Bài tập CNC exercises

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CNC Tutorials and Exercises

This tutorial gives examples of absolute co-ordinates and incremental co-ordinates.Absolute Co-ordinates

The code G90 is used to select this type of programming

Before programming commences the points on the path to be machined are definedrelative to the workpiece datum:

Examples of these co-ordinates are shown in the first table on the next page

Tutorial 1: X and Y Coordinate Calculation

-Absolute and Incremental Co-ordinates

Y+

B C

-2 -3 -4 -5 -6 -7 -8 -9 -10

1 2 3 4 5 6 7 8 9 10

G

H

ORIGIN X0 Y0

POINT DATUM A B C D E F G H

The Z axis is the vertical axis and the datum used is normally the surface of the work

Z is positive when moving away from the surface and negative when moving towards

or into the surface

Incremental Co-ordinatesThe code G91 is used to select this type of programming

The points on the path to be machined are defined relative to the previous position.The points for the example on the previous page are shown in the table below

The Z axis is again the vertical axis, and the points are defined relative to the previousposition; positive when moving away from the surface and negative when movingtowards or into the surface

Exercise 1 : Calculation of Co-ordinates

Tabulate the positions of the points A to H shown in the illustration below:a) in absolute co-ordinates

b) in incremental co-ordinates

B C

-1 -2 -3 -4 -5 -6

1 2 3 4 5 6

X-This tutorial illustrates the use of the G01 code; cutting takes place in a straight line

at a controlled feed rate

Consider the component illustrated below; it is required to mill the two L shaped slots

Absolute Co-ordinatesThe absolute co-ordinates of the points are shown in the table below:

X Y

PREP FUNCTION

MISC

FEED RATE SPINDLE SPEED

NOTES

N10 G90N20 G71N30 X0 Y0 Z25N40 M03 S1500N50 X15 Y15 Z2N60 G01 Z-2 F125N70 G01 X15 Y35 F125N80 G01 X45 F125N90 Z2

N100 X65N110 G01 Z-2 F125N120 G01 Y15 F125N130 G01 X35 F125N140 Z2

N150 M05 X0 Y0 Z25N160 M30

Incremental Co-ordinatesThe incremental co-ordinates for the component are shown in the table below.Using these co-ordinates the program can be written as shown as follows:

DUET PROGRAMMING SHEET-MILLING

PREP FUNCTION

MISC FUNCTION CO-ORDINATES

FEED RATE SPINDLE SPEED

NOTES

1 Examine the program listed

2 Enter the program into the computer

3 Simulate the machining process and compare the movement of the cutter with theprogram

STOP SPINDLE RAPID TO

POINT TOOL CHANGE A B C D E F G H

1 For the component shown below, use a programming sheet and write a program forthe cutter to cut a groove along the path from A to H

2 Enter your program into the computer and give it a test run

3 Edit your program if necessary

E F

H G

Exercise 2: Linear Interpolation - Absolute Co-ordinates

Enter Z incremental distance from the face of the workpiece to the bottom of the hole)

Tool change at:

Tool used:

X -5, Y -5 5mm Slot Drill

4 x Ø 5 holes

10 deepHole Drilling and Pocket Milling

PREP FUNCTION

MISC

FEED RATE SPINDLE SPEED

G88 Rectangular MillingThis code mills a rectangular pocket The tool should be positioned 2mm above thepocket centre on the previous line.

Enter

X the side length of the rectangle

Y the side width of the rectangle

Z the distance from the workpiece face to the bottom of the pocket

J the number of cuts

F feed rateThe tool returns to its start point when the cycle is complete

The program for the above component is shown on the following page:

40 80

DUET PROGRAMMING SHEET-MILLING DRAWING

NUMBER

TITLE PROGRAMMED BY

SHEET No OF

SEQUENCE No.

PREP FUNCTION

MISC

FEED RATE SPINDLE SPEED

NOTES

1 Examine the two programs

2 Enter each program into the computer

3 Simulate the machining process for each program and compare the movement of thecutter with the program

For the component shown below:

1 Tabulate the co-ordinates

2 Use a programming sheet and write a program to

• drill the holes

• mill the square pocket(For tool changing, refer to Section 9.9)

3 Enter your program into the computer and give it a test run

4 Edit your program if necessary

X 0, Y O

Exercise 3: Canned Cycles - Programming a Tool Change

- and can be complete (90°) or partial (less than 90°), within a single quadrant:

After entering G02 the following extra information is needed:

X - Y Plane X - Z Plane Y - Z Plane

Tutorial 4: Circular Interpolation

-Clockwise and Counter-clockwise

This tutorial illustrates the use of the code G02 (clockwise circular interpolation) andG03 (counter clockwise circular interpolation)

Circular Interpolation – ClockwiseThis code moves the table in such a way that a clockwise circular arc is cut in the workwithin a single quadrant The cutter is positioned at the start of the arc on the previousline of the program

The arc may be in the X – Y, X – Z or Y – Z plane:

I value – the distance from the arc centre (incremental) to the tool position at the start

of the cuts measured along:

a) the X axis when cutting in X-Y or X-Z planeb) the Y axis when cutting in the Y-Z plane

J value – the distance from the arc centre (incremental) to the tool position at the start

of the cut measured along:

a) the Y axis when cutting in the X-Y planeb) the Z axis when cutting in the X-Z or Y-Z planeNote that I and J are unsigned values

Alternatively the radius of the arc can be entered as the I value and J left blank.Clockwise Circular Interpolation (G02)

a) Single quadrant 90° arc in the XY plane

To mill from A to B arc of centre C – clockwise interpolation (G02)

b) Single quadrant partial arc in the XY plane

To mill from A to B arc of centre C clockwise interpolation (G02)

10 R

30 o

X Y

Circular Interpolation – Counter-clockwiseThis code moves the table in such a way that a counter-clockwise circular arc is cut inthe work within a single quadrant The cutter is positioned at the start of the arc on theprevious line of the program.

As with the G02 code, the arc may be in the X-Y, X-Z or Y-Z planes

- and can be complete (90°) or partial (less than 90°), within a single quadrant:

After entering G03 the following extra information is needed:

X value –

Y value –

Z value –

I value – the distance from the arc centre (incremental) to the tool position at the start

of the cut measured along:

a) the X axis when cutting in X-Y or X-Z planeb) the Y axis when cutting in the Y-Z plane

two of these values specify the co-ordinates of where the curve finishes, the othervalue must be left blank

X - Y Plane X - Z Plane Y - Z Plane

J value – the distance from the arc centre (incremental) to the tool position at the start

of the cut measured along:

a) the Y axis when cutting in the X-Y planeb) the Z axis when cutting in the X-Z or Y-Z planeNote that I and J are unsigned values

Alternatively the radius of the arc can be entered as the I value and J left blank.Counter-Clockwise Circular Interpolation (GO3)

a) Single quadrant 90° arc in the XY plane

To mill from B to A arc of centre C – counter-clockwise interpolation (G03)

b) Single quadrant partial arc in the X-Y plane

To mill from B to A arc of centre C

To calculate co-ordinates of B, construct triangle BCD

CD = 10 x cos60 = 10 x 0.5 = 5

BD = 10 x sin60 = 10 x 0.866 = 8.66Note that I and J are unsigned values

10 R

30 o

X Y

Tool change at: X -5, Y -5

E F G

Cutter: Ø 5 Arcs: 2 deep Radius: 10

The program for the above component is shown on the following page

Note:

Blocks N70 to N90 define the arc in terms of its radius

Blocks N100 to N120 define the arc in terms of the co-ordinates of its centre

DUET PROGRAMMING SHEET-MILLING DRAWING

NUMBER

TITLE PROGRAMMED BY

SHEET No OF

SEQUENCE No.

PREP FUNCTION

MISC

FEED RATE SPINDLE SPEED

1 Examine the program

2 Enter the program into the computer

3 Simulate the machining process and compare the movement of the cutter with theprogram

TUT4

1 1

For the cutter path shown above:

1 Tabulate the co-ordinates A to J

2 Use a programming sheet to write a program for the path of the cutter centre line

3 Enter your program into the computer and give it a test run

4 Edit your program if necessary

D A

Tool change at: X 0, Y 0

E F G

Material: 15mm deep Plastic Slot: 5 wide, 2 deep

H J

1 Mill the steps (8mm diameter cutter)

2 Drill the holes (5mm diameter drill)

3 Mill the 30mm diameter pocket (10mm diameter cutter)Note: Tool Changing

The program for the above component illustrates the method of programming a tool change; block N120moves the cutter to a tool change position and block N130 calls up a new tool

M06 denotes a tool change

-I gives the tool type,

J the tool diameter, and

This tutorial uses some cutters not supplied with the machine It illustrates how toolchanges can be made and a number of operation can be carried out on one component.Sequence of Operations

Tool change at: X 0, Y 0

Tutorial 5: Combining Operations and Tool Changing

DUET PROGRAMMING SHEET-MILLING

PREP FUNCTION

MISC

FEED RATE SPINDLE SPEED

DUET PROGRAMMING SHEET-MILLING

PREP FUNCTION

MISC

FEED RATE

SPINDLE SPEED

NOTES

1 Examine the program

2 Enter the program into the computer

3 Simulate the machining process and compare the movements of the cutters with theprogram

RAPID TRAVERSE 2MM ABOVE

SPINDLE OFF, RAPID FEED TO

TUT 5

For the component shown above:

1 Write down the sequence of operations required to produce the part

2 Tabulate the co-ordinates required

3 Use a programming sheet to write a program

4 Enter your program into the computer and give it a test run

5 Edit your program if necessary

80

5mm Groove O25

A subroutine can be regarded as a personalised canned cycle for use in a program whichhas repetitive shapes.

The illustration below shows such a component; the milled grooves can be programmed

The mode of programming is now changed: the line number automatically reverts to

10 and co-ordinate entry, if absolute, becomes incremental

There is no restriction on the range of G codes (except G25) and all the canned cyclesare available

Material:

Tool change at:

15mm thick Plastic

X 0, Y 0 Grooves: 5 wide x 3 deep

B A

A,B: start positions for subroutines

M44 subroutine terminate

On entry of the signal to end the subroutine the line numbers of the original programare restored and the current absolute position of the tool is shown in the X, Y and Zcolumns If the program was previously being entered with absolute co-ordinates, itreverts to its former style

M45 subroutine call

On entering M45 a prompt is made to input the reference number of the subroutine

in the I column A search is made in the subroutine file and the first file found withthat reference number is executed

Note:

Care is needed when allocating subroutine identification numbers

The program for the previous illustration shows subroutine blocks S10 onwards beingtyped into the system immediately after block N50 After this the cutter is repositionedbefore calling up the subroutine and completing the program

Editing of subroutinesThe program EDIT facility can be used If this is brought into use the program isdisplayed for editing but a further option (SUB) is offered:

If SUB is chosen, then the subroutine is displayed for editing

1 Examine the program

2 Enter the program into the computer

3 Simulate the machining process and compare the movements of the cutters with theprogram

N10 90 N20 71

PREP FUNCTION

MISC

FEED RATE SPINDLE SPEED

NOTES

20 30

For the component shown above:

1 Tabulate the co-ordinates required

2 Use a programming sheet to write a program; the L shaped grooves can be programmedusing a subroutine

3 Enter your program into the computer and give it a test run

4 Edit your program if necessary

2 1

4

3

This tutorial demonstrates how a program written as a subroutine can be reflectedabout the X axis or about the Y axis or about both the X and the Y axes It supportsboth linear and circular interpolation

Consider the shape shown in illustration A, which has been drawn in the sequence

1-2, 2-3, 3-4 and 4-1

Tutorial 7: Mirror Images

Alternatively, if the X co-ordinates are kept constant and the Y co-ordinates reflected,the outcome is:

4 3

with the 1-2, 2-3, 3-4 and 4-1 sequence maintained

If the X co-ordinates are reflected with Y co-ordinates unchanged, the shape becomes:

If both the X and y co-ordinates are reflected the result becomes:

If a program which calls a subroutine containing the original shape is written, then any

or all of the above variations may be implemented The ‘as programmed’ case isachieved by the usual method of calling the subroutine The mirror facility isaccomplished by inserting a line in the program after positioning the tool at the start

of the cycle but prior to calling the subroutine

The entry is:

G value 28

X value 0 or 1

Y value either 0 or 1For example

To reflect the X co-ordinate with Y unchanged:

For mirror image programming incremental co-ordinates must be used

2 1

4

3

D

In the program for the above illustration, note that blocks S10 to S80 onwards are typedinto the system immediately after block N40

1 Study the program

2 Enter the program into the computer

3 Simulate the machining process and compare the cutter movements with the program

50 80

10

DUET PROGRAMMING SHEET-MILLING

PREP FUNCTION

MISC

FEED RATE SPINDLE SPEED

DUET PROGRAMMING SHEET-MILLING DRAWING

NUMBER

TITLE PROGRAMMED BY

SHEET No OF

SEQUENCE No.

PREP FUNCTION

MISC

FEED RATE SPINDLE SPEED

Exercise 7: Mirror Images

50 80

20

For the component shown above:

1 Write a program to machine the grooved triangles using the mirror image technique

2 Enter your program on the computer and simulate the cutting action

3 Edit your program if necessary

The manufacture of the component shown below uses the G86 and G87 canned cycles

Tutorial 8: Further Canned Cycles

-Pitch Circle Drilling and Dish Milling

The manufacture of the component shown below uses the G86 and G87 canned cycles

G86 Canned Cycle – Pitch Circle Diameter DrillingThis code produces a series of holes on a circular pitch

The tool is positioned at a 2mm stand off point above the centre of a hole on the PCD

on the previous line

Enter:

X – number of holes to be drilled (must not be less than two)

Z – incremental distance from the face of the workpiece to the bottom

of the hole

I – the distance from the circle centre (incremental) to the first hole

measured along the X axis

J – as the I value but measured along the Y axis

F – Feed rate

G87 Canned Cycle – Dish MillingThis code will mill out a circular dish-shaped pocket The dish is produced by cutting

a series of concentric circular pockets starting at X diameter, with successive circlesgetting deeper as they reduce in diameter, until the last circle is at Y diameter and depth

Z The total number of circles is J Increasing the number of cuts will produce a betterdish but the time taken will be greater

Enter

X – the top diameter

Y – the bottom diameter of the dish

Z – The incremental distance from the face of the workpiece to the

bottom of the dish

I – For a complete dish enter zero, or for hollow circles (an outline

around the edge) enter a value

J – is the number of cuts to produce the dish

F – the feed rate at which the dish is to be milledThe cycle is best used in two stages For the first stage enter I = 0; this will rough out

a pocket, leaving a stepped profile On calling the code again for the second stage enter

a value for I = 1; this will mill around the circumference of the circles, thus smoothingthe profile

The program for the illustration shown earlier is shown on the following page

1 Study the program

2 Enter the program into the computer

3 Simulate the machining process and compare the cutter movement with the program

4 View the component in 3D