Page 23 - MetalForming February 2011

bility as the ability to get what you want, where you want it, when you want it there. Flexibility is essential because of the human component as well as product-demand fluctuations. We can- not escape the cause and effect of what happens in the lives of our workforce and the impact on individual produc- tivity. Neither can we avoid fluctuations in product demand—where one day a fabricator must satisfy a rush order for 100 units of widget A and the next day fulfill a rush order for 50 units of widget B. Unpredictable variants force flexi- bility to be a key component in our process evaluations. Flexibility trumps all when it comes to lean manufacturing.
We’ll define process integration as the combining of operations, thereby eliminating post-process or second- ary operations. New CNC punch-press technology has given fabricators the ability to leverage both of these con- cepts. Since the advent of hydraulic press technology and servo-driven ram technology, we’ve gained the ability to precisely control the ram stroke. This does much more than simply increase process speeds; it allows fabricators to take advantage of new tools that add more value to the parts and eliminate secondary operations.
Setup-Time Reduction
The continued development of laser-cutting technology has forced manufacturers of CNC punch presses to develop technology that combats some of the major drawbacks to tradi- tional punching operations. As a result, we’ve recently seen innovations such as quick-change tool holders, which great- ly reduce setup times. Also new are large-capacity tool turrets with multiple, large auto-index stations, which also promote setup-time reduction and flex- ibility, by having more tools available when they are needed. Many users of these newer-style turrets have reduced setup times by as much as 90 percent.
The key point to note here is that without implementing newer punch- press technology, your operation will be limited in its ability to increase opera- tional flexibility.
Additionally, the
need for automation
is increasing due to
the demands of
cost reductions and
the shrinking of the
skilled labor pool.
In the past, many
viewed automation
as being limited to
long-run high-vol-
ume jobs. With the
knowledge and
benefits of full
sheet processing in
a laser environ-
ment now being applied to a punching environment, the demand for automa- tion to handle full sheets of material has increased. The problem with that scenario is that in a functional, real- world environment, shops were not able to realize significant cost reduc- tions due to the added costs related to secondary operations—shake and break to separate parts from the skele- ton, part sorting and deburring and skeleton removal. Operational costs simply shifted from the front end of the operation to the back end.
Full-Sheet Processing
In the late 1990s, CNC punch-press manufacturers introduced automation with pick-and-place loading/sorting that made processing of full sheets a functional reality. Fabricators can cre-
Recent punch-press innovations include quick-change tool hold- ers, which greatly reduce setup times, and large-capacity tool turrets (shown here) with multiple, large auto-index stations, which also promote setup-time reduction and flexibility, by hav- ing more tools available when they are needed. Many users of these newer-style turrets have reduced setup times by as much as 90 percent.
ate part nests to accommodate what- ever the shop’s customers need, and parts can be punched and extracted from the blank to be sorted as a mirror image of the dynamic nest—as a kit or stacked according to the next process. Loading/sorting automation address- es the need for flexibility to meet small lot sizes and part-variety demands, and the need for process integration to eliminate post-op costs.
To understand why process inte- gration is the key to a lean punching operation, let’s first look at the total time that material is in a plant.
• Setup time—time spent waiting on a resource to be readied for processing. • Process time—time spent being
processed or adding value.
• Queue time—time spent waiting
on a resource while the resource is busy working on something else
ahead of it.
• Wait time—time spent
waiting for another part to be assembled or shipped.
It’s clear that lean-manu- facturing methods address each element of time. However, if our primary
New punch-press technology combined
with new tooling technology can
allow fabricators to produce parts with offsets, ribs, louvers and flanges formed
in process.
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