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Department of Mechanical & Chemical EngineeringHeriot Watt University

Abstract

The Advanced Manufacturing Unit (AMU) in the Department of Mechanical Engineering

has newly purchased a new CAD/CAM package called EdgeCAM, to produce computer

numerical control (CNC) for its machine tools. The primary objective is to fully interface

EdgeCAM to the University’s laser machining centre and create all the necessary material

database.

Final Year Project - EdgeCAM routines for Laser Cutting 1


Acknowledgements

First of all, I would like to thank God for his grace and guidance throughout my life.

I would like to express my thanks and gratitude to the following people for their

invaluable help and assistance throughout this project. My supervisor, Mr J.M Ritchie for

his undying assistance and encouragement. My co-supervisor Mr I Black for his

guidance. The AMU Manager Mr Brent Wilson and the whole AMU team for their

patience in condoning me during the time while I was working in the workshop. The

computer support advisor, Mr Pritchard for this help in setting up initial software.



Contents

Abstract I

Acknowledgements II

Contents III

Chapter 1 Introduction 1

1.1 Laser Machining 3

1.2 Laser Mechanics 3

1.3 Part Programming 4

1.4 EdgeCAM Software 4

1.5 Aims of Project 5

Chapter 2 Literature Review 6

2.1 Previous Work on Subject 6

Chapter 3 Theory 8

3.1 Lasers and Laser Machining Material 8

3.2 Mechanism of a CO2 Laser 8

3.3 Advantages and Disadvantages of Lasers 9

3.4 Numerical Control Programming 10

3.5 Part Programming 10

3.6 The CNC Machine Tool 11

3.7 NC Programming Applied to Laser Cutting 11

3.8 Pathrace EdgeCAM 11

3.8.1 Code Wizard 12

3.8.2 Main EdgeCAM 13

3.8.3 Editor 13

3.8.4 Tool Library 13



3.8.5 EdgeVerify 14

3.8.6 Code Generator 15

3.9 EdgeCAM Working Environment 16

3.10 EdgeCAM Macro 17

Chapter 4 Interfacing EdgeCAM with the Laser Machine 18

4.1 Structure of Project Development 18

4.2 Adoption of a Milling Post Processor 20

4.2.1 Selecting a Suitable Post Processor for Adoption 20

4.3 Alteration of the Okuma OSP Post Processor 21

4.3.1 Alteration of Milling Modal 22

4.3.2 Alteration of Circular Interpolation 22

4.4 Creation of Material Database 23

4.4.1 Material Database via Tool Library and Tool Store 24

Chapter 5 Macro Language Programming 25

5.1 Ease of Usage 25

5.2 Saving Macros as .PCI Files 25

5.3 Laser Cutting Toolbar 26

5.3.1 Manual Icons 27

5.3.2 Automated Icons 28

5.3.3 Structure of the Automated Icons 29

5.4 Testing 31

5.5 Limitations of Macro Icons 31

Chapter 6 Comparison 32

6.1 Comparison on Time Taken and Code Structure 32



Chapter 7 Discussion 34

7.1 Blank Lines within CNC Codes 34

7.2 Retract Option 34

7.3 Identifying the Internal and External Profiles 35

7.4 Lead In and Lead Out 35

7.5 Rapid Move 35

Chapter 8 Future Work 36

8.1 Fully Automated Macros 36

8.2 Direct Transfer to the Laser Machine 36

Chapter 9 Conclusions 37

Chapter 10 References 38

Appendix A Project Schedule

Appendix B Standard NC Codes

Appendix C Material Database

Appendix D Heriot-Watt University Laser Machine

Appendix E Bosch Alpha 3 CNC Controller

Appendix F DNC Link

Appendix G Actual Macro Files

Appendix H Sample Drawings of Parts

Appendix I Laser Cutting Parameter

Appendix J Actual Screen Display

Appendix K Example of Part Program

Appendix L Laser Cutting Toolbar Manual



Chapter 1

Introduction

For a number of years the Advanced Manufacturing Unit (AMU) in the Department of

Mechanical Engineering, Heriot Watt University have been using a Computer Aided

Manufacture (CAM) software called SmartCAM, but recently the university have

upgraded this software to a more enhanced program called EdgeCAM. The use of these

CAD/CAM packages has greatly improved the efficiency, set-up time, increased quality

and error reduction within the entire CNC manufacturing process.

The main objective of this project was to fully interface this new software package to

output the required laser cutting codes and call up require cutting feeds and speeds from

the material database for the laser machining centre. To achieve the main objective of

this project, it was necessary to establish a good understanding of the working of

EdgeCAM and the NC codes for the department’s laser machine.



Figure 1: Display of EdgeCAM



1.1 Laser Machining

Using a laser as material cutting tool has developed very rapidly throughout the past

decade. This is mainly due to the high precision and flexibility available to cut complex

shapes and new materials better than traditional machining methods, e.g. punching and

nibbling. When the laser beam is focused it generates a very high intensity beam of light,

which can vaporise any known material, therefore producing the cut. There are numerous

benefits in using laser over conventional cutting methods; these will be discussed in the

latter part of this dissertation.

1.2 Laser Mechanics

There are many different types of laser machines and different laser machining materials.

Many people confuse the meaning of the phrase “laser machining material” with the

actual material being cut by the laser. In actual fact “laser machining material” is

referring to the actual substance used to produce the high intensity laser beam. There are

four main different types of laser machining material: semi conductor; liquid; solid state

and gas. The laser machine employed by the department’s AMU unit is a Ferranti/Laser

Ecosse MF 400/600 CO2 controlled by a Bosch CNC alpha 3 controller. The machine is

linked to the EdgeCAM software via a DNC link (picture of the laser machine is in

appendix D, E & F).



1.3 Part Programming

Part programming is one of the most time consuming part of manufacturing a product. It

requires someone to sit down and analyse the actual part to be manufactured, then plan

out the route of manufacture and write the actual NC code required for the machining

centres. However, by using CAD/CAM software such as EdgeCAM, this laborious

process has been transformed into a relatively simple operation and, depending on the

geometry of the part, the entire process can be done in a matter of minutes compared to

the hours spent doing it by hand.

1.4 EdgeCAM software

As the way it is applied in this project, EdgeCAM can be classified as a generative

Computer Aided Process Planning (CAPP) system. Basically what this means is that, the

EdgCAM software would produce a process plan from first principles every time the

software is run. The codes produced by this would be accurate to the specific post-

processor it is using, depending on which machining centre is used to manufacture the

product.

EdgeCAM is separated into a number of different modules and the main ones used during

this project were:

Code Wizard - Editing of post processor.

Main EdgeCAM Program – Draw geometry and create part programs.

Editor – Viewing and editing of text.

Tool Library – Storage of machine tool data.

Edge Verify – Simulation of end part.

Code Generator – Generates CNC codes.

EdgeCAM Macro – Provide easy customisation.



1.5 Aims of Project

The primary aim of this project was to fully interface this new EdgeCAM software to the

university’s laser machine. To accomplish this primary aim, it required a completely new

post-processor for EdgCAM to run on, so that it can output the correct codes to instruct

the correct movement of the laser machine. The secondary aim was to make the interface

for the software as user friendly as possible. This was achieved by the use of internal

macro language facilities to create a completely new tool bar for laser operations within

the EdgeCAM software. To produce effective programs for different jobs, the correct

feeds and speeds had to be set up for all the necessary materials in the EdgeCAM tool

library so that they could be inserted into the correct position of the output codes. The

effectiveness of the system was to be measured by making a comparison between manual

part programming, part programming with the Laser Cutting Toolbar and the Automated

Macro Icons.



Chapter 2

Literature Review

2.1 Previous Work on Subject

Pervious work done on laser machines and CAD/CAM packages was by Abdullah, Ng,

Thomson and Wong.

Abdullah’s project was to interface a CNC laser cutting database with SmartCAM, this

was done via a macro command language which the macro detects the entire geometry of

the part and then generates the NC codes for that part with all the necessary job material

data be already inputted into the program. Some ideas were gathered from this

dissertation but majority of the work done in this project is very different from this

project.

Ng’s project was aimed at the integrating the SmartCAM software to the laser machine.

His dissertation identified there are 4 different files within SmartCAM, which require

compiling before a proper set of NC codes can be produced. He then altered the

necessary files to achieve his project aim. Ng’s project is similar to my project aim, but

the software and manufacturing domain involved were completely different. However,

slight insight on how to proceed with my own project was gathered for his dissertation.

Thomson did a series of experiments to determine the ideal cutting speed for different

materials, namely mild steel, stainless steel, Perspex and plywood. Material information

such as feed rate and material thickness was gathered from his report.



The focus of Wong’s project was to fully automate the code generation process in

SmartCAM for the milling machine. This was done with the SmartCAM Macro

Programming Language. Various files in SmartCAM were programmed to fully integrate

with the Fanuc milling machine. Different files with different applications were stored in

different folders. This dissertation was mainly focused on milling machine; therefore

nothing was particularly useful.



Chapter 3Theory

3.1 Lasers and Laser Machining Material

Many people talk about lasers in everyday life but do they really know the meaning of the

word “Laser”. “Laser” actually stands for Light Amplification by Stimulated Emission

of Radiation. Lasers are generally separate it into 4 different categories:

Semiconductor Lasers;

Liquid Lasers;

Solid State Lasers;

Gas Lasers.

This dissertation will mainly be focus on the last type mentioned, Gas Lasers. The

university uses a Ferranti/Laser Ecosse MF 400/600 CO2 machine.

3.2 Mechanism of a CO2 Laser

The basic mechanism of laser cutting is extremely simple and can be summarised as

follows: (see figure 3.2)

1. A high intensity beam of infrared light is generated by a laser.

2. This beam is focused onto the surface of the work piece by means of a lens.

3. The focused beam heats the material and establishes a very localised melt

throughout the depth of the material.

4. The molten material is ejected from the area by pressurised gas jet acting

coaxially with the laser beam.

5. The cut of the material is generated by the mechanical movement of the sheet

material.



Figure 3.2: Schematic of a CO2 Laser

3.3 Advantages and Disadvantages of Lasers

Laser cutting is a thermal process, which cuts by melting or vaporisation and it is a non-

contact process. These qualities give the laser machining some major advantages over

other mechanical machining processes, e.g.:

The main advantages of laser machining are:

It is a non-contact process, which means material is only require to be lightly

clamped.

Waste Reduction is reduced due to the diameter of the laser beam (about 0.1mm-

1mm).

Lower costs of tool replacement are apparent.

The machine down time for tool replacement and re-calibration are eliminated.

Laser machines are extremely safe compared to their mechanical counterparts.



The process is extremely quiet compared to other manufacturing processes.



The main disadvantages of laser machining are:

Skilled operators required operating and maintaining system.

High cost of installing the machine, because the machine requires fume hood,

warning lights, gas storage areas, changes in the workshop area have to be made.

High operating cost due to the use of operating gas, electrical power, and cooling

water.

High capital expenditure, the cost of purchasing and installing the machine is

much higher than a conventional machine.

3.4 Numerical Control Programming

Numerical Control (NC) is the term used to describe the control of machine movements

and various other functions by instructions expressed as a series of numbers. This then

leads us into the term Computerised Numerical Control (CNC), CNC is the term used

when the control system utilises an internal computer. The internal computer would

allow the storing of additional programs, program editing, running of program from

memory and additional special routines. A list of these codes for laser cutting is in

Appendix B. Computer Numerical Control (CNC) is applied to a wide range of

manufacturing processes such as metal cutting, wood cutting, welding, flame cutting,

sheet metal forming, sheet metal punching, water jet cutting and laser machining.

3.5 Part Programming

The expression “Part Programming” causes some confusion, since “Part” is often thought

to mean something that is incomplete. However in numerical control terms (NC), a part

program is infact a complete program of an entire component. The word “Part” meaning

the actual component. A short example of a part program is in appendix K.



3.6 The CNC Machine Tool

The CNC machine tool consists of two main components, the machine that carries out the

actual machining and the control system, which controls the machining operations. For

this case the CNC system, the information that is received by the machine via the

controller, is in the form of NC codes. The operator programs these codes either

manually, through a PC via a DNC link, or by punch tape. These codes are then

converted to the necessary movement or actions by the machine.

3.7 NC Programming Applied to Laser Cutting

For this project, which is to interface EdgeCAM to the laser-cutting machine, some of the

codes are not applicable due to the nature of the laser machine. Below are some of the

codes, which are not applicable (table 3.7):

Table 3.7: Tabulation of Non-Applicable Codes

3.8 Pathtrace EdgeCAM

Pathtrace EdgeCAM is a relatively new CAD/CAM software product in the market at the

present moment. One of the key benefits of this software is that it contains both CAD and

CAM. At a click of a button, the user can switch from CAD environment to CAM

environment almost instantly; therefore it is possible to make modifications to the initial

geometry to improve the manufacturing time and quality. Apart from the CAD/CAM

switching, EdgeCAM also contains a lot of other very useful facilities. These facilities are

as follows.

Final Year Project - EdgeCAM routines for Laser Cutting

Codes DescriptionG34 Thread cutting, increasing leadG35 Thread cutting, decreasing leadM03 Spindle onM04 Spindle offM06 Tool ChangeM07 Coolant OnM09 Coolant OffM10 ClampM11 Unclamp

17


3.8.1 Code Wizard

Every CAM system requires the ability to convert information into machine tool specific

CNC code and this was done traditionally performed using a post processor. However

code wizard has eliminated the need for the user to create complex and time consuming

source files for postprocessors. It works on the basis that the Wizard requests of the user

technical information regarding machine tool configuration and programming style. The

Wizard then creates the source file and postprocessor. The benefits of the Wizard are that

it reduces the cost of software and allows the user to be in complete control over CNC

output (refer to figure 3.8.1).

Figure 3.8.1: Screen Shot of the Code Wizard



3.8.2 Main EdgeCAM

The predominant section of the software is EdgeCAM itself. This is the key facility,

which you load up, create or edit your geometry and produce the CNC codes for the part

program.

3.8.3 Editor

EdgeCAM text Editor in its most basic form is a word processor, allowing the user to

manually type a CNC program. The editor will allow a CNC Programmer to quickly and

easily manipulate the program, copying sections, re-numbering and even formatting the

text. The editor models itself on any Windows Processor, e.g. Note Pad, Word Pad,

allowing text to be cut, copied and pasted amongst files (refer to figure 3.8.3).

Figure 3.8.3: Screen Shot of EdgeCAM Editor

3.8.4 Tool Library

The tool library comprises of nine sub libraries, each contain specific user defined tooling

information. The Tool library allows the user to create and store non-standard tools and

allows them to be brought into the CAM environment. Specifically, the material library

stores cutting information such as speeds and feeds and depth of cut for individual

material types. When used within the Manufacturing area, it governs the output feeds and

speeds, creating consistency throughout the program (refer to figure 3.8.4).



Figure 3.8.4: Screen Shot of Tool Library

3.8.5 EdgeVerify

EdgeVerify is software that graphically simulates the machining process. The image

produced by EdgeVerify is much better quality than the Solid model or Render found in

the Manufacturing environment. EdgeVerify is a valuable tool for all NC programmers

and operators. It significantly reduces the need for the physical verification process

(refer to figure 3.8.5).

Figure 3.8.5: Screen Shot of EdgeVerify



3.8.6 Code Generator

This item basically converts the man-readable postprocessor source files into the system

postprocessor (see figure 3.8.6)

Figure 3.8.6 Screen Shot of Code Generator



3.9 EdgeCAM Working Environment

EdgeCAM operates in a working environment similar to that of Microsoft Windows and

basically has two main set-ups, firstly the CAD set-up (where the user create, edit or

modify the geometry have input or imported from different software in either 2D or 3D

format). Then at a click of a button it switches from CAD set-up to CAM set-up,

basically it is still in the same environment but all the tool bars and pull down menus have

changed from drawing functions to machining functions (refer to fig 3.9).

Figure 3.9: EdgeCAM Work Environment



3.10 EdgeCAM Macro

EdgeCAM macro is a unique programming language used within the EdgeCAM main

program. It provides the user tools to review and edit commands easily. There are two

ways in which the macro could be programmed, namely via “record” command or writing

the commands manually. EdgeCAM allows the user to record steps and procedures in

macro files, stored in .pci extension, which can be re-used by executing the required file.

EdgeCAM macro can be programmed manually and customised to meet individual

requirements (refer to figure 3.10 for examples of EdgeCAM Macro). Below is a list of

example of what EdgeCAM macro can do:

It allows the scope of more automated functions.

Enables the creation of general-purpose routines.

It enables the creation of specific forms of interpolation.

It enables the development of user-canned cycles.

*Laser Down Command %InitCommand=cmd1=7,104%ClearMods=[cmd1]%SetModifier=[cmd1],108,Flood|1%InitDigInfo=gdh1%ExecCommand=cmdret=[cmd1],[gdh1]%FreeDigInfo=[gdh1]

*Laser On Command%InitCommand=cmd1=7,101%ClearMods=[cmd1]%SetModifier=[cmd1],108,CLW|2%InitDigInfo=gdh1%ExecCommand=cmdret=[cmd1],[gdh1]%FreeDigInfo=[gdh1]

Figure 3.10 Example of EdgeCAM Macro



Above is a short example of the EdgeCAM macro language in its simplest form, a

complete list of all the macro commands are in appendix G.



Chapter 4Interfacing EdgeCAM with the Laser Machine

Generating quality NC code is governed by the capability of the post processor to satisfy

both the needs of the machine control and those of the customer in terms of both style and

production methods. In terms of this project, the style and production method is basically

the usage of the CO2 laser machine and the ability to produce NC codes for complex 2D

shapes.

4.1 Structure of Project Development

The basic strategy for tackling this project was as shown below.

1. Learn EdgeCAM - basic functions of the main program (ie. tooling, profiling,

drawing functions etc).

2. Learn about the usage and editing of the post processor.

3. Learn (in detail) machining centre codes (ie. difference between milling/turning

codes compared to laser cutting codes).

4. Adoption of a milling post processor (elimination of redundant codes and

modification of codes).

5. Learn about EdgeCAM macro.

6. Created new Laser Cutting toolbar.

7. Discover scope for automation.

8. Learn more about macro programming.

9. Created more automated routines/icons.

Please refer to figure 4.1.



Figure 4.1: Schematic diagram of the project development structure

4.2 Adoption of a Milling Post Processor

One of the very first aims of this project was to fully interface this EdgeCAM software to

the university's laser machine. Basically, what this means is to alter the output CNC

codes of EdgeCAM to be fully compatible with the laser machine. To do this, one of the

key requirements was to investigate into all the different post processor templates

provided by the EdgeCAM. This was done using the code wizard.

4.2.1 Selecting a Suitable Post Processor for Adoption

Via the code wizard, users are supplied with twelve different post processor templates

(refer to fig 4.2.1). Due to the nature of EdgeCAM, all of the supplied post processors

were for milling/turning purposes, therefore a lot of codes were not required or accepted

by the laser machine. So a complete overhaul of a single post processor was necessary.

After a detailed examination of all twelve post processors and an analysis of the NC

codes, it was found that the Okuma OSP template was the most suitable for adoption.

Figure 4.2.1: EdgeCAM Post Processor Templates



4.3 Alteration of the Okuma OSP Post Processor

After selecting the Okuma OSP as the most suitable post processor, there were still a lot

of unwanted codes produced by this post processor. The first thing done was to

completely strip out all the standard codes even if they were compatible with the laser

machine. After this was done, it was necessary to identify how to incorporate the laser

cutting codes into the milling template. This involved careful analysis and editing of the

M, G, S, F and N codes. Since laser cutting does not require the use of milling codes

such as spindle on/off and fluid on/off, these were converted to two functions, which act

as laser operations, i.e. such as nozzle up/down and shutter open/close.

Figure 4.3: Modification Made to the Format Table

By modifying the format table; all changes take effect as soon as the post processor has

been complied. Refer to appendix B for a complete list of the laser codes.



4.3.1 Alteration of the Milling Modal

Since some of laser codes are completely different from the milling codes, an alteration of

the modal codes was required. Below is table 4.3.1 containing the original modal codes

and the modified modal codes.

Description Original Code New CodeSpeed S F

Arc Radius R ZDwell Time P H

Z Move C -

Table 4.3.1: Tabulation of Modification of Modal Codes

4.3.2 Alteration of Circular Interpolation

One of the key problems in the laser codes for circular interpolation was that for curves

smaller than 180 degrees requires a negative sign before the co-ordinate is required.

While curves greater than 180 degrees require a positive sign. This was a major barrier,

which took a considerable amount of time to overcome. Finally the solution was to use

the quarter quadrant division. This basically divides the circle into 4 quarters every time

and, by adding a negative sign within the post processor for circular interpolation, this

overcomes that problem of identifying a curve greater or smaller than 180 degree (refer to

figure 4.3.2a and figure 4.3.2b).

Figure 4.3.2a: Alteration of Circular Interpolation to

Single Quadrant Interpolation



Figure 4.3.2b: Alteration of Actual Code Token

Looking at the above Figure 4.3.2b, due to the unique requirement of the laser machine, a

modification of the actual macro token was required. By modifying this token, it

completely alters the output CNC codes that the post processor complies.

4.4 Creation of Material Database

Since the EdgeCAM software was initially designed for milling/turning purposes, all of

the material feeds and speeds are for these operations. Therefore the creation of an entire

set of material databases was required. This is basically created via the tool library with

the feeds and speeds in this database relate to laser cutting only.



Figure 4.4.1: Tool Library Prompting for Material Requirements

4.4.1 Material Database via Tool Library and Tool Store

The tool library will prompt for a number of material or tool requirements such as tool

material type, cut depth 1, cut depth 2 etc (refer to figure 4.4.1). After the all the

necessary requirements have been filled in, it can be saved into the tool library database.

After this has been done, it is also necessary to attach the appropriate feeds and speeds to

those material data in the tool store, where the calling up of these parameters will be

carried out. The tool store is basically where the user can select whatever material is

going to be cut, the feeds and speeds will then be automatically be inserted within the

Laser Operation or Profile commands, so no separate input of the feeds and speeds is

required. A list of the material database is shown in appendix C.



Chapter 5

Macro Language ProgrammingThe basic working of EdgeCAM is that the user uploads geometry into the Design

environment when the geometry is ready to be part programmed. The user then enters

into the CAM environment and selects the appropriate post processor. After the selection

of the post processor, the user is able to program in the part program by clicking on the

different icons on the new laser cutting toolbar. This new toolbar is create via macro

command execute icons. Basically once an icon is initiated, it will run a particle macro

command. This command is either supplied by the EdgeCAM software or written

manually for a unique purpose. All of the icons, which contain laser-cutting functions,

are all written to a specific specification. This new toolbar is separated into two types

icons. First there is the “manual” single command execute icons, which runs a single

macro command. Secondly there is the “automated” multi command execute icons which

runs an entire string of macros automatically.

5.1 Ease of Usage

The main aim of writing these macros was to assist the AMU team in code generation for

different cutting materials and different complex sub-contracted cutting shapes. In view

of the above, it was necessary that the execution of all these macro files should be simple

and easy. This was then the main priority when they were being designed.

5.2 Saving Macros as .PCI Files

Within the main EdgeCAM software, to use the macro facility, the user must first save all

the macro files as .PCI files since EdgeCAM software only reads and runs these files.

There are two ways in which you can obtain .PCI files. Firstly through the use of macro

record command supplied by the EdgeCAM, this is under the options pull down menu

either in CAD or CAM environment. Secondly, the user can write the macro themselves



in text editors and save it as .PCI. Both methodologies were used by the author to write

the extensive set of macros created in this project.

5.3 Laser Cutting Toolbar

The main purpose behind the creation of this toolbar is to make this laser cutting facility

in EdgeCAM as user friendly as possible. By using this laser cutting toolbar (refer to

figure 5.3a), it eliminates the requirement of having any detailed knowledge of

EdgeCAM. The toolbar itself contains a number of graphical representations of the actual

commands, so it is all quite self-explanatory. However if the user requires more

information about the use of the different icons, a manual has been created for a better

understanding of the icons (manual in appendix L).

Figure 5.3a: New Laser Cutting Toolbar

The graphics in this new laser cutting toolbar were drawn up via a graphic editor supplied

by the EdgeCAM package. Basically each macro is attached to its own graphic, so when

the user clicks on one of the icons, it initiates that particular macro. The chosen macro

will activate a certain laser cutting command via the post processor, and appear in the

instruction browser box (refer to figure 5.3b).



Figure 5.3b: Instruction Browser Box

5.3.1 Manual Icons (Single Command Execute)

Via the laser cutting toolbar there are two ways for a user to program in a part program.

The first way is to part program by using these manual icons. Basically the user just click

on the require icon representing the appropriate laser operation, ie. nozzle up/down,

shutter open/close, dwell, profile etc., until the entire part program has been completed.

The problem with using this technique is that the user might miss an operation that is

critical to the part program, ie. forgot to input a shutter close command or a nozzle down

command before shutter open. (Figure 5.3.1. shows all the manual icons)

Figure 5.3.1: Display of Manual Icons (Single Command Execute)



5.3.2 Automated Icons (Multi Command Execute)

To overcome this problem a second method of part programming was developed using

the laser cutting toolbar to initiate automated icons ie. Laser Operation or Laser Operation

with Retract (refer to figure 5.3.2a).

Figure 5.3.2a: Display of Automated Icons (Multi Command Execute)

These two icons, once initiated, will automatically run a series of linked macro

commands, prompting the user for number of internal and external profiles (refer to figure

5.3.2b). After the number of profiles has been input, the macro will then run and initiate

all the necessary laser operations automatically for the number of profiles specified,

leaving the user to select only the internal and external profiles. These automated icons

eliminate any command position errors such as laser on/off, nozzle up/down etc. because

all the operations have already been programmed into the macros.

Figure 5.2.2b: Macro Prompting for Number of Internal and

External Profiles



5.3.3 Structure of the Automated Icons

There are only two automated icons within the laser cutting toolbar. Firstly is the “laser

operation” icon, and secondly is the “laser operation with retract option”. Both icons

contains the same basic structure but the laser operation provides the user with a lead

in/out option instead of the retract option. Apart for those options both macros are

identical. The reason for creating a laser operation with retract option will be explained

in the discussion part of this dissertation. Refer to figure 5.3.3 for a diagram

representation of the automated macro structure.



Laser Operation Laser Operation with Retract Option



Figure 5.3.3: Diagram Representation of Macro Structure

5.4 Testing

Testing was completed on a number of materials such as Perspex, Mild Steel, Stainless

Steel and Plywood. The program generated the correct codes for the sample drawings

plus one or two sub-contract designs. These codes were then downloaded to the laser

machine and machining of the sample and sub-contract parts was carried out according to

the drawings on EdgeCAM. (Refer to figure 5.4 for a picture of actual cuttings of parts)

Figure 5.4: Actual Cuttings of Sample and Sub-Contract Parts

5.5 Limitations of Macro Icons

The written macros do have some limitations:

All macros written for this project only work in the EdgeCAM manufacturing

environment.

The selection of material is not combined with manual or automated macros;

therefore the selection of a material must be done before initiating any of the

macros.

It requires a user to prompt the profiles in the appropriate order.



The user requires a basic knowledge of the Laser Cutting Toolbar.

Output codes are saved as a different text format therefore it requires conversion

before transfer to the laser machine.



Chapter 6

Comparison

6.1 Comparison on Time Taken and Code Structure

After sample drawings and sub-contract parts have been part programmed by EdgeCAM.

A comparison on the part program structure and time taken was carried out. In figure 6.1

is a time comparison between manually written codes and codes produced by EdgeCAM.

From the figure, it is clear that by using the laser cutting toolbar, it dramatically cut down

the part programming time, and when examined carefully, a structure consistency can

also be found with the EdgeCAM part program. Overall the EdgeCAM part

programming method produced many advantages over manual part programming.



Figure 6.1: Comparison of Time Between Part Programs



Chapter 7Discussion

There were many problems encountered in the process of interfacing and developing the

EdgeCAM software with the laser machine. One of the key reasons for this is that the

nature of the laser machine is quite different from conventional milling/turning machines.

Also a lot of problems arose because EdgeCAM was initially designed for milling and

turning purposes, and some problems could not be resolved due to that reason.

7.1 Blank Lines within CNC Codes

One of the major faults found was that, sometimes a blank line would appear after a linear

interpolation. This is due to the Z-axis movement of the traditional CNC machines,

which has been altered to suit the 2D laser cutting machine property. A number of

attempts have been tried to eliminate this blank line but all were unsuccessful. This blank

line still exists in the final version of the laser cutting toolbar, however this does not cause

any error or conflict on the laser machine. After some testing, the conclusion was that the

laser machine would just read this blank line as “no command” and then move on to read

the next line of instruction.

7.2 Retract Option

In the initial laser cutting toolbar there was only one laser operation icon. The reason for

creating another laser operation with the retract option was because, during the time of

testing, the laser machine reacted too slowly to the input CNC codes. For example, for

short distance moves between cuts, the automated macro would insert a nozzle up and

down command at the beginning and end of each move. When this was actually being

machined, the nozzle up and down retract and detract too slowly and, before the nozzle is

completely down to the material, the shutter opens allowing the laser to burn the material.

This produced a huge crater in the material. The solution was to write another automated

macro with an option of retract on or off to eliminate this problem.



7.3 Identifying the Internal and External Profiles

One of the problems in the automated macros was the identification of the internal and

external profiles. For laser machining the internal profile must be cut first and then the

external profile. If the machine cuts the external profile first, the cut material would fall

away from the sheet material being cut out off, resulting in no internal profile. The

solution to this problem was to program in the macro the order of internal and external

profiles, therefore the macro would always prompt the user to select all the internal

profiles first before the selection of the external profiles (see appendix G).

7.4 Lead In and Lead Out

It is best not to start off the cut of a material from the profile, so a lead in and lead out

increases the quality of the overall product, therefore an option of lead in and lead out

was built into the macro. With the Laser Operation Icon, it provides an option to digitise

the position of the lead in and lead out function. However, EdgeCAM also provides a

lead in and lead out numerical input function, so if the user does turn off the digitise

option, EdgeCAM still enables the user to input a lead in and lead out using the input co-

ordinates.

7.5 Rapid Move

One of the faults of the system was the rapid move command. Due to the alteration of the

post processor, at the beginning of a profile after the shutter has opened, it would insert a

short fast rapid command to bring the nozzle to the start of the profile. This rapid move is

far too fast to enable the laser to burn through the depth of the material, therefore

scrapping the entire job. The solution to this problem was to insert a feed code after the

rapid code. This eliminated the fast rapid movement and replaced it with an appropriate

feed move.



Chapter 8Future Work

8.1 Fully Automated Macros

One of the drawbacks of the laser cutting toolbar at the moment is the number of

selections of profiles by the user. The macros currently require the user to click on the

necessary profiles for machining. For example, if a part has ten internal profiles and one

external profile, the user has to click on all the internal profiles and then the external

profile to produce the necessary part program. However, a future study of EdgeCAM’s

capability may eliminate this need. A macro with a searching algorithm might be written

in such a way that it can search the display and seek the number of internal and external

profiles, which can then be inserted as variables into the macros.

8.2 Direct Transfer to the Laser Machine

After the CNC codes have been produce by EdgeCAM, they still require some human

intervention before it reaches the laser machine. EdgeCAM outputs the codes in a .nc

format which the DNC link does not recognise, therefore the codes require to be saved

as .tap files before the actual transfer to the DNC link can take place. One of the ways to

make this process even more less time consuming is that, this entire human intervention

can be eliminated altogether. The CNC codes could be checked with EdgeCAM editor,

then be transfer directly to the laser machine for machining.



Chapter 9Conclusions

This project has fulfilled all the main aims mentioned in the introduction section of this

dissertation. The post processor modified can handle 80-90% of what is required, the

feeds and speeds are called up automatically via the use of macros. The ease of use by

the AMU team was also an additional aim fully fulfilled. Overall this project has been

very successful in achieving the initial aims plus a few additional ones.

A user manual has also been produced for the operators in the AMU team, explaining all

the necessary complications.



Chapter 10References

1. Chi-Kit Allan Ng “SmartCAM package development for CNC laser

machining”, BEng Dissertation, Heriot-Watt University, 1996.

2. Davies Wong L.Y “SmartCAM for conventional machining”,

BEng Dissertation, Heriot-Watt University,

1998.

3. Gareth Andrew Thomson “The development of a CO2 laser cutting

material evaluation procedure and the

construction of database to store this

information”, MSc Dissertation, Heriot-Watt

University, 1993.

4. Farouk Abdullah “Interfacing a CNC laser cutting database with

SmartCAM”, BEng Dissertation, Heriot-Watt

University, 1999.

5. David Gibbs & Thomas M. Crandell “An introduction to CNC machine and

programming”, Industrial Press Inc., 1991, Pg.1-

16.

6. Mike O’Neill “Basic EdgeCAM Training Course version

4.00”, Truline Automation, Pathtrace, 1999, Pg.

2-131.

7. ----- “EdgeCAM user manual”, Pathtrace, 1999.

8. John Powell “CO2 laser cutting 2nd Edition”, Springer, 1998,

Pg. xiii-18.

9. David L. Goetsch “Advanced manufacturing technology”, SME,

Delmar Publishers Inc., 1990, Pg. 139-145.

10. Charles S. Knox “CAD/CAM systems”, Macrcel Dekker Inc,

1983, Pg. 213-223.



11. A. Sona “Lasers and their applications”, Gordon &

Breach Publishers Ltd, 1976, Pg. 101, 135

&183.

12. Michael W. Sasnett “Industial CO2 lasers”, Laser Focus, Pennwell

Publications, 1998, Pg. 48-67.

13. Martin J. Haigh “An introduction to computer aided deign and

manufacture”, Blackwell Scientific Publications,

1985, Pg. 225-231.

14. Yvonne A. Carts “New technology boosts usefulness of low

power CO2 lasers”, Laser Focus, 1988, Pg. 47-

61.

15. Joseph Pusztal & Michael Sava “Computer numerical control”, Creston

Publishing Company Inc., 1993.

16. Graham T. Smith “CNC machining technology”, Springer –

Verlag, 1993.


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