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