Page 22 - MetalForming April 2012

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In the Classroom
Which Press is Right for You?
Generally, a traditional mechanical press can achieve the highest production speeds, especially when running relatively flat parts with simple, shallow forming requirements. A hydraulic press offers more versatility in tonnage and working energy to allow for more complex processes and forming. A mechanical servo press combines versatility and higher production speeds. Stamtec offers all three press types— mechanical, hydraulic and servo (of both drive types).
Characteristics of a traditional mechanical press:
• Fixed stroke length, although variable-stroke-length presses are available from some manufacturers.
• Special slide motions, such as link motion, are available, specific to a particular press.
• Variable slide velocity, although slide-velocity profile within a single cycle of the press is fixed.
• Working energy depends on flywheel mass and speed.
• Full press capacity near stroke bottom dead center (BDC).
• Simplicity of setup and operation.
• Typically the highest stroking speeds.
• High accuracy and repeatability, with relatively low initial cost.
A hydraulic press generally does not achieve the high cycling speeds of
a similar-sized mechanical press, but offers more versatility with its variable stroke length, die space and pressure. A hydraulic press often is the best choice when producing parts with deep, complex forms that require a lot of material flow, parts that require a dwell at the bottom of the stroke (including plastics) and when production speed is not as important.
Characteristics of a typical hydraulic press:
• Variable stroke length.
• Slide motion and position control throughout the stroke.
• Variable slide velocity, even within a single cycle of the press,
typically configured as fast approach, slow press and fast return.
• Full working energy at any speed.
• Full press capacity at any point in the stroke.
• Adjustability of stroke length, slide motion and velocity, and working energy. • Generally reduced throughput, accuracy and repeatability compared
to a mechanical or servo press, with relatively low initial cost.
A mechanical servo press (flywheel, clutch and brake are replaced by high-capacity motors): offers much of the versatility of a hydraulic press
at production speeds often approaching that of traditional mechanical presses. Stroke, slide motion and position, and speed are programmable to allow different combinations that can work with a variety of dies, part types and production speeds.
Characteristics of a mechanical servo press:
• Variable stroke profiles.
• Precise slide motion and position control throughout the range of the stroke. • Variable, precise slide-velocity control, even within a single cycle of
the press stroke.
• Full working energy at any speed.