MANF4430
Assignment 1
Faculty of Engineering / School of Mechanical &
Manufacturing Engineering
MADRIGAL FLEXOGRAPHICS
Steve Zeleb had just become operations manager at Madrigal Flexographics, a manufacturer of
high quality, gravure printed packaging material used in the packaging and wrapping of quality
food products such as chocolate bars, ice creams, biscuits and cookies. Madrigal had a very
successful history and a lot of satisfied customers, but lately its quality had started to suffer. A
good customer had returned an entire batch of packaging material (about AUD50k worth) when it
discovered that some of it had not passed their own inspection. The nature and source of the
problem were not immediately obvious to the manufacturing team at Madrigal, nor to Steve. He
would have to investigate.
Gravure Printing
Gravure is traditionally used to produce long-run and high quality magazines and flexible
packaging and is possibly one of the simplest of the printing processes but at the same time one
of the most difficult processes to control. Figure 1 shows a schematic of a gravure printing
process. The material, called the web, passes through a set of, in this case nine, cylinders, where
each cylinder prints a single colour onto the web. Each cylinder, the image carrier, is engraved
with the image specific to that colour and this engraving service is provided by an outside supplier.
Cylinder preparation is a complex process and there are a number of cylinder specific variables
that the engraver must get correct. One of these is the cylinder diameter. In order to guarantee
that there is constant tension on the web material along the entire length of the press, so that the
web does not flap or become baggy, there is a progression in the diameter of each consecutive
cylinder by about 0.001”. In addition the taper of each cylinder must be controlled to within
0.03mm over its length, which, for Madrigal, is around 1200mm.
The three main quality characteristics of print are the size of the registration error (Rx and Ry) and
the quality of the colour itself. There are other attributes as well such as blushing, blooming,
smudging and so on, but these did not appear to be a major issue. Figure 2 shows a close up
schematic of a single print station and identifies some of the key design features. Apart from the
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cylinder progression maintaining positive tension along the press, registration error in the y-
direction (along the press) is controlled by a single movable cylinder between each print unit
whose function it is to advance or retard material transport in order to bring the print back into
registration (zero error). This simple but effective system consists of a single passive cylinder that
can move up or down. It is called an autotron cylinder. It is driven by an electric motor that has
three states – off, constant speed up and constant speed down. Registration across the press
(the x-direction or more commonly, sidelay) is controlled manually by turning a wheel to bring the
print back into alignment. This function, unlike the registration correction in the y-direction, is not
automated. There is however, an alarm that sounds when the vision system notices a shift in Rx
and the operators are responsible for setting the alarm at the beginning of every production run. In
addition there is the pressure of the tension roller onto the print cylinder as well as the angle of the
doctor blade. The purpose of the doctor blade is to wipe excess ink of the print cylinder before
printing the image onto the web.

Madrigal’s press is a mechanical one. It is driven by a single three phase electric motor powering
a 18m long drive shaft. Each cylinder is connected to the shaft via a bevel gear and clutch
system. The motor is controlled using a PID controller and the maintenance department is
responsible for ensuring that this controller, as well as the controller for the correction cylinders are
periodically recalibrated and checked. Recalibrating a PID controller is quite an advanced task
and requires specialised training. It is often performed by external technicians in industry, but not
at Madrigal. Madrigal had undergone a number of management changes in the past ten years
and consecutive management teams had become more distant from the day to day issues
surrounding the press and maintenance had not performed a PID calibration since the previous
electrician retired. The press is twenty two years old. Madrigal’s press was designed to run at
180m/min.
Product quality characteristics
Print quality consists of a number of characteristics and attributes. Some are very quantifiable,
such as the registration error between two consecutive print cylinder impressions as mentioned
before. Figure 3 illustrates a print registration box that is routinely printed on the edges of the
material and sensed by a sophisticated vision system that also calculates the error and uses this
as part of a feedback control signal to the autotron system. At the time of this case study, the
commercially accepted norm for registration error was +0.100mm in either direction.
Production and Operations Management
Madrigal Flexographics operates 4 shifts, 7 days/week. Preventive maintenance is normally
carried out on Sunday. The maintenance team consists of Dave Carpenter (fitter and turner) and
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Eddie Carfax (electrician). 70% of the work carried out by maintenance is breakdown work and
30% consists of preventive maintenance and corrective maintenance. Eddie is confident that the
press works well since most of the critical functions, for instance the autotron as well as the drive’s
PID controller, are fully automated and do not need much human intervention.
There are four operator teams covering all the shifts throughout the week, in addition to the
maintenance department. Madrigal employed 4 QC technicians, headed up by Patrick Sykes. All
QC employees are university educated and meticulous in their job. But there is only so much they
can do. Manually checking 50,000 meters of product can take a long time! Madrigal once also
employed two process engineers, but they were made redundant about six years ago as a result
of corporate streamlining and cost-cutting. Last year, Madrigal turned over a cost base of
AUD40M. It wasted about AUD5M of bad quality print. The QC department seemed to be
working well, so Steve thought.
Steve’s quarterly results were due soon and he knew he would be grilled by senior management
about the worsening trend in customer returns, especially that large delivery that was recently sent
back. Steve was worried. Could there be a hidden problem and does the organisation have the
skills to fix it? His job depended on it.

Sampling Process
Four (4) shifts of data are recorded, along the following variables. Note that each shift is
conducted by a different operating team.
• Machine Operating Pressure
• Machine Operating Speed
• Blade angle
• Average Ambient Temperature
• Average Ambient Humidity
• Setup time for new run
• Setup time Operating Speed
The following data is recorded every 5 minutes and each observation is time-stamped
• Rx (error in the x-direction) measured in mm
• Ry (error in the y-direction) measured in mm
• Average Colour Quality of the print
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Your Tasks:
Steve decided to hire a consulting team – YOUR TEAM, to investigate the problems further. Your
team must address the following:
1. Verify if the print error (Rx and Ry) exceed 0±0.100mm
2. Determine the cause of variations in Rx and Ry
3. Determine the cause of variation in ‘Colour Quality’
4. Assess the sampling method conducted by Steve and his team.
5. Make recommendation to Steve and his team of how to operate their machine to reduce
product recall and wastage.
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Figure 1: Schematic of a Gravure Flexographic printing press

Figure 2: Close-up of a Printing Station and its Critical
Process Components
Figure 3: Close-up of a print registration reference
box
All figures adapted from: Gravure, Process and Technology, Gravure
Association of America, 1991, Rochester NY.
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MANF4430
Assignment 1
Faculty of Engineering / School of Mechanical &
Manufacturing Engineering
Assignment 1 Submission
• Complete ‘MANF4430 Assignment 1 Template’.
• The submission needs to be uploaded to Moodle by Week 7, Friday, 9PM (Sydney Time).
• Only 1 submission is required per team.
• Please nominate only 1 team member to make the final submission, further submission will
automatically overwrite the previous submission.