Computer Aided Automatic Design: Course Held at the Department of General Mechanics, October 1972

36 Pages·1974·2.534 MB·English

by  C. Bona, C. Galletti, A. Lucifredi (auth.)

INTERNATIONAL CENTRE FOR MECHANICAL SCIENCES
C 0 U R S E S A N D L E C T U R E S No. 155
C. BONA
RESEARCH ENGINEER, OLIVE1TI, IVREA
C. GALLETTI - A. LUCIFREDI
UNIVERSITY OF GENOVA
COMPUTER AIDED AUTOMATIC DESIGN
COL'RSE HELD .'\T TIIE DEPARTME~T
OF <~ENERAL ~ECHANICS
OCTOBER 1972
l'DINE 1974
SPRINGER-VERLAG WIEN GMBH
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whether the whole or part of the material ia concemed
specifically those of translation, reprinting, re-use of illustrations,
broadcasting, reproduction by photoeopying maine
or similar means, and storage in data banks.
© 1972 by Springer-Verlag Wien
Originally published by Springer-Verlag Wien-New York in 1972
ISBN 978-3-211-81205-1 ISBN 978-3-7091-2868-8 (eBook)
DOI 10.1007/978-3-7091-2868-8
PREFACE
The digital computer, when properly used,
has memory, Velocity and accuracy characteristics
which overcome the corresponding human characteris
tics in the same field. The development of time-sha~
ing systems has stimulated conversational forms of
the man-machine interaction, creating a strong inter
est for all kind of software enabling the user to
take full advantage of the computer possibilities in
every phase of an engineering job. Mainly in the lat
est years a number of programs has been developed,
having in general high interactivity possibilities
and enabling a designer not deeply specialized in the
use of computers to take full advantage of the typical
characteristics mentioned before. This, of course,
doesn't mean that the designer is replaced by a com
puter, since the intuition, the engineer's feeling and
the experience cannot at all, at least for the moment,
be transferred to the machine, but simply means that
the computer performs that part of the design steps
requiring computations, ripetitive operations, and
often a graphicism. In this way the creative possibil
ities of the designer are stimulated, being decreas
ed the number of the most tedious phases of his job.
The programs of such a kind, which many authors are
developing in many scientific fields, are referred to
4 Preface
as Computer Aided Design programs. In partiaular, the
authors of this paper have worked also to the soZution
of a number of speaifia probZems; nevertheZess it seems
more interesting here to pay attention to the more gen
eraZ programs instead of to partiauZar aases, and the
trends of the researah efforts in aZZ the worZd appair
to be oriented in this direation. Therefore the pro
grams of general kind deveZoped by the authors are ex
amined hereafter, with speaiaZ referenae to the prob
lems inherent to their use more than the speaifia de
saription of the teahniques and of the algorithms.
Udine, October 19?2
SUMMARY
After a survey of the design process to under
line the different stages in which the use · of a computer can
be utilized with profit, some programs developed to assist the
mechanical designers in their job are discussed.
These are organized into an integrated system
made up of a supervisor (MLINK),two basic languages (MEDES &
TEADI) and several post-precessors which will be briefly describ
ed.
Further improvements of the system are also
discussed concerning new programs to be developed andnew types
of hardware to be adopted.
The main target of this research is to improve
the qualit y of the design and to reduce the time from the set
tlement of performance specifications to the moment in which
a working prototype is available. From the very beginning the
activity of the team involved in this research has been two
fold: a consulting service for the solution of actual specific
problems requested by various mechanical design laboratories
and a research activity for the development of new computa
tion tools to handle recurrent problems.
The experience gained in solv ing specific prob
lems has been the base for indiv iduating the problems more
6 C. Bona, C. Galletti, A. Lucifredi
frequent and more critical that could be solved with profit
using a computer and for selecting the algorithms and defin
ing the programs or the basic software to be developed.
The research led to the definition of an integra,!
ed package of programs to cover those areas in the design and
.in the construction of a prototype that the experience proved
to be more critical or more promising.
The following is a list of the programs envisaged.
-Construction of automatic handbooks with
graphical and procedural informations: mec!!_
NUMBERAND
TYPE SYNTHESIS anisms data bank (~)
-Analysis of an act of plane motion (AMOTO)
-Point precision synthesis (BPOINT)
-Synthesis by mathematical programming
FUNCTIONAL
(OTMEC)
DIMENSIONS
-Cam design (PROTCAM, CAMTA, ACIN)
-Gears & envelopes (INVIL, INGR)
-Synthesis by trials & errors (ACIN)
SI'RUCTURAL -Stress analysis (STRESS, STRUDL,.INSI'R, OUSI'R)
DIMENSIONS
-Computation of geometric & dynamic properties
of nz1. D II ( ~~) bodies ( GEMAS)
2 -
-Dynamic analysis (VELAC, ANDIN, FORZE)
RELIABILITY -Tolerance analysis (TOLAN)
ANALYSIS
-Overall layout analysis (GROUP)
~~--------------
~~~) It 's customary to call "2 1/2 D" bodies those tridimensional
bodies where all the characteristics of interest refer to paral-
lel planes.
Computer Aided Automatie Design 7
-3D Drawings (PROIE)
-Characters drawings (CARAT)
AUTCMATIC -N/C Programming of:
DRAWINGS -Gears & envelopes (INVIL, INGR)
AND N/C -Cams & automatic lathes cams (CAMTA,
PROGRAMMING PROGRAM-SINSE) --
-contouring, scribing, milling (~
POST PRECESSORS)
As the reader can see practically all stages of the project can
be assisted by appropriate programs.
As no particular knowledge about the use of the
computer could be supposed for the potential users, from the
very beginning one of the main specifications settled for the
system was a great versatility and simplicity in use.
This led to the adoption of a video-display (i~)
as the main input-output device, to the development of a supe!
visor ''MLINK" to be able to link from any program of t;he system
to any other and to the development of two gr:tphic languages
''MEDES" and "TEADI" to facilitate the description to the compu!_
er of the mechanism or of the part to be studied. Before going
into a detailed description of these languages and of the other
programs few words must be said about the hardware used.
The initial configuration was an IBM 1130 with
(*) In these notes we will refer mainly to one specific hard
ware configuration; however the same philosphy has been suc
cessfully used with a different kind of computer and display
unit, as briefly discussed later on in these notes.
8 C. Bona, C. Galletti, A. Lucifredi
16K words of core memory, two 2315 500k words disks and a 2250
refreshing display. A modern and a 2400 bode line connected this
computer to an IBM 360/65, but very soon it became evident that
the increased power of the system did not pay the extra costs
because of the very low efficiency of the link and the large
amount of core storage requested on the large computer. There
fore the core storage of the 1130 was expanded to 32K and the
linkage to the 360/65 dropped.
All the system, the supervisor and the two basic
languages have been developed using a basic graphic soft\vare
developed by the same team. This package, called 11GODS11, has
been developed since the standard IBM software, the GSP, al though
very powerful, needed too much core memory and was slightly cum
bersome to be used, whilst the GODS was simpler and much smaller
(0.8 + 1.3 Kwordsusedagainst8 + 14 requestedbytheGSP).With
the IBM 1130 no mul tiprogramming is possible and the computer is
continuously dedicated to one display. This makes a very bad use
of the computer resources as it works with the designer1s time
constants instead of with the hardware time constants.
Because of this and of the high costs of refresh
ing displays, such a system would be too costly to be mul tiplied
to serve several users in real time, what is much advisable if
one wishes to take full advantage of the capabilities of the
interactive process.
The research is now oriented to the use of low
Computer Aided Automatie Design 9
cost storage displays connected to a small computer in a multi
programming or time sharing environment.
THE SUPERVISOR ( "MLINK")
This program can be considered as a swi tch to
jump to and from any program of the system. As it gains the con
trol of the CPU the page shown in Fig. 1 appears on the display
screen; this is a list of the programs available, any of which
can be executed by indicating its name with the light pen. Any
name can be added or deleted at any time by hitting the command
with the light pen and typing the name by the display keyboard.
Any program wri tten wi th the standard MLINK exi t routine can be
aborted by hitting any key of the functional keyboard. This ac
tion returns the control to MLINK.
As the files created during the session are sav
ed this procedure turned out to be very helpful to recover from
any wrang command which aborts the program in execution.
MLINK consti tutes for the user a very simple tool
to access to any program of the system or to link from any prog
ram to any other and therefore is the coMective tissue of the
system as a whole.