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Thesis-Generic Sorting System

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Thesis-Generic Sorting System

  1. 1. The Design and Build of a Generic Sorting System Blake Kiely & Simon O’Neill Waterford Institute of Technology B.Eng. in Manufacturing Engineering Year 3 Project Supervisor: Mr. Liam O’Shea
  2. 2. ii Abstract This thesis investigates industrial sorting systems and attempts to design and build a generic sorting system. The idea was to create a system which could be easily adapted to sort anything relative to the size of the machine. Firstly several objectives required to complete the project were established. These acted as guidelines to which the project followed. This project was carried out to attempt to create a generic sorting system for industrial use and also be capable of sorting objects for example bearings, nuts, screws, bolts, springs, Lego pieces, money coins etc. Firstly the objective to design three systems that sort objects was looked at. These systems were analysed and the most realistic one for the time available was chosen. Also the availability of parts was a major factor in the final decision. This design was then expanded and fully designed. The methodology used to meet the requirements of the objectives to this project involved the use of a Mitsubishi FX series PLC to control the inputs/outputs of the system. A load cell was used to detect the weights of the components. A conveyor belt was used to transport the components towards pneumatic cylinders for ejection. In conclusion this project was a success as its aim and objectives were fulfilled. There were many learning outcomes for both students and lecturers. A sorting system prototype was designed and built; this system is capable of sorting a vast range of products relative to the size of the machine and a components weight.
  3. 3. iii Declaration We, the authors, hereby declare that this submission is our own work, except where indicated by special reference in the text and that, to the best of our knowledge and belief, it contains no material previously submitted for the award of any other degree. Signature of Author’s: ..................................... ..................................... Date: ..........................
  4. 4. iv Acknowledgements We wish to express our sincere thanks to our supervisor, Mr Liam O’Shea, whose guidance and knowledge greatly contributed to the project and also his great humour. Liam showed great enthusiasm throughout the project and showed great determination to successfully guide us through our first thesis. We cannot thank Mr David Williams enough for his assistance in electrical problems encountered and also programming issues. Both Mr. Stephen Norton and Mr. John Manning deserve credit for contributing to our gathering of information on amplifying circuits. Great thanks go to Mr. Ned Cullinan for sharing his opinions on the project and his advice on improving certain aspects, and also his enthusiasm in helping with some electronic issues was valued greatly. Finally we would like to thank our families and friends in helping us through stressful times throughout this project and thesis.
  5. 5. v Table of Contents Abstract......................................................................................................................................ii Declaration............................................................................................................................... iii Acknowledgements...................................................................................................................iv Table of Contents.......................................................................................................................v List of Figures..........................................................................................................................vii List of Tables ......................................................................................................................... viii 1. Introduction........................................................................................................................1 1.1 Introduction.................................................................................................................1 1.2 Background .................................................................................................................1 1.3 Aim of Project.............................................................................................................3 2. Literature Review...............................................................................................................4 2.1 Introduction.................................................................................................................4 2.2 Sorting Systems...........................................................................................................4 2.3 Control.........................................................................................................................6 2.3.1 Hardwiring...........................................................................................................6 2.3.2 Programmable Logic Controllers (PLC’s)...........................................................6 2.3.3 Networking ..........................................................................................................8 2.3.4 Pneumatics.........................................................................................................10 2.3.4 Electric Motors...................................................................................................11 2.3.6 Three Phase Power.............................................................................................14 2.3.7 Star Delta Configuration....................................................................................15 3. Methodology....................................................................................................................17 3.1 Introduction...............................................................................................................17 3.2 Initial design concepts...............................................................................................17 3.2.1 Design Concept 1...............................................................................................17 3.2.2 Design Concept 2...............................................................................................18 3.2.3 Design Concept 3...............................................................................................19 3.3 Final Design Concept................................................................................................19 3.4 The Build...................................................................................................................22 3.4.1 Introduction........................................................................................................22
  6. 6. vi 3.4.2 Rewiring of the power circuit ............................................................................22 3.4.3 Control circuit....................................................................................................23 3.4.4 Installation of Pneumatics..................................................................................26 3.4.5 Chute Manufacturing .........................................................................................28 3.4.6 Load Cell signal conditioning............................................................................28 3.4.7 Configuration of the Analogue to Digital Converter .........................................29 3.4.8 PLC Code...........................................................................................................30 4. Results and Analysis........................................................................................................32 4.1 Introduction...............................................................................................................32 4.2 Results.......................................................................................................................32 4.3 Analysis.....................................................................................................................32 5. Discussion........................................................................................................................34 6. Conclusions and Recommendations ................................................................................38 6.2 Introduction...............................................................................................................38 6.3 Conclusion.................................................................................................................38 6.4 Recommendations.....................................................................................................39 6.5 Summary ...................................................................................................................39 References................................................................................................................................40 Appendices...............................................................................................................................42 Appendix A..............................................................................................................................43 Appendix B..............................................................................................................................45 Appendix C..............................................................................................................................48 Appendix D..............................................................................................................................50
  7. 7. vii List of Figures Figure 1: Fruit sorting machine.................................................................................................2 Figure 2: Domestic coin counter/sorter......................................................................................4 Figure 3: International mail sorting plant .................................................................................5 Figure 4: PLC Diagram..............................................................................................................7 Figure 5: Analogue to Digital Conversion.................................................................................8 Figure 6: Parallel and serial interface ........................................................................................9 Figure 7: Basic operation of a motor .......................................................................................11 Figure 8: Components of a DC motor......................................................................................12 Figure 9: Production of rotating magnetic field in an induction motor ...................................13 Figure 10: Three Phase Power .................................................................................................15 Figure 11: Star and Delta conections.......................................................................................16 Figure 12: Concept number 1 ..................................................................................................17 Figure 13: Concept number 2 ..................................................................................................18 Figure 14: Concept number 3 ..................................................................................................19 Figure 15: Final Design ...........................................................................................................20 Figure 16: FXo series PLC installed........................................................................................24 Figure 17: FX1N series PLC and ADC installed.....................................................................25 Figure 18: Electro-pneumatic solenoids ..................................................................................27 Figure 19: Pneumatic cylinders & solenoids installed.............................................................28 Figure 20: Load cell & ejection cylinder (Y5).........................................................................31
  8. 8. viii List of Tables Table 1: Control circuit I/O List ..............................................................................................23
  9. 9. 1 1. Introduction 1.1 Introduction Advances in technology have seen automated materials handling systems implemented into industry and replaced many tasks carried out by humans with automated machines. These advances have allowed production times to be noticeably reduced. Machines have become smarter and faster as technology advances. Mechanically operated machines were replaced with basic electronic sorting machines. Most modern machines use a vision system and a sophisticated software programme to control it. Industries are always changing and sorting systems require change also. To create an easily adaptable system was the main objective in this project. 1.2 Background The first sorting machine was the Hollerith Electric Tabulating System which was capable of punching, reading, sorting, and tabulating; it was first used at the US Census Bureau during 1879-82. Hollerith determined that data punched in specified locations on a card, in the now familiar rows and columns, could be sorted mechanically This machine was designed to reduce the labour and time that would be required to process the data that would be collected in the 1890 Census (Cruz, 2011). Since then industry has dramatically grown and naturally the requirement for sorting systems has also grown. In modern times there are thousands of industries for example the automotive industry, pharmaceutical industries etc.
  10. 10. 2 These run widely automated production systems which use sorting machines. Most of these machines are confined to sorting one main product type, an example of such a confined machine is a fruit sorting machine shown in Figure 1. Figure 1: Fruit sorting machine (diytrade, 2014)
  11. 11. 3 1.3 Aim of Project The overall aim of this project was to design and build a generic sorting system. At the beginning of the college year this project was given to us and the objectives where decided to be as follows: 1. To come up with three design concepts for systems that sort products safely. 2. To analyse these concepts and choose the most efficient and realistic one for the time frame available. 3. To expand on the chosen system and have it designed by December. 4. To build the system to sort objects for example money coins. 5. To test the system sorts approximately 205 coins/min.
  12. 12. 4 2. Literature Review 2.1 Introduction This chapter aims to discuss the research previously done by others in the fields of sorting systems and the control of such systems. Information about pneumatics, PLC’s, motors, conveyors and electrical and electronic circuits will be presented in this chapter. 2.2 Sorting Systems Sorting systems are used in many different scales and sizes, from small money sorters for home use to national mail sorters. Such sorters have many different mechanical systems and methods of sorting the product. An example of a money sorter can be seen in Figure 2 below. Figure 2: Domestic coin counter/sorter (Ribao Technology, Inc, 2012) A machine like this counts and sorts money coins into separate drawers at a rate of approximately 300 coins per minute. It operates from a 220V AC power supply and is controlled using a microcontroller chip (Ribao Technology, Inc, 2012). Shown in Figure 3 is an example of a mail sorting machine used in an international mail processing plant.
  13. 13. 5 Figure 3: International mail sorting plant (HowStuffWorks.com, 2014) In the international mail sorting plant, letters are separated by shape and size. They also rotate the packages so their addresses are facing up and in the same direction. A unique fluorescent bar code is imprinted on the back of each piece of mail. An optical scanner scans the address, and then a bar code representing the specific address is sprayed on the front of the envelope. Other processing machines read the bar codes and direct the letters into bins based on ZIP codes, this indicates the next processing plant, in the region where the letter will be delivered (Beck, 2012). The sorting systems discussed above are examples of small domestic sorting machines right up to large scale industrial sorting machines. This thesis is interested in designing a flexible sorting system of a scale somewhere in between the systems previously discussed. A large factor to consider in the design of such a machine in how the system is to be controlled, the following section of this Literature Review investigates the different control types available.
  14. 14. 6 2.3 Control This section of the literature review presents information researched previously by others in the area of machine control. This information has been sourced from the World Wide Web and books. 2.3.1 Hardwiring Hardwiring is defined as a fixed connection between electrical and electronic components and devices by means of wires (Bridged, 2014). There is no wireless connection. When hardwiring components safety precautions must be taken, often Residual Current Devices, (RCD’s), and circuit breakers are wired into the circuit. These devices protect the components of an electrical circuit from overload and short circuiting. 2.3.2 Programmable Logic Controllers (PLC’s) Electromechanical processes are automated through the use of small computers called programmable logic controllers (PLC’s). A microprocessor is contained within the PLC; this is programmed using a specialised computer language. Typically, the program for the automated process is written on a computer and then is downloaded onto the programmable logic controller directly through a cable connection. The program is stored in the programmable logic controller in non-volatile memory (wiseGeek, 2014). The Central Processing Unit (CPU) controls everything according to a programme stored in the memory which is called the RAM (D.J.Dunn, 2014). Shown in Figure 4 is a schematic diagram of a PLC. The system must be able to communicate with external devices such as programmers, display monitors and Analogue/Digital converters.
  15. 15. 7 Figure 4: PLC Diagram (Selectautomation.blogspot.ie, 2014) The basics of PLC’s operation can be broken down to input devices (e.g. mechanical contacts, proximity sensors), output devices (e.g. motors, solenoids) from the machine or process to be controlled are connected to the PLC (Crispin, 1990). The user enters a sequence of instructions into the PLC’s program memory and the controller monitors the state of the inputs and switches outputs according to the program. Different manufacturers of PLC’s use their own unique coding language. However these coding styles are similar to each other, for example a Mitsubishi FX series PLC’s use the letter ‘M’ to initiate internal relays, where Allen-Bradley use the letter ‘B’ but follow the same logic and programming style. PLC’s are digital devices, they are only capable of reading digital values; this can be a problem when the input is an analogue signal for example measuring speeds, weights, light, sounds etc. To resolve this problem Analogue to Digital Converters, (ADC’s), are used. An analogue to digital converter (ADC) produces a digital output from an analogue input. When the start convert signal is pulsed the ADC converts the analogue input at that time into an equivalent digital value, as shown in Figure 5. The ADC then produces an end of convert
  16. 16. 8 signal to indicate that the conversion has finished (Crispin, 1990). This digital signal can then be used by the PLC to control outputs. Figure 5: Analogue to Digital Conversion (Allaboutcircuits.com, 2014) 2.3.3 Networking Networking is a method which is used to communicate between two or more devices. The information transfer may involve a point to point link such as a computer to PLC or a network of various types of devices. All communication interfaces are either parallel or serial. A serial communications interface (SCI) lets devices exchange data one bit at a time. Usually to a microprocessor, printers external drives and USB's. Serial interfaces have specific advantages over parallel interfaces. The main advantage is simpler wiring. Serial interface cables can be longer than parallel interface cables. This is because there is much less crosstalk among the cables (Rouse, 2011). Parallel interfacing is an interface between a computer and a device where the computer sends multiple bits of information to the device simultaneously (princeton.edu, 2014). Parallel ports can have up to 9 inputs bits and 12 output bits at any one time because it uses multiple wires to transmit data.
  17. 17. 9 Parallel Port’s have been standardized under the IEEE 1284 standard. This was first released in 1994. This standard defines 5 modes of operation which are as follows, i. Compatibility Mode ii. Nibble Mode iii. Byte Mode iv. EPP Mode (Enhanced Parallel Port) v. ECP Mode (Extended Capabilities Port) This was done to make new drivers and devices compatible with each other (Peacock, 1998). Figure 6: Parallel and serial interface (newhavendisplay.com, 2002)
  18. 18. 10 2.3.4 Pneumatics In a very broad term, pneumatics is, "the branch of physics or technology concerned with the mechanical properties of gases" (Definitions, 2014). Pneumatics is compressed gas usually air. The air is pressurised and is used to actuate the end effecter and do mechanical work. The end effecter is usually a common cylinder but can range from grippers to vacuum cups. Pneumatics is commonly used in the following industries:  Medical  Packaging  Material Handing  Entertainment  Robotics Pressures of 100-150 psi are commonly used in pneumatic systems. This is only a fraction of the pressure hydraulic systems use. 3000-5000psi is common for hydraulic systems. Pneumatics are used when small loads apply, the gas can be compressed so this leads to low levels of accuracy. A pneumatic system typically comprises of many parts. A compressor takes in air at atmospheric pressure and compresses it to 100-150psi. when air is compressed it drops the moisture it holds so bleeder valves have to be incorporated into system. Hoses take air to the valves. Valves can be pure pneumatic or electro pneumatic. The valves activate or deactivate the cylinders.
  19. 19. 11 2.3.4 Electric Motors Electric motors have been an important element of the industrial and commercial economy for over a century. Electric motors operate through the interaction of magnetic flux and electric current. Electric motors are broadly classified into two categories: AC and DC. Shown below in Figure 7 is the basic principal of how a motor operates when current is passed through a coil, creating magnetic force. Figure 7: Basic operation of a motor (Elpaso.apogee.net, 2014) DC Motors DC motors operate with terminal voltage and current that is substantially constant. These motors are usually applied in two broad types of application. One of these categories is when the power source itself is DC. That is why motors in vehicles are all DC, from the motors that drive cooling fans to the starter motor. The other reason for using DC motors is that their torque-speed characteristics are easier to tailor (Beaty, 1998). DC motors have six basic parts: an axle, rotor, stator, commutator, field magnets, and brushes. In most DC motors the external magnetic field is produced by high-strength permanent magnets (Solarbotics.net, 2014). The stator is the stationary part of the motor; this includes the motor casing, as well as at least two permanent magnet pole pieces. The rotor
  20. 20. 12 rotates with respect to the stator. The rotor consists of windings, these windings being electrically connected to the commutator. Shown below in Figure 8 are the different components of a typical DC motor. Figure 8: Components of a DC motor (Electrical4u.com, 2014) AC Motors These are motors designed to operate with alternating current (AC) supplies, they are classed into two categories: induction and synchronous. AC motors work by setting up a magnetic field pattern that rotates with respect to the stator and then employing electromagnetic forces to entrain the rotor in the rotating magnetic field pattern (Beaty, 1998). Synchronous motors have a magnetic field which therefore rotates at the same speed as the stator magnetic field. Synchronous motors are not used as much as induction motors because their rotors are more complex and they require exciters. Induction motors are the most used motor today. Induction machines are simple, rugged and usually are cheap to produce. They dominate in applications at power levels from fractional horsepower to hundreds of horsepower (Beaty, 1998).
  21. 21. 13 A 3 phase induction motor gets its name from the fact that the rotor current is induced by the magnetic field, instead of electrical connections. The operating principle of a 3 phase induction motor is based on the production of r.m.f. The stator of an induction motor consists of a number of overlapping windings offset by an electrical angle of 120°. When the primary winding or stator is connected to a three phase alternating current supply, it generates a rotating magnetic field which rotates at a synchronous speed (Application basics of operation of three-phase induction motors, 2014). The direction of rotation of the motor depends on the phase sequence of supply lines, and the order in which these lines are connected to the stator. Switching any of the two phases will results in a change in direction of rotation. The number of poles and the frequency of the applied voltage determine the synchronous speed of rotation in the motor’s stator. Motors are commonly configured to have 2, 4, 6 or 8 poles. The synchronous speed is a term given to the speed at which the field produced by primary currents will rotate, this determined by the following expression: 𝑠𝑦𝑛𝑐ℎ𝑟𝑜𝑛𝑢𝑠 𝑠𝑝𝑒𝑒𝑑 = (120 × 𝑠𝑢𝑝𝑝𝑙𝑦 𝑓𝑟𝑒𝑞𝑢𝑒𝑛𝑐𝑦) 𝑁𝑢𝑚𝑏𝑒𝑟 𝑜𝑓 𝑝𝑜𝑙𝑒𝑠 𝑜𝑛 𝑡ℎ𝑒 𝑠𝑡𝑎𝑡𝑜𝑟 (James, 2012) Figure 9: Production of rotating magnetic field in an induction motor (James, 2012)
  22. 22. 14 2.3.6 Three Phase Power Three phase power is generated in a power plant. Three different AC wave forms of 220volts are generated simultaneously. These 3 phases are offset by 120 degrees each. Four wires come from the power plant, 3 AC phases and a neutral. Three phase power is derived by the following equation: √3 . 𝑉𝑖𝑛. 𝐼. 𝐶𝑜𝑠(𝜑) Vin = voltage per phase (V, volts) I = current (A, amps) Cos Φ = power factor For example when the voltage per phase is 220volts at 1amp and the power factor is 1, then: √3(220)(1)(1) 𝑉𝑜𝑢𝑡 = 381 𝑣𝑜𝑙𝑡𝑠 For large machines and some welders three phase power is preferred over single phase. This is due to many reasons such as:  Higher voltage  No need for rectification  Constant power delivery  No start capacitors or extra control wiring  Uniform torque  Motors are generally smaller
  23. 23. 15 Three phase power is just three single phase waveform brought together at 120 degree intervals. The following figure illustrates how three phase power works. Figure 10: Three Phase Power (Smith, 2012) The neutral wire is always at 0 volts relative to all three phases, while the voltage of the three phases never drops below positive. 2.3.7 Star Delta Configuration Star and delta connections are used on electrical motors. This is because three phase motors are generally always started off the supply lines. When starting a three phase motor large current is needed but large current surges cause’s disturbances in the supply lines. To overcome this problem low voltage is used when starting a motor and then full supply is connected when the motor is near rotational speed.
  24. 24. 16 When starting a large motor, the motor windings are connected in star. This reduces the voltage and torque by a factor of 3. When the motor gets up to speed the windings are reconfigured into delta. Figure 11: Star and Delta conections (JIGUPARMAR, 2012) A star/delta starter is made from many components such as:  Three contactors  A timer  A thermal overload  Time relay  Fuse elements The contactors only have to control winding currents so they are smaller than direct line contactors. When starting the motor only one contactor is open, this is called the star contactor. Star is one third the current of delta. A time relay is built into the starter. When the motor is started the star contactor opens, after a period of time it closes and the delta contactor opens. This is standard practice on all three phase motors over 5hp.
  25. 25. 17 3. Methodology 3.1 Introduction This section aims to discuss the different methods which were considered in meeting the overall aim of the project. It presents information on the design and build of the chosen method and any technical issues and problems met along the way. 3.2 Initial design concepts The first objective of the project was to produce three separate design concepts in which the aim; designing a generic sorting system, could be satisfied. These three concepts were all based around using a conveyor system. 3.2.1 Design Concept 1  The system is controlled by a PLC.  Coins loaded to a load cell for component detection via vibrating bowl.  Bursts of air from air valves used to eject components into their corresponding chutes. Figure 12: Concept number 1
  26. 26. 18 3.2.2 Design Concept 2  This system is controlled by a PLC.  Coins are loaded to a load cell for component identification via a vibrating bowl.  Stepper motors guide components to their corresponding chutes for ejection. Figure 13: Concept number 2
  27. 27. 19 3.2.3 Design Concept 3  This design uses ® Vision Assist to do two things: detect components, and decides where along the system a component is to be ejected.  Pneumatic cylinders are actuated to push components down their corresponding chutes. Figure 14: Concept number 3 3.3 Final Design Concept This section shows how the final design was arrived at. The final design concept is a combination of concept number 1 & 2 discussed above. In reference to Figure 15 below the logic behind the system is as follows:  Components are placed onto a load cell for identification based on their weight.  The conveyor belt transports the component down the line.  Pneumatic cylinders eject components into the desired chutes.  This system is controlled using a PLC
  28. 28. 20 Figure 15: Final Design The options of using LabVIEW® and PLC’s were analysed and the result was to use a PLC as there was no previous experience with LabVIEW®. A PLC was chosen to control the system as PLC programming was looked at theoretically in lecturers and the students have experience in PLC programming. Whereas LabVIEW® had never been covered and is a project in itself to gain the ability of programming complex systems with it. Analysis on component ejection methods were also carried out. The three ejection methods up for discussion were bursts of air, the use of stepper motors and pneumatic cylinders. The first ejection method to be eliminated was the use of bursts of air. It was felt that components could be more accurately ejected by physically guiding them off of the conveyor belt as opposed to blowing them off with compressed air. With the option of using bursts of air eliminated, left to discuss was the use of either pneumatic cylinders or stepper motors to guide components from the sorting machine to their next station.
  29. 29. 21 This discussion resulted in choosing the option of pneumatic cylinders for the ejection method. The main factors that influenced this decision were the fact that pneumatic cylinders were available on hand in a wide range of specifications as opposed to the range of stepper motors available. Another important factor taken into consideration was how complex stepper motors are to control in comparison to pneumatics.
  30. 30. 22 3.4 The Build 3.4.1 Introduction This section is dedicated to the building process of the project. This section aims to clearly highlight and outline the step by step process in which the project was unfolded and completed. Each step will be discussed in detail from the initial interaction with the previous project to the satisfactory outcome of the initial aim of this project. 3.4.2 Rewiring of the power circuit The previous students who had worked on the conveyor system were using it to fill water bottles. The first step was to dismantle the parts previously installed as they were no longer needed. The wiring of the power circuit was deemed unsafe by supervisor Mr. David Williams as the wiring previously carried out was not colour coded; all wires were blue, hence making it difficult to distinguish between live, ground and neutral wires. First the power circuit was fully stripped. The power supply is three phase so the first step taken was to wire each phase through 220V Mini Circuit Breaker’s (MCB’s). Next one of these phases was wired into the live terminal on the PLC. A contactor with a 220V coil was then installed and the three phases were wired to it. This contactor is used to control the three phase induction motor which drives the conveyor belt. (See appendix A for the power circuit diagram).
  31. 31. 23 3.4.3 Control circuit After analysing the control options a decision was made to use a PLC to control the inputs/outputs of the system. This control circuit consists of 3 inputs and 6 outputs, as shown in Table 1 below: Table 1: Control circuit I/O List Inputs Outputs X0 – Start Button Y0 – 3 phase induction motor (contactor) X2 – Stop Button Y1 – Electro-pneumatic solenoid 1 Analogue to Digital module signal Y2 - Electro-pneumatic solenoid 2 Y3 - Electro-pneumatic solenoid 3 Y4 - Electro-pneumatic solenoid 4 Y5 - Electro-pneumatic solenoid 5 Unfortunately due to inexperience it was not realised that the initial used FXo-30MR series PLC, as shown below in Figure 15, could not be networked with an analogue to digital converter which was required to carry out this project.
  32. 32. 24 Figure 16: FXo series PLC installed This problem was rectified by installing an FX1N series PLC (See Figure 16) and rewiring the control circuit as described below.
  33. 33. 25 Figure 17: FX1N series PLC and ADC installed The sync-source (s/s) terminal on the PLC was looped into the 0V terminal. This means that it is sinking outputs (NPN). The outputs pull current through the load and the common connection to the load is 24 VDC (+DC) line (Defining sinking and sourcing I/O, 2014). The current flows from +24 VDC to 0 VDC. The start button was installed and wired normally open into the PLC as input ‘X0’. The stop button was wired normally closed into the PLC as input ‘X2’. Normally closed means it’s a push to break button. Five electro-pneumatic solenoid valves were wired into the PLC. This consisted of connecting each of the 0V leads from the solenoids into the 0V terminal on the PLC. The
  34. 34. 26 24V leads from the solenoids were wired respectively into their corresponding output terminals on the PLC as stated above in Table 1. The last component to be wired was the three phase contactor which controls the induction motor. (See appendix A for control circuit). 3.4.4 Installation of Pneumatics Before installing the pneumatic system all the parts had to be sourced first. These included:  Air pressure regulator  Five 5/2 valves  5 pneumatic cylinders  Festo pneumatic hoses A bracket to hold the 4 pneumatic ejection cylinders had to be manufactured. (See appendix C for CAD drawings). The 4 cylinders were placed on the bracket at 45 degree angles to the conveyor as shown below in Figure 18. This ensured when a component approached an extended cylinder it would be pushed off the conveyor. The cylinders were bolted to the bracket with 4 bolts per cylinder. When a cylinder was activated its ram would cross the full width of the conveyor ensuring ejection of a component. Five 5/2 valves were also mounted onto the bracket, these can be seen in Figures 17 & 18.
  35. 35. 27 Figure 18: Electro-pneumatic solenoids These solenoids were connected to a manifold as shown above in Figure 17; the manifold is piped to the cylinders. The solenoids are wired to the PLC. They were controlled by an electric relay that was part of the 5/2 valve. The air pressure regulator was then connected to the 5/2 valves. This gave control over the amount of pressure that was in the system and was very helpful during testing. A heavy duty festo hose had to be sourced to connect the air pressure regulator to a line supply. This hose was rated to withstand a higher pressure then what the system was capable of delivering.
  36. 36. 28 Figure 19: Pneumatic cylinders & solenoids installed 3.4.5 Chute Manufacturing A way of collecting the coins after they were ejected had to be implemented. A cute was designed that would bolt to the conveyor, not interfere with the belt and safely carry away the components. See appendix D for final design. Four of these chutes were made for the 4 ejection cylinders. They were made from aluminium and could have a coin bag attached to catch coins. (See appendix C for CAD drawings). 3.4.6 Load Cell signal conditioning A load cell with a resolution of 0.1 gram increments was required. This ensured that light components such as money coins could be sorted. A 50 gram load cell with .001 gram resolution was sourced. This scale’s was stripped of the protective plastic exposing the
  37. 37. 29 circuit. The 2 signal wires coming from the load were identified and then tapped into. The voltage across these wires was approximately 600 micro volts. This voltage was far too small for the analogue to digital converter to read so this signal had to be amplified. This was done using an amplifying circuit. The amplifying circuit consisted of:  Five 100k resistors  2k potentiometer  One 620k resistor  LM 324 Chip (4 op amps)  9 volt power source  Breadboard This circuit gave a gain of about 8000. The gain was derived by the following equation. 𝑉𝑜𝑢𝑡 = (1 + 2 𝑅1 𝑅2 ) (𝑉1 − 𝑉2) Where R1 = 620k, and R2 = 2k. (See appendix D for electrical diagram of the amplifying circuit). The output from the amplifying circuit was about 4.7 volts. This output was connected to the VIN port in the analogue digital converter while the negative from the 9 volt power source was connected to the common. 3.4.7 Configuration of the Analogue to Digital Converter The ADC used is a Mitsubishi FXoN-3A series ADC which can be seen in Figure 16 in section 3.4.3. This ADC had one input; this input was from the load cell amplification circuit. Analogue voltage between 0 and 4.7 volts is taken from the load cell. The ADC is an 8 bit
  38. 38. 30 module so therefore it has 256 steps (28 ) minus one step for plus and minus sign. The voltage is translated into 255 digital steps so the PLC can read it. Channel 1 of the ADC was first calibrated for 0-5V. The digital value read in buffer memory 17 is placed into the PLC’s data register 0, so that this value can be put to use within the main program. The ADC configuration can be seen within the PLC program in (Appendix F). 3.4.8 PLC Code Once all mechanical parts were installed and all electrical & electronic circuits were wired the only task left to do was write a PLC code which would control the sorting system. This was one of the more difficult tasks and required a lot of troubleshooting before the finished product was arrived at. First in the program is the conditions required for the conveyor belt its self to run. Then the ADC is configured. Once the ADC was configured it was possible to do comparisons with the digital values being read from the ADC for different weights applied to the load cell. Comparisons were written in the program to prove that the system works. The weights of a €2 coin, a 10c coin and an M10 nut were calibrated within the program so that the machine recognises and sorts these products into the desired stations. This proves that such a system is capable of sorting more than just one component at a time. Once a component is placed onto the load cell the digital value is sampled and placed into data register 0 (D0). If the value within D0 falls within any of the pre-set constraints then the components is ejected from the load cell, onto the conveyor and guided to the desired station.
  39. 39. 31 The load cell and ejection cylinder (Y5) can be seen in Figure 19. Figure 20: Load cell & ejection cylinder (Y5) (See appendix E for PLC program).
  40. 40. 32 4. Results and Analysis 4.1 Introduction This section is used to present the overall results of the project and analyses the potential abilities of the system. 4.2 Results The majority of the projects objectives were complete; hence this produced some results as expected. The machine is capable of sampling a components weight and converting it to a digital value. A PLC program was generated to sort three separate components to prove that the sorting system works. An electro-pneumatic circuit was successfully installed. The three phase power supply was successfully rewired to a safe standard. The load cell’s analogue signal was amplified to the required voltage of 4.7 volts. Signal conditioning was carried out on the analogue signal wires and a great lesson learnt. A fully working prototype of a generic sorting system was produced. 4.3 Analysis The system has very good repeatability. When a component is placed on the load cell it is found that the digital value was being read accurate to two digital values. The PLC program required good repeatable readings from the load cell in order to set valid constraints within the code. For certain operations to happen the values must not fluctuate by more than 2-3 digital steps. The implemented pneumatic circuit worked 100% of the time and successfully carried out its purpose of both ejecting components from the load cell to the conveyor and also guiding components onto the chutes.
  41. 41. 33 The three phase power supply was colour coded correctly and the power circuit was implemented safely. An amplification circuit was designed and constructed to produce a gain of approximately 8000, hence which amplified the analogue signal to approximately 4.7 volts. It was found that electrical noise was affecting the analogue signal wires. To overcome this problem the two signal wires were twisted tightly together and then shielded using tin foil.
  42. 42. 34 5. Discussion This section aims to give an overall evaluation of the project. The learning outcomes of the project will be discussed along with the problems that were encountered. An overall opinion of the project will also be expressed. The overall aim of this project was to design and build a generic sorting system. The objectives for the project were as follows:  To come up with three design concepts for systems that sort products safely.  To analyse these concepts and choose the most efficient and realistic one for the time frame available.  To expand on the chosen system and have it designed by December.  To build the system to sort objects for example money coins.  To test the system sorts approximately 205 coins/min. The first objective required exploring the different methods of satisfying the aim of the project. This research was narrowed down to three design concepts, as shown in Figures 12, 13 and 14 in section 3. Second in the objectives list was to analyse and evaluate each aspect of the three design concepts to result in a final design with the most suitable configuration out of the three. The final design was then expanded in greater detail as the project progressed and different issues needed to be dealt with. The I/O’s of the system were planned; these can be seen in Table 1 and in the control circuit diagram found in Appendix B. The brackets required for mounting the pneumatic cylinders were designed using Solidworks®, also the ejection chutes were designed using this CAD software. Drawings for these parts can be found in the appendices section of this thesis.
  43. 43. 35 Once the final system was fully designed and analysed the objective of building the system to sort components for example money coins was undertaken. The process to which this objective followed is described within the methodology section of this thesis. In conclusion to this objective, it is evident that when the research that is reflected within the final design was put to physical use the build of the machine was a success. The machine operates by using electro-pneumatics, a conveyor belt and a load cell, which are controlled by using a Mitsubishi FX1N series PLC. The final objective of testing that the system sorts approximately 205 coins/min unfortunately was not completed. This is due to the simple fact that time ran short and hence the throughput of the machine was not tested. From observations an educated guess can be made that the throughput of the sorting system is much lower than the desired 205 coin/min. Although a number of factors could be taken into consideration in how the throughput could be raised towards the initial expectations. Some of these factors include:  Tweaking down some of the timers within the PLC code.  Using a variable speed controller on the induction motor which drives the conveyor.  Reducing the sampling time in which the load cell reads components weights.  Using limit switches with the pneumatics to ensure the smooth operation of the system. In order to control the sorting machine a number of things required research to be put in place before the control program could be wrote. First off, an amplification circuit had to be built. This was necessary as the analogue signal produced by the load cell was far too minute for an analogue to digital module and PLC to effectively use. The creation of this amplifying circuit required a good understanding of how operational amplifiers (op amp’s) work. This proved to be a challenging aspect during the project. An LM-324 chip, which contains four op amp’s,
  44. 44. 36 was the main component in the amplifying circuit. This amplifying circuit proved to be a very good learning outcome as the circuit was built and tested several times and a good understanding of how to adjust the gain of such circuits was gained throughout building this circuit. It was realised that and analogue to digital converter (ADC) was required. The amplifying circuit has two analogue signal wires which are referred to as V1 and V2. The circuit amplifies the difference in voltage between these two leads by the gain of the circuit. There is just one output wire from the amplifying circuit. This wire is the amplified analogue signal from the load cell. A PLC cannot read analogue signals. This is the reason why an ADC was used. The use of the Mitsubishi FXoN-3A ADC brought some learning outcomes with it. The calibration of an ADC was learned, which required the use of an external power supply to calibrate the module’s channel 1 (H00) between 0-5 Votls. Also so knowledge was gained on adjusting the ADC’s offset and gain. This process was carried out but turning the built in potentiometers on the module until the desired digital values were acquired. This part of the project was very interesting and a lot was learned about ADC’s. Once the analogue signal had been converted into a digital signal the PLC could now recognise the load cell signal changes. The actual writing of the PLC code turned out to be a challenge. Programming had been studied in a semester 1 module of the coarse called mechatronics 1, but when it came to putting this knowledge to practical use it brought some difficulty. The program required the configuration of the ADC so that the PLC could read the digital values from the ADC’s buffer memories into a PLC data register. Once the configuration was done, the values being read in D0 could be programmed to get the machine to carry out the tasks required to sort components. This was a great learning outcome and good experience putting the theory previously learned to practical use.
  45. 45. 37 Throughout the project many issues arose which required rectification. Some of these issues have been mentioned throughout the thesis. The greatest problem encountered in carrying out this project and by far the greatest lesson taken was electrical noise interference. Electrical noise caused problems in reading stable digital values within the PLC. After many hours of troubleshooting this problem, it was found that the analogue signal wires coming from the load cell and the amplifying circuit were picking up electrical interference. This problem was overcome by using some simple signal conditioning strategies. The signal wires were twisted tightly together, this aimed to share the error being conducted evenly across the wires and hence minimising fluctuation in digital values. Also these signal wires were shielded using aluminium foil. This was done to minimise the amount of electrical noise being conducted. After carrying out some signal conditioning on the signal wires, a huge improvement could be noticed in the amount of fluctuating that the digital values were doing. Not all fluctuation had been stopped so this lead to some more troubleshooting as to why. As a result of this troubleshooting it was found that static electricity had been affecting the breadboard on which the amplifying circuit was built. This problem was rectified by placing some anti-static foam between the control box and the breadboard. It was then found that almost all fluctuation in the digital values had been removed, this meant the signal could be used for programming. The use of timers within the PLC code required a lot of trial and error testing. The use of limit switches could have made the programming process a lot less complex, but this issue only came to attention when the code was to be written. There was not enough time to order limit switches and then install them so the more complex programming method had to be carried out using internal timers.
  46. 46. 38 6. Conclusions and Recommendations 6.2 Introduction This Section summarises the project and the major steps taken to achieve the aim and objectives. Major findings will be discussed and summarised and finally recommendations will be made based on observations that were made throughout the project. 6.3 Conclusion The aim of this project was to build a generic sorting system. This has been achieved and the design and build can be viewed in section 3 of this study. Five objectives were set out at the start of the year and in conclusion four out of the five objectives have been complete. Evidence from section 2 indicates that mechanical sorting systems are replacing manual human sorting operations. It is expected that the amount of mechanical sorting systems in industry will rise in the coming years. This is due to faster processing abilities and cheaper costs to run, implement and service these machines. There were various steps involved in the project. The initial steps taken in the project were to design systems that satisfied the aim. These designs were analysed and a final design was chosen. Much thought went into this step because the entire project would be made to this design. If this design didn't work or there was a flaw with a certain aspect of the design the system would not work. It was critical that the final design had no errors or short comings. The next step in the project was to acquire all of the components. This step involved many hours searching for pneumatic cylinders, valves, switches, hoses and most importantly a suitable load cell. Once these components were acquired they had to be assembled. This process consumed the most time that was allocated for the project because of the sheer amount of manual work involved.
  47. 47. 39 Finally when the mechanical, electrical and electronic components were in place, the program for which would operate the system was wrote. This step had many problems in it, but these were rectified after a lot of troubleshooting. 6.4 Recommendations Overall the project was a success. However if this project was attempted again there would be a few recommendations on different aspects of the project such as:  If components needed to be inspected for wear or damage a vision system should be implemented. The current system does not inspect for damage, wear or contamination of the components.  The implementation of LabVIEW® offers a wider range of freedom in programming capabilities and can also accommodate a vision system.  A safety unit should be made to protect users from the pneumatic cylinders, conveyor and electrical equipment when the machine is operating.  An automatic feeding system should be implemented to place components onto the load cell one at a time. This would remove human operators and the system could run entirely by itself. 6.5 Summary In conclusion the project was a success, as the aim and majority of objectives set out were satisfied. A system capable of sorting a vast range of products and components was designed and built. From a critical point of view there is room for improvement to be made by students who may take on this project in the future. Each of the above recommendations would be very beneficial to the project and if implemented would give more accurate results. The recommendations above can be carried out using the equipment provided by WIT.
  48. 48. 40 References Beaty, H. W., 1998. ELECTRIC MOTOR Handbook. New York: McGraw-Hill. Beck, R., n.d. http://people.howstuffworks.com/usps5.htm. [Online] [Accessed 19 March 2014]. Bridged, U., 2014. Dictionary.com. 19 march. Crispin, A. J., 1990. Programmable Logic Controllers and their Engineering Applications. Glasgow: McGraw-Hill Book Company (UK) Limited. D.J.Dunn, 2014. Programmable Logic Controllers. [Online] Available at: http://www.freestudy.co.uk/plc/outcome1.pdf [Accessed 20 March 2014]. Definitions, G., 2014. www.google.com. [Online] Available at: https://www.google.ie/search?q=what+is+pneumatics&rlz=1C1CHWA_enIE575IE575&oq= what+is+&aqs=chrome.0.69i59l3j69i57j69i59j0.2357j0j8&sourceid=chrome&espv=210&es _sm=93&ie=UTF-8 [Accessed 1 4 2014]. Goodwine, B., 2002. www.newhavendisplay.com. [Online] Available at: https://www.newhavendisplay.com/app_notes/parallel-serial.pdf [Accessed 1 4 2014]. Peacock, C., 1998. beyondlogic.org. [Online] Available at: http://retired.beyondlogic.org/spp/parallel.pdf [Accessed 1 4 2014]. princeton.edu, 2014. wordnetweb.princeton.edu. [Online] Available at: http://wordnetweb.princeton.edu/perl/webwn?s=parallel interface [Accessed 1 4 2014]. Ribao Technology, Inc, 2012. http://www.ribaousa.com/. [Online] Available at: http://www.ribaousa.com/showProDetail.asp?ID=16&ClassID=24 [Accessed 19 March 2014]. Rouse, M., 2011. http://whatis.techtarget.com/. [Online] Available at: http://whatis.techtarget.com/definition/serial-communications-interface-SCI [Accessed 1 4 2014]. wiseGeek, 2014. What Is a Programmable Logic Controller. [Online] Available at: http://www.wisegeek.org/what-is-a-programmable-logic-controller.htm [Accessed 20 March 2014].
  49. 49. 41 Selectautomation.blogspot.ie. 2014. SELECT AUTOMATION - Tuning your needs: PLC- basic Block Diagram. [online] Available at: http://selectautomation.blogspot.ie/2009/11/plc- basic-block-diagram_26.html [Accessed: 7 Apr 2014]. Allaboutcircuits.com. 2014. Introduction : Digital-analog Conversion. [online] Available at: http://www.allaboutcircuits.com/vol_4/chpt_13/1.html [Accessed: 7 Apr 2014]. Elpaso.apogee.net. 2014. Motors & Drives. [online] Available at: http://elpaso.apogee.net/md/mfphowm.asp [Accessed: 7 Apr 2014]. Allaboutcircuits.com. 2014. Introduction : Digital-analog Conversion. [online] Available at: http://www.allaboutcircuits.com/vol_4/chpt_13/1.html [Accessed: 7 Apr 2014]. Solarbotics.net. 2014. DC Motors -- principles of operation. [online] Available at: http://www.solarbotics.net/starting/200111_dcmotor/200111_dcmotor2.html [Accessed: 7 Apr 2014]. Smith, 2012. www.homebrewtalk.com. [Online] Available at: http://www.homebrewtalk.com/f170/3-phase-power-questions- 348783/index6.html [Accessed 2014 4 7]. JIGUPARMAR, 2012. electrical-engineering-portal.com. [Online] Available at: http://electrical-engineering-portal.com/star-delta-motor-starter [Accessed 7 4 2014]. Electrical4u.com. 2014. Working or Operating Principle of DC Motor | Electrical Engineering. [online] Available at: http://www.electrical4u.com/working-or-operating- principle-of-dc-motor/ [Accessed: 7 Apr 2014]. Application basics of operation of three-phase induction motors. 2014. [e-book] Aarau: Sprecher+Schuh AG Rockwell Automation. http://ecee.colorado.edu/~ecen5737/Files/induction%20machines%20paper%203.pdf [Accessed: 7 Apr 2014]. James, H. 2012. Three phase induction motors - Operating principle | EEP. [online] Available at: http://electrical-engineering-portal.com/three-phase-induction-motors-operating-principle [Accessed: 7 Apr 2014]. Defining sinking and sourcing I/O. 2014. [e-book] http://www.fluidairecompany.com/docs/pdfs/Q8answer.pdf [Accessed: 8 Apr 2014].
  50. 50. 42 Appendices
  51. 51. 43 Appendix A Electrical Diagrams
  52. 52. 44
  53. 53. 45 Appendix B CAD Drawings
  54. 54. 46
  55. 55. 47
  56. 56. 48 Appendix C Amplifying Circuit
  57. 57. 49
  58. 58. 50 Appendix D PLC Program
  59. 59. 51
  60. 60. 52
  61. 61. 53
  62. 62. 54
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