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Course is focused fundamental
possibilities of automatization of machine
tools and automatization of programme
preparation for CNC machine tools.
1+2, CA – classified assessment - 3 credits
Presentations
Exercises
› common tasks
› individual work
Project work – will be explained during
exercises – evaluation (work must be
completed and evaluated by more than
50%)
Test from knowledge – presentations and
recommended literature – test itselft
more than 50%
total is a sum (50 – 50%) from both
1+2, 1 hour of presentation, 2 of exercise =>
13 + 13 weeks (13+26) => 6 presentations + exercises.
presentation explain the work on exercise => presentation will be together on thebeginning of the semester and later duringsemester.
and then you will have time to make the taskand individual work!
Work on conventional machines is
replaced by automated work on
automatic machines. These
machines are working without
human control with higher speed,
precision, safer and more
productivly than humans.
But where did it start?
Is connected with the rising demands of
society and industry development.
Is the way to intensification of
manufacturing – increasing productivity,
improving quality and lowering costs
Is the way to improvements in
manufacturing technology, spreading
the technological possibilities and way to
make the inovation cycle faster.
Tool management
Tool change
Tool movements
Spindle start, devices start
Material loading
Finished piece remove
Machine tools:
general-purpose, manually operated
(conventional);
- The leading power is the worker
Machine tools:
automated:
a) fixed automation – mechanisms: cams,
gear wheels, links, levers, arms; mechanical
stops, limit switches, etc.
b) flexible automation – program control,
numerical control
NC/CNC machine consist of 3 basic elements.
List of instructions – NC code – a mix of alphabecial and numerical information. Contaion information about movements, feed, speed, tool change and other machine functions (cooling, measuring)
Control unit - control system – converts the program intosignal for machine and send them to machine (PLC controller)
Control
unit
(system)
MachineNC
code
Sensing
device
Drive
motor
NC/CNC machine consist of 3 basic elements.
Machine tool – fitted with drive motor to operateslides, support and spindle. Also with switchesto start/stop specific functions
Sensing device – optional(closed circuit)- sensingdevice control if a specific demand wasfullfilled. Support feed, Table position etc.
Control
unit
(system)
MachineNC
code
Sensing
device
Drive
motor
Three types of motion
1) point-to-point motion – tool is moved to specific location, path or speed of movebetween location is not controlled. (drilling)
2) Linear control – movement along one ofthe axes of the machine.
3) Contouring control – movement can bemade in two or more axessimultaneously.
Point-to-point control Linear control Contouring control (continual)
drilling milling machines, lathes machining c.(milling, turning)
MC combine a number of different machining processes in one operation
Programming of machine tools
Machining on CNC machines is controled by a NC code.
NC code is a list of instructions for the machineand also for the operator. Instruction are executed in time order.
NC code must have a specific format so thatthe control system of machine is able to readit.
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 coordinates
U,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 commang G98
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
Absolut
G90 X0 Y0 Z50
G0 X15 Y70 Z50
G1 X15 Y70 Z0
G1 X25 Y70 Z0
G0 X25 Y70 Z50
G0 X0 Y0 Z50
Incremental
G91
G0 X15 Y70 Z0
G1 X0 Y0 Z-50
G1 X25 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 linesDefinition of relation between coordinate
system of CNC machine and program, type of programing, work mode, workingconditions
Program bodyCutting and non-cuting moves, main program
and subprograms, tool changes Ending linesTool return to home point, change to first tool,
coordinates reconstruction
Subprograms
A link to another then thefollowing line is enteredinto main programm.
This subprogram isexecuted.
After finishing thisprogram we return to main program a wecontiue until end of 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
MikronexMikronex
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 limitations
HeidenheinHeidenhein
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
Partprogram
Proceso
r
Postproceso
r
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 generatedtoolpaths forfollowing reasons:
- Colisions- Undercuts (or rest material)- Postprocesingcheck
NXNX
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)
ArtCAM
FeatureCAM
Projects
- Common – same tasks for all
- Individual – own selection of part and
individual work on it. Evaluated.
Test – from theory of automation and
programming
Recommended