machining on cnc machines is controledu12134.fsid.cvut.cz/podklady/tcam/ccam - 2015...machining on...
TRANSCRIPT
Machining on CNC machines is controledby a NC code.
NC code is a list of instructions for themachine and also for the operator. Instruction are executed in time order.
NC code must have a specific format sothat the control system of machine is ableto read it.
The tool in machine is moving in
workspace.
The position of the tool is given by
coordinates.
We are using different coordinate
systems.
If we set some coordinates in NC code,
the machine moves the tool to the
specified place.
Basic is orthogonal system
X
Y
Z
Z axis is usually axis of spindle a X
axis is the working axis, or the
longest!
XY
Z
Z axis is usually axis of spindle a X
axis is the working axis –
diameter!!!X
Z
To set the position we can add rotation
along the axes.
X
Y
Z
A
B
C
Second set of coordinatesU,V,W resp. P,Q,R etc.
Refernce point – a specific point on
machine with given coordinates. Not
always in the workspace of machine.
A special command G98
Tool is moving to specific coordinates
with given speed.
On its way it may enter the material and
perform machining
Ways how to define a movement
a) Absolute programing – position is in all
point expressed as a distance from zero-
point
b) Incremental programing – position is
expressed as a change from last postion
AbsolutG90 X0 Y0 Z50G0 X15 Y70 Z50G1 X15 Y70 Z0G1 X25 Y70 Z0G0 X25 Y70 Z50G0 X0 Y0 Z50
Incremental
G91
G0 X15 Y70 Z0
G1 X0 Y0 Z-50
G1 X40 Y0 Z0
G1 X0 Y0 Z50
G1 X-45 Y-70 Z0
1.
2.
3.
2.
3.
1.
Structure and form of NC code is
standardized by international standard -
ISO 6983 – Numeric control programs
formating
Differences between different control
system manufacturers and differences
between versions.
Lines (blocks)
Words
Word has a meaning and value
part
S 1500
ISO is standardized code (G – code)
Some manufacturers devoloped their own standard for NC code – native standard
Mazak – Mazatrol
Heidenhein – iTNC
Siemens - Sinumeric
Heading lines
Definition of relation between coordinatesystem of CNC machine and program, type of programing, work mode, workingconditions
Program body
Cutting and non-cuting moves, main program and subprograms, tool changes
Ending lines
Tool return to home point, change to first tool, coordinates reconstruction
Subprograms A link to another
then the followingline is entered intomain programm.
This subprogram isexecuted.
After finishing thisprogram we returnto main program a we contiue until endof mainprogram(M30)
Manual/Hand programing
Shopfloor programming
Automated programing
Editors are used. Program is writtenmanually (by hand) line after line.
Used for simple parts (but complex too)
Toolpath is exactly
defined
Program can be adjusted
to save time
Can use canned cyles
Can be parametrized
Used in mass production
We need to know the functions: (many more function exist)
Movement functions:
G00 rapid movement
G01 linear interpolation/movement
G02/03 circular interpolation
G40 diameter compensation off
G41 diameter compensation on /right handed
G42 diameter compensation on /left handed
Support and help functions:
M06 tool change
M03/04 spindle start CW/CCW
M05 program stop
M30 program end
Specilzed editors
Predator G-code editor
G Wizard Mikronex
Somewhere in between manual and
automated
Uses cycles with parameters
We have to edit these
parameters manually
But the NC code
is generated
automatically
No postprocessing
Control system use – programming on
machine
- No costs (together with machine)
- Fast use (macros)
- Time waste (program x work)
- Comfort (on machine x in office with PC)
- Shape limitationsHeidenhein
Work with the „sequential NC code
preparation“
Uses CAM (Computer Aided
Manufacturing) software
For all parts including complex shapes
We dont need to compute the toolpath
We need correct postprocessor
Partprogram – workpiece, material, cuttingconditions, tools…
Procesor – according to technology
CL data – virtual toolpathson virtual machine
Postprocesor – „translator“ for the specific CAM-control systém-machinecombination
NC code – toolpaths of a real tool on a realmachine
Partprogra
m
Proces
or
Postproces
or
CL-data
NC-kód
is Computer Aided Manufacturing(machining)
From simple 2-axis turning up to multiaxismachining
Feature or technologically oriented
Special types of CAM for special purpose
Live presentation
2D – just in two axis - turning
2,5D – two axis, but in layers – not
simultaneously
3D – three axes simultaneously
multiaxis
4D – four axis - one rotary axis (rotary table)
5D – five axis - maching (two rotary axes)
CAM software uses „Strategies“
Strategy – is a general plan how to move the tool durign machining
Continual development
Roughing – offset, raster (Zig-Zagmethod) plunging
Finishing strategies – pencil milling, streaming, rest material maching
NX (Siemens PLM software) Catia (Dassault systémes) –both 10% market share
PowerMill, FeatureCAM, ArtCAM (Delcam company) ,InventorCAM (Autodesk) Wildfire – Pro/Ingineer (PTC) –5%
EdgeCAM, SurfCAM, SolidCAM, MasterCAM, OneCNC, ESPRIT, GibbsCAM
Simulation is used
to control
generated
toolpaths for
following reasons:
- Colisions
- Undercuts (or rest
material)
- Postprocesing
check
NX
We can do complex shapes, no need to calculate control points
We can use simulation and verification
We can change the tool easily
But
We need postprocessor
Expensive (SW, computer, learning…)
Program is always longer (againexpensive)
Projects
- Common – same tasks for all
- Individual – own selection of part and
individual work on it. Evaluated.
Test – from theory of programming and use
of CAM software