machining on cnc machines is controledu12134.fsid.cvut.cz/podklady/tcam/ccam - 2015...machining on...

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