1. Jose Ramirez, Rahel Mekonnen EGRE 553: Industrial Controls May 4, 2015
EGRE 553 – Industrial Controls
Metal Rejection System
Jose Ramirez
Rahel Mekonnen

2. Jose Ramirez, Rahel Mekonnen EGRE 553: Industrial Controls May 4, 2015
Final Design: Metal Rejection System on a Production Line.
Consider a production line of consumed goods. This production line has eatable goods
that are on their way to the customers. During this production process it is necessary to avoid
defects such as the presence of metal that may be mixed with the product. The system is
designed to detect the presence of metal, eliminate it, and keep track of how many specimens of
metal are being eliminated from the production line autonomously.
Procedure:
A metal object is placed on top of a rotary table that is driven by a variable frequency
drive motor. When the system is powered on, the red light is on, pressing the green momentary
push button when the motor is not active, should turn on the green light output on the light tower
and start the motor at 60rpm or at a frequency of 1Hz, rotating a disk connected to the AC motor.
Subsequent pushes of the green momentary push button to increase by 1Hz and up to a frequency
5Hz, Pressing the red momentary push button should decrease the FreqCommand by 1Hz,
decreasing frequency to 0Hz gives the motor the active motor stop command. Whenever the
motor is accelerating or decelerating the yellow light blinks.
As a metal object trips metal proximity sensor, a timed stepper motor is activated tossing
the metal object out to a chute where a trap door is tripped triggering a magnetic proximity
sensor that keeps count of how many metal objects go down the chute. If three trips of the
magnetic proximity sensor are detected, the system is given the active motor stop command and
the system shuts off. A limit switch is triggered to reset the count on the objects, signifying the
system is reset and it may continue operation. If at any point Emergency button is pressed the
system stops what is doing, the motor is given the motor stop command and the red light turns
on. If the red light is turned on, the motor may not be started using the green momentary push
button until the Emergency button is reset and system resumes operation.
System Hardware layout:
This system uses a PLC controller, Input Modules, and Output Modules. A light tower,
two momentary push buttons, one emergency push button, a limit switch, a PowerFlex 525 AC
VFD Controller, an AC motor, an arm processor, a 24 to 5V transformer, one stepper motor, one
metal proximity sensor, and a magnetic proximity sensor.
As seen in Figure 1, Schematic for this system. The green and red momentary buttons are
connected to their respected input on the terminal modules as Normally Open connections (NO),
and the system is connected in sourcing mode. The green momentary button is connected to
Input 0, and the red momentary button is connected to Input 1 on the input terminal module. The
emergency stop button is connected to Input 2 on the input terminal module, as a Normally
Closed Connection (NC). The Limit switch for the operation is connected to Input 3 on the
terminal module. The metal proximity sensor is connected to Input 4 and the magnetic proximity
sensor at Input 5.

3. Jose Ramirez, Rahel Mekonnen EGRE 553: Industrial Controls May 4, 2015
The output of the system is the light tower that consists of a red, yellow, and green light.
The green light of the light tower is connected to Output 0, on the output terminal module, the
yellow light connects to Output 1, and the red light connects to Output 2. The stepper motors
processor is connected on Output 3 of the system.
The system is powered by a 24V source that connects to each of the terminal modules.
LED on the terminal module are powered by a 24V source on the input terminal, and ground on
the output module. These connections can be seen leading to the back of the output and input
module. The PowerFlex 525 VFD Controller, is connected to the PLC controller via Ethernet,
where the AC motor connects to the PowerFlex Drive.
Figure 1: Schematic of System layout with wiring for the input and output devices.
Mechanical Hardware Design of the System Shown below in Figures 1.1- 1.8 . Show an
accurate representation of what the final design of the system looked like in proportion to the AC
motor and the Powerflex 525. All parts of the system are shown and described as they were built
in the system.

4. Jose Ramirez, Rahel Mekonnen EGRE 553: Industrial Controls May 4, 2015
Figure 1.1: Front View of overall System including all parts.
Figure 1.2: Top View of Overall System

5. Jose Ramirez, Rahel Mekonnen EGRE 553: Industrial Controls May 4, 2015
Figure 1.3: Gear system that drives the circular conveyor.
Figure 1.4: Gear system close up
Figures 1.3 and 1.4 shows the custom gear system build for this machine. Due the fact that the
AC motor could not be slowed down to a speed lower than what is allowed and the need for
horizontal rotation for the system, the system utilizes several small gears in series implemented
to decrease the rotational speed of the circular conveyer belt to a crawl. This allows for the
system to work as intended and keep the pieces on top of the conveyer until removed by the
stepper motor. Lowering the speed allowed for a smoother operation and the reduction of
centripetal force.

6. Jose Ramirez, Rahel Mekonnen EGRE 553: Industrial Controls May 4, 2015
Figure 1.5: Frame that holds the Metal Proximity Sensor and stepper motor at an approximate
half an inch above the circular conveyer belt on which the metal objects are placed.
Figure 1.6: Close look of placement of Metal proximity sensor and stepper motor for system.

7. Jose Ramirez, Rahel Mekonnen EGRE 553: Industrial Controls May 4, 2015
Figure 1.7: Overall view of Chute in which parts are discarded to by the stepper motor.
Figure 1.8: Close up of Chute shows placement of the Magnetic Proximity Sensor and the
Magnet which triggers it via trap door.
As the objects falls through the chute, the trap door is trigger moving the magnet closer to the
magnetic proximity sensor, enabling the sensor on.

8. Jose Ramirez, Rahel Mekonnen EGRE 553: Industrial Controls May 4, 2015
System software
System utilizes EQU and LEQ instructions to maintain the system within limits of
allowed frequency. ADD and SUB instructions increase or decrease the frequency command
value, FreqCommand, accordingly for desired output. Rung 0 is enabled by green_button bit
which sets true enable_light and motor start output. Rung 1 is enabled by the pressing the
red_button or the enable_light bit on Rung 0 enabling the yellow_light output. Rung 2 and 3
used to set the upper and lower boundaries of the system that affect the yellow_light ouput. If
either Rung 2 or 3 become true, XIO instructions on Rung 1 will enable and yellow_light ouput
will not be disabled. Rung 4 implements the ADD for every subsequent press of the
green_button. Rung 5 works in unison for when is true, Halt output is enabled enabling its XIO
instruction on Rung 4. This will not allow the FreqCommand exceed its limit. ONS (one shot)
instruction is used on Rung 4 make sure the rung is only enabled for one scan cycle as the button
is pressed preventing the frequency to increase with unintended results. Rung 6 controls when
the green_light output may be enabled. Only if Rung 0 or green_button is enabled, and the EQU
instruction holds true. Similarly as Rung 4 and 5, Rung 7 and 8 holds the same logic but to
decrease the FreqCommand to the limit of 0Hz every subsequent press of the red_button input.
Rung 9 is enabled at the press of the Emergency_button or when FreqCommand is equal to 0Hz
or if the total metal in box is greater than 3. At which point the motor stop output command is
enabled, red_light output is enabled, and diable_light_yellow_zero and disable_light_green bits
are enabled to disable the green_light and yellow_light outputs on Rungs 1 and 6.
In Rung 10 When the proximity sensor is energized or the stepper motor timer is enabled
and the stepper motor trigger timer is not done timing, then it enabled the output enable_timer
Boolean. In rung 11 when the enable_timer is energized then there will be continuity in this rung
which then starts the Stepper_Motor_Trigger_Timer. In rung 12, when the accumulator value of
the Stepper_Motor_Trigger_Timer is greater than 2500 then turn the stepper motor on. In
addition, in rung 13 it is observed that when the proximity sensory inside the box is triggered and
for the first scan and the drive motor is not stopped then the ADD instruction will add the value
of Source B to Source A. Ultimately, rung 14 shows normally closed limit switch is pressed it
energizes the rung and allows continuity which then energizes the MOV instruction. Likewise,
the MOV instruction moves a value of zero to the Total_Metal_In_Box tag value. Which resets
the total count of the metals in the box.
This may be visually and descriptively followed in more detail on Figure 2 , Figure 2.1
and Figure 2.2 ladder diagrams below.

9. Jose Ramirez, Rahel Mekonnen EGRE 553: Industrial Controls May 4, 2015
Figure 2: Ladder Diagram for System

10. Jose Ramirez, Rahel Mekonnen EGRE 553: Industrial Controls May 4, 2015
Figure 2.1: Ladder Diagram for System

11. Jose Ramirez, Rahel Mekonnen EGRE 553: Industrial Controls May 4, 2015
Figure 2.2: Ladder Diagram for System

12. Jose Ramirez, Rahel Mekonnen EGRE 553: Industrial Controls May 4, 2015
System Operation
When the user presses the green momentary push button, the AC motor starts and the
circular conveyor begins to rotate clockwise with metal objects placed on its surface. As these
objects are moving in a circular path on the rotary conveyer, the object passes through a
proximity sensor which detects its presence. As the metal object is detected , a delay after, a
stepper motor turns on tossing the metal object onto a chute. Every time a mental object is
dropped into the chute it passes through a trap door holding a magnet which triggers a magnetic
proximity sensor. Each trigger of the Magnetic proximity sensor counts how many objects are
tossed inside the chute. If three objects trigger the magnetic proximity sensor the system shuts
off until an operator resets the system by triggering the limit switch and the system may resume
operation. If at any point the user decides to press the Emergency stop button. The motor
decelerates to a stop and the red light output on the tower turns on. If the red light is turned on,
the user may not start the motor using the green momentary push button until the user
Emergency button is reset. At which point the user may press the green momentary push button
to start the motor again and resume operation.
Original design of the system was not able to be implemented due to the fact that the
order of parts that were necessary for the system were delivered incorrectly multiple instances. A
redesign of the idea was implemented which worked to an advantage and still was able to
demonstrate the proof of concept intended. One limitation that the system encountered was the
fact that that it had mechanical issues. Due to the fact that it was built with a limited amount of
time and limited resources. An improvement to the system may have been to use more
mechanically stable materials to insure stability and durability. Because the system had issues
mechanically, consistency in the output was the issue. The gears would pop out of place and the
system will stop or the stepper motor would lose its timing. Other than the physical limitations of
the system. The system preformed as expected and the proof of concept was demonstrated. The
system successfully detected the presence of metal, eliminated it, and kept track of how many
specimens of metal were being eliminated from the production line autonomously.