MFET 243 Lab 7 Fall 09

MFET 243 Lab 7 Fall 09 - MFET 243 Laboratory Assignment #7...

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MFET 243, Laboratory Assignment #7 page 1 of 10 MFET 243 Laboratory Assignment #7 Fall ‘09 Programming The MFET Conveyor System, Part 2 Objectives: In this assignment you will expand upon laboratory assignment #6. In this assignment, you will: Lower product stop #2 (PS2) if buffer #2 is not full Make your program more robust by trapping an error Create multiple programs under the continuous task Learn how to create and use a subroutine Learn how to use the GSV (Get System Value) instruction to read status information from the ControlLogix 5555 controller Learn how to create and program a periodic task Preparation: It is assumed that you have successfully completed ALL of the phases in lab #6 – Programming The MFET Conveyor System, Part 1 . Phase 1: Using File Save As , create a copy of the program you developed in Lab #6. Name the copied program “Lab7_Phase_1.ACD”. Recall from lab #6 that the shot pins are lowered when RPB0 is pushed. Modify your existing program such that product stop #2 (PS2) does not lower if buffer #2 is full. As shown in Figure 1, buffer #2 is the space along the dropline between PE5 and PE6.
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MFET 243, Laboratory Assignment #7 page 2 of 10 Figure 1 – Dropline Conveyor with Buffer Zones PE1 PE2 PE3 PE4 PE5 PE6 PE7 Since your program supports multiple pallets, its possible for pallets to get “backed up” in buffer #2. Note that only one pallet at a time can reside between PS3 and PS4. While the pallet located at PS4 is getting worked on (perhaps by a Fanuc robot), other pallets must wait their turn while they reside in buffer #2. Note that buffer #2 is full when PE5 turns on and remains on. Also note that RPB0 can only be pushed once per pallet. If the buffer is full and RPB0 is pushed the following should happen: 1) The shot pin device will lower. 2) RPB0’s light will turn off. 3) PS2 will not lower until the buffer is no longer full (when space in the buffer becomes available, PS2 will lower – RPB0 will not have to be pressed twice for the same pallet!) Note that you can simulate the buffer being full by holding your hand or a piece of paper over PE5. Buffer #2 Buffer #1
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MFET 243, Laboratory Assignment #7 page 3 of 10 Continue this phase as follows : Lets make our program more robust by trapping an error. Suppose pallets some time get stuck while traveling from product stop 1 (PS1) to product stop 2 (PS2). Occasionally, PS1 will lower, however, the pallet gets stuck and never reaches PS2 (PE3). Modify your existing program as follows: 1) Determine the normal time it takes a pallet to successfully travel from PS1 to PS2. Suppose this time is x seconds. 2) At the instant PS1 is lowered, start a timer. The preset value of this timer should be set at 2x seconds. For example, if it takes a pallet normally about 3 seconds to flow from PS1 to PS2, set the preset value of the timer to 6 seconds. 3) Under normal conditions (no errors) reset the timer when the pallet reaches PS2 (PE3).
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MFET 243 Lab 7 Fall 09 - MFET 243 Laboratory Assignment #7...

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