Thermal cutting of stacked metal plates arranged so that all the plates are severed by a single cut. See also THERMAL CUTTING.
The stack cutting technique is often used to cut sheet material that is too thin for ordinary oxyfuel cutting methods. Sheet thicknesses of 0.9 mm (20 gauge) and over are the most practical. Stack cutting is used in place of shearing or stamping, particularly where volume does not justify expensive dies. The flame cut edges are square and free of burrs. Stack cutting is usually limited to sheet and plate up to 13 mm (1/2 in.) thick because of the difficulty in clamping heavier material in a tight stack.
Successful stack cutting requires clean, flat sheet or plate. Dirt, mill scale, rust, and paint may interrupt the cut and reduce cut quality. The stack must be securely clamped, particularly at the cut location, with the edges aligned at the point where the cut is to start. Piercing of stacks with the oxyfuel torch to start a cut is impractical. Holes must be drilled though the stacks to start an interior cut.
The total thickness of the stack is determined by the cutting tolerance requirement and the thickness of the top piece. With a cutting tolerance of 0.8 mm (1/32 in.), stack height should not exceed 50 mm (2 in.); with a 1.6 mm (1/16 in.) tolerance, the thickness may be up to 100 mm (4 in.). The maximum practical limit of thickness is about 150mm (6 in.). When stack cutting material less than4.8 mm (3/16 in.) thick, a waster plate 6 mm (1/4 in.) thick is used on top. It insures better starting, a sharper edge on the top production piece, and no buckling of the top sheet.
Plasma Arc Cutting (PAC)- The plasma process has been used for stack cutting of carbon steel, stainless steel, and aluminum. The plates to be stack-cut should preferably be clamped together. PAC can tolerate wider gaps between plates than OFC.