Page 95 - How To Implement Lean Manufacturing

76 Cha pte r F i v e

• Even if they started jobs with plenty of time, they always seemed to need
overtime to complete jobs. Even after working overtime, 35 percent of the jobs
had unscheduled expedited freight charges that cut deeply into profit
margins.
We took a plant tour and it was obvious that Lean techniques were something they
desperately needed. Around their problems we designed a four-day training curricu-
lum in Lean. During the class, we also did a group project. The task was to apply the
Lean principles to one of their manufacturing applications. In the class they got so
excited about what we had accomplished on paper, they wanted to apply it to the floor.
They extended our contract and we went to the floor.

The Product
This plant was a metal fabricator. The product they had chosen to Lean out was a junc-
tion box used in the telecommunication industry. The external dimensions of the box
were 36 inches high by 24 inches wide and 8 inches deep. It was made from 12 gauge
precoated steel. In addition to the 80 rivets and 40 screws per assembly, there were
22 items on the bill of materials

The Process

The CNC Punch Press—Turret
The process consisted of using a Computer Numerical Control (CNC) punch press to
stamp out a topside assembly consisting of the top and seven other smaller parts. The
large sheets were manually loaded onto the punch press; each sheet made five assem-
blies. While it was cycling, the operator would separate the prior sheet, remove the
protective coating, segregate the parts, and load them into containers to be transported
to the deburring operation. After 100 assemblies were completed, the operator would
transport the production to deburring, change the setup, and produce the bottom-side
assembly. The bottom-side assembly consisted of the bottom and four other smaller
parts. These parts were handled the same as the topside assembly, with protective coat-
ing removal, segregation, and placement into containers for transportation to deburr-
ing. After 100 assemblies had been produced, these too were transported to deburring
and the operator would make a changeover to his next product. The machine cycle time
was ten minutes, or two minutes per assembly, for both the top and bottom-side assem-
blies. The changeover time for this product was 36 minutes.

Deburring
The work in process (WIP) from the Turret was then transported to deburring. With
automatic deburring machines, the cycle time per assembly was 36 seconds and no
changeovers were required. The deburring operator was very lightly loaded. He would
deburr a batch of 100 topside assemblies and transport them to the Press Break for
bending. He would wait for the bottom-side assembly to arrive and then deburr and
transport these to the Press Break.
The Press Break
At the Press Break, the operator would bend the pieces to the assembly and although
there were more pieces and more bends to the topside assembly, both the topside batch