Analytics Exercise 8-3 (Algo)

A Notebook Computer Assembly Line

A manufacturing engineering section manager is examining the prototype assembly process sheet (shown in Exhibit 8.15) for his companys newest subnotebook computer model. With every new model introduced, management felt that the assembly line had to increase productivity and lower costs, usually resulting in changes to the assembly process. When a new model is designed, considerable attention is directed toward reducing the number of components and simplifying parts production and assembly requirements. This new computer was a marvel of high-tech, low-cost innovation and should give the company an advantage during the upcoming fall/winter selling season.

Production of the subnotebook is scheduled to begin in 10 days. Initial production for the new model is to be 150 units per day, increasing to 230 units per day the following week (management thought that eventually production would reach 312 units per day). Assembly lines at the plant normally are staffed by 10 operators who work at a 14.4-meter-long assembly line. The line is organized in a straight line with workers shoulder to shoulder on one side. The line can accommodate up to 12 operators if there is a need. The line normally operates for 7.5 hours a day (employees work from 8:15 A.M. to 5:00 P.M. and regular hours includes one hour of unpaid lunch and 15 minutes of scheduled breaks). It is possible to run one, two, or three hours of overtime, but employees need at least three days notice for planning purposes.

The Assembly Line

At the head of the assembly line, a computer displays the daily production schedule, consisting of a list of model types and corresponding lot sizes scheduled to be assembled on the line. The models are simple variations of hard disk size, memory, and battery power. A typical production schedule includes seven or eight model types in lot sizes varying from 10 to 100 units. The models are assembled sequentially: All the units of the first model are assembled, followed by all the units of the second, and so on. This computer screen also indicates how far along the assembly line is in completing its daily schedule, which serves as a guide for the material handlers who supply parts to the assembly lines.

Exhibit 8.15: Notebook Computer Assembly Process Sheet

TASK		TASK TIME (SECONDS)	TASKS THAT MUST PRECEDE THIS TASK
1.	Assemble Cover	76	None
2.	Install LCD in Cover	56	Task 1
3.	Prepare Base Assembly	22	None
4.	Install M-PCB in Base	34	Task 3
5.	Install CPU	21	Task 4
6.	Install Backup Batteries and Test	46	Task 4
7.	Install Accupoint Pointing Device and Wrist Rest	32	Task 4
8.	Install Speaker and Microphone	44	Task 4
9.	Install Auxiliary Printed Circuit Board (A-PCB) on M-PCB	27	Task 4
10.	Prepare and Install Keyboard	24	Task 9
11.	Prepare and Install Digital VideoDrive (DVD) and Hard Disk Drive (HDD)	52	Task 10
12.	Install Battery Pack	7	Task 11
13.	Insert Memory Card	3	Task 12
14.	Start Software Load	9	Tasks 2, 5, 6, 7, 8, 13
15.	Software Load	291	Task 14
16.	Test Video Display	54	Task 15
17.	Test Keyboard	66	Task 16

The daily schedules are shared with the nearby Fujihashi Parts Collection and Distribution Center. Parts are brought from Fujihashi to the plant within two hours of when they are needed. The material supply system is very tightly coordinated and works well.

The assembly line consists of a 14.4-meter conveyor belt that carries the computers, separated at 1.2-meter intervals by white stripes on the belt. Workers stand shoulder to shoulder on one side of the conveyor and work on the units as they move by. In addition to the assembly workers, a highly skilled worker, called a supporter, is assigned to each line. The supporter moves along the line, assisting workers who are falling behind and replacing workers who need to take a break. Supporters also make decisions about what to do when problems are encountered during the assembly process (such as a defective part). The line speed and the number of workers vary from day to day, depending on production demand and the workers skills and availability. Although the assembly line has 12 positions, often they are not all used.

Exhibit 8.16 provides details of how the engineers who designed the new subnotebook computer felt that the new line should be organized. These engineers designed the line assuming that one notebook would be assembled every two minutes by six line workers.

Exhibit 8.16: Engineers' Initial Design of the Assembly Line

ASSEMBLY LINE POSITION	TASKS		WORKSTATION NUMBER	LABOR TIME (SECONDS)
1	1.	Assemble Cover (76)	1	76
2	2.	Install LCD in cover (56)	2	56 + 22 = 78
	3.	Prepare Base Assembly (22)
3	4.	Install Main Printed Circuit Board (M-PCB) in Base (34)	3	34 + 21 + 46 = 101
	5.	Install CPU (21)
	6.	Install Backup Batteries and Test (46)
4	7.	Install Accupoint Pointing Device and Wrist Rest (32)	4	32 + 44 + 27 = 103
	8.	Install Speaker and Microphone (44)
	9.	Install Auxiliary Printed Circuit Board (A-PCB) on M-PCB (27)
5	10.	Prepare and Install Keyboard (24)	5	24 + 52 + 7 + 3 + 9 = 95
	11.	Prepare and Install Digital Video Drive (DVD) and Hard Disk Drive (HDD) (52))
	12.	Install Battery Pack ((7))
	13.	Insert Memory Card (3)
	14.	Start Software Load (9)
	15.	Software Load (13)
6		Software Load (108)
7		Software Load (132)
8		Software Load (38)
9	16.	Test Video Display (54)	6	120
	17.	Test Keyboard (66)
10		Empty
11		Empty
12		Empty

In words, the following is a brief description of what is done at each workstation:

Workstation 1: The first operator lays out the major components of a computer between two white lines on the conveyor. The operator then prepares the cover for accepting the LCD screen by installing fasteners and securing a cable.

Workstation 2: The second operator performs two different tasks. First, the LCD screen is installed in the cover. This task needs to be done after the cover is assembled (task 1). A second independent task done by the operator is the preparation of the base so that the Main Printed Circuit Board (M-PCB) can be installed.

Workstation 3: Here the M-PCB is installed in the base. After this is done, the Central Processing Unit (CPU) and backup batteries are installed and tested.

Workstation 4: The Accupoint Pointing Device (touch pad) and wrist rest are installed, the speaker and microphone installed, and the Auxiliary Printed Circuit Board (A-PCB) installed. These are all independent tasks that can be done after the M-PCB is installed.

Workstation 5: Here tasks are performed in a sequence. First, the keyboard is installed, followed by the DVD and Hard Disk Drive (HDD). The battery pack is then installed, followed by the memory card. The computer is then powered up and a program started that loads software that can be used to test the computer. Actually loading the software takes 291 seconds, and this is done while the computer travels through positions 6, 7, and 8 on the assembly line. Computers that do not work are sent to a rework area where they are fixed. Only about 1 percent of the computers fail to start, and these are usually quickly repaired by the supporter.

Workstation 6: The video display and keyboard are tested in this workstation.

After assembly, the computers are moved to a separate burn-in area that is separate from the assembly line. Here, computers are put in racks for a 24-hour, 25C burn-in of the circuit components. After burn-in, the computer is tested again, software is installed, and the finished notebook computer is packaged and placed on pallets for shipment to distribution centers around the world.

Tweaking the Initial Assembly-Line Design

From past experience, the engineering manager has found that the initial assembly line design supplied by the engineers often needs to be tweaked.

a. If the line could be redesigned to operate at the initial 230 units per day target, assuming that no overtime will be used, what is the maximum cycle time and efficiency of your new design? Assume that the supporter is not included in efficiency calculations. (Round "Maximum cycle time" to the nearest whole number and "Efficiency" value to 2 decimal places.)

b. How many workstations would be necessary for this new layout? (Round up your answer to the nearest whole number.)