Shear cutting

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Unfolded fine blanking tool

The shearing or scissors is used for cutting a material by two moving past each cutting ( DIN 8588). The material is sheared off by shear forces .

In the sheet metal working this part of separation procedures to the most commonly used manufacturing processes . Tools for this cutting process are scissors ( household scissors , plate shears , tin snips , cable shears ) and others. a. Punch press , rescue scissors or nibbler .

Cutting process

The material separation by shear cutting can be divided into four phases:

1. Attachment of the upper and lower knife with elastic deformation of the material with displacement in the cutting direction and at right angles to the axis of movement.
2. plastic deformation and flow of the material
3. Cracking from the cutting edges
4. Tear through

The material thickness, the cutting gap in relation to the material thickness (3–5% with an open cut, 5–10% with a closed cut, with fineblanking 0.5–1%), the state of wear of the cutting tools, are decisive for the quality of the cut surfaces during production . the type of material, the tool guide and the part geometry.

The quality of an inner shape is significantly influenced by the punch, since only a relative movement takes place between the punch and the inner shape. The same applies to the cutting inserts for an outer shape.

Procedure

A distinction is made between the following processes depending on the position of the workpiece limitation:

• Cutting - When cutting, the part is usually cut out of a sheet metal strip ( coil ), sometimes also from sheet metal blanks. The strip is waste after the cutting process, the cutting line is always closed when cutting. The cutting edge leads around the outside of the workpiece. See also punching . The process should not be confused with pruning (see below).
• Punching - Punching involves cutting one or more holes in the workpiece. The shape of the holes or openings is arbitrary, the cutting line is always closed when punching. The cut out is waste when punching. See also punching .
• Cutting off - When cutting, the workpiece is usually cut off from a metal strip without waste. The cutting line is open and runs once across the sheet metal strip. The course of the cutting line is determined by the shape of the workpiece to be manufactured. See also guillotine shears .
• Notching - Notching is the process of cutting out one or more pieces from the side of a sheet metal blank (workpiece). In this process, the cutting line is open and begins and ends at the workpiece edge on one side.
• Trimming - Trimming is the cutting of a deep-drawn part to its exact dimensions after forming .
• Cutting - When cutting, the sheet metal blank is cut along a line that ends in the workpiece and is therefore not closed. The cutting usually occurs together with the bending process .

Furthermore, the procedures can be divided according to the following criteria

• Shape of the cutting edges
  • Open cutting
  • Closed cutting
• Geometry of the cutting edges
  • Shear cutter
  • Rotary cutter
• Arrangement of the cutting edges
  • Full-edged cutting
  • Cross cutting