Methods and apparatus for forming a pierce hole in a workpiece

Patent metadata

Field	Value
Publication number	US-11504794-B2
Application number	US-202016732440-A
Country	US
Kind code	B2
Filing date	Jan 2, 2020
Priority date	Jan 2, 2020
Publication date	Nov 22, 2022
Grant date	Nov 22, 2022

Abstract

Methods for forming pierce holes in a metal workpiece are disclosed. According to one implementation, upon a plasma torch be energized, the cutting axis of the torch is rotated repeatedly between first and second angular positions to produce successively deeper pierces in a workpiece until a pierce hole is produced through a thickness of the workpiece. According to other implementations pierce holes are produced by rotating the cutting axis of the plasma torch tip around a designated central axis of the pierce hole in a diametrically reducing manner so that the produced pierce hole has a tapered profile with a cross-sectional area of the pierce hole at a top surface of the workpiece being greater than a cross-sectional area of the pierced hole at a bottom surface of the workpiece.

First claim

What is claimed is:

1. A method of forming a pierce hole in a workpiece made of a metal using a plasma torch coupled to a carriage of a multi-axis positioning system, the multi-axis positioning system including a processor and one or more memory devices that store data and software instructions for execution by the processor, the processor being configured to execute the software instructions to cause the carriage to translate and rotate with respect to the workpiece during formation of the pierce hole in the workpiece, the workpiece having a length and a depth that is a distance between a top surface and a bottom surface of the workpiece, the method comprising:
translating the carriage to position a tip of the plasma torch at a first position above the top surface of the workpiece and at first height above the top surface of the workpiece;
rotating the carriage to cause a cutting axis of the plasma torch to assume a first angular position that is non-orthogonal to the top surface of the workpiece;
energizing the plasma torch to cause a plasma arc to attach to the workpiece to melt the workpiece 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;
while the plasma torch is energized, causing a first rotation of the carriage to cause the cutting axis of the plasma torch to rotate from the first angular position to a second angular position that is orthogonal or substantially orthogonal to the top surface of the workpiece to create a pierce having a depth; and
while the plasma torch is energized, increasing the depth of the pierce by causing a second rotation of the carriage to cause the cutting axis of the plasma torch to rotate from the second angular position to the first angular position or to a third angular position different from the first angular position, the third angular position being non-orthogonal to the top surface of the workpiece.

2. The method of forming a pierce hole according to claim 1 , further comprising one or more additional rotations of the carriage to cause the cutting axis of the plasma torch to rotate between different angular positions while the plasma torch remains energized and until the pierce hole is produced, the pierce hole being produced when the plasma arc pierces through the bottom surface of the workpiece.

3. The method of forming a pierce hole according to claim 1 , further comprising positioning the plasma torch tip a second height above the top surface of the workpiece before or during the second rotation of the carriage, the second height being less than the first height.

4. The method of forming a pierce hole according to claim 2 , further comprising positioning the plasma torch tip a second height above the top surface of the workpiece before or during the one or more additional rotations of the carriage, the second height being less than the first height.

5. The method of forming a pierce hole according to claim 1 , wherein the workpiece includes a portion intended to comprise a final work product, the method comprising orienting the carriage to cause the plasma torch tip to face away from the intended final work product throughout the formation of the pierce hole.

6. The method of forming a pierce hole according to claim 1 , wherein the second rotation of the carriage causes the cutting axis of the plasma torch to rotate from the second angular position to the third angular position, the first and second angular positions being separated by a first angle and the first and third angular positions being separated by a second angle, the first angle being greater than the second angle.

7. The method of forming a pierce hole according to claim 1 , wherein the first rotation of the carriage between the first and second angular positions is at a first rotational rate and the second rotation of the carriage between the first and second angular positions is at a second rotational rate different from the first rotational rate.

8. The method of forming a pierce hole according to claim 6 , wherein the first rotation of the carriage between the first and second angular positions is at a first rotational rate and the second rotation of the carriage between the first and second angular positions is at a second rotational rate different than the first rotational rate.

9. The method of forming a pierce hole according to claim 1 , further comprising translating the carriage to position the tip of the plasma torch at a second position above the top surface of the workpiece, the second position being different from the first position.

10. The method of forming a pierce hole according to claim 9 , the carriage is translated from the first position to the second position after the first rotation of the carriage and/or after the second rotation of the carriage.

11. The method of forming a pierce hole according to claim 2 , further comprising translating the carriage to position the tip of the plasma torch at a second position above the top surface of the workpiece, the second position being different from the first position, the carriage being translated from the first position to the second position after the one or more additional rotations of the carriage.

12. The method of forming a pierce hole according to claim 1 , wherein as the depth of the pierce hole increases, a cutting current delivered to the plasma torch also increases.

13. The method of forming a pierce hole according to claim 12 , wherein as the depth of the pierce hole increases, a flow rate of a process gas delivered and or a shield gas to the plasma torch also increases.

14. 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.

15. The method according to claim 14 , wherein the tip of the plasma torch is advanced below the first height as the plasma torch tip is rotated.

16. The method according to claim 14 , wherein the plasma torch tip is rotated in a spiral manner about the designated central axis of the pierce hole.

17. The method according to claim 15 , wherein the plasma torch tip is rotated in a spiral manner about the designated central axis of the pierce hole.

18. The method according to claim 14 , wherein when the plasma torch is energized a current and a process gas at a flow rate are delivered to the plasma torch, and thereafter as a depth of the pierce hole is increased, increasing one or both of the current and the flow rate of the process gas to the plasma torch.

19. The method according to claim 14 , wherein when the plasma torch is energized, the shield gas is

Assignees

• Esab Group Inc

Inventors

• Nadler Michael
• Lynaugh Ryan

Classifications

• B23K9/013

  Arc cutting, gouging, scarfing or desurfacing · CPC title

• H05H1/3494

  Means for controlling discharge parameters · CPC title

• B23K7/102

  for controlling the spatial relationship between the workpieces and the gas torch · CPC title

• B23K10/006 Primary

  Control circuits therefor · CPC title

• B23K37/0258

  Electric supply or control circuits therefor · CPC title