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Full power stroke - The full power of a hydraulic press can be delivered at any point in
the stroke. Not only at the very bottom, as is the case with mechanical presses.
Advantages? No allowances for reduced tonnage at the top of the stroke. In drawing operations,
for example, you have the full power of the press available at the top of the stroke.
You don't have to buy a 200-ton press to get 100 tons throughout the stroke. Other
advantages are faster set-ups and no time consuming job of adjusting the stroke nut on
the slide to accommodate different dies.
Built-in overload protection - A 100-ton hydraulic press will exert only 100
tons pressure (or less, if you have set it for less) no matter what mistakes you make in
set-up. You needn't worry about overloading or breaking the press or smashing a die.
When hydraulic press reaches its set pressure, that's all the pressure there is. The
relief valve opens at that limit and there is no danger of overload.
Much lower original cost and operating costs - Hydraulic presses are relatively simple,
and you may be surprised at the significant cost advantage over mechanical presses in comparable
sizes. The numbers of moving parts are few, and these are fully lubricated in a flow
of pressurized oil. Breakdowns, when they occur, are usually minor; not, for example,
like a broken crankshaft. Replacements of packing, solenoid coils, and occasionally a
valve, are typical maintenance items. Not only are these parts inexpensive, but also
they are easily replaced without tearing the machine apart. This means more up-time and
lower maintenance costs.
Larger capacities at lower cost - It is easier and less expensive to buy certain
kinds of capacity in hydraulic presses. Stroke lengths of 12, 18, and 24 inches are
common. Extra stroke length is easy to provide. Open gap (daylight), too, can be added
without much additional cost. Similarly, larger table areas and small presses with big
bed areas can be provided. Large 200-ton presses with relatively small beds are
available; tonnage of the press doesn't dictate what the bed size will be.
More control flexibility - Hydraulic press power is always under control. The
ram force, the direction, the speed, the release of force, the duration of pressure
dwell, all can be adjusted to fit a particular job. Jobs with light dies can be done
with the pressure turned down. The ram can be made to approach the work rapidly, then
shifted to a slower speed before contacting the work. Tool life is thus prolonged.
Timers, feeders, heaters, coolers, and a variety of auxiliary functions can be brought into
the sequence to suit the job. Hydraulic presses can do far more than just go up
and down, up and down.
Greater versatility - A single hydraulic press can do a wide variety of jobs
within its tonnage range. Commonly seen are deep draws, shell reductions, urethane bulging,
forming, blank and pierce, stake, punch, press fits, straightening, and assembly. They
are also used for powered metal forming, abrasive wheel forming, bonding, broaching, ball
sizing, plastic and rubber compression, and transfer molding.
Quiet - Fewer moving parts and the elimination of a flywheel reduce the overall
noise level of hydraulic presses compared to mechanical presses. Properly sized and
properly mounted pumping units meet and exceed current Federal standards for noise, even
with the pump under full pressure.
Because each phase of the ram movement can be controlled, noise levels can also
be controlled. A hydraulic ram can be controlled to pass through the work slowly and
quietly.
More compact - A typical 20-ton hydraulic press is eight feet high, six feet
deep, and two feet wide. A 200-ton press is only ten feet high, nine feet deep, and a
little over three feet wide. At ten times the capacity, the 200-ton press only takes up
50 percent more floor space. Hydraulic presses become less and less expensive compared
to mechanical presses.
Lower tool costs - the built-in overload protection (see advantage 2) goes for
the tools, too. If they are built to withstand a certain load, there is no danger of
damaging them because of overloading. Tools can be sized to withstand the load of
a particular job, not a particular press. The pressure of the press can be set down to
suit the job. The lack of impact, shock, and vibration promotes longer tool life.
Safety - No manufacturer will (or should) claim that hydraulic presses are safer
than mechanical presses. Both types of machines are designed and built to be safe if
the controls and safety features built in are used properly.
Improperly used, all machines are potentially dangerous. But the factor of control of
the ram movements makes hydraulic presses easy to make safe. Non-tie down, anti-repeat, dual
palm button controls are used. The interlocking of guards, as well as other safety devices,
is relatively easy because of the nature of a hydraulic press control system.
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