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Improving automation and process control of an indirect gravure (Pad) printing machine

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Because pad printing can be used on 3-D substrates, it has attracted the attention of many researchers in the field of printed electronics. This paper presents developments in the automation of a pad printing machine that improve its specifications for use in scientific fields and equip it with some unique features. Users of this machine can obtain graphs of printing force and printing step durations for tracing and analyzing the printing process. Here, to explain the design method, the printing technique features, the pad printing working process and related machine parts, as well as the development and design process, are described. In this section, some hardware, such as National Instruments CompactRIO, as well as software (LabVIEW) and data transferring under the EtherCAT protocol will also be discussed. Finally, the machine user interface and some analytical graphs of the machine will be explained. © 2016, Budapest Tech Polytechnical Institution. All rights reserved.
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Acta Polytechnica Hungarica Vol. 13, No. 4, 2016
Improving Automation and Process Control of
an Indirect Gravure (pad) Printing Machine
Arash Hakimi Tehrani, Edgar Dörsam
Technische Universität Darmstadt, Institute of Printing Science and Technology,
Magdalenenstr. 2, 64289 Darmstadt, Germany,
Jann Neumann
PERFECTA Cutting Systems GmbH, Schäfferstraße 44, D-02625 Bautzen,
Germany, e-mail:
Abstract: Because pad printing can be used on 3-D substrates, it has attracted the attention
of many researchers in the field of printed electronics. This paper presents developments in
the automation of a pad printing machine that improve its specifications for use in
scientific fields and equip it with some unique features. Users of this machine can obtain
graphs of printing force and printing step durations for tracing and analyzing the printing
process. Here, to explain the design method, the printing technique features, the pad
printing working process and related machine parts, as well as the development and design
process, are described. In this section, some hardware, such as National Instruments
CompactRIO, as well as software (LabVIEW) and data transferring under the EtherCAT
protocol will also be discussed. Finally, the machine user interface and some analytical
graphs of the machine will be explained.
Keywords: Automation pyramid; Mechatronic system structure; Indirect gravure printing;
Pad printing control system; LabVIEW
1 Introduction
Indirect gravure printing is the collective name for an indirect printing process
having one transferring part (pad) and one gravure printing form. In many cases, it
is referred to as pad printing [5, 10]. Pad printing has some advantages over other
printing methods. Because it is a gilt-edged technique for printing on non-smooth
objects having concave and convex surfaces, it has a competitive advantage for
work with 3-dimensional substrates, which have differing shapes, thicknesses and
A. Hakimi Tehrani et al. Automation and Process Control of Indirect Gravure (pad) Printing Machine
dimensions. This capability makes pad printing suitable for a wide range of uses
in a variety of production processes, such as medical instruments, electrical
devices, automotive parts and printed electronic devices. This technique has been
applied in the medical imaging field to print piezoelectric thick-films on a curved
substrate [15]. It has also been used in the production processes of gas sensors [4],
solar cells [6, 13], UHF RFIDs [16], OLEDs, biomedical sensors [24], mobile
phone antennas [27], and microelectronic circuits [11]. Moreover, it can also be
combined with other methods, such as screen printing. For example, in [14], some
research success was achieved by combining pad and screen printing to produce
an ultrasonic transducer in high frequency scales. Because of the importance of
pad printing usage in such scientific fields, this paper focuses on the development
of control and automation for pad printing machines, with a focus on their usage
in scientific fields. According to scientific research, a more highly automated pad
printing machine represents a new demand. Here, automation should provide high
accuracy, high value of data transfer and management and high controllability of
printing parameters. So, the main contribution of this work is an improvement of
the automation level of pad printing machines.
This paper is organized as follows: the next section, introduces basic concepts of
mechatronics, automation and pad printing machine. Second, the development
concept for the pad printing automation system is presented. Third, the various
components of the pad printing machine and its structure are described.
Afterward, a flowchart diagram of the machine's working process is offered. Next,
we focus on the development of the machine structure, automation level, data flow
and software designing process as parts of the development process for the pad
printing machine. Then, as examples, some reports of the system are mentioned.
Finally, the paper is concluded with a brief summary.
1.1 Mechatronic System Description
To achieve this goal, the pad printing machine is developed in the three fields of
electronics, control systems, and mechanics. As shown in Figure 1 (a), these fields
are all related to a mechatronic system [8]. Therefore, to provide a better
description, the pad printing machine is considered as a mechatronic system.
Figure 1 (b) shows the structure of a mechatronic system, which consists of four
units: control, sensors, actuators and mechanics [9].
The level of controlling and processing and the user interface is related to the level
of system automation, which is described in the next section.
Acta Polytechnica Hungarica Vol. 13, No. 4, 2016
Figure 1
(a): Mechatronics field concept. The connected lines represent the synergistic integration of these three
scientific fields in generating the mechatronics concept. The orange color defines the developed parts
that are described in this paper. (b): The mechatronic system structure [9], with its four units of control,
sensors, actuators and mechanics. The arrows show the direction of information flow.
1.2 Automation Description
Automation is the application of a control system in a process toward the end of
reducing human intervention, improving process throughput, and decreasing
production losses [1]. The automation pyramid in Figure 2 shows different levels
of automation.
Figure 2
The automation pyramid. The automation development direction is from bottom (low level) to top
(high level). In some cases, levels 0, 1 and 2 are considered as one group; hence, the dashed lines [9,
23, 26]
A. Hakimi Tehrani et al. Automation and Process Control of Indirect Gravure (pad) Printing Machine
The possibility of passing through each level to a higher level varies from system
to system. In some cases, achieving a particular level is very difficult, or even
impossible. Level 0 is achieved merely by use of sensors and actuators to control
the (mechatronic) system. Level 1 involves controlling and processing the signals
of the system and is called the field level. Level 2 (the cell level) depends on user
interface and process monitoring. Level 3 (the plant level) involves optimal
scheduling and maintenance, as provided by the manufacturing execution system
(MES) and the management information system (MIS). Level 4 (the company
level) involves enterprise resource planning (ERP) and the programming and
production control of an entire company [9, 23, 26].
1.3 Description of Pad Transfer Printing
Pad printing machines come in two types: pad transfer printing and rotary pad
transfer printing. This paper focuses on pad transfer printing. A schematic diagram
of pad printing is given in Figure 3. As shown, the pad and printing form are
initially located in their reference positions (red dash). The printing form table
then advances (step 2). Next, the pad comes down to pick up the ink (step 3), a
movement reversed in step 4. In step 5, the printing form table returns to its
reference position. Finally, the pad descends to transfer the ink film to the
substrate [5] (step 6), and then returns to its reference position in step 7.
Figure 3
Pad transfer printing schematic diagram showing the pad, printing form table and printing object. The
1st picture shows the start of the process and the 7th picture shows the end, where pad, table and object
return to their original position. The arrows define the movement direction [2].
2 Concept of an Automated Pad Printing Machine
Over time, there have been some improvements in pad printing machines. Today,
most well-known models have features such as variable speed control, printed-
pieces counter and variable pad position [17, 18, 25]. The pad printing machine
Acta Polytechnica Hungarica Vol. 13, No. 4, 2016
developed in this project has 4 extra capabilities: printing process force tracing on
the substrate and printing forms; position control in both the X and Y directions;
velocity control in both the X and Y directions and user-defined contact time.
Within each printing cycle, these parameters can be changed and/or saved for
future batches and are traceable in different graph formats for each printed sample.
These parameters have been classified in Table 1. As indicated, the force as a
printing parameter can be controlled and traced when the pad is pressed on either
the printing form or the substrate. The position and velocity of the pad and
printing form axes are controlled and traced in two directions: X and Y. The
contact time of the pad on the printing form (for obtaining ink) and on the
substrate (for transferring ink) can also be controlled and traced.
Table 1
Categorization of printing parameters according to their controllability and traceability (C&T) at
different axis directions in newly developed pad printing machine
C&T at Y (pad) axis
C&T at X (printing
form) axis direction
Pad on printing form
Pad on substrate
Pad on printing form
Pad on printing form
Pad on substrate
3 Categorization of Pad Printing Machine
Components according to a Mechatronic System
The most important movable parts of a pad printing machine are its axes (See
Figure 4). These are referred to as the printing form axis and the pad axis. The
printing form axis movement is in the forward (X) direction. The movement along
the pad axis (Y) is downward, so it has negative values compared to the reference
coordinate system.
As shown in Figure 1 (b), a mechatronic system has four parts: control unit,
sensors, actuators and mechanics [9]. Thus, the pad printing machine structure can
be illustrated as in Figure 5.
A. Hakimi Tehrani et al. Automation and Process Control of Indirect Gravure (pad) Printing Machine
Figure 4
Pad printing machine schema. The dimensions of the machine are 1200 by 980 by1850 mm. The Y
positive direction is upward and X positive direction is forward [18]. These elements are highlighted to
promote a better understanding of the printing machine structure given in Figure 5.
According to the mechatronic structure of Figure 1 (b), the four general units of
the new pad printing machine structure and their relationship to each other are
described in Figure 5. All processing and logical calculations happen in the
control unit. This unit consists of the machine's real-time embedded industrial
controller and electric servo drives. As shown, the vertical and horizontal drives
receive control data from the real-time controller and send the results back to it.
The control unit has another element, identified as software. This element receives
the demands of the user in the UI (user interface) and sends them to the Main
software block. After processing, these demands are then sent to the real time
controller. Further, the controlling program is located at the Main block. The
actuators receive the commands of the controlling unit and execute them on the
mechanical parts. For example, the vertical drive controls the vertical servomotor
(actuator). This actuator moves the vertical axes (mechanical unit), which
ultimately moves the pad as a printing unit. The sensors unit is another part of
system that measures some parameters of the mechanics unit and then sends them
to the control unit for processing. The mechanics unit has the role of mechanically
executing user commands. The most important elements of the mechanics unit are
shown in Figure 4 and Figure 6 (a). The printing unit is located in the mechanics
unit and consists of the pad unit, the inking unit and the object-holding unit [10].
They can be called the operational, input and output units respectively, according
to the operating maintenance model for printing [7]. Each of these has special
parts, which are shown in Figure 6 (a).
Acta Polytechnica Hungarica Vol. 13, No. 4, 2016
Figure 5
The pad printing machine structure. It is divided into control, actuators, sensors and mechanics units,
according to the mechatronic system structure. The arrow directions indicate the machine data flow.
The orange color defines the developed parts. The printing unit is considered a part of the mechanics
unit and consists of pad, inking and object-holding units. It is classified to help illustrate the
development points of the machine.
Figure 6
(a): The pad printing machine unit. The component parts are labeled in the (a) segment. (b): The
printing form (X) axis elements [18]. The reference position line and forward direction of movement
have been defined here. The printing form table is located at the reference position when the table tip is
positioned at the reference position. The printing form receives the ink when moved in the forward
direction. (c): The pad (Y) axis elements [18]. The reference position line and printing direction have
been defined. The printing direction is in the -Y direction. The pad and pad axis are located at the
reference position when the pad coupling is at the reference position line.
A. Hakimi Tehrani et al. Automation and Process Control of Indirect Gravure (pad) Printing Machine
The main material of the pad is silicon. The pad shape has the two important
parameters of pad angle (from side to print area) and pad printing surface [22].
The pad's role is to transfer ink from the printing form to the substrate. The
printing form is an etched plate of print motif. Pad printing is divided into two
main types: closed and open inking systems. In open inking systems, there is no
cover on the ink trough, whereas in closed systems, the ink trough is sealed. Thus,
there is more solvent evaporation in open systems than in closed [5, 10]. The
inking system discussed in this paper is a closed system. The ink cup (the closed
system ink trough) is an ink storage device located on the printing form that
delivers the ink to the printing form in each printing cycle [6]. The substrate is an
object located on the substrate table on which the printing process is performed.
More detailed pictures of the printing form and pad axes from Figure 6 (a) are
given in Figure 6 (b) and Figure 6 (c), respectively. The reference (home) position
and printing direction of each axis are shown in these figures. The reference
position of the printing form table and its forward direction are shown in Figure 6
(b). The printing form table has an electrical servomotor that has been connected
to the linear axis by means of a coupling and flange. These accessories allow
forward and backward movement of the printing form table. The reference
position and Y direction of the pad axis are shown in Figure 6 (c) (vertical
direction). The Y axis positive direction is upward. In other words, the printing
process is performed in the negative direction. The reference position is the
connection point of the pad with the pad coupling. The tip of the pad is not
selected as the reference point, since pads with different heights may be used at
this location.
4 Pad Printing Working Process
The pad printing working process is described in Figure 7. The inputs of the
flowchart are printing form, ink, pad and substrate (2D or 3D).
Initially, the printing form and pad goes to their reference positions. In the next
step, the substrate is fixed on its table. The substrate fixer could be a vacuum
table. Briefly, according to this flowchart, the printing form gets the ink from the
ink cup and then moves forward. Next, the pad descends and receives the ink from
the printing form. The pad then goes up again and the printing form table comes
backward. The pad then comes down and is pressed onto the substrate, thus
transferring the ink. Finally, the pad ascends, and the printing project is
Acta Polytechnica Hungarica Vol. 13, No. 4, 2016
Figure 7
Pad printing working process flowchart. The different steps of the printing process are described here
from start to end. The pad, printing form, ink and substrate are input materials and the printed substrate
is the output.
5 Development Process of Pad Printing Machine
The hardware type, software design and automation level of the system are related
to the machine's application.
The hardware for use in scientific fields should be capable of highly accurate
control. Then, pursuant to its application, one designs the desired data flow
A. Hakimi Tehrani et al. Automation and Process Control of Indirect Gravure (pad) Printing Machine
between hardware, software and final user. Next, one selects appropriate software
according to the hardware and data flow system. Eventually, the programing
process is started. In the following, the development process of the machine
structure is described. Then, the development of the system's automation level and
its data transferring route are discussed. Afterward, the uniquely designed
software is presented, with concentration on the user interface (UI).
5.1 Development of the Machine Structure
The parts of the machine units we developed are shown in Figure 5. As the most
important control unit element, the National Instrument CompactRio (cRIO) 9074
has been used. The cRIO is a real-time, embedded industrial machine controller
with additional monitoring capabilities. Its specifications have been described in
[20]. With this device, we were able take advantage of features such as a high
speed, real-time processor, the ability to add measurement devices as I/O modules
and the ability to expand external devices through networking. So, by utilizing
these advantages and software features, an on-line controlling and data mining
system with data measurement and processing capabilities could be created. Two
Kollmorgen AKD servo drives were used as the vertical and horizontal drives of
the controlling unit in Figure 5. These drives are capable of multi-axis
programmable motion. Moreover, they can measure and control the speed,
acceleration, position, torque and current of servomotors. Their response to
mechanical load changes is immediate, thus allowing for an appropriate control
level. Motor control is possible in three operation modes: torque, velocity and
position. In torque mode, the motor current is controlledand the current loop is
updated every 0.67 microseconds to achieve an accurate control system. The
drives used in the scientific pad printing machine support the EtherCAT protocol
for data transferring [12, 19]. An EtherCAT connection was used as a network
protocol in this project [21]. By using EtherCAT, the contact time between the
process steps and the CPU load is decreased [3]. It has high-speed performance
with an accurate synchronization of less than 1 microsecond between master and
slave, a feature important for coordinated motion between the motion axes.
Because of its features, EtherCAT is used in machine design, motion control and
measurement equipment applications [3, 21]. To ensure precise, delicate motion
control, a quick and synchronized data transferring system is needed. Therefore, in
our scientific pad printing machine, the EtherCAT has Kollmorgen drives
connected to the cRIO.
An overview of industrial communication systems is shown in Table 2. The
maximum bit rate of the EtherCAT data transferring system is 100 Mbit/s, which
compares favorably with other methods [9]. The communication relationship of
the EtherCAT protocol is master/slave. This means that a device has one-sided
control over one or many devices. In the system described in this paper, the
CompactRIO hardware, as a real-time, embedded industrial controller, has the role
of master for controlling the horizontal and vertical AKD servo drives (slaves).
Acta Polytechnica Hungarica Vol. 13, No. 4, 2016
Table 2
Different industrial communication systems [9]. The most important parameters of industrial
communication systems are the Max. bit rate, Max. number of nodes and the communication
relationship. According to the communication specifications of the system hardware, the EtherCAT
system is one of the best candidates for the new pad printing machine, since it has a high bit rate
(100Mbit/s) and master/slave communication (because in this case two drives are to be controlled by
means of a real-time controller).
Max. bit
Max. Nodes No.
167 kbit/s
1 Mbit/s
12 Mbit/s
0.5 Mbit/s
2 Mbit/s
16 Mbit/s
100 Mbit/s
100 Mbit/s
100 Mbit/s
As shown in Figure 5, a force sensor has been appended to the sensors unit. A
single-point load cell with a maximum capacity of 100 kg and a safe load limit of
150 kg at a maximum eccentricity of 150 mm and accuracy class C3 has been
used as a force sensor. In addition, a force measurement capability has been added
to the printing form table. Ultimately, all of these forces are measured and
controlled at a high accuracy level (Min. LC verification interval of 0.1961 N for
max. capacity of 980.665 N) as part of the effective parameters of printing quality.
In addition to controlling the printing process, the user can store these data for off-
line data analysis. These capabilities, along with high-speed data transfer over the
EtherCAT protocol, validate this machine as a scientific pad printing machine.
5.2 Development of the Automation Level
In accordance with the automation pyramid (Figure 2) and the specifications of
conventional pad printing machines, most well-known pad printing machines [17,
18, 25] have normal sensors and actuators and controller devices, such as PLCs.
Therefore, based on their features, they are located at level 0 or 1. Although many
of them have an input system for entering printing parameters, they do not have
process monitoring on their user interface, and thus do not advance to level 2. The
newly designed and automated pad printing machine has reached the second
automation level due to its on-line monitoring of the printing process and the
parameters on the user interface. Moreover, the ability to alter printing parameters
for the next printing sample according to the monitored data and the ability to
store, handle and trace data with DIAdem (Version 14, National Instruments) is an
A. Hakimi Tehrani et al. Automation and Process Control of Indirect Gravure (pad) Printing Machine
improvement in the pad printing information management system that could lift
the automation level of the new pad printing machine to level 3.
5.3 Data Flow of the Pad Printing Machine Structure
The data flow between different units of the pad printing machine is illustrated in
Figure 5. In this picture, the arrows point in the direction of the pad printing
machine data flow. The user interface (UI) receives demands from the user and
sends them to the software Main program of the control unit. After that, at the
same unit, these data are transferred to the real-time controller for processing and
translating into machine language. Then, the electrical command is sent to the
horizontal and vertical drives. Then the data are sent to the actuator unit and,
finally, executed by means of printing units in the mechanics unit.
The outputs of this newly designed machine are divided into the two categories of
printed objects (printed outputs) and printing specification reports (software
outputs). The printed substrate could be a 3-D object (e.g., printed electronic
devices on 3-D surfaces). The other output is software based and produces such
useful machine reports as printing force or inking force. It should be noted that the
data flow route of the machine parts takes place via the EtherCAT protocol with a
high-speed data transfer rate (max. bit rate of 100 Mbit/s) [9, 21].
5.4 Software Design
In this work, the LabVIEW (Version 13, National Instruments) was used to
program the embedded FPGAs. The programing procedure of this new machine
has been classified into two parts. One part is the Main program and the other part
has been designed as a machine user interface (UI). The Main program has
various block diagrams. This part has been designed for the control and data
processing of different machine units (Control, Actuators, Sensors, Mechanics)
according to user demands and the working process flowchart of Figure 7. The
LabVIEW programing structures of the Main program were defined pursuant to
the flowchart steps of Figure 7 and related working functions were then
programmed inside each program structure. This program also processes all
measured machine data. In another step, all measured data is sent to another
program part, where data management is performed. In every 4 milliseconds, a
package of data is sent to the data inventory for research and scientific analysis.
Acta Polytechnica Hungarica Vol. 13, No. 4, 2016
Figure 8
The Operational sub-User Interface (O-UI). The left side of picture shows the on-line printing process
graphically. Other parts are the printing operational keys. They are called operational, because of their
effect on the operation of the printing process. By pressing the “Find home position”, the axes will go
to their reference position, and by pressing the “start” button, the printing process will be started.
In front of all these complex processes, there is a supporting program with a
graphical part as a mask. We refer to this part of the machine as the user interface
(UI). It is divided into different sub-UIs, as shown in Figure 8, Figure 9 and
Figure 10. The UI receives the demands of the user and translates them into useful
parameters for the control program part. Figure 8 shows the operational sub-UI
(O-UI), so named because of the execution functional keys located there, such as
"start printing process". In a graphical segment of this sub-UI, the machine
working process (pad and printing form movement) is shown on-line as a
graphical animation.
In Figure 9, the machine set point sub-UI (SP-UI) is shown. In the SP-UI, the
values of the printing parameters are defined. For an easy definition of values, all
parameters have been categorized according to the printing steps shown in Figure
3 and the speed limitations have been defined here for input parameters. The
ability to save and load parameter data has been added in the SP-UI to make it
easy to use the machine and print with the same parameters at different times. The
user can define the pad printing working process via automatic force control on
the printing form or substrate merely by pushing a button on the SP-UI. The
A. Hakimi Tehrani et al. Automation and Process Control of Indirect Gravure (pad) Printing Machine
contact time on the printing form and the substrate are two other parameters that
the user may choose to influence the printing process. All of these options
represent advantages of our pad printing machine over conventional machines.
Figure 9
The Set Point sub-User Interface (SP-UI). The different printing parameters are described here by the
user. The printing parameters have been categorized according to the printing step involved; the
number and description of each step is described at the left side of picture. These classifications make
it easy for the user to operate the machine.
Figure 10 shows the on-line Graph Panel sub-User Interface (GP-UI). This panel
displays the on-line graphs of the printing force, the printing form force, the
position and velocity of the X-axis, and the position and velocity of the Y-axis
over time during the printing process. The user can also save the data of the
desired graphs in the host computer for further scientific analysis.
Acta Polytechnica Hungarica Vol. 13, No. 4, 2016
Figure 10
The Graph Panel sub-User Interface (GP-UI). This panel shows the position and velocity of pad and
printing form axes, the printing force and ink delivery force (of printing form). All of these 6 diagrams
are shown on-line for the duration of the printing process. By means of these graphs, the user can
monitor and trace the printing process and make decisions that improve the parameters for subsequent
printing iterations.
The main contribution of this work is an improvement of the automation level of
pad printing machines. As described in section 5.2, the most well-known pad
printing machines [17, 18, 25] are located at the automation level 1 or 2, whereas
the presented developed machine has reached the automation level 3. According
to this novelty, the printing parameters (Figure 9) can be set with sufficient
precision. Afterward, the printing process will be executed by the developed
control system and other parts (Figure 5) according to the set values, identically.
These parameters are adjusted independently of each other. This feature will cause
to better controllability of the printing process. As an example, the printing force,
speed and pad position can independently be adjusted and controlled. Then, the
effect of these parameters on the printing quality and process can be controlled.
Whereas, the conventional pad printing machines can not support such aspects.
The pad printing is a complex process and it is important to investigate its process,
systematically. Future work should aim to decrease the complexity of the system
and to investigate the unknown behaviors of the system during the printing
process. The highly automated pad printing machine developed in this work forms
an ideal basis for further researches, since it allows for measurement of the
printing parameters, and the ability of the database analysis.
A. Hakimi Tehrani et al. Automation and Process Control of Indirect Gravure (pad) Printing Machine
6 First Results
Data related to the force, velocity, position and torque of the printing and printing
form axes are saved in every 4 milliseconds as software outputs of the machine.
These data have a relationship to some of the parameters affecting the printing
quality. Thus, depending on user demands, different types of graphs and analyses
may be obtained using these data. For example, using an 85 by 75 by 66 mm pad
of hardness 12 Shore A together with a polyethylene terephthalate (PET) substrate
of thickness 125 micrometer, a length of 297 mm and a width of 210 mm, the
following results were obtained: Figure 11 shows the movement of the printing
form (X) and pad (Y) axes according to the printing steps of Figure 3. The X
curve (green) describes the position and movement of the printing form axis and
the Y curve (red) delineates the pad axis movement versus time. For example,
steps 3 and 4 are related to ink pick up. In step 3, the pad goes down to retrieve
ink; thereafter, in step 4, the pad goes up again. According to this diagram, you
can easily measure the time duration of each printing step.
Figure 11
Axes movement diagrams. This graph shows the pad axis movement (red curve) and printing form axis
(green curve) over time. The vertical dashed lines show the time duration (millisec) of each printing
step, as numbered according to Figure 3. The highly accurate system measurements permit time units
of milliseconds (mSec). The values of pad axis position are negative, since the printing direction is
along the -Y axis.
Acta Polytechnica Hungarica Vol. 13, No. 4, 2016
One type of scientific graph is shown in Figure 12. This graph shows the pad
movement behavior versus force for measured data in the pad printing process.
The pad movements can be obtained approximately by calculating the force-Y
(pad movement) using equation (1) (See dashed line in Figure 12). The F-Y
diagram is divided into two parts: Increasing pad force when the pad moves
downward on the printing form (step 6 from Figure 3) and decreasing pad force
when the pad moves upward (step 7 from Figure 3).
Figure 12
Printing force versus pad movement and its approximate equation diagram. The printing force curve
(red) has two parts. The left part is related to pad downward motion for ink transferal and the other is
related to pad upward motion after printing on the substrate. They have been signed according to
printing steps 6 and 7 (See Figure 3). Because of the printing direction (against Y direction) the pad
position values are negative. According to increasing of absolute position value from |-112| mm till |-
128.66| mm, the pad is in contact with the substrate and the force is increased. The force-increasing
behavior according to pad position in this experiment is an eighth-order equation (equation (1)) whose
approximated curve (blue curve) has been derived by means of DIAdem.
Using equation (1), the pad axis movement for printing with a special force (for
this type of pad) can be calculated.
A. Hakimi Tehrani et al. Automation and Process Control of Indirect Gravure (pad) Printing Machine
Thus, our scientific pad printing machine was able to generate scientific graphs
and allow conclusions about printing processes and situations, especially for
highly intricate objects, such as printed electronic devices.
7 Summary
This paper has described the process of development at the automation level and
the resulting structure of a pad printing machine, with a focus on scientific
applications. The mechatronic system structure has been taken as a machine
structure model and the printing unit has been incorporated as part of this system.
Some developments have been made regarding the machine structure, such as the
use of force sensors, National Instrument CompactRio hardware and Kollmorgen
servo drives over EtherCAT data transferring protocol. The goals for these devices
are highly accurate data measurements, processing and controlling functions, and
high speed data transfer. As a validation of our work, we were able to generate
various scientific graphs that reflect the printing process for each printed object
(2-D or 3-D). Via these graphs, the user can improve the printing quality for future
printing iterations and achieve traceable and repeatable printing. The user can
follow the printing graphs on-line via the machine user interface or off-line via
DIAdem or related software. All of these developments have led to an increase in
the automation level of the pad printing machine. For example, the graph tracing
the X-Y position movement versus time has been used to determine the duration
of different printing steps. The graph of the pad movement versus force for a
special pad has been generated and its approximated equation has been derived.
This diagram and its related equation are useful for calculating pad axis movement
for obtaining a printed object with a special force. The scientific pad printing
machine can be used for unique applications, such as printed electronic devices (e.
g., OLEDs).
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... Conventional printing processes are multiparametric and highly dynamic processes. For this reason, the use of sensors, actuators, mechanics and a control unit, which represents the structure of a mechatronic system (Tehrani et al., 2016), is highly advanced here in order to be able to achieve high and consistent print quality. Technologies for measuring and adjusting pressure, position, temperature and air bubbles play a crucial role in industrial printing applications and thus are broadly applied. ...
Full-text available
Biofabrication, specifically 3D-Bioprinting, has the potential to disruptively impact a wide range of future technological developments to improve human well-being. Organs-on-Chips could enable animal-free and individualized drug development, printed organs may help to overcome non-treatable diseases as well as deficiencies in donor organs and cultured meat may solve a worldwide environmental threat in factory farming. A high degree of manual labor in the laboratory in combination with little trained personnel leads to high costs and is along with strict regulations currently often a hindrance to the commercialization of technologies that have already been well researched. This paper therefore illustrates current developments in process automation in 3D-Bioprinting and provides a perspective on how the use of proven and new automation solutions can help to overcome regulatory and technological hurdles to achieve an economically scalable production.
... When it comes to printed and hybrid electronics, pad printing has mostly been employed in scientific research so far; e.g., for the deposition of SMD soldering paste (Videkov, 2019). This can be attributed to the still low automation level, when high printing accuracies are required (Tehrani and Dörsam, 2016). ...
Printing technologies are a convenient enabler for the rapid and cost-efficient prototyping as well as for the manufacturing of flexible sensors, which can be integrated in different types of materials and wearables. At the same time printing is considered to have a low environmental impact, provided that sustainable materials are used. As part of this article, a systematic review of different printing technologies for printed electronics applications is provided, including the basic working principles, the achievable resolutions and processing speeds, specific challenges, processable materials, as well as focusing on the usage for the fabrication of flexible sensors and sensor systems.
... The pad-printing machine used in the experiments is based on the machine described by Hakimi Tehrani, Dörsam and Neumann (2016) and Hakimi Tehrani (2018). We modified it, by replacing the pneumatic drives of the gravure plate and pad holder by linear stepper drives. ...
Full-text available
We describe the specificities of the pad-printing form production. In printing experiments, we show the influence of different printing forms, in dependence on raster frequency and printing form material, on the printing quality of pad printed patterns. A typical defect in pad-printing, the ‘stamp effect’, which occurs as a wavy contour, was determined and traced to the printing form production. By incorporating so-called outlines into the printing form, we were able to reproduce patterns with an edge roughness of less than 3 μm. We provide descriptions of the implementation of these outlines. To measure and analyze the edge roughness and edge defects we developed an image-based method to quantitatively assess the quality of edge patterns. With the use of outlines in the printing form, it seems feasible to use pad-printing for source and drain contact manufacturing on printed thin film transistors. Thus, the reproduction of electrically conductive, interdigital patterns for sources and drains having an electrode distance of less than 10 μm appears possible.
... The pad printing press used in the experiments is described by the work of Hakimi Tehrani. 3,19 The particular feature of this machine is the replacement of the standard pneumatic drives by electrical servo drives, which permitted precise control of velocity and forces. ...
Precision printing of particulate slurries with particle sizes of 5–20 µm using an indirect gravure printing, specifically with pad printing technology, offers interesting applications of functional printing on 3D surfaces. We present our results for printed electroluminescent panels (EL), where printing inks containing luminescent and dielectric particles of such comparatively huge size are transferred from a gravure printing form with gravure patterns not much larger than the particles. Compared with screen printing, the benefit of pad printing is that fairly complex and corrugated surfaces of 3D printed bodies can be endowed with a particulate functional surface. We demonstrated this using commercially available materials for electroluminescent panels. From the electrical point of view, EL panels are capacitors with a luminescent and insulation layer which enables a careful investigation of the printed surface by the characterization of their electrical and optical performance. We emphasize that the printing process we developed is not restricted to EL panels but could also be used for printing protective, electrochemically active, or radiation absorbing metal or metal oxide coatings to 3D printed fused deposition modeling polymer bodies. Printing parameters such as pad hardness, printing velocities, and pad surface tension are investigated. Further, we consider the relation between the printing process, the thickness of the insulation layer, the volume fraction of particulate BaTiO3 in this layer, and EL panel luminance. Our pad printed EL panels, using adapted ink formulations, achieved average luminance of 140 cd/m² on curved surfaces which also corresponds to the performance standards of conventional screen printed panels.
... The FEM simulation results were validated by means of experimental investigations. An improved pad printing machine (Hakimi Tehrani and Dörsam, 2016) is used to monitor the pad displacement and reaction force during printing by the use of sensors and it stores the data for analysis. Afterwards, the measured parameters are compared with the simulation results. ...
Conference Paper
Full-text available
Pad printing is a method to print on objects with complicated geometries or rough surfaces. Although pad printing is widely used in advertising and industrial printing, there are few scientific studies. The process parameters are therefore still determined today by experience. This applies in particular to the selection of the pads. Experienced experts select a suitable pad shape from the wide range of sizes and geometries. The finite element method (FEM) could be a method to support the selection of pad shapes. The FEM software requires various input parameters such as material model, material parameters and mesh types and sizes for simulation. For many FEM applications, the material parameters as well as the type and size of the mesh have a large influence on the quality of the simulation result. There is therefore a great uncertainty as to which parameters should be used. Therefore, this paper first examines the determination of material parameters using tensile tests and then the influence of different mesh types and sizes. The results are shown here as examples for a medium pad size with a hardness of 6 Shore A. It turns out that simple FEM tools are suitable for rough estimation of the forces in a pad during the printing process.
... The pad printing machine used in the experiments is based on the machine described by Hakimi Tehrani and Dörsam (2016). We modified it, by replacing the pneumatic drives of the gravure plate and pad holder by linear stepper drives. ...
Full-text available
We analyzed the edge sharpness and edge defects of pad-printed patterns and developed an image-based method to quantitatively assess the quality of edge patterns. We traced the two types of observed defects, filament formation and stamp effects, to the printing parameters, and the gravure features of the printing form, respectively. By optimizing the printing velocity, printing pressure and gravure, we were able to reproduce patterns with an edge roughness of less than 2 μm. With this process optimization, it seems feasible to use pad printing for source and drain contact manufacturing on printed thin film transistors. Thus, the reproduction of electrically conductive, interdigital patterns for sources and drains having an electrode distance of less than 5 μm appears possible.
Full-text available
Pad printing is an indirect gravure printing for printing on objects with complicated geometries or rough surfaces. Although pad printing is a proven and widely used printing process, there are few scientific studies on the shape and hardness of printing pads and their influence on printing quality. The shape and hardness of printing pads are therefore still determined today by experience. Even in the age of digitalization, the manufacturing of printing pads is still a manual process. So far, no modern tools are known to support this manufacturing process. In this paper, using simulations with commercially available finite element method (FEM) software (Abaqus) or open source software (Salome-Meca) as possible development tools for silicone rubber printing pads is investigated. The FEM simulation of this hyperelastic material requires various input parameters such as material model, special material parameters as well as mesh types and sizes. This paper shows how these parameters are determined, which material tests are necessary and how sensitive the simulation result is to these input parameters. Based on the comparison with experimental data, the results show that silicone rubber printing pads with small deformations can be simulated very well with both the commercial FEM software Abaqus and the free open source FEM software Salome-Meca. Mooney–Rivlin or the polynomial material equations are used. Finally, a workflow is shown with which the geometry of a printing pad can be evaluated and optimized.
Printing electroluminescent panels (EL) with pad-printing technology opens up a new scientific and barely investigated area. An EL panel works like a plate capacitor, where doped ZnS particles are embedded between two electrodes one of which is transparent and emit light in an AC electric field. By means of printing technology and a printed multilayer design the light source can be structured and reproducible realized. EL is well known in screen-printing technology. Pad-printing technology imposes completely different conditions as the printing ink is transferred by adhesion forces on a flexible silicone pad. This intercarrier takes the ink from a planar printing plate to planar or 3D curved, non-planar target surfaces. Contrary to screen-printing where layer thicknesses of 10-50 microns are typically reached, pad-printed layers have thicknesses of only 1-2 microns. In this work we study pad-printed EL manufacturing on curved surfaces. We consider the effect of ink for the insulating layer, formulated with different ratios of BaTiO3 and transparent pad-printing varnish. Printing parameters such as pad hardness, printing velocities, pad surface tension are investigated and presented in this work. Further, we consider the relation between the printing process, the thickness of the dielectric layer, the volume fraction of particulate BaTiO3 in this layer, and EL panel luminance. Our pad-printed EL panels, using adapted ink formulations, achieved average luminance’s of 140 cd/m2 on curved surfaces which also corresponds to the performance standards of conventional screen-printed panels.
Full-text available
Deutsch: In diesem Beitrag werden unterschiedliche Ansätze von Automatisierungspyramiden gegenübergestellt. Leider gibt es in der Literatur keinen Konsens über die Benennung und die Anzahl an Ebenen, die eine Automatisierungspyramide umfassen sollte (es exis-tieren Modelle mit drei bis sieben Ebenen). Im Folgenden werden die unterschiedlichen Ansätze tabellarisch erfasst und eine Einordnung vorgenommen. Diese Publikation soll Autoren und Forschern als Orientierungshilfe zur Auswahl eines der Konzepte dienen. English: In this article, different approaches to automation pyramids are compared. Unfortunate-ly, there is no consensus in the literature about the naming and the number of levels that an automation pyramid should comprise (models with three to seven levels are existing). In the following, the different approaches are tabulated and a classification is carried out. This publication is intended to help authors and researchers to provide guidance on how to select one of the concepts.
Conference Paper
A system for the excitation of numerous capacitive loads such as electroluminescent devices is presented. It is based on a controller equipped with up to 16 driver boards which are based on an arbitrary waveform generator. Besides the three template waveforms, any requested waveform can be generated by a Digital-to-analog converter whose output is amplified. Signals can be generated with up to 400 V pp , 500 mA and 5 kHz. Costs are kept at a minimum to enable mass production.
Full-text available
Water is a vital resource for life, and its management is a key issue nowadays. Information and communications technology systems for water control are currently facing interoperability problems due to the lack of support of standardization in monitory and control equipment. This problem affects various processes in water management, such as water consumption, distribution, system identification and equipment maintenance. OPC UA (Object Linking and Embedding for Process Control Unified Architecture) is a platform independent service-oriented architecture for the control of processes in the logistic and manufacturing sectors. Based on this standard we propose a smart water management model combining Internet of Things technologies with business processes coordination and decision support systems. We provide an architecture for sub-system interaction and a detailed description of the physical scenario in which we will test our implementation, allowing specific vendor equipment to be manageable and interoperable in the specific context of water management processes. © 2015, Innovative Information Science and Technology Research Group. All rights reserved.
Full-text available
Different thick-film printing techniques have been used for the fabrication of one-electrode semiconductor gas sensors in the form of thick films on insulating alumina substrate. In a typical one-electrode sensor construction, a thin platinum wire (diameter 20 μm) spiral is embedded inside a sintered oxide semiconductor button. The platinum wire spiral is replaced by a platinum thick-film resistor in our prototype sensor, and the oxide semiconductor is screen printed over the platinum resistor. Both screen printing and gravure off-set printing (pad printing) were used for the printing of platinum thick-film resistors. Tin dioxide, an n-type semiconductor, was used as the sensing (shunting)_thick-film layer over the platinum resistor, and diferent amounts of either silver or antimony were used as additives in SnO2. H2S and CO at different concentrations in synthetic air were used to test the response properties of two different sensor types with, respectively, screen-printed and pad-printed platinum thick-film resistors.
Highly automated production and logistics facilities require mechatronic drive solutions. This book describes in which way the industrial production and logistics work and shows the structure of the drive solutions required for this purpose. The functionality of the mechanical and electronic elements of a drive system including the software is described, and their basic dimensioning principles are explained. Furthermore the authors outline the engineering, reliability, and important aspects of the life cycle. The great number of applications within the fields of conveying and material handling technology in continuous and cycled production lines and for machining processes are divided into twelve drive solutions. They comprise the motor, the inverter with its software, the gearbox, and mechanical drive elements. The specific requirements and the functionality of these twelve solutions are presented. The authors focus on the energy conversion with controlled electric drive systems. Dr. Edwin Kiel (49) has been working in the field of controlled electric drives since he has completed his studies of electrical engineering (TU Braunschweig). 1994 he was received the Dr.-Ing. degree from Prof. Leonhard. He has been working at Lenze since 1998 and is director of innovation there. Dr. Kiel is an acknowledged expert in the fields of automation, mechatronics in production machines, and in the field of electric drive technology. Lenze: innovative solutions Being an expert for drive and automation technology, Lenze offers mechatronic drive solutions with scalable products and automation systems, including the corresponding range of services offered. The group of companies comprises more than 30 subsidiaries worldwide with production plants in Europe, China, and the US. Altogether Lenze employs about 3,300 employees, more than 300 of them are working in the field of research and development. © 2008 Springer-Verlag Berlin Heidelberg. All rights are reserved.
Conference Paper
Automation of a technical process involves the feedback of sensor data for the automated control of particular aspects of the process itself. The same feedback data can be used for other applications such as health monitoring of systems or to update a graphical user interface or to analyze process performance. In order for this data to be utilized effectively, a system architecture must be designed to provide such functionality. This architecture must accommodate the dependencies of the system and sustain the required data transmission speed to ensure stability and data integrity. Such an architecture is presented in this paper, which shows how the data needs of multiple applications are satisfied from a single source of data. Also it will show that the flexibility of this architecture enables the integration of additional data sources that can be used to protect the performance of applications that consume the data as the order of data dependencies grows. This research is based on the development of a fully integrated automation system to test fuel controls for civil transport aircraft engines.
The aim of this paper is to present a methodology for optimizing the operation of compressors in parallel in process industries. Compressors in parallel can be found in many applications for example in compressor stations conveying gas through long pipelines and in chemical plants in which compressors supply raw or processed materials to downstream processes. The current work presents an optimization framework for compressor stations which describe integration of a short term and a long term optimization approach. The short-term part of the framework suggests the best distribution of the load of the compressors (where the time scale is minutes) and the long-term optimization provides the scheduling of the compressors for large time periods (where the time scale is days). The paper focuses on the short-term optimization and presents a Real Time Optimization (RTO) framework which exploits process data in steady-state operation to develop regression models of compressors. An optimization model employs the updated steady-state models to estimate the best distribution of the load of the compressors to reduce power consumption and therefore operational costs. The paper demonstrates the application of the RTO to a network of parallel industrial multi-stage centrifugal compressors, part of a chemical process in BASF SE, Germany. The results from the RTO application showed a reduction in power consumption compared to operation with equal load split strategy.
New technologies are essential for intelligent wound management and to provide tools that facilitate a greater understanding of wounds and healing physiology. pH is an important marker for many processes in the wound environment; it cannot be fully utilised due to the inherent lack of suitable technologies currently available. The development and proof-of-concept testing for an electrochemical system that exploits pad-printed carbon-uric acid composite electrodes is detailed. Uric acid is incorporated to act as a biologically-safe pH probe within in the sensor assembly that can be manipulated to offer a simple voltammetric response. The development of the composite sensors, the activation of the basal carbon, and the surface deposition of 1,2-diaminobenzene to prevent biofouling are detailed. The prototype sensing assembly is shown to enable the interference-free measurement of pH (and linear quantification of endogenous uric acid) even in the presence of high ascorbic acid concentrations. The experimental developments culminate in a standard deviation of 0.164 for 20 replicates performed in simulated wound fluid, and sensitive monitoring of pH across a wide analytical range (pH 4-10) in simulated wound fluid. These findings suggest that printed carbon-uric acid composites may offer a novel, cheap and reliable mechanism for simple pH measurements at wound surfaces, a potentially powerful tool with clinical utility for wound management and one that may enable a greater understanding of pH implications on wound physiology, and the effects of dressings and treatments.
The aim of this work was to study the suitability of pad printing in connection with fine-line printing on solar cells. Pad printing is a kind of gravure offset printing technique that offers the possibility of a simple, economic and high throughput production of fine lines up to 32μm even on uneven surfaces, which is not possible with traditional screen printing (Hahne et al., Proceedings of the Second World Conference on Photovoltaic Solar Energy Conversion, Vienna, 1998, p. 1646). The different inks and silicone rubber pads have been characterised by several methods like thermal analysis, rheological, hardness and surface tension measurement. Simple solar cells on multicrystalline wafers with rapid thermal sintering show efficiencies up to 13.4%.
The possibility of pad printing in RFID tag antenna manufacturing is investigated. Passive UHF RFID tags were printed on flat and on convex surfaces with two different polymer thick-film silver inks. The effect of the ink and substrate material properties on tag antenna performance was examined. The goal was to provide information which is needed in adapting the pad-printing technique in RFID tag manufacture. The results show that pad printing is suitable for tag manufacturing on flat and on convex surfaces. The curvature of the substrate did not significantly affect the tag performance. It was more important to take into consideration other substrate properties, ink characteristics, morphology, and printing parameters. The best practice is to take these matters into consideration in the initial tag design process to ensure proper tag performance at the desired frequency. KeywordsPrintable electronics–RFID–Pad printing–Polymer thick films–3d substrate
Conference Paper
A fabrication process is described to fabricate an integrated structure involving a curved piezoelectric thick film. The development of this multilayer structure is performed to minimize the fabrication steps of the corresponding high frequency single element transducer. On the basis of previous work carried out in order to choose the material of each layer and in particular a porous PZT substrate directly used as the backing, a pad-printing process has been developed and used to deposit several layers of PZT paste to obtain a curved PZT thick film. The effective thickness coupling factor has a value of 47% and resonant frequency can easily reach 50 MHz. Two high frequency transducers have been successfully fabricated and characterized for medical imaging with center frequencies at 20 and 30 MHz. Very good axial resolution is obtained (41 mum at a center frequency of 20 MHz) while keeping satisfactory sensitivity. Images of human skin in vivo and of phantoms confirm the good properties delivered by the transducers using these integrated structures