Download CIT Mechanical Engineering Exam - Systems & Design and more Exams Systems Engineering in PDF only on Docsity! Cork Institute of Technology Bachelor of Engineering in Mechanical Engineering - Award (NFQ – Level 7) Summer 2006 Engineering Systems and Design ENGINEERING SYSTEMS (Time: 3 Hours) Answer Four Questions Examiner: Dr. M. J. O’Mahony Mr. J. Connolly Mr. R. Simpson Q1. Figure Q.1 is a schematic diagram of an automated drilling station. A hydraulic cylinder moves the drilling platform vertically up and down while a single acting cylinder is used to clamp the workpiece. When the operator actuates the start switch the clamping cylinder extends to hold the workpiece. The hydraulic cylinder is then fully extended lowering the drill to its lower limit of travel; the hydraulic cylinder is then fully retracted having completed its drilling operation. The clamping cylinder can now be released allowing the workpiece to be removed so that the cycle can be repeated for the next part. It may be assumed that the hydraulic pump and motor run continuously. (i) What is the sequence to be implemented? 3 Marks (ii) How many groups are required are required if a cascade system is used? 4 Marks (iii) Design and draw a PLC ladder diagram for the above sequence. Assume that all internal PLC relays have to be latched. Use Figure Q.1 and Table Q.1 as a guide. 18 Marks The following nomenclature is to be used: A: Double acting hydraulic cylinder A+, etc:The extend stroke of cylinder A A+p: The pilot signal to cause the A+ stroke of cylinder A A-p: The pilot signal which initiates the return stroke of cylinder A C: Single acting pneumatic cylinder C+, etc:The extend stroke of cylinder C C+p: The pilot signal to cause the C+ stroke of cylinder C C-p: The pilot signal which initiates the return stroke of cylinder C Cd: The logic complement of C-p, used to reset single solenoid valves by disabling the latch function. V,W: Internal PLC relays which can be set on or off Vp: Signal which sets relay V _ Vp: Signal which resets relay V Vd: The logical complement of Vp which disables relay V by disabling the latch. Note: The nomenclature suggested is as a guide. It does not imply that all the inputs, outputs, internal relays, etc are required to solve this question. Name Address Comment LS1 I0.0 Hydraulic Cylinder is retracted (Drill Motor Retract limit switch) LS2 I0.1 Hydraulic cylinder is extended (Drill Motor Extend limit switch) LS3 I0.2 Clamp Cylinder is retracted LS4 I0.3 Clamp cylinder is extended START I0.5 Cycle start SOL_A Q0.0 Causes the hydraulic cylinder to extend SOL_B Q0.1 Causes the hydraulic cylinder to retract SOL_C Q0.2 Used to actuate the Clamp cylinder W M10.0 Internal relay (Group relay) Table Q.1 Event tracking, MAIN (O81)
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Fig Q.3 Device PLC Device Description Conveyor move I0.5 Indicated product conveyor has moved one station along Test_1 I0.1/V100.0 Test station 1 Active = Failure Test_2 I0.2/V100.1 Test station 2 Active = Failure Test_3 I0.3/V100.2 Test station 3 Active = Failure Test_4 I0.4/V100.3 Test station 4 Active = Failure Test_5 I0.5/V100.4 Test station 5 Active = Failure Q0.0 Activate Reject Ram Always_off M100.6 Data to shift into shift register. SM1.1 Shift register Overflow bit Fail_test M10.3 Fail-test T37 Switch debounce timer T38 Time delay before reject ram operates Shift Register SHRB Shift Register Bit instruction. Table Q.3 Symbol table T 1 T 2 T 3 T 4 T 5 Product conveyor Test Stations Reject Station
