Vision Systems
The claims for vision systems are they support smaller, faster,
and more efficient production. There are several applications
for vision systems in the industrial market today. As the need
for smaller components and parts made from new materials increase
the error proofing of the past become less and less efficient.
The speed at which the assembly processes are working make it
impossible for a human to check each part properly. Vision guided inspection
provides a means for the manufacturer to get the flexibility and
quality that customers demand.
There are many applications for the Acuity Imaging Systems.
In automotive assembly, the vision system inspects castings for
voids and flashing problem. Fluorescent light bulbs can be checked
for cracks blemishes and defective ends. In electronics, bent
and missing leads can be identified. Vision systems can be used
to inspect food to see if the proper amount of fat has been trimmed,
and berries can be sorted, separating flawed fruit at an incredible
rate of speed by using a burst of air to deflect the imperfect
berries. Even our recreation is affected by this new inspection
process. The labels on golf balls are inspected by a vision system.
Equipment in the construction are inspected such as pipes are
threads per inch and pitch.
How does a vision system work? Picture
Lighting is very important to properly sense the part. There
are mainly four ways to illuminate the part. Front lighting is
the most common and easiest to install. Diffused back lightning
using many lights large nearby source such as sunlight on a cloudy
day produces no shadows or reflections. Structured light produces
a line or point used to establish presence, orientation, and contour.
Strobes such as the ones used to separate berries is a structured
light for high speed processes. The fourth method of lighting
is collimated back which can be used to enlarge a small part for
attribute verification. The vision sensing cameras optically sense
the presence of the object. The charge coupled device such
as a digital camera
store the images digitally. The RS-170 is the most common camera
in machine vision. The image is then send to the analog to digital
converter. The image is stored in a two dimensional array to form
a 640X480 pixel image with 256 gray scale levels. This discrete
image is brought to the processor to be processed and analyzed.
The pixels can be analyzed as a whole or individual portions of
the image can be evaluated.
Assembly
The first of many applications is to inspect the assembly
processes. Alternative error proofing either has the complete
assembly process to be automated or the operator must inspect
his or her own work. In the automotive world where zero defect
tolerances are to be expected, the few errors that even the most
competent operators make is unacceptable. Vision systems allow
each step of the assembly process to carefully monitored. After
each step is verified a positive indication is given to the operator
and after the operation is complete the vision system will give
a signal to the PLC that the operation is complete.
Automotive
Loranger manufacturing use a vision system to detect flaws
in molded plastic parts. The ignition components are produced
in a four cavity mold with less then a five second cycle. Originally
they needed to perform a 100% inspection on the ignition system.
Loranger manufacturing used a Power Vision 90 from Acuity Imaging System
with two cameras and a two step process. The Power Vision 90 signals
to an arm to reject a bad part.
Ford electronic division used a vision system to inspect a
LCD clock. the system inspects four clock displays with a total
of 130 LCD segments every 0.4 seconds. Total test time for the
four clocks is 30 seconds. This involves over 2800 operations.
Land Rover
uses a vision system to inspect their electronic calibration of
the electronic air suspension (EAS). Measuring the height of each
air suspension unit throughout its range and stores the information
for each position of the suspension.
Packaging
There are two basic systems of machine vision: linear array
and matrix array. In linear arrays only one dimension is sensed
such as a common bar label. The matrix arrays sense up to three
dimension. Two dimensional bar codes hold more information than
one dimensional and three dimensional arrays can be used to detect
a properly inserted component. Packaging is the most popular
use of a vision system. In addition to two dimensional array can
contain the encoding for two thousand characters. Biocraft
use a data matrix reader from Saddle Brook Control Systems for
the inspection and two dimensional labeling of test tubes.
Although there are many uses for a vision system it is best
recommended not to just order a camera and hook it up to a PLC.
Several companies have solved many of the problems with vision
systems:
1. Lighting
2. Expensive
3. Interaction with the operators
4. Problems due to programming errors
5. No intuitive abilities
I have explained the four types of lighting, and how they
can work with different projects. The price of the equipment is
coming down as the technology is improved. To interact with operates
requires training and could involve a push button or button. Most
of the turn key systems run approximately twenty five thousand
dollars but some systems such as the Keyence Compact Vision System
CV series is approximately five thousand dollars. The programming
errors are being diminished by incorporating visual indicating
system. The intuitive abilities of the processors are increasing
at an incredible rate. As more is learned about the needs of
the industry and the abilities of the vision systems.
Other sources of information.
[Sample]
Solutions for Challenging High-Speed Applications. The HR+60
from ESI Vision Products Division is a machine vision system designed
for quality assurance in automated manufacturing and assembly
processes. The HR+60 system combines powerful machine vision hardware,
flexible and sophisticated software, standard communications,
and networking options for simplified integration in a work cell.
The result is a superior platform for use in demanding high-speed
vision applications in the Semiconductor, Electronics, and General
Manufacturing industries.
[Sample]
At speeds up to 12,000 parts per minute, SCOUT meets requirements
for countless demanding vision applications such as electronic
and mechanical assembly verification, character verification,
packaging integrity, surface flaw detection, plus numerous gauging
and measurement tasks. When used with the new PPT Vision Optical
Character Verification Tool, it will meet the requirements for
Federally-mandated verification of date codes for pharmaceutical
labeling. When used with PPT VISION's sub-pixelation Line Gauge
Tool, the SCOUT is ideal for use in critical dimension inspection
and verification for electronic components and medical applications.