Department of Engineering and Design- Room T405 PLC Application Exercises

Transcription

1 Application Exercise 4 - Industrial Control Trainer Introduction The system has been designed to realistically represent a component sorting, assembly and inspection process that can be controlled from virtually any PLC that is commonly available. In principle, the unit is designed to sort an aluminium peg from a plastic ring then assemble these two components and check for correct assembly. The components are initially randomly placed on the chain conveyor which lifts them to a higher level. When the higher level is reached the plastic components are detected by an infra red emitter/detector and ejected by a solenoid down an assembly chute. The aluminium pegs continue on the conveyor and are finally deflected down the feeder chute. From the feeder chute the aluminium components are automatically fed onto the belt conveyor. An infra red emitter/detector is used to determine whether or not the plastic ring hopper is empty. If it is, a rotary solenoid is used to dispense a ring from the assembly chute into the hopper. The hopper is positioned just above the belt conveyor and, when the aluminium peg passes, the peg engages with hole in the ring and the two are thus assembled. Inductive, capacitive and infra red sensors positioned along the belt conveyor are used to check for the correct assembly. Components that have not been assembled are ejected by a solenoid into a scrap or recycle bin while correctly assembled components pass into a finished parts tray.

2 Sensors Inductive Sensor Inductive proximity switches consist of three stages, namely oscillator, trigger, and output amplifier. The oscillator generates a high frequency electromagnetic field which radiates from the sensing face. As a metal target appears within the sensing range, a change in the strength of magnetic field occurs. The sensor is triggered and therefore the output is switched. Capacitive Sensor Capacitive proximity switches consist of 3 stages, namely a capacitance coil, trigger, and output amplifier. As a component passes the capacitive probe within the sensing range it acts as the dielectric. The trigger circuitry is activated and therefore the output is switched. Photoelectric Sensors Photoelectric sensors all have an emitter and receiver. The emitter transmits a beam of infra red light, nm wavelength. The tuned receiver is either on or off depending on whether the emitted light is being received or not. Connections to Triangle Research F1616BA PLC PLC Input Sensor Type Comments Inductive Capacitive Senses metal components. Senses plastic components. Through Beam. Metal peg detector. Senses object at Capacitive sensor. Senses component at reject position. Senses component at sort area. Senses component at assembly hopper. PLC Output Actuators Comments Belt Motor Chain Motor Reject Solenoid Rotary Solenoid Sort Solenoid Rejects components off the belt. Guides plastic components down to assembly hopper Sorts plastic components into assembly chute Exercise A Sorting routine Objectives 1. Detection of the plastic component travelling along the chain conveyor and ejection into the assembly chute. 2. Detection of the metal component travelling along the chain conveyor and non-rejection into the assembly chute. Allowing the component to pass the sorting area and be deflected off the chain conveyor, down the feeder chute.

3 Procedure 1. Activate the chain motor (output 13) 2. In the sort area there are two infra red (IR) proximity sensors: a. Input Sensor 7: Proximity Sensor at sort area. b. Input Sensor 4: IR reflective sensor to sense the metal peg. 3. Sensor 7 is a proximity sensor that detects the presence of any object. Sensor 4 is set up to detect at a higher level than the plastic ring, therefore it only detects the metal pegs passing. These two sensors may be logically gated to produce a sorting signal for the sort solenoid to eject the plastic rings down the assembly chute. Exercise B Queue counting & Operation timing Objectives 1. Combine the sorting routine developed in exercise 1 with a queue counting routine, that increments a counter each time a plastic ring is identified and ejected down the assembly chute. 2. Load the assembly hopper using the rotary solenoid. Generate a queue decrement as the plastic rings are taken from the queue into the assembly area. Procedure 1. Activate the chain conveyor (output 13) 2. Sort the metal and plastic components using sensors 7 and 4 as done in exercise On detecting and ejecting a plastic ring down the assembly chute, increment a counter. When the counter exceeds 5 either ignore ring sorting or stop the chain conveyor. 4. In the assembly area an IR reflective sensor (input 8) detects the presence of a plastic ring in the assembly hopper. If this sensor indicates the hopper is empty then the rotary solenoid (output 15) can be indexed, loading the hopper with a plastic ring. The queue count can now be decremented, thus enabling the sorting routine.

4 Exercise C Component/Assembly detection and sorting Objectives 1. Detection of a plastic ring travelling along the belt conveyor and ejecting it into the reject bin. 2. Detection of a metal component travelling along the belt conveyor and ejecting it into the reject bin. 3. Detection of an assembled product travelling along the belt conveyor and accepting it. Procedure 1. Activate the belt conveyor (output 12) 2. Use the feedback sensors to determine the type of component travelling along the belt conveyor. Consider the sequence for the unassembled metal peg and plastic peg before considering the sequence for an assembled product. The signal sequences can be easily observed on the circuit board LED s by turning the unit on and manually passing the products along the belt conveyor. 3. Reject unassembled components at the reject solenoid but allow assembled products to pass by to the finished product area. Further Work - Component queue handling Your solution so far can sort and assemble a component, identify the difference between a good and bad component and reject accordingly. However, in industry the system should be capable of monitoring decisions made for each product assembled. You should develop your routine so that parts are stored in a queue that records decision data. This allows the operator to see which components on the production line were rejected, and for what reason and allow totals of assembled and rejected components to be displayed.

5 How to transfer programs to the PLC This section describes the step by step procedure for transferring programs to the PLC. It is essential that you carry out the steps given below exactly. Ensure the PLC is connected to the power supply and switched ON Ensure the power supply of any other Rig connected to the PLC is also switched ON. Ensure that RS232 Serial cable is connected to the PLC s COM port Run the TLserver Software if it not already loaded. You will see the following window appear. Now click on the Serial Port Setup button above. The following window appears:

6 Ensure the message COM1 opened at 38400bps is displayed in the Response window. If not please call the Technician in charge to assist you. If the message confirms that the port is opened as shown above then, proceed to the next page. Click on Controller and select Program transfer to PLC. The following window is opened: Now type in 01 in the Detect ID box and click on Memorize Username & Password to clear the Tick sign. This means the PLC should not be set with a username and password. Note: you must not set a Password for any other subsequent experiment or project. Username can be ignored and left alone as samples. Therefore the window should appear as shown below before you proceed to the next step.

7 Now click OK. Click Yes to Overwrite PLC s program. The i-trilogi software will now compile the Ladder logic to machine code. If the code contains errors, then the PLC will display an error message that the compilation is not successful. You must then go back to editing and correcting your errors. If the compilation is successful, you will see the message Success! In the Compilation window shown above.

8 Now click on Start Transfer, the following window is displayed: Click on Yes to Reset PLC? The program in the PLC will Execute and read data from input ports or output data to the devices you have programmed. The status of the PLC can be monitored by the following: Click on Controller and select On-Line Monitoring. The following example window appears:

9 The status of all devices can be monitored from this window. If A/D converters are used then the Raw Data from the converters can be seen at the top of the window in ADC1-8 boxes. This concludes a successful PLC Program transfer. The same procedure is used to transfer any program to the PLC. Virtual LCD Display You may view the Virtual LCD Display to see other status data by clicking on the View button. Click View now. You will see the Virtual LCD display window: This window is used to output up to 4 lines of text to display messages or values of Global variables. It also displays, the state of the A/D converters 1 to 8,PWM outputs 1 to 8 and the data that is output the D/A channels.