Linear Pattern G72.2

We have seen how the circular copy of the program is done. Now we will see how the linear of the program is copied. 

Just like a copy of a program circular is done in a linear copy. 

Only a few changes are made in the circular copy, the rest is just like the circular program. So let's see the linear copy of the program.

The programming format is

G72.2...P...L...I...J...R...

L is a no. of program in linear(compulsory)

I is program shift in X direction
J is program shifting in Y direction

Main Program

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O0001

N1 G0 G90 G54 X0 Y0 M3 S200 (Point A)

N2 Z5

N3 G01 Z0 F300

N4 X10 Y25 (Point B)

N5 G72.2 P0002 L3  I50

N6 G90 G01 X180 Y25 F300

N7 G0 Z100

N8 M30

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Subprogram

O0002

N1 G91 G01 X20  (Point C)

N2 Y30 (Point D)

N3 X30 (Point E)

N4 Y-30 (Point F) 

N5 M99

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Circular Milling Using Macro Variable

All parameter in form of variable while you make a program of circular milling. 

You just have to set only cutter diameter and hole diameter. This program is automatically calculate path of rotation.

Now see step by step what i did.

Hole Milling

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O0001

N1 #100=12 (Hole Diameter)

N2 #101=8 (Cutter Diameter)

N3 #102=#100 - #101 (Center Distance)

N4 #103=#102/2 (Calculation)

N5 #104=1 (First Depth of cut)

N6 #105=1 (Global Depth of cut)

N7 #106=15 (Total Depth of cut)

N8 G0 G91 G28 Z0

N9 G90 G54 X0 Y0 M03 S2000

N10 Z5

N11 WHILE[#104LE#106]DO1

N12 G1 Z-#104 F200

N13 X-#103

N14 G03 X#103 I#103

N15 X-#103 I-#103

N16 #104=#104+#105

N17 END1

N18 G01 Z5 F200

N19 G0 G91 G28 Z0

N20 M05

N21 M30

%

Here i make only program for hole milling while i using climb milling, but whenever you make a program for boss milling you should change parameter of above program. 

There are only two changes made in program in line no. 3 and line no. 14.

Now we are using G02 for climb boss milling and  equation should be like this  #102=#100+#101 instead of subtraction. 

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Loop: While...Do...

While Do loop is used when a pass in a program is constantly repeat.

There are main three logic are used in this loop.

LT: Less than

LE: Less than or equal to

GT: Greater than

GE: Greater than or equal to

For example

from XOYO (Left Front Corner)to

N01 X200

N02 Y100

N03 X0

N04 Y0

Here shown program is rectangular single planner pass at some height. Now this pass is continuously repet in at some depth. So the conventional program like. If depth of cut is 5 mm(only for understanding) and depth is 15 mm than

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O0001

N1 G0 G91 G28 Z0

N2 G90 G54 X0 Y0 M03 S2000

N3 Z5

N4 G01 Z-5 F200

N10 X200

N11 Y100

N12 X0

N13 Y0

N14 Z-10

N15 X200

N16 Y100

N17 X0

N18 Y0

N19 Z-15

N20 X200

N21 Y100

N22 X0

N23 Y0

N29 Z5

N30 G0 G91 G28 Z0

N31 M05

N32 M30

%

So now the While...DO... program is done in such a way.

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O0001

#100=5 (First depth of cut variable)

#101=5 (Global depth of cut variable)

#102=15 (Total Depth)

G0 G91 G28 Z0

G90 G54 X0 X0 M03 S2000

WHILE[#100LE#102]DO1 (Looping below pass until #100 does not get less than or equal to #102)

G1 Z-#100 F200

X200

Y100

X0

Y0

#100=#100+#101 (additional for next cut)

END1 (loop end)

Z5

G0 G91 G28 Z0

M05

M30

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Simulation

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Simple Calculation for Hole and Boss Milling

During hole and boss milling there are center distance of cutter axis and hole/boss center is very important.

This CD is defined the pitch circle diameter of cutter rotation. One condition is affect on hole milling that the cutter diameter is greater than half of hole diameter and stating point of program must be at center of hole/boss.

Formula of hole milling from the fig.

CD= (Hole Diameter - Cutter Diameter)/2

For Boss milling

CD= ( Boss Diameter + Cutter Diameter)/2

For example

The hole is 12mm of Dia. and cutter Dia. is 8mm than...

• CD = (12-8)/2
• CD = 2

Program:

N01 G01 X2 F200
N02 G03 X-2 R2
N03 X2 R2

And if Boss dia. is 15mm and cutter dia. 10mm than

• CD =(15+10)/2
• CD = 12.5

Program:

N01 G01 X-12.5 F200
N02 G02 X12.5 R12.5
N03 X-12.5 R12.5

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Circular Pattern G72.1

Often the program comes in a circular pattern. Which often seems to be repetitive. Let's learn how to copy it instead of doing it. 

When a program is rotated in a circular fixed degree, the G72.1 is used. You see how the subprogram is linked to the Maine program. In the same way, it is also linked to the subprogram and to copy it in a fixed degree.

The programming format is 

G72.1...P...L...X...Y...R...

L is a no. of program in rotation(compulsory)

R is degree between two program(compulsory)

Note : The program gets easy if your starting point of program is same with end point of program after completion of rotation copy.

G16,G17, G18, G19, G28, G51, G51.1 must not be specified in this program.

Main Program

%
O0001
N1 G0 G90 G54 X65 Y-37.53 M3 S200 (Point A)
N2 Z5
N3 G01 Z0 F300
N4 X31.681 Y-18.291 (Point B)
N5 G72.1 P0002 L6 R60 X0 Y0
N6 G90 G01 X65 Y-37.53 F300 (Point A)
N7 G0 Z100
N8 M30
%

  
Subprogram

O0002
N1 G91 G02 X5.20 Y3 R6  (Point C)
N2 G01 X3.12  (Point D)
N3 X16.02 Y10.23  (Point E)
N4 G03 Y10.11 R6  (Point F)
N5 G01 X-16.02 Y10.23  (Point G)
N6 X-3.12   (Point H)
N7 G02 X-5.20 Y3 R6   (Point I)
N8 M99
% 

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Macro Programming

macro programming is not duffer from the standard programming of CNC mill, its just used only some mathematical formulas and equations.

For macro programming learn you should have sound knowledge about the standard programming and good practical experience. The basic fundamental of macro is old G and M codes. There are nothing to new here i told only some kind of formulas are used.

In every new technologies the program get shorter and easy to use by operators. By the macro programming program gets shorten and flexible. The only one program held lot of data.

This macro condition i only used in fanuc advanced controller, i don't know others controller.

For the macro programming development there are basic three areas to understand

Variable: Stored value 

this is a main parameter of macro. Its stored the predefined value. In macro programming real data replaced by the variable

Logical Formulas: Looping

You might have heard that people of computer engineering are programming software applications or websites. Also know that If.....else is also used in it. Its called logical function.

For simple example: If I have a job I will call you. In this statement condition is i have job otherwise i will not call you. Such types of logic are used in macro for looping.

Function and constant: significant numbers

Function are used to calculate the formula and constant like basic math constant is л and its value is 3.14

The simple Program for macro is

%

O0001

N1 #100=500                ⇐ (Variable defined)

N2 #101=250                ⇐ (Variable defined)

N3 G0 G90 G54 X0 Y0

N4 Z10

N5 G01 Z0 F440

N6 Y50 F#101                                       ⇐ (Variable applied)

N7 G03 Y-50 I0 J-50 F#100                  ⇐ (Variable applied)

N8 Y50 I0 J50 F#101                            ⇐ (Variable applied)

N9 G01 Z50

N10 M30

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Simulation of simple macro programming.

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Heat Treatment: Annealing

Annealing is made to increase machining abilities and to soften the metal. Generally the purpose of annealing is as follows.

To refine the grain size.

To increase mechanical properties such as strength and ductility.

During casting, to remove those holes that are trapped in metal.

To make changes to the magnetic and electrical properties.

Annealing are processed in two types

Full Annealing

To soften the metal, Full annealing to refine the grain structure and relieve the strain.

In this process hypoeutectoid steel heated over 32 to 50 degree above than the upper critical temperature and for hypereutectoid steel heated over the 32 to 50 degree above than the lower critical temperature.

Hold this temperature until internal structure is not change, this maturation period is 1 mm per thickness square area 3 to 4 minutes.

And in the furnace it slowly cools down.

Process Annealing

Process annealing is used to remove internal stress due to previous setup.

In this process, the steel is heated to a lower temperature than the lower critical temperature.  Keeping it cool for a while at a temperature, it is cooled gradually.

This process increases in machinability.

It happens a recrystallization in steel.

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Canned Cycle: Tapping

Tapping is most common word for industrial use. Tapping is crucial parameter of production line system. The tap is used for the tapping. Tapping means make a thread in to the hole.

Generally small to medium size of tap available in market. For any special size or any higher size according to the pitch of threading thread mill to be used.

For the tapping, you have to knowledge about pitch and TPI. So, the new word is pitch and TPI ...Now, What is pitch?, The pitch defined as the center distance between two nearby thread, 

Now, What is TPI?, TPI means thread per inches. In the picture below you will understand exactly.

From shown into the fig the total length of thread is 25.4mm and pitch is 1.5mm, So the total thread per inch 

25.4 / 1.5 = 16.93 ≈ 17 TPI

Now, tapping cycle based on the pitch, without breaking a tap tapping needs relation between RPM, given feed and Tap pitch. Here the relation of 

Feed = RPM x Pitch

If your pitch is 1.5mm and RPM is 30 than feed must be 45 mm/min, if you change the feed without consideration of pitch and RPM, The tap gets broken. The format of tapping cycle like a drill cycle, just G83 replaced by G84.

For the tapping make hole first, According to the thread, there are many standards available. It gets differ by its standard, here are some data of standard for general use.

            G98  G84 X....Y....R....Z....Q....F....

Example of Tapping M10 x 1.5 Tap

N100 G0 G91 G28 Z0

N102 G0 G90 G54 X15 Y25 M03 S30 

N104 Z50

N106 G98 G84 X15 Y25 R5 Z-10 Q3 F45

N108 X50 Y40

N110 X60 Y20

N112 G80

N114 G0 G91 G28 Z0

N116 M05

N118 M30

Rigid tapping does not need a Peck its go throughout to the hole without pecking. Its depends on material types of TAP and workpiece. 

This program has no need to simulation. Its simulation like drill program. You can view here

Thank you

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Normalizing of Steel

The finished product of casting is processed to get good properties by heat treatment. Certain properties or desirable condition is obtained by heating or cooling of the metal by without any changing of chemical composition in solid state. 

The metal consists of micro structure of grain particals. It is a mechanical and metallurgical process in which, By the changing of grain size or micro structure we can obtain some challenging properties of metal.

Following properties to be obtained by the heat treatment process.

• To Soften metal.
• To increase the hardness and strength of metal.
• To change the magnetic properties.
• To Increase the resistance of wear.
• To change grain size.
• To change the electric properties.
• To Improve machinability and quality of casting.

Considering its different properties in way of engineering, its 1st topic is normalizing 

Normalizing

Normalizing process is used to soften the metal. By the normalizing we can achieve highest machinability and improve tensile strength. By this improvement in electric and magnetic properties of metal.

The cold working process like hammering, knockout, bending causes strain on metal, its remove by normalizing.

It used to refine grain structure and uniformity of grain size and composition. It makes the material brittle and unreliable. This process less expensive than annealing.

For Hypo eutectoid steels the heating temperature is 45 to 50 degree above to its upper critical temperature and for Hyper eutectoid steels, the temp. is 45 to 50  above to its lower critical temp. The metal is kept for a while at this temperature and then cooled down by air.

The upper and lower critical temp of steed depends upon the total percentage of carbon consists in steel.

For best quality and machinability it performed after forging and casting.

In Hypo-eutectoid steel less than 0.8% of C in its composition. It is composed by pearlite and α-ferrite and Hyper-eutectoid steel has between 0.8% and 2% of C, composed by pearlite and cementite. It is very important to understand Iron-Carbon phase diagram to understand the Hypo-eutectoid and Hyper-eutectoid.

This process provides a uniform structure consisting of ferrite and pearlite for hypoeutectoid

steels, and for hypereutectoid steels pearlite and cementite.

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Climb and Conventional Milling

The basic concept of machining in any CNC machine like CNC Lathe, Milling, Wirecut, EDM, etc. is better surface finishing with less cycle time and lowest cost. Many technical terms are affect for this. Cutting direction is one of those. 

Cutting direction depends upon the rotation of flute. Many people do not even that how to set preferred cutting direction. 

There are two types of cutting direction: Climb milling and Conventional milling. The difference between climb and conventional is relation between cutting direction means direction of feed and rotation of flutes of milling cutter. Lets take a small definition of climb and conventional milling and when to use it. Also in CAM software option for the climb, conventional  and mix.

Climb Milling

Climb Milling also known as down milling. When the milling cutter comes to the workpiece the first flute removes maximum amount of material. As a result when rest flues comes to the workpiece, it gets less material than a first flute. So it decrease the chance of recutting and increase the tool life.

Due to removing of maximum material cause more chip. In climb direction chip is go away from the workpiece and milling cutter and removed behind the cutter. The rest of flutes do the smooth surface.

For better surface area and better finishing climb cut is mostly used. Climb cut reduce the wear of tooling and also reduce the vibration when L/D ratio is high. It generates less heat of tool. You can view the climb milling in below figure.

Conventional Milling

Conventional Milling also known as up milling. When the milling cutter arrives on the workpiece, the first flute cut off the material less than the last flute. Due to increase the vibration in milling cutter.

As a result, a chip is collected by the cutter and takes time to remove it. As the chip is filled in a cutter, finishing decreases. And when the chip gathers, its generates heat in the cutter. It reduce the life of cutter and increase the chances of breakdown. You can view the Conventional milling in below fig.

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G02 G03: Interpolation Programming with I and J

In previous post we discussed about interpolation with R. To understand this post you have to knowledge about R

In this case R is replace by I and J

Lets see how to program with I and J. first of all you should know about what is I and J. 

The distance between center of arc and start point of arc in X direction is shown by I and The distance between center of arc and start point of arc in Y direction is shown by J. But Its value is positive and also negative, So how to be determined it

In below picture you can understand how to be calculate I and J value.

If direction from start point of arc to the center of Arc is in X axis +VE than 'I' is +VE if -VE than I' is -VE. 

Similarly start point of arc  to the center of Arc is in Y axis +VE than 'J' is +VE if -VE than 'J' is -VE

Lets take an simple example 

Here start point of arc is X60 Y50 and the distance between center of arc and start point of arc in X direction is 40 and in Y direction 30.

• G01 X60 Y50 F200
• G03 X41.794 Y65 I-40 J-30

Here both direction are negative so I and J value is Negative.

We still have an entire program of Interpolation in form of I and J

N100 G0 G91 G28 Z0

N102 G90 G54 X0 Y0 M03 S2000

N104 Z5

N106 G01 Z0 F100

N108 Y75

N110 G02 X25 Y100 I25 J0

N112 G01 X50

N114 G02 X100 I25 J-20

N116 G01 X200

N118 G02 X225 Y75 I0 J-25

N120 G01 Y60

N122 G03 X250 Y35 I25 J0

N124 G01 Y10

N126 G02 X240 Y-0 I-10 J0

N128 G01 X0

N130 Z5

N132 G0 G91 G28 Z0

N134 M05

N136 M30

You can view this program by this simulation.

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G02 G03: Interpolation Programming with R

For interpolation programming G02 and G03 code are use.

G02 use for Clockwise Interpolation and G03 use for Counter Clockwise Interpolation. For better understand you can view below picture.

when programming is in arc or radius, it also require a feed like a G01 liner Interpolation.

This code require a selection of plane for example

G17 XY Plane selection

G18 XZ Plane Selection

G19 YZ Plane Selection

If feed rate is defined by previous G01 than its not require.This method requires synchronization of both axes, otherwise the finishing does not occur.

This method can only be used for arc less than 360 degree. This program is made by putting the value of the radius (R) along the last coordinate  of the arc.

The Simple format of Interpolation:

For example

G17 is by default selecion  in VMC and HMC Machine.

For Counter Clockwise from X50Y0 to X0Y50

• G01 X50 F200
• G03 X0 Y50 R50

For Clockwise from  X0Y50 to X50Y0

• G01 Y50 F200
• G03 X50 Y0 R50

We still have an entire program of Interpolation.

N100 G0 G91 G28 Z0

N102 G90 G54 X0 Y0 M03 S2000

N104 Z5

N106 G01 Z0 F100

N108 Y75

N110 G02 X25 Y100 R25

N112 G01 X50

N114 G02 X100 R30

N116 G01 X200

N118 G02 X225 Y75 R25

N120 G01 Y60

N122 G03 X250 Y35 R25

N124 G01 Y10

N126 G02 X240 Y-0 R10

N128 G01 X0

N130 Z5

N132 G0 G91 G28 Z0

N134 M05

N136 M30

You can view this program by this simulation.

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