1. A mobile phone assembly plant has the following process, currently using 4 staff - one on each process step - and 1 test machine. The first step, phone body assembly, takes 9 seconds per phone. The next operator carries out a manual test of the screen and controls at a rate of 200 phones per hour. The next step is an electronic test which is done on a batch of 24 phones at a time by one operator running the test machine. Each batch takes 3 minutes to test including loading and unloading the machine. In the final step an operator packs the phone, charger and user manual in a labelled box, which takes 15 seconds.

   1. (a) Calculate the current cycle time and balancing loss for the process with one operator per process step. (20 marks)

   2. (b) What is the minimum throughput time of the process in (a) above for

      1. a single phone (5 marks)

      2. an order for a batch of 96 phones? (20 marks)

   3. (c) If the demand were for 750 phones to be assembled per hour, how many staff and test machines would you need for the process to meet the demand? What would the new cycle time and balancing loss be for the process after adding the new staff and equipment? State any assumptions made in the calculation. (20 marks)

   4. (d) Consider a situation where due to quality problems 30% of the phones fail the electronic test and failing phones must then go through a repair step taking 2 minutes with one operator. The repaired phone is then tested manually and electronically again to ensure compliance before being packed as normal. What impact does this have on the process in terms of the number of staff and test machines needed to meet the target demand in (c) above and the balancing loss?