A manufacturing engineering section manager is examining the prototype assembly process sheet (shown in Exhibit 8.15) for the 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 or 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 210 units per day the following week (management thought that eventually production would reach 306 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 include 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

The daily schedules are shared with the nearby Parts Collection and Distribution Center (PCDC). Parts are brought from the PCDC 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

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 (touchpad) and wrist rest are installed, the speaker and microphone is installed, and the Auxiliary Printed Circuit Board (A-PCB) is 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 287 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 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. Consider the following questions that the engineering manager is considering:

If the assembly line is to be redesigned to operate at 306 units per day without using overtime, what is the maximum cycle time to meet this production rate?

Note: Round DOWN "maximum cycle time" values to the next smallest integer.

b. Develop an assembly line layout with the fewest possible assembly line positions and the fewest possible workstations with labor to produce 306 units per day without using overtime. What is the efficiency of this new assembly line layout?

Note: Round Efficiency to 2 decimal places.

In your new layout, how many workstations include labor?

Can this assembly line layout fit on the existing 12-position conveyor belt system?

Yes

No

\begin{tabular}{|l|l|} \hline Efficiency & % \\ \hline \end{tabular} \begin{tabular}{|l|l|} \hline Number of workstations with labor & workstations \\ \hline \end{tabular} \begin{tabular}{|l|l|} \hline Cycle time & seconds per unit \\ \hline \end{tabular}