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Ik University - Industrial Engineering Department IE321 Industrial Production Systems - Spring 2012 Homework 1 due on Wednesday May 16 Question 1 A...

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Işık University Industrial Engineering Department IE321 Industrial Production Systems Spring 2012 Homework 1 due on Wednesday May 16 Question 1 A hydraulic pump manufacturer plans its production on a 10-week rolling horizon. The company is currently working on its production plan for the next 10 weeks. After considering the inventory levels, confirmed orders, and the demand forecast, a production plan has been devised. The table on the right shows this production plan. The two tables below show the cycle times and the setup times of each product at the production departments that it visits. Cycle times are given in minute/part and the setup times are given in minute/batch. Note that products do not need operations at each and every department. Products PC12, PC16, PC24, EN10 and EN20 are produced in batches of 10 parts whereas SG12 and SG16 are produced in batches of 20 parts. The numbers of machines/workstations at each department are 1 Press, 3 Turning machines, 4 Milling machines, 1 Grinding machine, and 4 Assembly workstations. All machines/workstations in a department are identical. The company works 6 days a week and one 8 hour shift per day. a) Find the batch production times (hr/batch) of each product at each department that it visits. Summarize your results in a table like the ones given above. b) Find the average processing time per part (min/part) and summarize in a table. c) Find the weekly utilization (as a percentage) of each department at each week over the 10 week planning horizon. Summarize your results in a table. Assume that the total workload at a department is shared equally among the machines/workstations at that department if it has multiple machines/workstations. Note: Utilization of the department during a week is equal to the utilization of any of the machines/workstations in that department during that week. Number of machines in a department will not play any role in the calculation of batch production times or average processing times. Production Plan (parts) PC12 PC16 PC24 SG12 SG16 EN10 EN20 Week 01 20 0 20 20 20 30 30 Week 02 0 30 30 20 0 50 0 Week 03 0 20 40 0 0 50 30 Week 04 20 20 30 0 0 40 20 Week 05 30 30 0 0 40 0 50 Week 06 40 0 0 40 40 0 0 Week 07 0 0 0 40 40 0 0 Week 08 0 0 0 40 40 50 30 Week 09 0 30 20 0 0 40 40 Week 10 30 20 20 20 20 30 40 Cycle Times (min/part) PC12 PC16 PC24 SG12 SG16 EN10 EN20 Press 10 15 20 Turning 45 60 Milling 30 45 60 50 Grinding 16 18 25 16 20 Assembly 25 30 36 40 50 70 50 Setup Times (min/batch) PC12 PC16 PC24 SG12 SG16 EN10 EN20 Press 120 150 180 Turning 60 75 Milling 50 60 75 90 Grinding 24 24 30 40 40 Assembly 20 30 30 20 20 45 45
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Question 2 In order to estimate the availability of a CNC milling center, 11 failure-records and repair-records (explained below) are compiled from the ERP database of the company. Use the data is given in the table on the right to estimate the availability of the milling center. The company works 8 hours a day, 5 days a week (Monday through Friday). For simplicity, assume that there is no lunch break and the shift goes from 8:00 to 16:00. A failure-record indicates the date and time the milling center experiences a break down. At this point the maintenance department is notified and a repairman is dispatched. Then when the repairman finishes the repair and the center is up and running again, the date and time is recorded as a repair- record . Use the 11 failure-records to calculate 10 TimeBetweenFailure observations, the average of which will yield the MeanTimeBetweenFailures ( MTBF ). Use the 11 (failure-record,repair-records) pairs to calculate 11 TimeToRepair observations, the average of which will yield the MeanTimeToRepair ( MTTR ). Let us say we would like to calculate the TimeBetweenFailure between records 04/14/2009 14:44 and 04/24/2009 09:34. We first need to calculate the number of workdays (business days, Monday-Friday) between these two dates. Excel worksheet function NETWORKDAYS comes in handy. Let us suppose you extract the date part of the records using the LEFT(text,numchars) function in cells E8 and E9 which show the result of the formulas as “04/14/2009” and “04/24/2009”. Then NETWORKDAYS(E8,E9) will calculate the number of workdays between these two dates as 9 including the start and the end days. Note that on two consecutive dates (such as Tuesday 04/14/2009 and Wednesday 04/15/2009) NETWORKDAYS(“04/14/2009”, “04/15/2009”) will yield 2, it does not calculate the difference, we need to subtract 1 to obtain the difference. In order to calculate the time difference between two times, first extract the times from the records (e.g. use RIGHT(text,numchars) function). Then you may use HOUR(“14:44”) - HOUR(“09:34”) to calculate the hour part of the difference and MINUTE(“14:44”) - MINUTE(“09:34”) to calculate the minute part of the difference. HOUR(“14:44”) - HOUR(“09:34”) yield 5, and MINUTE(“14:44”) - MINUTE(“09:34”) yields 10. Finally TimeBetweenFailure is calculated as 58.83 hours (it is not simply 9*8+5+10/60, you need to figure out how to convert the differences reported by Excel into a TimeBetweenFailure calculation). a) Report the calculated TimeBetweenFailure and TimeToRepair values in a table and calculate MTBF and MTTR. Finally estimate the availability of the milling center. Record Number Failure Record Repair Record 1 04/28/2011 13:19 04/29/2011 08:45 2 05/12/2011 08:36 05/12/2011 12:28 3 06/10/2011 14:14 06/13/2011 10:24 4 06/27/2011 10:02 06/27/2011 14:04 5 07/14/2011 11:23 07/15/2011 08:34 6 08/02/2011 09:12 08/02/2011 12:06 7 08/10/2011 09:56 08/10/2011 13:41 8 08/23/2011 14:48 08/24/2011 09:10 9 09/06/2011 15:29 09/07/2011 13:16 10 09/16/2011 11:47 09/16/2011 15:12 11 09/28/2011 08:10 09/28/2011 12:33
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