Automated SPC Data
Collection and Monitoring
PCs are rapidly
displacing specialized SPC data collection terminals, for the same
reason specialized labor collection terminals are being displaced by
PCs. Most of the SPC data collection software suppliers are
converting their software to run under DOS/Windows, and are
designing their software for central monitoring of SPC chart
activity of all the terminals on the network.
Almost all standard
quality measurement tools such as micrometers, calipers, height
gauges, and the like can be purchased with a digital output. Several
manufacturers manufacture a small electronic box called a
multiplexor that translates the measurement gauge reading digital
output for PC input. The user calls up the right SPC chart at the
terminal and with a button on the gauge sends a measurement to the
computer system when ready. When all the sample readings are
completed, the software calculates the sample average, range (or
standard deviation) for plotting the sample results on the SPC
charts and checks for statistical violations.
(Software is also
available for attribute data and attribute SPC charts and related
analysis such as Pare to charts, etc.)
applications, many SPC software packages offer one or more
monitoring stations that display on computer screens the status of
all the active SPC charts on the PC network. A quality engineer can
glance at a screen and see those SPC charts out of control, or
approaching out of control conditions. Moreover, the quality control
engineer can get a full display of any SPC chart of interest, view
the original data and review any operator messages or comments about
the samples taken.
The cost of the SPC
data collection software and instrumentation per terminal typically
ranges from two to three thousand dollars. The software enables
manufacturers to extend quickly the number of SPC control chart
applications, to improve the productivity of both workers and
quality engineers, and avoid making parts that are scrapped or
reworked. We have visited manufacturers who obtained a pay back from
their investments from these systems in a few months.
Production Simulation Software
A specialized type
of simulation software has emerged in recent years for modeling
production operations. The newer production simulation software has
built in subroutines and commands that save hours of coding time
compared to using a basic simulation language. Industrial engineers
are now able to quickly develop simulations of a wide variety of
production problems using PC simulation software in hours that once
required days and weeks of coding. We have evaluated several
production simulation software packages for PCs with costs from
$10,000 to $30,000.
In our factory we
have set up JIT lines but we have a wide variety of products that
use the same lines. Simulation provides just about the only
practical way to simulate how to best balance these lines for a
given mix and quantity of work.
Finite Scheduling Software
The detailed data
files built for line balancing simulations are also part of the data
required for finite scheduling. Capacity of production facilities is
not static but also dependent on the mix and sequence of the work
scheduled. Until recently the cost, the difficulty and the time to
make finite scheduling runs made finite scheduling impractical. Our
shop has some tricky job shop scheduling problems associated with
many of our product lines, and we believe that finite scheduling
will help us to more realistically assess our trade-off in meeting
schedule, and/or optimizing our production costs. We believe that we
can implement finite scheduling where we need it for less than
$50,000 in software costs and each 1% improvement in labor
utilization is worth double that amount. Our company has
investigated several finite scheduling applications that have
improved throughput in other factories from 3 to 10%.
Bar Code Lot
Traceability Data Collection
The purpose of this
application is to develop computer records so that parts from any
production lot can be quickly traced to the shipment lots that used
the parts. We plan to use a modified version of inventory-by-lot
software with bills of materials software to solve this problem. We
don't need to maintain our inventory records by lot, but we plan to
scan in the bar code lot trace numbers associated with each
component part used in an assembly operation at the time of
Benefits of this
software application include the accuracy of bar code input and the
speed at which the parts can be traced into higher and higher levels
of workorders on the computer versus manually digging through boxes
and boxes of closed work order documents.
Perhaps an even
more important benefit of lot traceability is the ability to develop
statistical correlations between quality parameters of components
and final product performance. For example, how did the critical
parameter of lot A versus lot B of a component affect the end
performance of the product?
displays drawings and manufacturing instructions on screens or can
print hard copy on demand. The software can import drawings from CAD
systems or transmit video frames or still video images. Users can
zoom in on details for a better view. To more rapidly prepare
manufacturing instructions, users can "cut and paste" these drawings
or video pictures into other documents, or can "mark up" these
drawing sections with arrows and labels. The advantage is the speed
of preparing manufacturing instructions with more pictures and
fewer words for more rapid comprehension on the shop floor.
Sometimes associated with this software is the ability to add
inspection verifications after certain steps are performed via the
use of passwords and/or security codes. Thus we can have computer
records of inspector stamps and signatures that normally are made on
the shop traveler that accompanies the material.
Developments—The Paperless Factory?
After our company
implements all of the above applications, our factory will be close
to a paperless shop floor. At present we feel we will still need a
traveler piece of paper to attach to the physical material on the
shop floor as identification. We also plan on using this work order
traveler document as the source of needed bar coded part numbers,
work order numbers, sequence numbers, and the like for rapid bar
code data input. Nevertheless, implementing the previously
described applications will help our factory become a "less paper"
It is fun to
speculate on what future computer technology holds for the factory.
RF systems are beginning to replace wires to computer terminals.
Voice recognition systems may replace keyboards and touch screens.
The storage capacity of the CD and higher capacity systems will
likely make full motion video more practical. (Today one video
screen image requires a megabyte or two of data.) Manufacturing
instructions may more easily be made available with video images
accompanied with spoken words in several languages. Also
manufacturing instructions could soon be made interactive with
computer based verbal commands based on synthesized speech and
spoken computer input based on voice recognition software.
But we do not need
to wait until tomorrow. We can find many cost effective client
server and PC computer software applications today that will improve
the profits and competitive position of our factories.
For balance of this article, click on the below link:
Lean Manufacturing Articles and go to Series 01
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