Manual vs. Automated Statistical Process Control in the Food Industries.
Written by: Ryan Titmas, Applications Engineer, Sartorius Corp, 1-800-635-2906 x 8307
The Prime Example
Our recent visit to a food packaging plant in New Jersey highlighted the
inconsistent results of statistical
process control routinely faced by
Quality Control Managers. Product
weight readings were taken from the
manufacturing floor, entered into an
Excel spreadsheet and analyzed.
Product Weight Scatter Graph.
The results produced no predictable under or over filling trend despite the fact
that the same people used the same scales at the same time of day.
The problem is simple and fundamental. Human error is an inevitable part
of the process of collecting statistical data. This is consistently overlooked in
companies that utilize manual SPC1 (statistical process control) for their
manufactured goods. To ensure the human error factor is eliminated, resulting in
lower costs and increased profitability, manufactures must begin utilizing more
“high-tech” means of collecting, analyzing, and storing SPC data.
The Hidden Problems of the Current Manual SPC Process
To better understand the core problem, and find a solution, it is pivotal to
understand how this food packaging plant utilizes manual SPC. Generally,
several samples are taken from a product line at different times of day, usually 15
1
Statistical Process Control is the use of statistical methods to view and reduce process variation
so that a particular process can be monitored, controlled and improved by using statistical tools
like frequency distribution, histograms, scatter diagram, Pareto chart, thereby reducing defects
and wastes from the process.
or 20 samples at a time. These samples are then individually weighed; a line
worker records the results on a clipboard for analysis. The individual weight
readings are entered into a computer and various statistical calculations are
derived from the weighing results, including frequency distribution charts and
Pareto charts that are used to adjust the actual filling machines to deliver a
consistent result. The Quality Manager must then resolve any conflict between
under filling a package, which breaks government laws and overfilling a package
which causes lost revenue.
Error Filled SPC System
START
Random Batch of
Product taken from
Production Line.
Each product is
placed on scale.
Weight is
recorded on
clipboard in order
weighed on scale.
Data transferred
from clipboard to
spreadsheet for
statistical evaluation.
Statistical data evaluated and
translated into adjustments to
correct filling machine fill
volumes.
Data collected by
Quality Control
Manager.
Filling machines
manually adjusted
according to
collected data.
FINISH
Using the diagram to get a better understanding of SPC will make it easier
to locate the fundamental problems with the manual SPC system in use. The
problems begin with the manual recording of 15 identical products by the line
workers. The simple act of weighing an item then transferring the result to a
clipboard by pencil or pen is flawed and full of possible errors, i.e. the incorrect
number can be recorded or a sample can be weighed accidentally more than
once. This means the human emotion factor begins to play a large part in the
problematic result.
In addition, the manager obtains the clipboard results from the same
worker who is required to climb inside the hot filling machine to adjust the volume
if the weight results are not consistent. A line worker therefore might also
assume that weight readings on the clipboard that differ from each other might
mean he/she is not doing a good job.
The underlying result of a manual SPC system is the company loses
money resulting when each package of food is either overfilled beyond the
nominal weight or worse being under-filled which could mean hefty government
fines.
To summarize, the current manual SPC process allows too many errors
and offers no traceability of weighing results throughout the system. The
implementation of an automated SPC scale system would eliminate these
manual user errors with only a few changes and a small capital investment.
The Advantages of an Automated SPC System
Designing an automatic SPC system that eliminates human error begins
by removing the manual element from employee responsibility. This will alleviate
human recording errors and the fudging of actual weight results. To accomplish
this, the old scale, clipboard, and pencil must be removed and replaced with a
scale system equipped with automated SPC software. This software is fully
configurable to satisfy all SPC tolerances. The scale display will actually prompt
the worker when to place a product on the scale.
The fully automated “SPC Scale System” will not allow products placed on
the scale to be removed; rather only permit the addition of new products. This
will eliminate the possibility of placing the same product on the scale more than
once, as well as any confusion and/or fudging. The scale will then calculate the
statistical data after the last product is placed on the scale and store this data in
a password-protected memory for collection by the Quality Manager. This
statistical data can then be sent wirelessly to a spreadsheet, printed on a label to
accompany the sampled product, or simply viewed on the scale interface. The
flow diagram below shows the improved SPC process.
Optional
Filling Machines adjusted
automatically by SPC scale
system.
FINISH
START
Random Batch of
Product taken from
Production Line.
Each product is
placed on scale.
Scale
automatically
calculates
statistical data.
Statistical Data transferred to
computer database directly via
wireless or Ethernet
connection.
Companies can also utilize various connectivity and software options that
can integrate filling machines to automated SPC scale systems. This means that
fill volumes based on trends calculated by the scale can be adjusted via an
automated system. Quality Control Managers and Plant Managers can also
connect all the SPC scale systems in a factory via a central control computer that
will provide easy access to “real-time” data. Integrating an automated SPC Scale
System into a manufacturing environment will have the following advantages
over the older manual SPC systems:
Automated recording and evaluation of weighing results without ever
manually entering data.
Completely traceable results following GMP (good manufacturing
practice)
Direct integration into filling machines with automatic adjustment of fill
volumes.
Streamlines SPC processes to better utilize work hours.
Conclusion
Upgrading outdated manual SPC processes is the first step to improve
overall quality, efficiency, and trace ability. This can be accomplished with as
little as $5,000 in capital investment. Quality Control Managers and Plant
managers have to take a hard look at how their product samples are being
weighed and how these measurements are turned into results that can improve
production line efficiency. It is now time for companies to step into the 21 st
century and upgrade to a fully automatic SPC weighing system.
For more information on automated SPC systems contact a specialist:
Sartorius Corporation
Application Engineers: 1-800-635-2906, Extension 8284
131 Heartland Blvd.
Edgewood, NY 11717
www.sartorius.com