Managing Bottlenecks

Read this article. It details a bottleneck analysis and proposes a bottleneck management process. From the reading, can you describe why bottlenecks occur in a production process?

Background

The assembly line of the case in point produces seven truck models and six bus models, operating in batch mode. A summary of vehicles assembled in 2011 is shown in Table 1. The assembly plant is made up of 15 workstations (WS), divided into three zones with different supervisors and group leaders. Zone 1 includes WS 1 to WS 6, zone 2 includes WS 7 to WS 11, and zone 3 WS 12 to WS 15. There is a quality inspection bay at the end of the assembly line where all vehicles are inspected for faults. All detected faults are noted in the vehicle's protocol book

Table1: Vehicle sales in 2011

Vehicle Type	Jan	Feb	Mar	Apr	May	Jun	Jul	Aug	Sep	Oct	Nov	Dec
VW	41	35	37	18	17	26	16	28	45	63	62	35
TGM	14	2	10	5	19	3	5	14	22	34	26	11
TGS	54	73	100	50	100	136	148	134	140	66	79	37
CLA	4	25	27	20	18	16	23	18	21	34	18	11
HB	25	15	28	50	19	39	38	33	9	17	40	13
Total	113	150	202	143	173	220	230	227	237	214	225	112

In collective working, as practised in the final assembly of motor vehicles, several operators work on one or more products at a workstation designed for group work. The product is released from this workstation when all operators have completed their work. It is then replaced by another product. Correctly designed, this method of working provides the opportunity to reduce time losses caused by variations in work pace, imbalances in the division of labour, and product variant differences, or so-called balance loss . The case in point operates its fifteen-station assembly system in an asynchronous mode, and there are no storage buffers between the stations owing to the facility's space constraints and the firm's policy on minimising work-in-progress inventory. For the sake of job enrichment, workers are dedicated to particular assembly stations and are trained to perform a restricted set of assigned tasks. On the 15 assembly plant workstations, bottlenecks keep on migrating due to variation in station cycle times and other system dynamics.