ALGORITHMS IN CAPP (CAD-T) ACTIVITY

ALGORITHMS IN CAPP (CAD-T) ACTIVITY
Anisor Nedelcu, Maria Mihali
Transylvania University of, Brasov, Romania
Abstract:
Key words:
The actual obtaining of the technological documentation is achieved in the AutoCAD system, the designed
system generating a number of SCRIPT files, which perform calculation and provide the necessary
information to fulfill the operation plan sheet. The operation plan is also recorded on the disk, in the
AutoCAD library, in a block format with attributes: the block attributes are the information required from the
Computer Aided Design of Technology system, for the completion of the operation plan. On the disk the
operation drawings are recorded also in block format with attributes. All these blocks are AutoCAD files with
the extension *.dwg.
CAD-T/CAPP, AutoCAD
1. INTRODUCTION
This paper treating how to acquire with electronics equipment the technological documentation
(the operational plans) needed for the manufacturing of a concrete part supported by typical
technological process of the group pieces. The real implementation of the automation in the design of
the technological processes of the various parts in the field of mechanical engineering involve the
necessity of creation in this field of an information system integrated in the general frame of the
information stream for the technological design. Achieving such information system for the Computer
Aided Design of the manufacturing processes, through cutting procedures have a direct contribution to
the quality improvement of this activity as well as to the achievement of high rate of production in the
design phase. Thus, the information systems for the Computer Aided Design of the Technological
processes is a distinct module, which can operate both independently with numerical data introduced
from the Keyboard and connected to the other modules composing the computerized technological
system, in which case the outputs and inputs are transmitted between the various modules according to
the information stream.
The final goal of an information system is to provide results to the user. Namely, the information
system for the Computer Aided design of the technological processes (CAD-T) aims to obtain printed
results or in a file recorded on the disk, i.e. the technological documentation )the operational plans)
needed for the manufacturing of a concrete part.
2. THE TECHNOLOGICAL COMPUTER AIDED DESIGN PROGRAM
The design programs follow in a logical order all phases [1] needed for a complete design. The
program include several modules (procedures, figure 1), which automatically (or conversationally if it
is the case) solve the various stages of the design alghoritm. The main program achieves the link
between the various modules, call the databases matrices [1] for data extracting in order to design the

320 Anisor Nedelcu, Maria Mihali
technological process for a concrete part manufactured with cutting technology from a part group or
class and record all the obtained information for a late ruse.
The program is writing in TurboPASCAL 6.0 language. The main program structure is very
simple, as following:
BEGIN
Header; Page 1;
Screen; General Data;
CaseldProc; Addition;
Int-dim; Speed;
TimeNorm; RegenScr;
END.
Figure 1. The main program structure
The main program makes simple calls of the various procedures (modules). A short description of
the utilized procedures is given below:
a) Header, Pagel1.Screen, RegenScr are procedures for the display area gestations in text mode; they
interface the user to the computer, making, and a „user-friendly” environment. It is generally
accepted that the fashion of a program is very important for as commercial success.
b) General Data is the procedure allowing the taking over the general input deformation regarding the
concrete part.
c) CaseldProc is the procedure which materializes the case identification process [1] and within the
surface information is taken over with their complete geometric description, including the precision
and the quality of manufacturing. This procedure returns the technological process for the concrete
part (the technology matrix type 2) selected from type technology process (the technology matrix
type 1).
d) Addition, Int-Dim is procedures which solve the problem of manufacturing supplements
determining and of the intermediate technological dimensions.
e) Speed is the procedure which solves the problem of cutting condition parameters determining.
f) TimeNorm is the procedure which determines the technical norm of time
g) Printer is the procedure for the printer administration, in order to print a document containing some
data needed for marking the technological dimensions on the operation drawings.
h) Edit is the procedure for the postprocessor, which do not anything else but generate a series of
SCRIPT files (*.scr), containing the data to be recorded in the operation plan sheet; for each
operation a separate SCRIPT file is generated.
To use in practice systems based on such programs all parts being in manufacturing in a given
Company must be classified in parts groups or classes depending on the geometrical shape and
dimensions. For each class or group of parts a complex part must be selected or designed for the
manufacturing of which the type technological process must be used [1].
From the type technological process of the complex part which represents a class or a group, the
program selects the operations needed to manufacture a concrete part, with the indication of the
manufacturing methods, tools utilized, the cutting speed, the technical norm of time etc.
For a better understanding of the diagram from the figure 2, as well as of the application programs
chain, a description of the algorithm for database utilization is given hereafter:

Algorithms in CAPP (CAD-T) activity 321
– Identification of the type technology matrix using the surface code surface quality and precision
class marked on the execution drawing.
Figure 2. A description of the algorithm for database utilization
– Selecting the technological method or procedure corresponding to the respective manufacturing
process.
– Machine tool identification with the related data.
– Using the data selected from the other matrices the manufacturing supplement is calculated and the
intermediate technological dimensions, the cutting speed parameters and the technical norm of
time. The calculated data or taken over during the matrices during the process are recorded in the
second part of the type technology matrix. The record will be located at the same position on which
the surface was identified.
– Comparison between the surface codes from the type technology matrix according the type of
manufacturing. This latter type will be that in which the quality surface and precision are greater
and the position are to be identified (number, operation number, phase number).
– The alghoritm stages are iteratively replayed beginning from the point 2.
– The process continues for the same surface until the greater values for the dimensional surface
quality and precision are found.
– The input program is loaded and the next surface data are introduced.
– The alghoritm is replayed from the beginning for each surface composing the concrete part from a
group for which the technological process with cutting tools is designed.
The results of the program package running are recorded in the second part of the type technology
matrix. By exploiting this matrix the operation plan can be derive don the printer.

322 Anisor Nedelcu, Maria Mihali
3. ACQUIREMENT OF THE TECHNOLOGICAL DOCUMENTATION
As already stated, the information is carried throughout the system in a numerical code format. The
results provided by the system are also coded in a numerical format. This code is usually decrypted
only by dedicated computer procedures or experienced programmers. In the next stage a postprocessing
phase is needed in order to prepare the technological documents in the usual format, i.e.
translation from the computer numerical format to the natural language easily understood. The postprocessing
work is performed using the processor (the post-processor), embedded into the procedure
EDIT, presented in [1].
As presented in [1], the system has a core element the technology type matrix. All needed
information to edit the technological documentation for a given part manufacturing with cutting tools
are provided by this matrix. The only needed operation is decoding and then recording in the usual
table on the manufacturing plan sheet. The way in which the information is recorded from the type
technology matrix in the manufacturing plan sheet is the following: using the surface code introduced
through the input procedure of the initial data, the type technology matrix derived and the surface
position is recorded, the operation number, phase number, operation title, the manufactured surface
title etc).
Using the surface position previously identified a procedure or method is searched for the
technological process according to the manufacturing type. For this procedure all features are taken
into consideration: the procedure code, the procedure title, the machine tool code, preparatory-ending
time, the necessary data for the technical norm of time calculation (for the technological procedures or
methods of manufacturing for which there is no any mathematical model for calculating the technical
norm of time) such as: auxiliary time, supply time, organizational time, resting time, the number of
parts simultaneously/successively manufactured etc. Also, using the procedure code and the machine
type code, the machine tool type is identified and all characteristic data are selected: the machine tool
name, producer, the machine tool code etc.
For this operation of the manufacturing process for the respective surface, using the data selected
from the other matrix during the process 2, 3 the manufacturing supplement and the intermediate
dimensions are calculated as well as the cutting conditions parameters, the technical norm of time and
likely the manufacturing cost. These technological data are taken from the second part of the type
technology matrix. Using the surface code the technology group matrix is searched, the cutting tool
address, the auxiliary tool address, the manufacturing device address and the dimensional check
device address. In this way the technology documentation is fulfilled for manufacturing part faces the
cutting technology process of which is in fact designed.
In the AutoCAD geometric modeler, deriving the manufacturing operations drawings for the
surface is a very simple task if SCRIPT files are used. The numerical information of the drawing has
been obtained following the previous calculations and the database exploring using a TurboPASCAL
program. The SCRIPT file method is used when there is no need to keep the real proportions between
the dimensions of the drawing (e.g. the drawings for the operation plan, the drawings for the adjusting
sheets in case of automate lathe use, some drawings for calibrated tools etc) [1].
The SCRIPT files contain AutoCAD commands which are successively executed, in an automatic
way. These files are TXT files, in which the commands are recorded with respect to the usual syntax
and operation order in AutoCAD. The SCRIPT files are recorded on the disk with a name and the
extension “SCR”.
A SCRIPT file may be created in an automatic way using a TurboPASCAL program: obviously,
specific procedure are needed in order to process the numerical results and decisions obtained by the
main design program (in our case the program for Computer Aided Design of Technology).
The design program [1] decides what surfaces are manufactured at each operation. A SCRIPT file
was created which to put into the operation plan sheet only those blocks corresponding to the results.
The blocks library contains all possibly shapes which may be obtained, in each manufacturing
operation (each operation correspond to a line). The blocks have the name coded in the following way:
B + Operation Number (of the line in which the drawing is made, counted from the top to bottom) +

Algorithms in CAPP (CAD-T) activity 323
the drawing position in the respective line. A matrix of the form [b ij ] is obtained, where, i-the
operation number, j-the drawing position on the respective line.
Figure 3. Acquirement of the technological documentation
From the main program, the intermediate dimensions and corresponding block are obtained for
each surface to be manufactured. These data are systematized in tables like the following model:
Table 1. The systematized of intermediate dimension and corresponding block are obtained for each surface to be
manufactured
Operation Phase Surface Surface Block Dimensions
number number group code type code position D13= L1= D11=
10 1 1 01 4
The SCRIPT file contains AutoCAD the necessary commands as well as the appropriate answers in
the corresponding dialogues. These files are executed from the AutoCAD session with the command
SCRIPT and the text lines are automatically executed one by one as AutoCAD is an interpreter based
language. At the SCRIPT end file the control is returned to AutoCAD.
Figure 4. The editing process of the technological documentation
Because the files are in text format, they can be generated easily with a TurboPASCAL processor
program. In conclusion, the editing processor only writes the output data in a precise established
format and order. The editing process of the technological documentation is presented in figure 4.
REFERENCES
1. NEDELCU A., „Modele matematice, algoritmi si aplicaţii privind proiectarea asistată de calculator a proceselor
tehnologice de prelucrare prin aşchiere”, Teza de doctorat, Universitatea Transilvania din Braşov, Romania.