Hydraulic presses

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Hydraulic Presses © 1993, 1999 Rev 9 Dec 1999
C07.doc Smith & Associates, 530 Hollywood Drive, Monroe, Michigan 48162-2943

HYDRAULIC PRESSES
The hydraulic press is one of the oldest of the basic machine tools. In its modern form, is
well adapted to presswork ranging from coining jewelry to forging aircraft parts. Modern
hydraulic presses are, in some cases, better suited to applicationswhere the mechanical
press has been traditionally more popular. 1

Advantages of Hydraulic Presses
The mechanical press has been the first choice of many press users for years. The
training of tool and die makers and manufacturing engineers in North America has been
oriented toward applying mechanical presses to sheet-metal pressworking.
Modern hydraulic presses offer good performance andreliability.
Widespread
application of other types of hydraulic power equipment in manufacturing requires
maintenance technicians who know how to service hydraulic components. New fast
acting valves, electrical components, and more efficient hydraulic circuits have enhanced
the performance capability of hydraulic presses.

Factors That May Favor the Use of a Hydraulic Press
Factors that mayfavor the use of hydraulic presses over their mechanical counterparts
may include the following:
1. Depending on the application, a hydraulic press may cost less than an equivalent
mechanical press.
2. In small lot production where hand feeding and single stroking occurs, production
rates equal to mechanical presses are achieved.
3. Single stroking does not result in additional press wear.4. Die shut heights variations do not change the force applied.
5. There is no tonnage curve derating factor.
6. Forming and drawing speeds can be accurately controlled throughout the stroke.
7. Hydraulic presses with double actions and or hydraulic die cushions are capable
of forming and drawing operations that would not be possible in a mechanical
press.
1

R. Lown, "Hydraulic Presses inthe 80's", Based on SME Technical Paper, MF82-918, The Society of
Manufacturing Engineers, Dearborn Michigan, © 1982. The paper has been updated by Mr. Lown for
subsequent public presentations.

1

Hydraulic Presses © 1993, 1999 Rev 9 Dec 1999
C07.doc Smith & Associates, 530 Hollywood Drive, Monroe, Michigan 48162-2943

Example of a Gap-Frame Hydraulic Press
Like the mechanical press,hydraulic presses deliver a controlled force to accomplish
work. The style of the press frame and the hydraulic components vary depending on the
intended use. Figure 1 illustrates a gap-frame or C-frame hydraulic press.

Gap Frame Hydraulic Press

Figure 1. A typical hydraulic press featuring gap-frame construction.
Greenerd Press & Machine Company

The press shown in Figure 1 has a frameand bolster that are similar to the construction
used for open back stationary (OBS) mechanical presses. The frame is of robust
construction to limit both angular and total deflection. The bolster and ram provide a
surface to mount tooling. The ram is actuated by a large hydraulic cylinder in the center
of the upper part of the frame. Additional alignment is provided by two round guiderods.The motor drives a rotary pump, which draws oil out of the reservoir housed in the
machine frame. The control system has electrically-actuated valves which respond to
commands to advance and retract the slide or ram. A pressure regulator is either
manually or automatically adjusted to apply the desired amount of force.

2

Hydraulic Presses © 1993, 1999 Rev 9 Dec 1999
C07.doc Smith &Associates, 530 Hollywood Drive, Monroe, Michigan 48162-2943

Unique Features of Hydraulic Presses
In most hydraulic presses, full force is available throughout the stroke. Figure 2
illustrates why the rated force capacity of a mechanical press is available only near the
bottom of the stroke. The full force of a hydraulic press can be delivered at any point in
the stroke. This feature is a very...
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