Chapter 6 Production Activity Control

Formula

1)      Critical Ratio (CR)            =          Actual Time Remaining

                                                              Lead time remaining 

2)      Actual Time Remaining    =          Due date – present date

CR  <  1 (Actual time < Lead time)  =  Order is BEHIND schedule CR  =  1 ( Actual time = Lead time )  =  Order is ON schedule CR  >  1 ( Actual time > Lead time )  =  Order is AHEAD schedule CR  =  0/- ( Today date> Due date)  =  Order is ALREADY LATE

Example Problem

          1.     An order for 500 of buns is processed on machine 001 and 002. The set up time on 001 is 30 minutes, and the run time is 2 minutes per unit. The set up time on 002 is 20 minutes, and the run time is 5 minutes per units. Wait time between the two operations is 50 minutes. The move time between 001 and 002 is 4 minutes. Wait time after operation 002 is 50 minutes, and the move time into stores is 7 minutes. There is no queue at either workstation. Calculate the total manufacturing lead time for the order.

001                                                      002

Setup time                   30 minutes                                          20 minutes

Run time                     2 minutes                                             5 minutes

Wait time                    50 minutes                                          50 minutes

Move time                  4 minutes                                             7 minutes

Solution:

Work center 001 operation time = 30 + (500 x 2) = 1030 minutes

Wait time                                                              = 50 minutes

Move time                                                             = 4 minutes

Work center 002 operation time = 20 + (500 x 5)  = 2520 minutes

Wait time                                                               = 50 minutes

Move time                                                             = 7 minutes

Total Manufacturing lead time                                 = 3661 minutes

                                                                             = 61 hours 1 minute             
  2.  An order for 400 of product is processed on work center 111 and 222. The set up time on 111 is 20   minutes, and the run time is 10 minutes per piece. The set up time on 222 is 40 minutes, and the run time is 20 minutes per piece. Wait time between the two operations is 4 hours. The move time between 111 and 222 is 2 hours. Wait time after operation 222 is 2 hours, and the move time into stores is 25 minutes. There is a queue at work center 111 is 15 hours and at 222 is 20 hours. Calculate the total manufacturing lead time for the order.

111                                          222

Set up time                              20 minutes                              40 minutes

Run time                                 10 minutes                               20 minutes

Wait time                                4 hours                                    2 hours

Move time                              2 hours                                   25 minutes

Queue time                             15 hours                                 20 hours

 

            Solution:

            Work center 111 operation time  = 20 + (400 x 10) = 4020 minutes

            Wait time                                    = 4 hours x 60       = 240 minutes

            Move time                                  = 2 hours x 60       = 120 minutes

            Queue time                                 = 15 hours x 60     = 900 minutes

            Work center 222 operation time = 40 + (400 x 20)  = 8040 minutes

            Wait time                                   = 2 hours x 60        = 120 minutes

            Move time                                                                   = 25 minutes

            Queue time                                   = 20 hours x 60   = 1200 minutes

            Total manufacturing lead time                                   = 14 665 minutes

                                                                                           = 244 hours 25 minutes

   3.    If today is manufacturing day 100 and an order has a due date of 120 and a lead time remaining of 25 days, the critical ratio would be?

Solution:

Critical ratio   = Due date – present date

                           Lead time remaining

                        = 120 – 100

                                25

                        = 0.8

                       

Ø  CR < 1 (actual time < lead time) = order is behind schedule.

   4.     If today is manufacturing day 100 and an order has a due date of 120 and a lead time remaining of 12 days, the critical ratio would be?

Solution:

Critical ratio    = Due date – present date

                            Lead time remaining

                         = 120 – 100

                                  12

                          = 1.67

Ø  CR > 1 (actual time > lead time) = order is ahead schedule.

    5.      If today is manufacturing day 100 and an order has a due date of 125 and a lead time remaining of 25 days, the critical ratio would be?

Solution:

Critical ratio    = Due date – present date

                            Lead time remaining

                         = 125 – 100

                                 25

                         = 1

Ø  CR = 1 ( actual time = lead time) = order on schedule.