Upload
muhammad-eka
View
230
Download
0
Embed Size (px)
Citation preview
7/31/2019 1 - Introduction to CNC
1/21
Computer Numerical ControlledMachining
7/31/2019 1 - Introduction to CNC
2/21
Conventional
Machine
CNC Machine
Motion ControlThe Heart Of CNC
7/31/2019 1 - Introduction to CNC
3/21
Numerical Control Programming
CNC user must be able to view the machine
tool from two distinctly different
perspectives
First as a programmer.
Secondly, when machining the component.
7/31/2019 1 - Introduction to CNC
4/21
A programmer needs to be
comfortable with:
the machines most basic components.
the direction of the machines axes.
any additional accessory equipment. and finally be aware of what programmable
functions are included.
7/31/2019 1 - Introduction to CNC
5/21
From the machine tool manual
you should find answers to:
What is the machines maximum RPM?
What is the spindle and drive axis motorhorsepower?
What is the maximum travel distance ofeach axis?
How many tools can the machine hold?
What is the machines rapid traverse rate?
What is the machines fastest cutting speed?
7/31/2019 1 - Introduction to CNC
6/21
Machined Example
7/31/2019 1 - Introduction to CNC
7/21
Axis Reference Point
Most machine tool builders make the
reference position the extreme plus side of
each axis.
Note: always make sure that all the axes are
set to zero (0,0,0) before you carry out any
operation on any machine tool.
7/31/2019 1 - Introduction to CNC
8/21
Absolute Versus Incremental Motion
In the absolute mode, theend points for allmotions will be specifiedfrom the program zeropoint. Assign By G90
In the incremental mode,end points for motionsare specified from the
tool's current position,not from program zero.Assign by G91
7/31/2019 1 - Introduction to CNC
9/21
+ve X table
direction
Machine
table ref.
Pt 0,0
-ve Y table
direction
Table movement from machine reference
point.
7/31/2019 1 - Introduction to CNC
10/21
Machine
table ref.
Pt 0,0
It is more convenient to think of the tool moving
around the component, than thinking of the table
direction when writing programs.
AB
C D
To move tool from A to B table needs to movein theve X direction, from B to C the table
moves in the Y +ve direction, and to move
from C to D the table moves in the +ve
direction.
7/31/2019 1 - Introduction to CNC
11/21
Vice position with respect to
machines set datum
7/31/2019 1 - Introduction to CNC
12/21
Controller Reference Setting
7/31/2019 1 - Introduction to CNC
13/21
7/31/2019 1 - Introduction to CNC
14/21
Program Writing
What we need to know:
Where the tool starts from.
Where the tool moves to.
The tool path.
How it gets there.
When the machine needs to start and stop.
When coolant is turned on or off.
What tools are available.
How is the workpiece held.
7/31/2019 1 - Introduction to CNC
15/21
Program Makeup
Programs are made up of commandsand commands are made up of wordsor LeterO - Program number (Used for program identification)N - Sequence number (Used for line identification)G - Preparatory function (See below)
X - X-axis designationY - Y-axis designationZ - Z-axis designationR - Radius designationF - Feedrate designationS - Spindle speed designationH - Tool length offset designationD - Tool radius offset designation
T - Tool DesignationM - Miscellaneous function
The preparatory function (G)specifies is commonly used toset modes.
Miscellaneous functions (Mwords) allow a variety ofspecial functions.
7/31/2019 1 - Introduction to CNC
16/21
Tool Setting
7/31/2019 1 - Introduction to CNC
17/21
Common Mistakes
Spindle not on before cutting.
Coolant not turned on during machining.
Toolpaths out of order. Eg. holes weretapped before they were drilled.
Incorrect tool installation.
Improper feed and speed entered. Start program in wrong place.
7/31/2019 1 - Introduction to CNC
18/21
Simple Program Example 1
Start and end
50
45
8
34
29
7/31/2019 1 - Introduction to CNC
19/21
Program start
N10 G40 G49 G90; Safe line
N20 M06 T10 ; tool change sequence
N30 G43 H10; tool length offset N40 G00 X410.0 Y-192.0 Z-340.0;
work ref. Pt.
N50 M03 S2000;turn spindle on
Typical start to NC program ie. Set the
machine parameters.
7/31/2019 1 - Introduction to CNC
20/21
Tool path
N60 G91 G00 Z-4.0;incremental
N70 G01 Z-9.0 F100;
N80 Y45.0;
N90 X50.0;
N100 Y-45.0; N110 X-50.0;
N120 G00 Z15.0; clear workpiece
7/31/2019 1 - Introduction to CNC
21/21
Typical end of program.
N130 MO5; stop spindle
N140 G28 X0 Y0 Z0; return to machine ref. pt.
N150 M30; end program