A punch press is essentially any machine which creates holes in sheet metal by forcing a tool tip through the metal.  This action removes a slug of metal leaving the hole.  Punch presses can refer to any size machine from a simple single tool manual punch to a large CNC controlled press with a turret of dozens of tools.

Types of Punch Presses

Punch presses are typically first described by their frame.  The two most common frame types are C-Frame and Portal Frame.  C frame presses have the die set suspended at the end of a C shaped structure where portal frames are rectangular shaped with the die set suspended in the center.  Because of the additional support from the portal type most heavy duty industrial punches feature some variation of this design.  Most hand powered and mechanical presses have C-Frames.

C-Frame / Portal Frame

Much the same as a Brake Press, punch presses can be further classified by the machines method for delivering power to the punch tip.  The mechanisms for powering punch presses are: mechanical, pneumatic, hydraulic, and servo-electric.  Mechanical presses use a fly wheel, spun by an electric motor, to store energy.  When the operator engages the presses the fly wheel is connected to the punch tip through a clutch and mechanical linkage.  This method for powering presses is very slow and requires an operator to engage the linkage, lending itself to low tonnage presses.  Pneumatic and Hydraulic presses use air and water pressure, respectively, to drive the punch tip through the material.  These types of presses were at a time very popular but have generally been replaced by servo driven types.  Servo-electric presses use a heavy duty servo-motor to drive the punch at very high speeds with a great deal of control and positional accuracy.  Servo driven presses are much quieter than most of their counter parts and do not suffer from oil, air or hydraulic leaks.

Further characterizing punch presses are their capacities.  Work-bed size, tonnage rating and tool capacity are the three most distinguishing features of most presses.  Work bed size will determine the size of sheet that the press can process without re-positioning of the holding clamps.  A typical industrial press will be able to process a sheet in the area of 50” x 100”.  The die sets of punch presses are fixed, compared to that of a flying optic laser, so actuators need to move the sheet under the tool.  This happens to lend the C-Frame presses a slight advantage because there is no throat depth on one side of the machine, meaning a much wider sheet can be processed, though only a specific area can be punched.  Tonnage ratings will determine the thickness of sheet which can be processed, as well as the limitations of forming tools.  Tool capacity is simply how many stations of tooling the machine can handle.  Tooling capacity is also referred to as tool shop capacity.

Speed is determined by sheet movement speed and punch speed.  Sheet speed is typically rated without load or with a light load on the clamps.  Heavier sheets often are run at slower speeds to reduce wear on the bearings.  Punch speed is also determined by the thickness of metal being punched.   Holes per minute at 1” on center is often used to describe how many equally spaced holes the unit can produce on a given sheet size.

Other distinguishing features are safety features, supported tool types, bed type and software controls.

Punch Press Video

http://www.youtube.com/watch?v=Z26pEs8bocs