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Hydra-Chief Mechanical Press
Simulator
Precision Compacting Technologies, Inc. new Hydra-Chief
"mechanical press simulator" combines all the advantages of a
mechanical press with the flexibility of a hydraulic press. We
found many of our customers were replacing their old mechanical
presses for hydraulic presses. These hydraulic presses provide a
free range of motion to produce complicated parts that may not be
made easily on a mechanical press, as our customers were producing
these complicated parts they were also using these presses for
their simple parts. Many times, these simple parts could be made
faster and easier on the old mechanical presses. Our engineers at
Precision Compacting Technologies, Inc. started coming up with
ways to meet all our customers' needs and the mechanical press
simulator was created. The Hydra-Chief mechanical press simulator
combines the ease of setup of the mechanical press with the
flexibility of the hydraulic press.
How it works
The two key compaction properties that the mechanical press
simulator is based on are the press cam profiles and the
programmable limit switch. The cams in a mechanical press along
with the crank angle, create the motions of the press. The
programmable limit switch creates a 360 degree reference to one
stroke of the press. The mechanical press simulator takes these
cam profiles and maps them along a 360 degree reference via
software. Each axis of the hydraulic press has a cam profile to
follow just as the motions of the mechanical press follow the
internal cams. As the virtual master cam rotates 360 degrees the
hydraulic axis follow their cam profiles creating the same motion
as the mechanical press. Because the hydraulic press is freely
programmable it is not limited to the fixed profile of a
mechanical press. The positions of each axis are set to limit the
travel of the axis and still fit the cam profile of the axis. This
saves resource in the hydraulics providing a higher speed.
One of the great advantages of a mechanical press was the
coordinated motion of multiple axes, for example, the ram moves up
while the die table and feed shoe are simultaneously moving to
fill position. This was not typical with hydraulic presses.
Hydraulic presses in the past tended to move one axis at a time.
Now the coordinated motion of the Hydra-Chief "mechanical press
simulator" provides an efficient press cycle with no wasted
motion, similar but better than the mechanical press.
Because the mechanical press simulator is software driven it is
just another variable in the press setup. This mode of operation
is enabled or disabled and stored in the setup of the part. So, as
with all other part variables the mode of the press is loaded with
the part data during setup.
Ram Motions
The ram motions of a mechanical press are somewhat simple and
efficient. However, we have been able to make some improvements to
the ram motions. In a typical mechanical press the ram can have
wasted motion at the top of the stroke. Many times the top punch
will travel very high based on the cam profile of the press. With
our simulator, you can provide an amount from TDC to limit the up
motion of the ram. If it is not needed for clearance of the feed
shoe it is wasted motion and wasted resources in a hydraulic
press. Therefore, we can limit the upward travel of the ram and
use the hydraulic resources in the other parts of the cycle.
As with most hydraulic presses we can go to a position or a
pressure. We have applied this same concept to our mechanical
press simulator. If the tonnage set point is reached before the
ram gets to the position programmed, the travel of the ram will be
limited at that tonnage. The virtual master cam is not affected by
this and continues the cycle. When the cam gets to the limited
position on the up stroke the ram will resume the cam profile.
This allows us to run to a tonnage on each cycle creating equal
density parts, and option not available on a mechanical press.
Other advantages to the ram motions are dwells at press position.
We also have the ability to give a custom eject motion of the ram.
We can emulate the gradual lift off of the upper ram during
ejection. Also, because the speed of the upper ram is set by the
RPM of the master cam, no speed settings are applied to the ram
during setup. Less parameters to be set during setup allows for
faster setup.
Table Motions
Like the ram, we have been able to make many improvements to the
motions of the table in a mechanical press. Because the cam
profile is electronic, we are able to freely adjust the motions of
the die table providing many prepress options. One of the
challenges of a mechanical press is repeating equal density of the
part. We are able to adjust the motions of the die table to
emulate the motions of an opposed ram press creating equal density
in the part and still maintain the cam profile of a mechanical
press. Because we are not limited to the cam motion on the table
we can provide overfill and under fill motions with the table
easily.
Feed Shoe Motions
The feed shoe setup on a mechanical press is very efficient in
motion, however, can be one of the most challenging aspects of a
setup. On a standard mechanical press the feed shoe motions are
related to an external cam on the main crank. By adjusting the two
halves of this cam the feed shoe extend and retracts are set. If
shakes are needed in the cycle, many times different speed bumps
are added to the cam to give shaking motions. Our feed shoe is
following the virtual master cam which gives several advantages.
First the extend and retract of the shoe is set by a degree of the
master cam. This allows precise timing of the feed shoe to the ram
and die table. The number of shakes needed is just entered along
with the position parameters. Any extra motions needed for part
removal are added into the setup electronically.
Multi Platen Motions
The motions of the extra platens in a multi platen press are still
very flexible. The motion can be allowed to follow the motion of
any other axis of the virtual master axis or both. Pressure
control can also be added to enable limited motion or tonnage on
the platen. If slide blocks or any other on/off devices are used,
they can be referenced to the virtual master much like a
programmable limit switch on a mechanical press. Die fault inputs
can be created in the same manner using on/off degrees of the
master.
Automation
Many times when automation is added to a mechanical press, the
press must be stopped or a dwell added for removal of the part. By
creating a cam profile for the automation that follows the virtual
master, the part removal process can be added into the press cycle
with little to no delay. Grippers and vacuum can be reference to
the virtual master for on/off degrees. All the variables added by
the automation are stored with the part setup to ensure quick
repeat setups.
Setup
The setup time of a press has quickly become a point of concern
with our customers. Many times our customers are making more
setups a day than they did in a week a few years ago. A
traditional mechanical press setup is hindered by not being able
to retrieve the positions of a previous job. The Hydra-Chief
presses do not have this problem as we save the part parameters to
a recipe system. However, a hydraulic press with all its options
can create a big task for initial setup. With our Hydra-Chief
"mechanical press simulator" software we have combined the good
parts of each setup and limited the bad. Because the speed of the
press is based on the the RPM of the virtual master axis all speed
settings are reduced to just one RPM setting. Many times during
the setup of a mechanical press the press is inched through the
cycle to ensure the operation of the press. This feature has been
added to our "mechanical press simulator". Not only can we inch
through the cycle a few degrees at a time, can also reverse the
cycle and inch backwards. Because this is based on the virtual
cams we can also remove axis from the inch mode. For example, we
can disable the ram and feed shoe axis and just inch through the
table and extra platens of a multi platen system. This proves to
be a major benefit when using automation. Being able to move back
and forth around the pickup position drastically reduces setup
time and scrap parts created during setup.
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