Methods and apparatus for forming a pierce hole in a workpiece

A method of forming a pierce hole that extends between a top surface and a bottom surface of a workpiece made of a metal using a plasma torch, the method comprising:

• positioning a tip of the plasma torch a first height above a first location of the top surface of the workpiece with a cutting axis of the plasma torch tip oriented orthogonal to the top surface of the workpiece;
• energizing the plasma torch to cause a plasma arc to emit from the plasma torch tip and attach to the workpiece to melt the metal and to cause a pressurized ionized process gas of the plasma arc and/or a shield gas exiting the plasma torch tip to propel melted metal away from the plasma torch tip;
• and
• rotating the cutting axis of the plasma torch tip around a designated central axis of the pierce hole in a diametrically reducing manner to cause the plasma arc to produce a funnel-shaped pierce hole with a cross-sectional area of the pierce hole at the top surface of the workpiece being greater than a cross-sectional area of the pierce hole at the bottom surface of the workpiece.

A method of forming a pierce hole that extends between a top surface and bottom surface of a workpiece made of a metal using a plasma torch, the method comprising:

• positioning a tip of the plasma torch a first height above a first location of the top surface of the workpiece with a cutting axis of the plasma torch tip oriented non-orthogonal to the top surface of the workpiece;
• energizing the plasma torch to cause a plasma arc to emit from the plasma torch tip and attach to the workpiece to melt the metal and to cause a pressurized process gas and/or shield gas exiting the plasma torch tip to propel melted metal away from the plasma torch tip;
• and
• rotating the cutting axis of the plasma torch tip around a designated central axis of the pierce hole in a diametrically reducing manner to cause the plasma arc to produce a funnel-shaped pierce hole with a cross-sectional area of the pierce hole at the top surface of the workpiece being greater than a cross-sectional area of the pierce hole at the bottom surface of the workpiece.