Automation of machine tools programming

Ing. Jan Tomíček

Course description

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

Presentations

1+2, 1 hour of presentation, 2 of exercise => 13 + 13 weeks (13+26) => 4 + 9 approx.

(12+27)presentation explain the work on exercise =>

presentation will be together on the beginning

and then you will have time to make the task and individual work!

Lesson 1 – Automation overview

longer presentationno exercise or task

Introduction

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?

Automation of machining

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.

What we need to automate?

Tool management Tool change Tool movements Spindle start, devices start Material loading Finished piece remove

AUTOMATION OF MACHINING

Machine tools: general-purpose, manually operated

(conventional);

- The leading power is the worker

AUTOMATION OF MACHINING

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

Fixed automation elements

Cam

Is a disc or cylinder with a curve shaped path. A boss in support is in the path and as the cam turns the support moves. Cam are connected together to provide complex movement of support, feed, rotation and other.

Cylindrical cam use – automatic lathe carriage

Fixed automation machine tools

automatic general-purpose machinee.g. a semiautomatic or an automatic lathe

single-purpose machine (usually unit-built)workpiece oriented function design

transfer lineintegrated workpiece transport system

Unit-built machine

Modular units design

Single purpose machine

Just one operation, of op. Step is done. Sometimes a batch of operation steps Special machine designed to maximize

the production:› Multiple spindles› High feed drives› Multiple clamping› Automatic part in feed› Special tooling usage

Single-purpose machine efficiency

Transfer line – a concept

Transfer line – a schema

Block machining transfer line

Video – Transfer line

Transfer line station – an example

2) Flexible automation

(soft, programable automation) is aimed at piece and small batch production due to easy reprogramming.

Two basic forms Program sequence control Numerical control

Program sequence control

The sequence of motions and switchings is controlled by relays, timers, switches, perforated tape, programable cylinders, plugboards and other controllers.

Easier reprogramming, limited program options, almost no adjustments

Perforated tapeEach line presents a different movement or switch. It has to be printed correctly, no error control.

FYI:8 line perforated paper tape can contain one byte of information in one column of holes. Normal pitch of columns is 2,54 mm. That means you need 2,6 m of tape to store 1kB of data. A dual-layer DVD is then approx. 22100 km of perforated tape.

Numerical control

The most important type of automation. Almost all of new machines are numerically controlled.

Priciple:Machine and all of its movements are controlled by a program. Program is a list of instructions written is specific syntax and having specific format.

Mechanical vs. numerical

Limitations – speed, length of program, possible motions on cams.

FLEXIBLE AUTOMATION1. Conventional machine tool

FLEXIBLE AUTOMATION2. NC machine tool (stand-alone)

FLEXIBLE AUTOMATION3. NC machine tool with tool magazine

FLEXIBLE AUTOMATION4. CNC machine tool

Mechanization vs. automation

Mechanization – human power is replaced by machines, drives, hydraulic or mechanic devices

Automation – human control is replaced by sequentional machine, cams, computer, PLC controller

Automation degree

Semiautomatic run – tools are changed automatically, blank or finished workpiece is renowed by operator

Automatic run – both the tool and pieces are placed and removed automatically by robot (line, tables)

What we need to automate?

Tool management Tool change Tool movements Spindle start, devices start Material loading Finished piece remove

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NC / CNC definition

Originaly only NC control was used. Program was stored on tape or disc and read one line after another. Influence of rapid development of computers resulted to CNC control (Computer numerical control). Now the program is loaded into computers memory and executed from here.

CNC advantagesOption NC control CNC control

Program length Limited by data storage capacity (tape)

Unlimited (limited by data storage capacity – HDD drives over 1TB)

Program sequence One line after another Allows jump forward, backward, subprograms.

Jump to other programs N/A Yes

Canned cycles N/A Yes

Coordinates correction Manually only Yes, automatically

Tool length compensation Manually only Yes, programable

Tool diameter compensation

N/A Yes, programable

Reading in advance N/A Yes, continual mode

Start after breakdown N/A Yes

Basic principles of CNC machines

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 into signal for machine and send them to machine (PLC controller)

Control unit

(system)

MachineNC

code

Sensing device

Drive motor

Basic principles of CNC machines

NC/CNC machine consist of 3 basic elements.Machine tool – fitted with drive motor to operate

slides, support and spindle. Also with switches to start/stop specific functions

Sensing device – optional(closed circuit)- sensing device control if a specific demand was fullfilled. Support feed, Table position etc.

Control unit

(system)

MachineNC

code

Sensing device

Drive motor

CNC machine tool

Motions

Three types of motion1) point-to-point motion – tool is moved to

specific location, path or speed of move between location is not controlled. (drilling)

2) Linear control – movement along one of the axes of the machine.

3) Contouring control – movement can be made in two or more axes simultaneously.

MotionsPoint-to-point control Linear control Contouring control (continual)

drilling milling machines, lathes machining c.(milling, turning)

CNC machining centre(MC)

MC combine a number of different machining processes in one operation

Modular tool set

Modular tool set – tooling system

All manufacturers around the worldBasic concept:1) Holder with standadized conecting

part – ISO, BSK cone, CAPTO system etc.

2) Extension bar – active (vibration elimination) adujstable and balanced

3) Quick change tooltip/insert

SECO - Combimaster

Tool exchange

Tool exchange

Flexible cell – a concept

Flexible manufacturing system

Conveyors

Device used for transportation of blank and semiproduct in production

Types:Belt conveyorPulley(rolls) conveyorCradle conveyor

Conveyors – Belt conveyor

Used for small parts and loose material Endless belt made of rubber, plastic

particles, short boards (grids)

Conveyors – pulley(roller) conveyor

For large solid parts and products Low force needed (gravity slide ways) Use of pallets

Video – conveyor

PalletBoard used for

transportationEquiped with jigs and

other positioning elements

Together with pallete changer is used for automatic blank material loading and parts unloading

Pallet changeraka Switch table2-4 pallets in one machine

Loading of blank/semiproducts

- Manual- Accumulation conveyor

- Accumulating pieces to balance production- Robot loading

- For single standing, large production usage (common machine tools)

- Line(conveyor) loading- For FMS and large batch production

(special machine tools)

Loading

Flexible manufacturing system

Flexible manufacturing system for 4 types of automobile cylinder heads

(GM 3801 – 3811)

BZ 400 BZ 500 Other Reserve

Flexible to suit various part variants

9 Flexible transfer machines (some incorporating BZ 400 machining centers),

and 16 high-dynamic BZ 500 machining centers

Completely automated

Approximately 500,000 parts p.a.

Process automation and integration levels

AUTOMATION OF MACHINING

Effects of automation- Cost reducing

(per piece)- Higher

investments- Speed

improvement- Productivity

improvement- Repeatability

improvementC

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CN

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FMS

Cam

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Mach

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cost

s (K

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Productivity (pcs/hour)

Flexibility

next part…

Programming of machine tools

Programming of machines

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.

Coordinate systems

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.

Coordinate systems Basic is orthogonal system

X

Y

Z

Coordinate systems - millsZ axis is usually axis of spindle a X axis is

the working axis, or the longest!

XY

Z

Coordinate systems - latheZ axis is usually axis of spindle a X axis is

the working axis – diameter!!!

X

Z

Coordinate systems - multiaxis

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.

Coordinate systém - origin

Refernce point – a specific point on machine with given coordinates. Not always in the workspace of machine.

A special commang G98

Coordinate systems

Ways how to define a movementa) 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

IncrementalG91G0 X15 Y70 Z0G1 X0 Y0 Z-50G1 X25 Y0 Z0G1 X0 Y0 Z50G1 X-45 Y-70 Z0

1.

2.

3.

2.

3.

1.

NC code form

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.

NC code structure

Lines (blocks)WordsWord has a meaning and value part

S 1500

ISO nc code and the others

ISO is standardized code (G – code)Some manufacturers devoloped their own

standard for NC code – native standard

Mazak – MazatrolHeidenhein – iTNCSiemens - Sinumeric

NC code structure II.

Heading linesDefinition of relation between coordinate

system of CNC machine and program, type of programing, work mode, working conditions

Program bodyCutting and non-cuting moves, main program

and subprograms, tool changes Ending linesTool return to home point, change to first tool,

coordinates reconstruction

Program sequenceSubprograms 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 of main program(M30)

Ways of programing

Manual/Hand programing Shopfloor programming Automated programing

Manual 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

Manual programingWe need to know the functions: (many more function exist)

Movement functions:G00 rapid movementG01 linear interpolation/movementG02/03 circular interpolation

G40 diameter compensation offG41 diameter compensation on /right handedG42 diameter compensation on /left handed

Support and help functions:M06 tool changeM03/04 spindle start CW/CCWM05 program stopM30 program end

Manual programming

Specilzed editorsPredator G-code editor

G Wizard

Mikronex

Shopfloor programing 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

Shopfloor programming

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

Automated programming

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

Sequential NC code preparation

Partprogram – workpiece, material, cutting conditions, tools…

Procesor – according to technology

CL data – virtual toolpaths on virtual machine

Postprocesor – „translator“ for the specific CAM-control systém-machine combination

NC code – toolpaths of a real tool on a real machine

Partprogram

Procesor

Postprocesor

CL-data

NC-kód

CAM software

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

xD software

2D – just in two axis - turning2,5D – two axis, but in layers – not

simultaneously3D – three axes simultaneouslymultiaxis4D – four axis - one rotary axis (rotary

table)5D – five axis - maching (two rotary axes)

Tool movement programming

CAM software uses „Strategies“Strategy – is a general plan how to

move the tool durign machining

Continual developmentRoughing – offset, raster (Zig-Zag

method) plunging Finishing strategies – pencil milling,

streaming, rest material maching

CAM software developers

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

Simulaton and verification

Simulation is used to control generated toolpaths for following reasons:- Colisions- Undercuts (or rest material)- Postprocesing check

Verification

NX

Automated programing - review

We can do complex shapes, no need to calculate control points

We can use simulation and verification We can change the tool easilyBut We need postprocessor Expensive (SW, computer, learning…) Program is always longer (again

expensive)

What software we will use? ArtCAM

FeatureCAM

Course

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

individual work on it. Evaluated.

Test – from theory of automation and programming