DFMA as Applied to the Swingline 747 Desktop ... - University of Utah

DFMA as Applied to the Swingline ® 747 Desktop Stapler
The total assembly time can therefore be derived from Table 6 to be 108.86 seconds.
2.6a Efficiency
Using Nmin = 19 (two fasteners), ta = 3 seconds, and tma = 108.86 seconds from
Table 6, the efficiency for assembling t he stapler is then 53%.
2.6b Chamfers
The insertion of the pin and the anvil actuator are subjects for chamfer analysis.
We present the analysis for the pin only. Table 7 gives the chamfer dimensions for the
pin.
Table 7 – Insertion Parameters for the Pin
There is no chamfer around the insertion point. The pin has a rounded chamfer, therefore
no angle or chamfer width is given. From these data, we can calculate the clearance c
between the pin and the base to be 0.016 in. Since the clearance is so small, the pin uses
a rounded chamfer. The insertion time is 44.2 ms using ti = -70 ln c + f(chamfers) + 3.7L
+ 0.75d where f(chamfers) is -250. Despite the fact that insertion into the base, cover,
and subassemblies is progressive, we consider the diameters D to be the same and the
length L to be the entire width of the base along the insertion axis. As the pin is inserted
and parts through which it travels added, the stability of the pin increases. There is also
the draft on the base to consider. Since the clearance is such that the pin is inserted rather
easily, the draft need not be a concern.
2.7 Recommended Changes
D 0.189
d 0.186
L 1.253
w2
θ2
A few changes in the manufacturing process led directly to changes in assembly.
For instance, if the spring is halved and the upper staple guide is redesigned, the spring
31
0
0