Buying a Used Shearing Machine
For sheet metal fabrications, an essential piece of equipment is often the shearing machine. Frequently the first step in metal fabrication is cutting the metal to the correct shape and size. A shearing machine may use a scissor-like, angular shear action to cut metal. For big parts, it may use a straight shear action with a blade fixed at an angle. The shearing operation is performed between two blades, one fixed in the shear bed and the other moving vertically. The angular configuration of the blades is called the rake.
Powering up a Shearing Machine
The shear can be powered by several methods, defining the shearing machine types.
- Hydraulic shears Powered by a hydraulic cylinder when an operator steps on a pedal. These can generate extremely high forces.
- Air (pneumatic) shears A pneumatic cylinder powers the crosshead and upper blade. Usually for material up to about 14 gauge and 12 long.
- Hydromechanical shears Hydraulic cylinder(s) power a mechanical device like an arm to move the blade beam down to make a cut. Can produce faster cutting speeds with less power because the mechanical device produces power.
- Servo-driven shears Driven by a direct connection to a servo motor.
- Manual shears Driven by manual force leveraged by screw, levers, or other mechanical means.
Shearing Machine Terminology
A metal shearing machine from any shearing machine manufacturer will have specifications and terminology defining that machines intended use. Shears are manufactured all over the world. A few popular brands include the JMC, Cincinnati, Kruman, and Durmark. Here are some standard terms:
- Sheet / Stock Thickness: The sheet thickness that can be sheared.
- Sheet / Working Length: The largest dimension of working distance from right to left that can be cut.
- Throat Depth: The distance from the centerline of the ram to the back frame
- Automatic Indexing: CNC, PCL or Windows/PC controlled actions which may automatically load parts into the system and operate without operator intervention.
- Square Arms: Used for squaring the sheet for trim cut, may also be used for front gauging and support of longer sheets.
- Stops: Various kinds of stops are used to position material. A swing stop is used for squaring and support arms, and a disappearing stop on front support arms allows the plate to move over the stop and pops up when the material is gone.
- Ball Transfers: Accessories mounted on the machines table to facilitate plate movement.
- Conveyor/Stacker/Scrap Separator Unit: A stacker is added to the back of the shearing machine. The conveyor moves the material, and a scrap/separator attachment separates the trim cut or scrap material from good material.
- High-speed Shearing Machine: Increases the number of strokes per minute
- Power Blade Gap Adjustment: Adjusts the blade gap with a motor, may be computer (CNC) controlled.