A Reference Manual
July 1996
Copyright © 1986-1996, Purdue University,
Center for Collaborative Manufacturing,
West Lafayette, Indiana 47907
All rights reserved.
TABLE OF CONTENTS
Chapter 1 Introduction to the Quick Turnaround Cell...... 1
1.1 Introduction...... 1
1.2 The Center for Collaborative Manufacturing...... 2
1.2.1 Research Program...... 2
1.2.2 Education Program...... 3
1.2.2 Industrial Participation...... 3
1.3 The QTC Testbed: A Collaboration Project...... 4
Chapter 2 QTC Software Installation...... 5
2.1 System Installation...... 5
2.2 Postprocessors...... 5
2.3 Databases...... 6
2.3.1 Machine Database File...... 6
2.3.2 Machinability Database File...... 8
2.3.3 Tool Database File...... 10
2.3.4 Vise Fixturing Database File...... 16
2.4 Feed and Speed Calculations...... 17
Chapter 3 QTC System UserÕs Guide...... 19
3.1 Name...... 19
3.2 Synopsis...... 19
3.3 Description...... 19
3.4 Arguments...... 20
3.5 Environment...... 20
3.6 Preferences...... 23
3.7 Interaction...... 32
3.7.1 Selecting Features and Handles...... 32
3.7.2 Selecting Menu Items...... 33
3.7.3 Working with Dialog Items...... 33
3.7.4 Rotating...... 33
3.7.5 Scaling...... 33
3.7.6 Translating...... 33
3.7.7 Changing Workfaces...... 34
3.7.8 Alternate Picking Functionality...... 34
3.7.9 The Feature Reference Datum...... 34
3.7 QTC Menu Items...... 35
3.7.1 Feature-Based Design Window Menu Items...... 35
Chapter 4 A QTC System Tutorial...... 40
Chapter 5 The QTC Design File Format...... 50
Chapter 6 Cutter Location Data Format...... 54
6.1 Introduction...... 54
6.2 CL-data Instructions...... 54
6.2.1 Comment...... 54
6.2.2 Linear Interpolation...... 55
6.2.3 Circular Interpolation...... 55
6.2.4 Feed Rate...... 55
6.2.5 Rapid Traverse...... 56
6.2.6 Coolant Selection...... 56
6.2.7 Automatic Tool Load...... 56
6.2.8 Spindle Operations...... 57
6.2.9 Cutter Diameter Compensation...... 57
6.2.10 Canned Cycle Operations...... 57
6.2.11 Measurement Unit...... 58
6.2.12 Probe Cycles...... 58
6.2.13 Index Pallet...... 59
6.2.14 Program Interrupts...... 60
6.2.15 Operator Message...... 60
6.2.16 Coordinate System Operations...... 60
6.2.17 Fixture Offsets...... 60
6.2.18 Program Label...... 61
6.2.19 Polar Linear Interpolation...... 61
6.2.20 Radius/Fillet...... 62
Bibliography...... 63
The QTC Document1
Chapter 1Introduction to the Quick Turnaround Cell
1.1 Introduction
The Quick Turnaround Cell (QTC) project began in 1986 as one of a number of research projects in PurdueÕs Engineering Research Center for Intelligent Manufacturing Systems (ERC) which was reestablished as the Center for Collaborative Manufacturing in 1995. The original goals of the project were to design and implement a working prototype of a system for the design and automatic machining and inspection of one-of-a-kind prismatic parts. Outlined in Figure 1.1, the QTC system is self-contained software which closely couples feature-based design, automated generative process planning and fixturing, automated numerical control programming, and direct NC downloading and CNC machining of small batch prismatic and axisymmetric parts into a fully integrated CAD/CAM environment. First demonstrated in 1987, the system currently runs on Silicon Graphicsª IRIS workstations.
Figure 1.1. The QTC System.
The intelligence of the QTC system is based on the use of geometric features and geometric reasoning throughout the system. The design module provides object-oriented, graphical, three-dimensional design based on a small number of form features, basic volumetric shapes used to construct parts. Each feature, such as a hole, circular slot, or a NURB surface, is easily positioned, oriented and sized on a workface of the stock (which is also an editable feature) with graphical interaction. Characteristic positions and dimensions of features are displayed as graphical icons called handles. Features are nominally positioned with respect to other features with offset vectors between position handles. The system makes use of much of the ANSIY14.5M tolerancing standard, including explicit datums, material conditions, and all ANSI geometric tolerance types. The resulting part model is a high-level representation of the design containing all feature information, including the geometric dimensions and tolerances (and surface finish tolerances).
The QTC process planning system reads the part model produced by the design system and generates a complete process plan that includes tools, tool paths, and fixturing information. The system performs geometric reasoning on a specially attributed boundary representation (BRep) of the part to translate the design features into machining-process features using a computation method called Òfeature refinement.Ó Feature refinement creates a global precedence graph of feature relationships. This graph represents significant geometric relationships between features that are used to determine correct process sequences. For example, if the design model contains a hole feature that intersects a slot feature, the process planner will determine the appropriate machining sequence by reasoning about the precedence information for these features. The process planner then selects tools, determines approach directions, fixture setup information, and finally creates cutter location files. Once the process planning is completed, the designer can choose to machine the part using the cell controller module, graphically simulate the machining using the numerical control verification module, or edit the part further based on the machining information now available.
The QTC project is an active, evolving research effort in quick turnaround manufacturing. Some related research projects include frameworks for multiple domain feature modeling, assembly modeling with QTC parts, five-axis sculptured surface finish machining, intelligent fixture configuration planning, and collaborative manufacturing.
1.2 The Center for Collaborative Manufacturing
The Center for Collaborative Manufacturing at Purdue University is a new cross-disciplinary center dedicated to research and education in manufacturing. With support for the next five years from the National Science Foundation, it will support innovations in the technologies of product and process realization and also in the ways of collaborating to achieve them. The new Center builds upon ten years of accomplishments of the Engineering Research Center for Intelligent Manufacturing Systems, now refocused and renamed. Through collaborative projects of diverse topics and durations conducted jointly with manufacturing companies, with other universities, with national laboratories, and with other centers and consortia, the Purdue Center will foster research and education in a new manufacturing paradigm based upon multi-site, multi-organization technical collaboration using high speed electronic networks.
1.2.1 Research Program
The Center will conduct research through focused projects that will operate at two levels. Each project will pursue internal objectives that are determined by the needs of some particular industry sector as determined by the project team participants. For example, one project may focus on advancing process capability for precision grinding, another may focus on software to assist rapid product realization, while yet another may focus on innovations in semiconductor fabrication. The projects will vary in structure, duration, and size, as well as in the focus problem definition. Each will involve multiple participants at multiple sites and cover multiple disciplines. Each focused project, viewed in isolation, can be viewed as a joint venture among the participating organizations to achieve advances in the area of its unique focus. Viewed from a broader perspective, the collection of projects represents a set of experiments in Collaborative Manufacturing. The diversity of projects will provide cases in which the factors affecting success will vary.
1.2.2 Education Program
The Center will also foster continuing innovations in education and outreach. The prior Engineering Research Center pioneered innovations in such areas as undergraduate participation in research projects, short and medium term graduate internships in industry, and experience in cross-disciplinary team projects. The new Center will carry these further. Alternatives are being considered for a new kind of financial support for highly qualified beginning graduate students which will provide several supervised educational experiences in industy. There will be a program to involve high school and middle school teachers in center activities, which will influence the awareness of opportunities in manufacturing among pre-college students. We are also planning to increase the university's flexibility to undertake short term projects of only a few weeks or months duration. These might focus on, for example, benchmarking studies, the installation of a new technology, or assessments of alternative approaches to a manufacturing problem. While such projects are not normally undertaken in universities (because they do not constitute research as we normally view it), we believe that they can benefit students' education and can form a healthy part of an overall program. We have developed innovative approaches to the management of such projects that can make them compatible with the constraints of an academic environment.
1.2.2 Industrial Participation
Companies will be able to participate in the activities of the Center in two ways. They may join one or more of the focused projects as project participants engaged in the planning and execution of that project. This would be an appropriate avenue of participation for those companies whose primary interest is at the level of some specific problem or technology. Or they may join as a member of the Center, participating in the cross-cutting project, helping to guide the education and outreach programs, and obtaining the benefits of an overall perspective of the Center. The information and methods to enhance collaborative work will be shared among the members for their own evaluation and use, as well as directly serving the focused projects. Access, early participation, and learning about the benefits and pitfalls of Collaborative Manufacturing will enable member companies to conduct their own exercises in this increasingly important and difficult area with greater foresight.
1.3 The QTC Testbed: A Collaboration Project
Collaboration between the Army Missile Command Production Engineering Division in Huntsville, Alabama and the Purdue ERC began in 1990. The goals of this project have been to adapt, extend and apply the research demonstrated by the Purdue QTC system in MICOMÕs PED environment. The QTC system was installed at the Huntsville facility in 1991. This project complements the ongoing QTC research program by extending it toward industrial application, thereby providing MICOM with the newest technology in quick turnaround manufacturing and providing the Purdue research team with critical feedback regarding industrial needs. The QTC system and research have seen significant enhancements due to this collaboration.
Additional testbeds have been established with Loral Vought Systems in Dallas, Texas, the Agile Aerospace Manufacturing Research Center at the University of Texas at Arlington, the University of Missouri at Rolla, Brigham Young University, and the Naval Air Warfare Center in Indianapolis.
Figure 1.2. The QTC Testbed Project.
The QTC Document1
Chapter 2QTC Software Installation
2.1 System Installation
The QTC System consists of several binary executable programs and site dependent database files. To make the installation of the QTC System as site independent as possible, the QTC software files may be installed in any directory. Once the installation directory has been chosen, typically the executable modules and database files are located in two subdirectories called ÒbinÓ and ÒdatabaseÓ respectively.
The QTC ÒbinÓ directory must contain the following executable modules;
qtc, design, cadint, axicadint, amps, turn, ncv, ancv, cell, and tooldb
as well as one or more postprocessors written for the system which typically has a .post extension such as t10.post and emco.post. Each postprocessor must be accompanied by a program or UNIXª shell script used to facilitate the transfer of NC files. Usually these files have a .send extension such as t10.send and emco.send.
The QTC ÒdatabaseÓ directory must contain the following database files;
machines.dat, machinesT.dat, fixtures.dat, machinability.dat, tools.dat, and gouges.dat.
The postprocessors, their send script files and the database files will be described in more detail in the following sections.
2.2 Postprocessors
The format of CL-data files generated by the QTC process planning system called Micro APT (MAPT) was developed to suit the specific needs of the QTC project. Each line of a MAPT file represents an instruction to be translated by a postprocessor to generate CNC programs. The MAPT instructions have the following format; code [options] parameters. A detailed description of each code in the MAPT CL-data file format is given in Chapter 6.
A postprocessor transforms the QTC MAPT file into an NC part program (M and G code). Postprocessors have been developed for the Cincinnati Milacron A950, Emco T2, K&T 1015, and proLIGHT 2000 controllers. Interface to additional machine tool controllers requires developing and testing of new postprocessors. Since most NC controllers are similar in functionality, the present postprocessor programs can serve as a guide to creating new MAPT postprocessors. QTC postprocessors accept two command line arguments. Take for example the following command line input;
Ònew.post p1.SETUP_1 p1.cnc_1Ó.
The first argument (p1.SETUP_1) is the name of a MAPT file to be translated and the second argument (p1.cnc_1) is the name of the resulting NC part program containing the M and G code.
Each postprocessor should be accompanied by an executable program or UNIXª shell script used to facilitate the transfer of NC part programs from the workstation to the machine tool. These programs accept one command line argument. Take for example the following command line input;
Ònew.send p1.cnc_1Ó.
The argument (p1.cnc_1) is the name of the NC part program to be downloaded. The QTC Cell Controller module executes this script file after converting a MAPT file using the postprocessor specified by the user. For example, the following ÒcÓ shell script file might be used to transfer NC programs;
#!/bin/csh -f
# Transfer the given file to the T10 device
/usr/ecn/kermit -l ttyd7 -s $1.
2.3 Databases
The QTC System obtains information regarding specific characteristics of the machining environment, fixturing configurations, tooling, and machinability from ASCII text database files. With the exception of the machinability database, these files must be modified to accurately represent each distinct machining environment to be used with the QTC System. The following sections outline the content and form of these files.
2.3.1 Machine Database File
In the QTC System, vital statistics for each NC machine tool are specified in the database file Òmachines.datÓ. The file may contain data for more than one machine but only the first machine is considered by the system. The following represents an example machine data file.
horizontal-3-axis-mill: {
id: T-10
command-language: MAPT
coordinate-system: MACHINE
custom-machine-origin: ( 0.0000 0.0000 0.0000)
home-position: ( 2.0000 3.0000 3.0000)
rapid-traverse-rate: 4800.0 // inches per minute
min-cutting-feed: 0.1 // ipm
max-cutting-feed: 100
feed-reduction-factor: 1.0 // use 100% feed
min-spindle-speed: 200 // rpm
max-spindle-speed: 5000
reference-plane-distance: 0.10 // inches
retract-distance: 0.20 // inches
tool-change-position: ( 10.7000 4.1000 10.0000)
tool-change-time: 0.2 // minutes
}
The data for each machine is contained between the lines with open and closed braces. The open brace is preceeded by a string which identifies the machine type (either vertical-3-axis-mill or horizontal-3-axis-mill). The following is a description of the variables contained in each machine data record;
¥ id Ñ The string following this variable indicates the machine tool name which is associated with the rest of the data in the record. The machine tool name is recorded in the process plan document, when a part is process planned. The name is useful to distinguish between multiple configurations of the same machine tool within the same database file.
¥ command-language Ñ This specifies the language used by the process planning system when creating part programs. Currently, QTC supports only the MAPT option. In the future, other options such as APT and M-G may be supported.
¥ coordinate-system Ñ This option allows the user to specify the coordinate system used by the process planning system when creating part programs. The cutter location data can be transformed into PART, FIXTURE, MACHINE, or CUSTOM machine coordinates. The last three options depend on the fixturing database described below.
¥ custom-machine-origin Ñ This vector specifies the offset between the global origin and the origin of the custom machine coordinate system.
¥ home-position Ñ This position vector specifies the home position of the tool. It is used as a starting point for the calculation of machining time.
¥ rapid-traverse-rate Ñ This variable specifies the machine toolÕs maximum rapid traverse speed in inches per minute.
¥ min-cutting-feed: Ñ This parameter represents the machineÕs minimum cutting feed rate in ipm. Feed rate calculations will result in values greater than or equal to the machines minimum.
¥ max-cutting-feed: Ñ This parameter represents the machineÕs maximum cutting feed rate in ipm. Feed rate calculations will result in values less than or equal to the machines maximum.
¥ feed-reduction-factor: Ñ This parameter reduces the computed cutting feed rate represented as a percentage of the computed rate (i.e. 1.0 = 100% and therefor no reduction). See section 2.4 for more informaiton.
¥ min-spindle-speed: Ñ This parameter represents the machineÕs minimum cutting spindle speed in rpm. Spindle speed calculations will result in values greater than or equal to the machines minimum.
¥ max-spindle-speed: Ñ This parameter represents the machineÕs maximum cutting spindle speed in rpm. Spindle speed calculations will result in values less than or equal to the machines maximum.
¥ reference-plane-distance Ñ This variable indicates the distance in inches between the ÒfrontÓ or ÒtopÓ face of the stock and the machining reference plane.
¥ retract-distance Ñ This variable specifies the clearance distance in inches between the workpiece and the bottom of the tool. After completing a machining operation the tool is retracted to a plane which is this distance from the ÒfrontÓ or ÒtopÓ face of the stock. Rapid motion may be used above this plane.
¥ tool-change-position Ñ This vector specifies the machineÕs tool change position.
¥ tool-change-time Ñ This variable represent the average time in minutes required to change from one tool to another tool.
An update utility is not yet available and therefore any modifications to this data must be performed manually using a text editor. In the future, coolant capabilities as well as other machining cell environment variables could also be specified in this file.