ISE 403: Homework Lab #2, Fall 2013

Due: Thursday, September 26, 2013 at 11:59pm

1. Modify Model 3-1 with all of the following changes:
   1. Add a second machine to which all parts go immediately after exiting the first machine for a separate kind of processing(e.g., the first machine is drilling and the second machine is washing). Processing times at the second machine are the same as for the first machine. Gather all statistics as before, plus the time in queue, queue length, and utilization at the second machine
   2. Immediately after the second machine, there's a pass/fail inspection that takes a constant 5 minutes to carry out and has an 80% chance of a passing result; queuing is possible at inspection and the queue is FIFO (first in, first out). All parts exit the system regardless of weather they pass the test. Count the number that fail and the number that pass, and gather statistics on the time in queue, queue length, and utilization at the inspection center. (HINT: add a new process followed by a decide and two other modules for counting).
   3. Add plots to track the queue length and number busy at both stations.
   4. Run the simulation for 600 minutes.
      
      
2. In problem 1, suppose that parts that fail inspection after being washed are sent back and re-washed, instead of leaving; such re-washed parts must then undergo the same inspection, and have the same probability of failing. There's no limit on how many times a given part might have to loop back through the washer. Of course, this time there's no need to count the number of parts that fail and pass, since they all eventually pass. Run the model for 6000 minutes Monitor the dynamic plot for the inspection queue and make an assessment on how it varies (is it relatively constant, increasing, or decreasing?)
   
   
3. Environment: Incoming materials arrive in the Receiving area of an electronic assembly and test operation facility. Depending on the type of materials, Mechanical or Electronics, they are received in two separate areas. Mechanical lots go through a one-stage process where an operator inspects the container for possible damage and then scans the bar code on the container to cut the receiver. These lots are then sent to Stockroom. The Electronic lots first go through a similar process but they could be sampled for inspection. The "skip lots" are sent to Stockroom. The "sample lots" are sent to Inspection. The lots that pass the inspection are sent to Stockroom and the rejected lots are quarantined for further investigation. Specifications: Lots arrive in a Poisson stream at the rate of 20 per hour (remember that a Poisson stream of 20 per hours has an Exponential interarrival of 3 minutes). Lots are splits, 40% Mechanical, 60% Electronics. The process for receiving Mechanical lots takes 4 to 8 minutes, uniformly distributed, and is staffed by two operators. The process for receiving Electronics lots takes 5 to 10 minutes, also uniformly distributed, and is also staffed by two operators. 10% of Electronic lots are sampled and 15% of inspected lots are quarantined. The inspection for the electronic lots is performed by one operator and the inspection time is Triangular with mode of 60 and a minimum of 40 and a maximum of 100 minutes.

   Construct a simulation model of the operations and run it for 10 replication, each for five days, each day consists of three 8-hour shifts. Review the output report and answer the following questions:

   • What are the expected utilization of the operators?
   • What is the average WIP in Receiving?
   • What is the overall cycle time for the Electronic lots sent to stockroom, either before and after Inspection?
   • What is the overall cycle time for the Mechanical lots?
   • What percentage of time lots spend waiting?
   • How many lots can be received per replication?

   
   

4. For your model in problem 3, include dynamic plots for all queue lengths and resource utilization using the animate plot tool. Hint: change the time range to 7200, fix the "maximum" value of the expression, and specify a "stepped" plot. Also animate entities and servers with their queues. Monitor the dynamic plots and make an assessment on how it varies (is it relatively constant, increasing, or decreasing?) Place your comment in a text box.

5. Using the results from each of the ten runs in question 3, compute (manually) a 95% confidence interval for:
   (1) the overall cycle time for Mechanical lots,
   (2) the number of Mechanical lots waiting, and
   (3) the number of lots received per replication

In addition to any possible MS Word/Excel/PowerPoint files, called yournameLAB2, turn in following ARENA files:

Q1. Turn in the model file (.doe) you used from before and call it "yournameLAB2p1.doe".

Q2. Turn in the model file (.doe) you used from before and call it "yournameLAB2p2.doe". Add a text box in your model explaining your assessment.

Q3. Turn in the model file (.doe) and call it "yournameLAB2p3.doe".

Q4. Add a text box in your model explaining your assessment of the dynamic plots.

Q5. Turn in a spreadsheet(table) with your answers, showing your work.