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导联线数控铣床外文翻译(英)

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2021-01-19 19:10
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2021年1月19日发(作者:carefully)
V
ision Assisted NC Milling Path Generation

Vision Assisted NC Milling Path Generation
With
the
rapid
development
of
computer
technology,
Fundamentally
changing
the
traditional manufacturing industry


the industrial developed countries spent huge sums of money
on
the
modern
manufacturing
technology
research
and
development,
to
create
a
new
model.
In
modern
manufacturing
systems,
CNC
technology
is
the
key
to
technology,
which
combines
microelectronics, computers, information processing, automatic detection, automatic control, such
as
the
integration
of
advanced,
a
high-precision,
high-efficiency, flexible
automation,
and
other
characteristics,
the
manufacturing
industry
Flexible
automation,
integrated,
intelligent
play
the
pivotal
role.
At
present,
NC
technology
is
undergoing
a
fundamental
change,
from
a
special
closed-loop control mode to general-purpose real-time dynamic open all closed-loop control mode.
In
the
integrated
on
the
basis
of
the
CNC
systems
ultra-thin,
ultra-light;
on
the
basis
of
the
intelligent,
integrated
computers,
multimedia,
fuzzy
control,
neural
network
and
other
technical
disciplines,
NC
system
to
achieve
high-speed,
high-precision,
Efficient
control,
automatic
processing can be amended to regulate compensation and the parameters for an online intelligent
fault
diagnosis
and
treatment
of
the
network
based
on
the
CAD
/
CAM
and
CNC
systems
integration
as
one
machine
network,
makes
the
central
government
centralized
control
of
the
group control processing


For
a
long
time,
the
CNC
system
is
traditional
closed
architecture,
but
only
as
a
non-intelligent
CNC
machine
controller.
Process
variables
based
on
experience
in
the
form
of
pre-fixed parameters, processing procedures before the actual processing by hand or through CAD /
CAM
and
automatic
programming
system
prepared.
CAD
/
CAM
and
CNC
have
no
feedback
control link, the entire manufacturing process CNC is a closed ring-opening implementing agencies.
In a complex and changing environment under the conditions of processing tool
in the process of
composition, workpiece material, spindle
speed, feed rate, tool path, cutting depth, step, allowance
and
other
processing
parameters,
not
at
the
scene circumstances
under
external
interference
and
real-time dynamic random factors, not by random amendment feedback control link CAD / CAM
settings volume, in turn, affect the work of CNC machining efficiency and product quality. Clearly,
the traditional fixed CNC system that controlled mode and closed architecture, limiting the CNC to
the development of more intelligent control variables, can no longer meet the increasingly complex
manufacturing process, therefore, the CNC technology in the potential for change inevitable.

CAD/CAM software are an interrelated mesh of computer programming systems that serve
to
monitor,
process
and
control
the
flow
of
manufacturing
data.
Modern
day
techniques
rely
extensively on the integration of standards like the initial graphics exchange specification (IGES)
with automated path planning modules. The intent of such an integration is to maintain the system
as generic as possible. Integration of the various aspects of manufacturing systems provides total
automation of the system.
A

machine
vision
system
was
used
to
generate
the
NC
code
to
face
mill
any
planar

polygonal
part.
The
vision
system
helps
to capture
the
image
of
the face
of
a
polygonal
object.
This image is decoded into edges and vertices by performing computations in software, based on
simple
image processing rules. Then the software passes the control to a path planning module.
This module selects the most efficient tool path and generates the part program to face mill the
part.
This
paper
presents
a
detailed
description
of
the
algorithm
developed
along
with
its
application environment.

- 1 -
V
ision Assisted NC Milling Path Generation

Keywords:
Machine Vision, Path Planning, NC Milling
Introduction
Machine vision systems have been used for a wide variety of applications. These include
the inspection of routine industrial parts ~.4 and robotic assembly. 5.6 V
ision systems have also
been integrated with robotic systems to provide automatic sensing of pose and velocity of the end
effector.
With
the
advent
of
inexpensive
computational
hardware,
machine
vision
systems
have
emerged as an economic component in manufacturing systems.
During
this
century,
the
development
of
manufacturing
was
characterized
by
the
increasing
efforts
to
automate
machine
processes.
Numerical
control
(NC)
of
machine
tools
marked the beginning of the era of computers in manufacturing. Numerous techniques have since
been
developed
to
assist
in
this
process.
The
NC
machine
tools
have
been
interconnected
by
material flow systems and assembly cells. The NC machines are supported by off-line software to
generate part programs and tape formats to machine a variety of part geometries. Off-line software
is created by path planning experts using NC CAD links like NC vision and NC link.
CNC
and
DNC
machines
provide
direct
access
to
the
machine
via
a
control
computer.
However, there are special occasions in a job shop where the part geometry changes (either due to
design change or vendor specification). In such cases, altering the NC path plan proves to be very
cumbersome and expensive. Hence, an integral module of vision, CAD and CAM should be used
in facilities with changing part environments.
This module will help the machine to 'see' the part, extract its geometrical features and
organize
them
in
an
IGES type format.
By
the
organization
of
geometric
data,
the
machine
can
automatically plan the machining sequence to attain better process efficiency. The pick and place
devices, such as a robot, can also be instructed based on the information generated by this integral
module.
Extensive
research
has
been
done
in
the
field
of
machine
vision
systems
and
in
path
planning.
However,
there
is
no
evidence
of
a
machine
vision
system
being
integrated with
path
planning procedures. In the present paper, a combination of machine vision, CAD and CAM are
used
in
order
to
develop
a
structure
to
define
an
efficient
tool
path
for
milling
flat
surfaces
on
parts.
Requirements for Path Planning
The
initial
graphics
exchange
specification
is
a
communication
file
structure
for
data
produced on and used by CAD systems, The objective of IGES is to provide a common standard
for automatic interchange of data between CAD and CAM systems. At the present time, there are
three types of computer models commonly used to represent solid are the wireframe,
boundary,
and
volume
representation
models.
Each
of
these
models
has
advantages
and
disadvantages.
In its present
form, IGES does not accommodate volume representations. It stores data for
an object in terms of its exact position and orientation. This data is split up into various parts. For
example, a polyhedral shape is captured by the faces which form it. tThe daa for these faces are
stored by splitting them into edges that form them. These edges are further defined by the vertices
forming them. The vertices are stored in terms of their position and orientation with respect to the
coordinate
axes.
Consequently,
the
data
for
an
entire
object
is
stored
in
terms
of
its
space
geometrical specification. Thus, IGES pertains to computer- oriented product definition and deals
with both CAD and CAM.

- 2 -
V
ision Assisted NC Milling Path Generation

The data stored in an IGES format can form the input for many CAD/CAM applications.
Modern
day
techniques
rely
extensively
on
integration
of
such
standards
with
automatic
path
generation
routines.
There
are
a
number
of
programs
developed
to
generate
the
tool
path
to
machine
objects.
These
CAM
software
packages
are
mostly
off-line
and
used
to
generate
the
required
part
programs
to
machine
objects
in
NC
machines.
Path
planning
modules
provide
the
user with a more efficient planning tool for generating efficient NC code. The only
information
needed by the path planning module is the geometric features of the part to be machined.

These
path
planning
modules
should
be
generic
as
well
as
flexible.
Hence,
they
should
comply
with
the
rules
of
optimal
machining strategies. In face milling, there are
two
types
of
path
generating
strategies:
staircase milling and windowing, illustrated in
Figure
1.
Both
techniques
find
application
in
the industry. Though efficient path planning is

possible, optimal path planning
is not evident
in the literature.
Hardware/Software Structure
Image
Acquisition
and
Processing.
A
video capture system was used in this study to
acquire
the
image
of
the
polygonal
faces
of
flat
cast
parts.
The
video
capture
system
is
illustrated
in
Figure
2.
The
video
capture
system consists
of
three
main
components:
a
vidicon camera, a frame grabber, and a video
interface board. The video capture system is a part of the IBM PC based PC-EYE system.
The images were binary thresholded (black image on a white background). Pre-calibration
was done using strips of known dimensions to estimate scale factors. The boundary pixels of the
object
were
identified
to
detect
the
edges
of
the
object.
A

two
dimensional
boundary
walking
technique
was
used
to
encode
the
boundary
of
the
object.
The
Hough
transform
technique was
applied
to
identify
the
edges
of
the
object.
Intersections
of
these
edges were
obtained
by
using
Cramer's
rule.
Thus,
the
vertices
of
the
object were
deciphered.
A

bounding
box
was
used
to
define the valid intersections of the edges (taken two at a time, in order). The image capture and
processing is a separate topic in itself and is explained elsewhere in the literature. Only a summary
is presented here so as to understand the contents of this paper.
Organization of Data. After obtaining the geometrical information of the part in terms of
its faces, edges and vertices, these data were organized in an IGES type format. Working on input
obtained through the vision system, the path planning module was created. Data for one face of
the object is obtained at one time. This face is then broken down into edges and vertices. The first
task
of
the
developed
algorithm
is
the
renumbering
of
the
vertices.
This
step was
done so
as
to
keep
an
orderly
track
of
the
vertices
and
to
keep
it
as
generic
as
possible.
The
program
then
determines the maximum Xcoordinate of the face in question. At this point, the face is split into
two parts, the upper part and the lower part, defined as the forward and reverse loops, between the
maximum and minimum Xcoordinate.

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