Manufacturing Systems and Automation Dr. Dimitris Mourtzis 2.61