machine and also for the operator. Instruction are executed in time - - PowerPoint PPT Presentation

Machining on CNC machines is controled by a NC code. NC code is a list of instructions for the machine and also for the operator. Instruction are executed in time order. NC code must have a specific format so that the control system of machine is able to 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!

X Y 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 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



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 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

• wn standard for NC code – native

standard Mazak – Mazatrol Heidenhein – iTNC Siemens - Sinumeric

Heading lines

Definition of relation between coordinate system of CNC machine and program, type

• f programing, work mode, working

conditions

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 following line is entered into main programm.

 This subprogram is

executed.

 After finishing this

program we return to main program a we contiue until end

• f main

program(M30)

 Manual/Hand programing  Shopfloor programming  Automated programing

 Editors are used. Program is written

manually (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 limitations

Heidenhein

 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, cutting conditions, tools… Procesor – according to technology CL data – virtual toolpaths

• n virtual machine

Postprocesor – „translator“ for the specific CAM- control systém-machine combination NC code – toolpaths of a real tool on a real machine

Partprogra m Proces

• r

Postproces

• r

CL-data

NC-kód

is Computer Aided Manufacturing (machining)

 From simple 2-axis turning up to multiaxis

machining

 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-Zag method) 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 (again

expensive)

Projects

• Common – same tasks for all
• Individual – own selection of part and

individual work on it. Evaluated. Test – from theory of programming and use

• f CAM software