Page 404 - Design for Six Sigma a Roadmap for Product Development

Design for X 373

recorder to reach the PCB, the item requiring service. In the disassem-
bly process, the team will access several disassembly locations and
record all operations taken in the disassembly worksheet row by row.
Subassemblies are treated as parts when disassembly is not required
for service; otherwise the disassembly operation recording will continue
for removing them. Reference to the Abbatiello (1995) database is given
in columns 3, 5, and 7 of Table 10.5. For example, the time in 4.2 s in
column 4 is the average taken from hours of videotaped service work
and includes a fraction of the time for tool replacement at the end of
service. The estimated time for PCB disassembly T d is 104.3 s. This
time can be converted to labor cost by multiplying by the service labor
hourly rate. *
The serviceability efficiency is determined by parts necessity for
removal or disassembly if they satisfy any of the following:

■ The part or subassembly must be removed to isolate the service
item(s).
■ The part or subassembly removed contains the service item.
■ The part or subassembly removed is a functional cover part enclos-
ing the service item. For example, the plastic cover in the pressure
recorder does not enclose the PCB; thus it is not considered a cover.

When a part or subassembly does not satisfy any of these require-
ments, it is not considered as a necessary part for disassembly. The
sum in column 11 of Table 10.5 is the theoretical minimum justifiable
and necessary number of disassembly operations N m . In this example,
only the removal of PCB is justified, N m 1.
The next step is to fill out the corresponding reassembly worksheet
(see Table 10.6). The reassembly worksheet format is similar to the
disassembly worksheet and requires reference to the insertion and fas-
tening database.
The DFSS team noticed that the total removal time T r equals 130.9 s
and does not equal the total disassembly time.
On completion of both worksheets, the overall service efficiency of
the service performed, replacing the PCB, can be calculated using the
following steps:
1. Calculate the total time of service T s as T s T d T r 235.2 s.
2. Determine the ideal service time based on the minimum amount of
time required for all necessary operations, which include removal,
set-aside, acquisition, and insertion. Several assumptions need to
be made:

* Note that the division by 36 in column 10 of Table 10.5 is intended to convert dollars
to cents and hours to seconds.