Page 332 - Design for Six Sigma a Roadmap for Product Development

302 Chapter Nine

Rotor Link

Steel Aluminum

Approach 2: Separation in time. Separation in time means that at one
time period an object has property P, and at another time period it has
an opposite property P.
In order to accomplish this, we need to study the time property of
the conflict. If it is again a conflict of useful action versus harmful
action, we need to identify the periods of both the useful action and the
harmful action. We must then identify the time periods when the use-
ful function has to be performed and harmful function eliminated. If
we can separate these two periods completely, we may be able to elim-
inate this contradiction.

Example 9.8. Separation in Time (Terninko et al., 1998)
Problem. When an electrotechnical wire is manufactured, it passes
through a liquid enamel and then through a die which removes excess
enamel and sizes the wire. The die must be hot to ensure reliable calibra-
tion. If the wire feed is interrupted for several minutes or more, the enamel
in the hot die bakes and firmly grips the wire. The process must then be
halted to cut the wire and clean the die.
Contradiction. The die should be hot for operation and cold to avoid bak-
ing enamel. The separation-in-time principle suggests that the die should be
hot when the wire is being drawn and cold when wire is not moving. Is there
a way to automatically control heating of the die? While the wire is being
drawn on the die, there is a significant force pulling the die in the direction
of the wire pull and when the wire stops, there will be no pull.
Solution. The die can be fixed to a spring. When the wire moves, it pulls
the die, which compresses the spring into the heating zone. The die is heated
either by induction or by contact with the hot chamber walls. When the wire
stops moving, the spring pushes the die back into the cold zone.