technovision - an advanced mechanical cadcam system

Technovision — an advancedmechanical CADCAM system

by P. W. ReachNorsk Data Ltd.

The potential capability of CADCAM systems has increasedconsiderably since the introduction of the early wire-frame systems.This article suggests that systems have evolved through four distinctgenerations, and argues the claims of a 'fifth-generation' systembased on a solid geometric modeller and a flexible databasemanagement system.

Introduction

Computer-aided design and manufac-turing (CADCAM) can be said to haveevolved through four distinct phases,distinguished by the technical featuresof available systems. The characteristicsof each generation can also be cate-gorised against key functional require-ments, which have changed signifi-cantly as the available technology hasdeveloped and improved. These func-tional requirements include:

• A three-dimensional database:Design engineers have traditionallyworked in two dimensions because theonly tools available to them were thedrawing board and pencil. With theadvent of high-speed, low-cost interac-tive computer graphics these engineerscan now work effectively in threedimensions to evolve their designideas, and with the same data they cantest those designs with a range of designanalysis tools.• A friendly user interface: The math-ematics of design and design analysis iscomplex and repetitive, and so thedegree to which the complexity is trans-parent to the user has a direct effect onthe ease of use of the system. Replacinga complex geometric calculation with asimple graphical interaction on a screenis a good illustration of this in practice.A simple but powerful menu structure,extensive prompting to help the user

interact with the system and rapidgraphical response to commands allhelp to reduce interruptions to thecreative thought process.• Fully integrated applications: Com-ponent design is only the first in a seriesof tasks necessary to produce a finalproduct, and all these tasks must beeffectively managed and documented.CADCAM systems must therefore havethe potential to link all these tasksthrough integrated application mod-ules sharing common data and a con-sistent user interface. These modulesmust include:

• three-dimensional design — thedesign tool used to create a completeproduct description in the computer-internal representation

• two-dimensional drafting — todocument design data in a 'hard' form;this means of communicating designinformation will be necessary for theforeseeable future

• engineering database — to permitthe efficient retrieval of existing designdata and associated information, whileproviding a channel to other manufac-turing systems such as MRP

• numerically controlled (NC) sys-tems — to generate manufacturingdata; this must extend beyond metal-cutting machines and should includeinspection machines, robots and othermanufacturing tools

• finite-element analysis — to ana-lyse design validity through stress, tem-

perature and vibration analysis• word processing — for the crea-

tion of catalogues, service manuals andother textual information requiring theuse of complementary graphic data.

In addition to specific application toolsthere is an increasing user awareness ofthe need for company-specific appli-cations, i.e. special programs whichaddress their unique requirements. Ifthe vendors were to attempt to addressthese requirements for a very smallpotential market then the developmentcost would be prohibitive, and so thesolution is increasingly seen as offeringspecial application programming toolswhich give the user access to the CAD-CAM database or ideally to the specialCADCAM functions of the system.

Historical perspective

Why is Technovision an advanced CAD-CAM system? The distinction can beargued, but it is possible to see thedevelopment of CADCAM in terms ofsuccessive generations of systems.

First-generation systemsThe earliest CADCAM systems were

based on a wire-frame data structure.This fulfilled the need for a three-dimensional database and allowed sev-eral applications to access commondata, but the data were stored in'theform of lines and connecting points inthree-dimensional space, with no refer-ence to where the solid material relatedto those points.

This meant that the user had to com-plement the computer data with manualinput; for instance hidden-line removalhad to be carried out by interactive edit-ing. So the first-generation systemsfulfilled the need for a three-dimen-

Computer-Aided Engineering Journal February 1986

sional data structure, but their ambigu-ity meant that they were not userfriendly, were not capable of automat-ing many design tasks and were there-fore not productive for design.

Second-generation systemsIn second-generation systems the

lines and points of the first-generationsystems were linked to represent theedges of the bounding surfaces of themodel. This data structure was morecomplete, but it still contained no refer-ence to the two spatial domains solidand non-solid. Limited hidden-lineremoval was possible, but mechanicalproperties were difficult or impossibleto derive from the data.

During the life of surface modellersprogress was made in the developmentof sculptured surface representation,which helped in the application of CADtools to manufacturing problems. Thiswas particularly true in the aerospaceindustry, where sculptured surfaces

represented a high proportion of thedesign and manufacturing tasks.

Third-generation systemsThird-generation systems saw the

emergence of the first solid modellers.Their data structure was complete inthat they could now differentiatebetween the solid and non-soliddomains, but their geometry wasrestricted to planar faces. These model-lers approximate the geometry ofcurved surfaces by facetting, partly torestrict the mathematics to plane inter-sections and partly to reduce theprocessing power utilised by this morecomplex data structure.

Now hidden-line removal was auto-mated and volumetric properties couldbe computed, but the inaccuracy of thefacetted model restricted its value, par-ticularly for generating manufacturingdata. The inaccuracy could be reducedby increasing the number of facets, butthis also increased dramatically the stor-

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10

age requirements for the model and thecomputation time needed to carry outmodelling operations.

Fourth-generation systemsAt the fourth-generation stage we see

the emergence of analytical modellers.Analytical solid geometric modellersare able to store an accurate representa-tion of all of the basic shape primitivesthat can be formed into a mechanicalcomponent or assembly design. Thisgeneration is important in that it repre-sents the maturity of the mathematics ofsolid geometric representation.

However, until now little effort hasgone into making the solid modeller auser-friendly, application-oriented de-sign tool. The user interface is oftenclumsy with limited graphical inter-action, and the links to other appli-cation systems such as drafting and NCare restricted to data transfer ratherthan data sharing. They also tend toimpose a considerable load on the pro-cessor, so optimisation of thealgorithms is important.

There are some systems whichattempt to achieve the benefits of bothfacetted and analytical representationsby storing both types of structure dur-ing the modelling process, but thisrequires the user to have a much greaterawareness of the mathematics of themodeller and also increases the storagerequirements even more.

Fifth-generation systemsThe fifth-generation modellers must

combine the accuracy of an analyticalrepresentation with a high level of inte-gration and user friendliness. Techno-vision represents a fifth-generationCADCAM system which combines anaccurate unambiguous data structureand a high level of true integration withengineering application modules.Technovision is a single module con-taining both a solid geometric modellerand a productive two-dimensional draf-ting system, both elements beingaccessible at all times through a com-mon interactive user interface.

Technovision is built on SIBAS, NorskData's proprietary database, whichprovides links to office automation andadministrative data processing tools. Apilot version of TECHNOTIS, NorskData's word processing system capableof receiving any Technovision gener-ated drawings, is running and has pro-duced the results illustrated in thisarticle (Fig. 1).

Technovision system concept

Technovision is a CADCAM system formechanical engineering companies. Itis based on the concept of generating a


complete product database containingall the technical, commercial andadministrative details of a company'sproducts in a consistent form whichallows all associated company functionsto access and analyse that information 'in the most appropriate manner. Thesource of all the technical information isthe two-/three-dimensional designmodule Technovision; the SIBASdatabase management system handlesthe storage of that information so that itcan be accessed by all current andfuture application modules.

Fig. 2 shows a schematic representa-tion of the total Norsk Data concept formechanical engineering companies. Itincludes the total Norsk Data range ofproducts, which is as follows:

• COSMOS — a complete range offacilities for communications bothbetween Norsk Data computers andwith other standard communicationsprotocols• NOTIS — office automation toolsincluding word processing, documentstorage and retrieval and electronicmail; there are also personal computingtools such as a spread-sheet, a reportgenerator, business graphics and a per-sonal time manager• DIALOGUE — administrative dataprocessing tools including a non-pro-cedural language for on-line appli-cations development, a relational querylanguage for ad hoc interrogation of thedatabase and a high-performance trans-action system

, • Technovision — a CADCAM systemconsisting of a series of modules for arange of design, drafting and manufac-turing activities:

• TECH2D — the base module fortwo-dimensional drafting and design

• TECH3D — a three-dimensionalsolid geometric modellerfordesign andanalysis applications

Q TECHARC — a design/drawingoffice archive system for the storageand retrieval of product documentation

• TECHLIST — automatic drawingparts listing system for the.creation ofparts lists on the drawing or in files

• TECHVAR — variant design sys-tem for rapidly generating families ofpart drawings

• TECHFTN — a Fortran appli-cations interface capable of accessingTechnovision data and functions

• TECHNC — an interface systemfor the interactive generation of NCdata

• TECHIGES — a communicationsinterface to other CADCAM systems

• TECHDIN — a standard partslibrary

• TECHNOTIS —atextand graphicsprocessing system.

Fig. 2 Schematic representation of Norsk Data's CADCAM system for mechanical engineering

Fig. 3 Variant part drawing generated by TECHVAR

Technovision system description

TECH2DThe Technovision two-dimensional

module offers a full range of geometrycreation and manipulation commands.Points, lines, circles and arcs, ellipses,splines, centre lines and equidistancescan all be created from a single com-mand, with dimensional input eitherfrom the keyboard or by graphical inter-action. Geometry can be created assingle elements or as groups which canbe structured heirarchically, thus repre-senting the true structural relationshipsof the mechanical parts in the drawing.

There is a full range of editing and


manipulation commands, includingduplication, translation, rotation, mir-roring and scaling. These commandscan be applied to elements, groups orcollections of elements containedwithin a user-specified window.

Drawing aids include automaticcross-sectioning and semi-automaticdimensioning of horizontals, verticals,distances, lengths, diameters and radii.The user can define his own object sym-bols on 99 pages, each page containingup to 100 objects with any level of com-plexity. Recall of these symbols is per-formed by selecting the page andpointing at the object on the page. Stan-dard pages are supplied for engineeringparts, hydraulic symbols and electrical

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Fig. 4 Four default views — seven options available

symbols, but these can be redefined ifthey are not appropriate.

A particularly productive feature ofthe system is that graphical display com-mands can be executed at any stage inthe drawing process, even when a draw-ing command is only partially complete.For instance, if the user wishes todimension a long component whichrequires local zooming to pick thedimensioned element, thezoom can becarried out between each graphical pickwithout interrupting the dimensioncommand.

Individual users can often multiplytheir productivity by tailoring the sys-tem to their special application needs.This requirement is catered for by theprovision of a Fortran interface. The

Fortran interface gives the user accessto almost all the Technovision drawingfacilities and allows him to capture thedesign/drafting logic of his specialapplications in a very efficient manner.For instance, a user in the constructionindustry has been able to create fullydimensioned drawings of beams, gus-sets, hole patterns and many other stan-dardised drawing elements by writing atailored set of functions which promptfor a minimal number of parametersbefore automatically generating com-plete drawing sets.

The system is menu-driven through asimple user interface, and, although thecommands are structured, the userdoes not have to climb a command treeto exit from a function as most of the

commands can be selected at any stagein the drawing process. The commandscontained on the menu pad are easy tounderstand for the novice user but arecomplemented by sub-menus andprompts displayed on the dialoguescreen. The experienced user cantherefore work very efficiently from themenu pad without the need to refer tothese prompts unless he is unfamiliarwith the command he is using.

The variant design module TECHVARallows the user to create parameteriseddrawings interactively. These drawingscan include variable dimensions whichcan be modified interactively to showthe effects of any changes immediately.The variable dimensions can be asso-ciated with other features of fixeddimensions to avoid unexpected resultsfrom variant part generation. Variabletables can be incorporated in the draw-ing to allow the user to select a tablefield; all the variables contained in thatfield are then applied to the drawing.Variable fields can contain the results offormulas which will be updated auto-matically if they contain another vari-able which is changed by the designer(Fig. 3). In an environment where partsbelong to families, this feature can beextremely productive compared withmanual methods, and by producingaccurate drawings of each family mem-ber this productivity is passed on to theNC tape generation.

It can be seen from the above descrip-tion that the two-dimensional modulecontains many features which canimprove productivity but that it alsooffers a degree of flexibility whichallows it to be applied to a diverse rangeof applications.

TECH3DThe Technovision design module is

an interactive system for designingmechanical parts and assemblies in avolumetric three-dimensional fashionwhich represents the exact shape of thecomponents. The two-dimensionaldrafting module is an integral part of thethree-dimensional system, and so allthe two-dimensional functions of Tech-novision are available at any time duringthe three-dimensional design processfor the creation of two-dimensionalprofiles, the addition of constructionlines, or for dimensioning the resultantviews of the three-dimensional design.

The system defaults to display fourwindows on the design space. Thesewindows contain three orthogonal"views together with one isometric view,all of which can be used to interact withthe model. Up to seven views or spatialpositions are simultaneously availablefor graphic dialogue operations (Fig. 4).

12 Computer-Aided Engineering Journal February 1986

The three-dimensional module util-ises boundary representation (orB-rep). Using this approach, every face,edge and vertex of the final object isrepresented. The data structure definesboth the topology and geometry of eachdetail to allow fast picture generation,direct user interaction and a wide var-iety of modelling operations.

All parts and assemblies can be con-structed by taking the union, intersec-tion and difference of primitive shapes.These shapes may be basic volume ele-ments, such as cube, cylinder, cone,sphere and torus, or they can be gener-ated from basic two-dimensional pro-files by linear and rotational sweep.Prismatic shapes can be generated byconnecting the edges of two parallelplanes provided they contain an equalnumber of geometric elements.

In addition to these conventionalmodelling facilities there are higher-level modelling commands for the gen-eration of technical elements. These areengineering commands for the creationof a variety of combined basic shapeprimitives. For instance, a countersunkhole would normally require the defi-nition of a cone and a cylinder, followedby the Boolean subtraction of both ele-ments from the main body. Techno-vision combines all these commands inone technical element command whichrequires the user to provide dimensionsrelated to the functional characteristicsof the countersunk hole. This allows theengineer to think in his own languagerather than in a modeller-basedlanguage.

System structureThe entire system is of modular struc-

ture and can be extended at will. Thisapplies to graphic dialogue, computer-internal representation and diversefields of application. The user has theopportunity to access the system at dif-ferent points so as to influence theoperation in those areas where his intel-lectual capabilities make him superiorto the computer. This applies to thedescription of the component as well asgenerating and using computer-inter-nal representations of the component.

There are, on the other hand, mod-ules, such as logic volume elementfunctions or hidden-line removalalgorithms, which perform complexsystem functions completely auto-matically.

The system incorporates interfacesrelated to user dialogue, graphic repre-sentation and data handling, which areso designed that all system modules areable to operate with these interfaces. Itis the data interface in particular whichpermits interconnection with other sys-

Fig. 5 Benchmark component with exploded view

terns intended to solve previous andsubsequent tasks related to design andproduction planning. All system inter-nal functions, such as spline interpola-tion, sectional curve calculation, logicvolume element functions and manyothers, are available for company-speci-fic applications via a Fortran interface.

The computer-internal representa-tion contains volume-oriented compo-nent information subdivided into theelement groups of sub-assemblies,individual components, surfaces, con-tour elements and points, all of whichare related to each other. The varioustypes of an element group are classifiedby codes and dimensioned by descrip-tive data.


Redundant-free structuring leads to amore rapid presentation and modifica-tion of the computer-internal represen-tations. A data interface which permitshandling of any desired tree and net-work structure is an essential pre-condition. The design of this interface isexclusively syntax oriented. Anydesired model extension — for examplethe addition of technological infor-mation — becomes as easily achievableas the model representations, which aresemantically very different from eachother. Micro-geometrical data regard-ing the surface finish, material, toler-ances and production processes can beassociated with the surfaces and vol-ume elements. Screw threads, gear

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Fig. 6 Sculptured surface superimposed on a solid model

rings or even complicated plunge-cutshapes can be represented in para-metric form or by substitution ele-ments, without each detail being shownwithin the computer-internal repre-sentation.

Graphic dialogue manipulation per-mits editing of points, edges, surfaces,part objects and complete componentsby displacement, deletion, duplicationor rescaling of selected elements. Localoperations are permitted on edges andsurfaces for the creation of chamfersand fillets.

Apart from the user interface and thelevel of graphical interaction, the mostsignificant characteristic of solids mod-elling systems is response time.Boolean operations and hidden-lineremoval have typically been measuredby the length of the coffee breakrequired to complete a command. Mea-surements have been taken usingTECH3D to model the componentshown in Fig. 5; the results tend to showthat efforts to optimise the algorithmswithin the system have achieved con-siderable improvements in responsetimes. For instance, the CPU time tomodel the complete pump was 58 sec-onds and the time to perform hidden-line removal on the exploded view was55 seconds. The model itself incorpo-rates 122 surfaces, 183 contour ele-

ments and 109 points. Thosemeasurements were taken on anND-560 processor; using an ND-570halves the above times.

Perhaps the most frequent questionasked by potential users of three-dimensional modelling systems is:'Where do I start?'. They are not surewhether to work in two dimensions firstand then create a three-dimensionalmodel from the two-dimensional data,or to work in three dimensions todesign the component or assembly andthen transfer views to the two dimen-sional system for drawing documenta-tion. This question really stems from thelimitations imposed by many modellersowing to their unintegrated data struc-ture. The designer must transfer databetween the separate systems and istherefore forced to sequence his designtasks to accommodate this limitation.

The integrated structure of Techno-vision means that the designer nolonger needs to ask 'Where do I start?',because he can use both systems simul-taneously and develop a natural designtechnique without any artificialconstraints.

The engineering database

In the past companies have tended toautomate tasks within their engineering

and manufacturing organisations in anisolated manner. This has been partlydue to the fact that computer aids haveonly been available or developed in anisolated manner for specific appli-cations. For instance, NC systems havebeen available since the late 1960s,finite-element systems were availableperhaps even earlier, and material con-trol suites emerged in the early 1960s.All these systems have required productinformation of a geometric or tech-nological nature and have tended toinclude their own facilities for productmodel creation; this has involvedduplication of effort in each applicationarea.

Now that solids modelling is becom-ing a practical solution for completeproduct definition it has become muchmore important to provide a databasemanagement system that allows all thedifferent applications to access andinterchange the right data in a timelymanner. In Technovision this require-ment is met by a range of database man-agement tools built around the SIBASdatabase system. The TECHARC systemis able to hold entries for:

solid modelsdrawingsstandard partsmacrosdrawing elementsfree text.

TECHARC handles the archive andretrieval of, and provides aid for themanagement of, all CAD-related data.Information on the location and con-tent of drawings can be searched; thedate of the last change or access tospecific data helps to maintain theintegrity of the information duringdesign revisions and ensures that every-one within the organisation is workingwith the correct common data.

Basing this system on SIBAS hasmeant that all the application toolslisted in the following section can beintegrated with the Technovisiondatabase with the minimum effort.

Integrated applications

For the purposes of this article it is notessential to detail the functionality ofthe existing SIBAS-based tools, and sothe following is simply a list of the estab-lished systems running with SIBAS onNorsk Data processors:

• NOTIS:• WP — a sophisticated but easy to

use word processing system; a pilot ver-sion of TECHNOTIS which allows theinsertion of any Technovision drawing

14 Computer-Aided Engineering Journal February 1986

into a text document for output on astandard WP printer has produced theresults shown in Fig. 1

• ACCESS — for handling lists ofrecords containing text and data itemsand for merging this information withother text

• RG — an easy to use' reportgenerator

• IR — for document filing andretrieval using searches on file keys orfor specific words or phrases within thedocument

• ID — an electronic mail system forcommunicating internally or over pub-lic and private networks; there are alsolinks to the international telex and tele-text networks

• CALC — a large-scale spread-sheet system

• BC — for business graphicspreparation

• PM — a multi-user calendar andtime management system.• DIALOGUE:

• UNIQUE — a non-procedural lan-guage for on-line applicationsdevelopment

• ACCESS — a query language forad hoc interrogation of the database,offering a logical relational view

• ABM — application building andmaintenance for high-performancetransaction systems.

Technovision hardware

Technovision systems are configuredon a range of Norsk Data processors,workstations and peripherals. The pro-cessor can be selected from the 32 bitND-500 range; the performance of therange is summarisecMn the panel.

The ND-500/(J:X range is based on a

distributed processor design aroundNorsk Data's multiport memory system.A front-end processor performsresource allocation, interrupt handlingand maintenance tasks. One or moreprocessors prepare and execute theuser programs. Technovision runsunder the standard operating systemSINTRAN, which is a multi-user virtualstorage system. It supports simul-taneous batch, real-time and time-shar-ing use and is therefore well matched tothe CADCAM environment.

o

o

Fig. 7 Movement simulation

Computer-Aided Engineering Journal February 1986 15

Fig. 8 Shaded view of fabrication

Fig. 9 Shaded view of complex machined casting

The workstationThe Norsk Data CADCAM work-

station incorporates high-resolutioncolour graphics of 1448 x 1024 pixelsand an intelligent graphics processorwith structured display file memory anddisplay generation hardware. A secondscreen displays system prompts andsub-menus and echoes commands initi-ated from the menu pad. This screen isalso configured to access non-graphicalapplications within the CADCAMenvironment, such as word processingand database management.

The local processor allows very fastlocal picture regeneration and transfor-mation, such as pan and zoom, without

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imposing any load on the host pro-cessor. Communication with the host iscurrently through asynchronous linesrdnning at up to 19.2 kbaud, but theOctober 1985 release of Technovisionprovides for parallel communication at51.2 kbaud through a programmableinput/output controller; this will resultin a considerable increase in drawingspeed from the host without imposingany noticeable increase in load on theCPU. This increase in performancestems from Norsk Data's ability todevelop both hardware and software

functions within a single organisationwithout reliance on an outside supplierfor system elements.

Future development of the work-station will concentrate on the userinterface, but will also take account ofthe needs of other users for a commonapproach across a wide range ofapplications.

Technovision future development

The development of Technovision isbeing carried out by Norsk Data teamsbased in West Germany, the UK andNorway. In parallel a number ofresearch institutions in West Germanyand Norway are working on medium-and long-term development projectsbased on the same basic system. Thisresearch is in the main areas of:

information systemsman-machine communicationgeometric modellingdesigntechnological planning.

Many of these developments will beavailable to Norsk Data as a co-operat-ing partner in the Advanced ProductionSystem project. Early in 1986 the pre-liminary results of integrating a B-splinebased sculptured surface facility will beavailable in the Technovision product(Fig. 6). Other developments to beincorporated include movement sim-ulation and colour-shaded picture gen-eration; examples are included in thisarticle (Figs. 7-9).

Conclusion

The most significant advance that Tech-novision represents is that it is one ofthe first integrated CADCAM systems tooffer such a wide range of applicationswhich have been based on a solid geo-metric modeller and a flexible databasemanagement system at an early stage ofdevelopment. Many of the large turn-key CADCAM suppliers are finding itdifficult to advance technically becausetheir systems are based on the earliergenerations of software and hardwaretechnology.

Users are now much more aware ofwhat CADCAM is and of the technologythat is available; they are more discern-ing in selecting the right solution fortheir company. Norsk Data believes thatfor many companies in the mechanicalengineering sector Technovisionprovides the right solution to theirneeds, and is committed to ensuringthat it will be capable of meeting theirfuture needs also.

P. W. Reach is with Norsk Data Ltd., Benham Valence, Newbury, Berks. RC16 8LU, England.


technovision - an advanced mechanical cadcam system

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