Tips and Techniques
for
 Punch/Shear
Combination Machines
by
Andrew McCarlie
Applications Engineer
At
first glance, there are many obvious advantages offered
by apunch/shear combination machine. Below are a few
suggestions for maximizing the potential productivity of
either the Shear Genius (SG) or the Shear Brilliance
(SB) Flexible Manufacturing Cells.
Common line
shearing provides the best material utilization and the shortest
cycle time. In many cases, with standard punching tooling and
programming techniques this cannot be achieved because the tools
extend from one part into the next when common line cutting is
attempted.
 A
good example of this is when parts have radiused corners. The
normal 4-way radius tool used means the parts must be spaced the
width of the parting tool apart – wasting material and
increasing cycle time. The solution: Use a zero clearance or
star radius tool in a Multi-Tool station. This allows common
line cutting. Using a Multi-Tool reduces the cost and allows up
to 0.5” (13mm) 4-way radius in an MT8. You can then have several
different radii in one station.
This practice
should be considered for all the tooling where possible when
using the punch/shear machine. Another example is custom tooling
for special shape notches shared between parts. With the ability
of the SG machine to have up to ten 3.5” full tonnage auto index
stations and 15 in the SB, large complex shapes can be shared
over more than one tool, allowing common line shearing of parts.
Eliminating
Sheet Distortion
A frequent issue
that occurs in the punching process is sheet distortion when
punching many holes in a sheet or large special forms. The SG is
able to circumvent this problem. For example, a standard
punching machine must contain all the parts in a shaker sheet
until the end of the punching process. However, with the SG you
can decide in the programming process to punch only a portion of
the sheet and then shear those parts free working your way
through the sheet. This means that you are not limited to small
sheet sizes to minimize the sheet distortion from many holes or
forms.
The SG can take
the above process even further in the case of parts that have
large forms down on a sheet. These normally will not run due to
the damage that would be caused to them when they pass over the
turret. Forms su ch
as these usually cause the sheet to crash in the machine.
Usually the parts are run in two different operations with the
already punched part being flipped for the form down so it can
be run in the up position in the turret punch press or as a
secondary operation in another machine. With the SG, parts such
as these can be nested on a large sheet by utilizing the ability
of the SG and the upforming option to process each part
individually as the large form down features are formed
as the last punching operation before shearing. The part is then
programmed to move directly out of the turret and straight
across to the shear where it is freed from the sheet. In the SG,
there is only a small delay going from punching to shearing and
none at all with the linear drive SB machines. The advantage of
this is a single operation producing high quality parts with
minimal scratching in one operation from a large sheet.
By coupling the
FINN-POWER NC
Express® programming software with the integrated punch/shear
machine, the customer has the ability to automatically punch and
shear the largest possible sheet areas with maximum efficiency,
accuracy, and working area. The software recognizes the part
sizes and punches and shears in the same clamp zone to provide
for maximum accuracy. With the latest linear drive SB machine,
this can include sheets up to 160”x60” with no repositions.
Multi-Part
Another technique
that can be used with the SG is to group smaller parts together
so that they form one long multi-part which is treated by the SG
as a single part. The multi-part is usually punched with a
parting tool on two sides when it is grouped together as a
single shear part. When the multi-part is sheared, all the parts
are freed from the sheet with one blade stroke. This is much
faster and more cost effective than shearing each small part
individually. Material utilization is still kept high by common
line shearing the multi-parts into groups with a minimal scrap
width being used between the groups of multi-parts.
The SG can
process parts that have no common rectangular side as well by
nesting them in a frame. This allows the user to realize the
benefits of the SG’s part processing with the automatic sorting
of parts and no shakeout skeletons to deal with.
With the 11.0
series and higher SG machines, the shear can be programmed for fast or slow cutting based on the material thickness. With NC
Express, the programmable blade gap and shear speed are set for
each material thickness and type once at the time of generating
the NC code for that specific material. This is particularly
important for obtaining the best shear edge quality for the type
and thickness of material you are cutting.
The use of the
“last part in clamp” technique allows for the maximum material
utilization. This uses the 3rd clamp option on the SG that
allows for individual clamp movements independent of reposition.
The technique allows the customer to use the mill edge of the
sheet in the clamps as a part edge provided the edge is not
punched so that the single clamp move does not lose contact with
the sheet edge. Special clamp teeth protectors are available to
reduce part marking.
The 2 or 3 clamps
are automatically programmed with the NC Express to be parked on
the last part which (last part in clamps) is then automatically
dropped by the carriage onto the shear conveyor rather than
being sheared free onto it. The NC Express programming system
automatically trims the left hand part edge with a punching tool
as the shear is not used to cut the part from the sheet because
the LAST_PART command does this.
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710
Remington Road 
Volume
15 Issue 1 -
July 2005