Methods and systems for plasma machine processing of steel beams and other long products using a pantograph plate bevelling gantry-type plasma cutting machine
11065708 · 2021-07-20
Inventors
Cpc classification
B23K37/0288
PERFORMING OPERATIONS; TRANSPORTING
B23K37/0235
PERFORMING OPERATIONS; TRANSPORTING
B23K37/0258
PERFORMING OPERATIONS; TRANSPORTING
G05B19/182
PHYSICS
B23K37/04
PERFORMING OPERATIONS; TRANSPORTING
B23K10/00
PERFORMING OPERATIONS; TRANSPORTING
International classification
B23K10/00
PERFORMING OPERATIONS; TRANSPORTING
B23K37/02
PERFORMING OPERATIONS; TRANSPORTING
Abstract
A plasma-torch cutting machine gantry moves in a first axis and the torch mounted through a pantograph to a drive box moves along the gantry in a second axis. The drive box rotates the torch about a third axis, and tilts the torch about a fourth axis. The drive box moves vertically in a fifth axis. The torch is mountable with tip at pantograph focal point or in an extended position. A controller firmware computes and apply offsets in the first, second and fifth axis to maintain the plasma torch tip in desired position despite the torch being mounted in extended position, rotation and tilt of the torch. In embodiments the torch is rotatable −/+90 degrees from vertical; and a laser scanner maps surfaces and edges of beams to determine movements and rotations for cutting beams.
Claims
1. A gantry-type plasma-torch cutting machine comprising: a gantry configured to move along a bed in a first (X) axis; a plasma torch coupled through a pantograph to a drive box, the drive box coupled to a backing plate configured to move along the gantry in a second (Y) axis perpendicular to the first (X) axis; the drive box configured to rotate the plasma torch about a third axis, the third axis being an axis of rotation, and to operate the pantograph to tilt the plasma torch about a fourth axis, the fourth axis being an axis of tilt perpendicular to the third axis; the drive box being configured to move along the backing plate in a fifth (Z) axis perpendicular to the first and second axis, the fifth axis being vertical; a controller coupled to control movement of the gantry in the first (X) axis, movement of the backing plate along the gantry in the second (Y) axis, movement of the drive box along the backing plate in the fifth (Z) axis, rotation of the plasma torch in the third axis and tilt of the plasma torch in the fourth axis; a laser scanner mounted to the drive box and configured to measure a height of a long product; wherein the plasma torch is adapted to be mounted in the pantograph in a first position with a tip of the plasma torch beyond a focal point defined by an intersection of the third axis and a central axis of the plasma torch; wherein the controller comprises a processor configured to use floating point arithmetic to, when the plasma torch is mounted in the first position, compute and apply offsets in the first, second and fifth axes as required to maintain the tip of the plasma torch in a desired position despite the plasma torch being rotated in the third axis, and the plasma torch being tilted in the fourth axis; and the processor configured to compute the offsets in the first (X), second (Y) and fifth (Z) axes as the plasma torch is rotated in the third axis and tilted in the fourth axis.
2. The gantry-type plasma-torch cutting machine of claim 1 wherein the torch is adapted to be mounted in the pantograph in a second position with the tip of the plasma torch at the focal point of the pantograph in addition to being adapted to be mounted in the first position.
3. The gantry-type plasma-torch cutting machine of claim 2 wherein the drive box is adapted to rotate the plasma torch to angles of − and +90 degrees from vertical.
4. The gantry-type plasma-torch cutting machine of claim 3 wherein the drive box is adapted to operate the pantograph to tilt the plasma torch in the fourth axis 45 degrees from vertical.
5. The gantry-type plasma-torch cutting machine of claim 1 wherein the laser scanner is adapted to scan the long product to prepare scans across the long product and the controller is configured to prepare an electronic map of surfaces and edges of long product from the scans across the long product.
6. The gantry-type plasma-torch cutting machine of claim 5 wherein the controller is configured by firmware to determine if the long product matches a desired long product using the electronic map of surfaces and edges of the long product.
7. A gantry-type plasma-torch cutting machine comprising: a gantry configured to move along a bed in a first (X) axis; a plasma torch coupled through a pantograph to a drive box, the drive box coupled to a backing plate configured to move along the gantry in a second axis perpendicular to the first (X) axis; the drive box configured to rotate the plasma torch about a third axis, the third axis being an axis of rotation, and to operate the pantograph to tilt the plasma torch about a fourth axis, the fourth axis being an axis of tilt perpendicular to the third axis; the drive box being configured to move along the backing plate in a fifth axis perpendicular to the first and second axis, the fifth axis being vertical; a controller coupled to control movement of the gantry in the first (X) axis, movement of the backing plate along the gantry in the second axis, movement of the drive box along the backing plate in the fifth axis, rotation of the plasma torch in the third axis and tilt of the plasma torch in the fourth axis; wherein the plasma torch is adapted to be mounted in the pantograph in a first position with a tip of the plasma torch beyond a focal point defined by an intersection of the third axis and a central axis of the plasma torch; wherein the controller comprises a processor configured to use floating point arithmetic to, when the plasma torch is mounted in the first position, compute and apply offsets in the first (X), second (Y) and fifth (Z) axes as required to maintain the tip of the plasma torch in a desired position despite rotation of the plasma torch in the third axis, and tilt of the plasma torch in the fourth axis; and the processor configured to compute the offsets in the first (X), second (Y) and fifth (Z) axes as the plasma torch is rotated in the third axis and tilted in the fourth axis; the gantry-type plasma-torch cutting machine comprising a laser scanner adapted to scan the long product to prepare scans across the long product and the controller is configured to prepare an electronic map of surfaces and edges of long product from the scans across the long product; wherein the laser scanner is mounted to the drive box and is configured to measure a height of the long product.
8. The gantry-type plasma-torch cutting machine of claim 7 wherein the controller is configured to scan the drive box across a bed of the cutting machine a plurality of times to locate, and prepare the electronic map of, the surfaces of the long product.
9. The gantry-type plasma-torch cutting machine of claim 7 wherein the long product is an H-beam and the controller comprises firmware configured to prepare a numerical control program to drive movement of the gantry, backing plate, and drive box in the first, second, and fifth axes, to cut the H-beam, the numerical control program based upon the electronic map of surfaces of the long product.
10. The gantry-type plasma-torch cutting machine of claim 9 wherein the controller is configured by firmware to determine locations of penetrations to be formed in the long product from information comprising the electronic map of surfaces of the long product and desired locations of the penetrations relative to ends and sides of the long product.
11. A plasma-torch cutting machine comprising: a laser workpiece-mapping system configured to provide measurements of a workpiece to a control processor the measurements including height measurements of the workpiece; a gantry movable by command of the control processor along a length of a bed of the plasma-torch cutting machine, movement of the gantry defining an X axis; a drive-mounting box coupled to and movable under command of the control processor along the gantry, movement of the drive-mounting box along the gantry defining a Y axis; a plasma cutting torch coupled by a pantograph to the drive-mounting box, the pantograph rotatable about a rotation axis perpendicular to the Y axis and tiltable in a tilt axis perpendicular to the rotation axis, the pantograph configured such that with the plasma cutting torch attached to the pantograph in a first position a tip of the plasma cutting torch remains at a focal point despite rotation of the plasma cutting torch in a rotation axis, and with the plasma cutting torch in the first position the tip of the plasma cutting torch remains at the focal point despite changes of tilt; the focal point being at an intersection of an axial axis of the plasma cutting torch with the rotation axis; the pantograph movable under command of the control processor in a Z axis perpendicular to the X and Y axes; the plasma cutting torch configured to attach to the pantograph in a second position, the second position characterized by the tip of the plasma cutting torch being distal to the focal point and a body of the plasma cutting torch intersecting the focal point; wherein the control processor is configured to use floating point arithmetic to compute and apply offsets in the X, Y and Z axis as required to maintain the tip of the plasma cutting torch in a desired position despite the torch being mounted in the second position, rotation of the plasma cutting torch in the rotation axis, and tilt of the plasma cutting torch in the tilt axis; and the control processor is configured to compute the offsets as the torch is rotated in the rotation axis and tilted in the tilt axis.
12. The plasma-torch cutting machine of claim 11 wherein the control processor is configured to use a map provided by the laser workpiece-mapping system to determine positions of the tip of the plasma cutting torch for cutting in the X, Y, and Z axes.
Description
BRIEF DESCRIPTION OF THE DRAWINGS
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DETAILED DESCRIPTION OF THE EMBODIMENTS
(28) The inventor's program FastBEAM™ as used in this invention creates a common platform for all such machines and file formats to suit all beam lines in a machine independent way and independently from the manufacturer. The proprietary FastBEAM V (FBV and FBW) formats predate the 1995 creation of the German DSTV standard (see below) but were not published. FastBEAM™ and its file formats including .FBX files are used in the invention to provide both an external programming system and internally to convert incoming files specifications such as DSTV into a fixed machine independent input. The .FBX file is used in conjunction with the catalog and the scan data results to create an individual NC program for the plasma torch for each beam to be processed.
(29) A recent standard description language to describe long product is also known as DSTV language specification (Deutscher STahlbau Verband/German Steel Construction Association) introduced in 1998. A further version was released in 2007 which changed the computer format to a newer XML style format but has not yet found favor commercially. The intent of this file format was to describe the requirements for beams and attachment plates for the automation of processing by Numerical Controlled machines in a machine and manufacturer independent way. Strictly it is not a direct coordinate path for a machine as is common for NC languages. Rather it is a parametric specification of what holes, shapes, marks and copes are required for a given section and relative to which datum such as centerline, top flange, bottom flange. The actual machine movements cannot be determined until the specific beam is measured and the datum lines established as hot rolled product is highly variable and the positions are critical to a millimeter.
(30) While an industry standard description language was most welcome to bring together a fragmented industry of bespoke machines without standards in programming, it did not change the fact that so many different machines were needed to process many different cross sections of long product. Another change was required to simplify the processing problem.
(31) The invention uses a single-pantograph machine which can process both beams and plates as needed. The mechanical differences from prior plate cutting machines include allowing extension of the torch from the focal point to obtain adequate clearance, adding laser measurement devices to map the beams so hole locations can be calculated, and replacing arc-voltage sensing feedback torch-height controls with full Z-axis computer control independent of arc voltage. In particular, the invention effectively converts a common style of gantry plasma plate processor into a machine which can also process Long Products. In this machine the pantograph functions as a 3-axis robot of limited movement but is attached to a gantry allowing unlimited movement in X and Y.
(32) There are of course long products and plate shapes which are not used in construction but are used in general fabrication. However as 60% of all steel is used in buildings, a single machine to cut both plate and beams is potentially very useful.
(33) The technical challenge here is to convert the plate bevel-cutting machine to process beams with a completely different set of problems while retaining ability to accurately process entire plates. If this can be achieved the impact on steel processing for construction would be profound if there is little additional cost.
(34) In addition to mechanical changes, development is required in the NC control and involves complex mathematics and an entirely novel way of mapping and cutting unclamped free-standing beams without a workcell or hydraulic clamping. Basically, in situ cutting and marking is required without touching and without clamping. The solutions require embedded real time high speed computation with complex computations which are even today not possible in majority of plate cutting NC controls with their limited 2 axis dedicated systems built for processing 2D plate programs. The Z axis is used only for height adjustment which is generally completely independent axis and not programmable.
(35) The challenges for converting a gantry based beveling plasma gantry to also cut and drill long product are many, substantial and complex. It is not just a matter of making the torch rotate to horizontal, although that alone for a pantograph torch holder is a major technical challenge.
(36) Processing Beams with Plasma
(37) 1. The primary processing function is drilling. However, each hole requires a pierce of the material. So, plasma cutting is required with a pierce time of a second, not oxy-acetylene with a pierce time measured of minutes.
(38) 2. While cutting times are comparable, for oxy-acetylene and plasma on heavy plate, the long pierce time of oxy-acetylene overheats the area and heat affected zones are still a problem for oxy-acetylene.
(39) 3. Plasma is a very limited distance technology, unlike drilling or oxy-acetylene. The surface position must be known to millimeter precision to calculate the required standoff position. A few mm in error and the plasma will not work or the torch will collide, damaging the torch.
(40) 4. Most plasma torches of adequate power are large, 50 mm in diameter and will collide with flanges whether cutting inside or outside the flanges.
(41) 5. To get into the corners of beams and around rounded corners, angles other than vertical and horizontal are required. 6. The long product is usually bent 1 mm per meter is nominally straight for a beam but for a 10-meter beams this is 10 mm. At the very least you need height control horizontally as well as vertically and plasma cutters only have vertical height control.
(42) 7. As holes must be positioned accurately and the material is often bent, cutting without a workcell and hydraulic clamping will not be accurate enough.
(43) 8. Beams are often twisted and flanges bent or not square to the web again an argument for forced clamping in a work cell.
(44) 9. Sizes and thicknesses of hot rolled beams can vary significantly even down the length of a beam precluding prepared NC programs.
(45) 10. Large, if not obvious bends require computation to adjust hole position as in assembly the bend is removed by force.
(46) 11. Prior NC programming is not possible as hole position is shape dependent from the centerline for columns or from one of the flanges for floor or roof designs. NC programs must be generated based on multiple beam surveys.
(47) 12. In the art of preparing beams for assembly, the critical dimensions relate to the position of the central web between the two flanges and the width of the web. Depending on whether the beam is used for a floor or a roof or a column, different reference lines must be used. These cannot be programmed as fixed XYZ positions until each beam is measured and at or close to the point where the holes are to be drilled.
(48) 13. In traditional beam lines, each beam is measured and the individual NC program prepared internally. In fact, prepared NC programming of coordinates XYZ is impossible as the material is too variable. All that is specified in a prepared program is defined in such a way as to require each beam to be measured before cutting and drilling.
(49) These facts eliminate use of most of the world's NC plasma cutters for beams. Typical 2D profiling NC controls expect preprepared NC coordinate programs generally of nests of parts to be cut from the one plate. That is not possible with the high variability of rolled or extruded beams.
(50) These beams largely are somewhat-unpredictable hot rolled extruded sections with variations in bend, twist, thickness, height, flange width and more.
(51) With the present invention, where beam processing differs greatly from plate processing is that multiple surfaces of each beam are involved and must be measured and hole positions calculated based on actual beam measurements.
(52) Plate Processing
(53) Plate processing is intrinsically a 2D process for a single ideally flat surface. When the plate is not flat an independent vertical control known as Automatic Voltage Height Control (AVC) varies the torch height based on the arc voltage so this axis does not have to be in the NC program. In this way an NC program for a plate can be pre-prepared. AVC is on a separate machine without knowledge of the height profile of each plate. Plate thickness also does not vary.
(54) For weld preparation, changes in height directly impact an angled torch and AVC is not good enough for multi pass cutting. Our U.S. Pat. No. 9,539,664, METHODS AND SYSTEMS FOR PREDICTIVE HEIGHT CONTROL, teaches a laser scanning method to produce a 3D image of the actual plate prior to cutting so that a Z axis can be added to the incoming NC program, increasing critical height accuracy 3D processing of plate. However, U.S. Pat. No. 9,539,664 is about only one surface, an upper surface of a monotonic, nominally flat, and level plate. The present document describes development of mapping of beams which can often have 5 or more surfaces, sharp breaks and discontinuities between horizontal surfaces and vertical surfaces, none of which are covered by U.S. Pat. No. 9,539,664. Special analysis is required to obtain and map these surfaces in conjunction with idealized shapes from an embedded catalog. In total contrast, there is only one cross section for all plate, a rectangle.
(55) The challenge is to take a plate beveling plasma gantry and change its operation completely to be able to accurately measure, sever, drill, cope a whole range of beams. These largely must sit on or above the cutting bed under the gantry without hydraulic clamping in a work cell.
(56) The modified gantry must accurately process the unrestrained bent and twisted beam in situ without forcing the beam to fit by hydraulic clamps and rollers. Also in the development of beamlines, the use of a workcell with large forces was necessary to prevent movement and vibration while drilling. For machines like the Python-X, the same work cell and hydraulic constraints are needed for accuracy but a workcell also is essential because of the limited working distance of a large heavy (often weighing 0.5 ton) floor mounted robot.
(57) So, although in one form Applicant's machine resembles a common 2D and NC programmed plate processor, with many invisible innovations it can accurately drill, sever and cope an unrestrained beam.
(58) The system described herein uses a plasma cutting torch to cut steel. As noted, our machine in
(59) With a single adjustment of the torch position (
(60) 1. The pantograph bevel head must be able to rotate to and beyond the horizontal, something unknown and unnecessary in plate beveling heads. The rotation of plate pantographs are generally restricted mechanically by design, by software, by tables and by limit switches to 45 degrees from vertical. This particular pantograph (U.S. Pat. No. 8,865,056) has no limits in rotation and a 58-degree limit in tilt, far above that of other pantographs but for a plate beveling torch to be able to rotate to horizontal is not known to the inventor.
(61) 2. The torch must be able to be pushed far past the focal point to get clearance for vertical surfaces (See
(62) 3. Both pantograph and drive box must be as narrow as possible to approach vertical surfaces with a horizontal torch. (See
(63) 4. The original pantograph drive box must be completely redesigned internally and externally to be nearly as narrow as the pantograph itself and rounded and raked to be able to process around corners and pipe. This can be seen in
(64) 5. Our machine uses a very different approach to handling and manipulation than a beam line or Python-X. In the invention the beam does not move, is not clamped hydraulically, is not forced into a fixed accurate position on the machine and does not necessarily have to be aligned perfectly with the machine axes although that is advisable. Normal bends and twists are measured and such variations compensated mathematically rather than removed through high force hydraulic clamping in a workcell.
(65) 6. There is no ‘work cell’ concept unlike known drilling beamlines and later plasma beamlines, as shown in
(66) 7. Our machine has no rollers in a transport system. (
(67) 8. Our machine can process all areas of a beam in any sequence, not being restricted to the front end, cantilevered into space and the back end, also cantilevered into the workspace.
(68) 9. Many sections can be processed from the one beam, even very short sections.
(69) 10. Sections are supported at all times, so there is no tipping moment as there is with a short projecting segment.
(70) 11. The clamping problems and end of the beam problems of Python-X do not exist in our machine, assuming that the accuracy can be achieved without a hydraulically clamped workcell concept.
(71) 12. In using a gantry to move what is essentially a light weight 3 axis robot, the range in XY is far greater than any floor mounted fixed robot. This means many things, like processing of multiple beams on the one pass or multiple parts from one beam.
(72) 13. As the beam does not move through a workcell, the machine only must be as long as the beam, not more than twice as long as with a beamline. This is a huge saving in valuable clean, covered factory floor space.
(73) The torch extension described in Patent Application 2014/0236339, but additionally the drive box design was completely changed internally and externally. The additional developments include
(74) 1. An ability to build a 3D model in the computer of all the varying surfaces of a beam and the surface intersections, rounded or square. As the beam is unrestrained, bent, twisted and very long, this is a complex task using at least 11 separate scans across the beam down its length, as illustrated in
(75) 2. Modifications to the plasma bevel head to allow beam processing a) Projecting the plasma torch to a second cutting position sufficiently far past the essential focal point that the clearances to adjacent vertical surfaces are adequate. Such a move is impossible with a traditional pantograph and defeats the purpose of the pantograph which is to traditionally to decouple XY from ACZ. The complex implications of this are shown mathematically in equation 2.2.3.1 below. b) High speed and complex computations are used to offset XYZ with changing AC as the axes are coupled mathematically with the extended torch. Consider that to adjust AC in a pantograph normally requires no change XY or Z. Now all five axes are mathematically coupled and must move synchronously in real time, something impossible without high speed computation and mathematics within the real-time system.
(76) Such complexity is only on two commercial NC controls known, Power Automation and Beckhoff. Both controls are designed for the multi surface multi axis machining market, not the simple 2D plate cutting market. The ability to embed complex computations at high speed is a major development, but invisible to the naked eye where everything just works smoothly. This makes the torch extension possible. Existing plate beveling NC controls lack this functionality. They are universally simple 2D XY controls with an independently controlled third Z axis, often an entirely separate Z-axis control system. c) Development of the mathematics to allow completely formulaic control of the bevel head, including the offset. Table driven systems as in Buccella (U.S. Pat. No. 9,687,933) are inadequate for the five simultaneous movements required. The Buccella system relies totally on the independence of XY from AC and from Z provided by having the torch tip at the focal point. Using a fine thread push pull mechanism in the Buccella head, even A is disconnected from C meaning a simple table lookup is possible and real-time mathematics is not used.
(77) 3. Complete redesign of the bevel drive box (
(78)
(79) 4. The backplate or fixed mounting plate attached to the gantry (
(80) 5. The depth the bevel head drops below the back plate (
(81) 6. The cone shaped tip of the plasma torch must be less than or equal to 90 degrees to get into corners between web and flange (580,
(82) 7. The narrow drive box must now be supported on light weight outriggers (
(83) 8. Substantial milling of surfaces to reduce the weight of the drive box closer to and under 50 kg, sufficiently light to be added to a common gantry machine with redesign of the machine. (
(84) 9. In all this the rigidity must remain as any vibration from motion and harmonics will destroy accuracy and the accuracy required at all times is around 1 millimeter.
(85) In general, use of a mobile lightweight robot-like device eliminates both problem of the limited reach of a fixed location robot arm, while also eliminating the vast amount of investment required to move the beam smoothly and accurately through a work center. However accurate positioning of holes relative to edges requires innovation in how a beam is measured and how those measurements are used to create the NC program inside the machine.
(86) To get access to the bottom of a beam (
(87) To avoid collision with such supports the NC control can indicate to the operator the places in which supports are to be placed or alternatively support locations are established by laser scanning and potential collisions calculated and avoided. Specialist supporting frames could also be manufactured cheaply and they could contain the ability to flip or accurately roll closed or near closed beams or pipe where needed. It is advisable to include a way to align the frame with the X axis to minimize corrections and to lightly restrain and align the cut material to minimize thermal movement or unintended rolling.
(88) A large plate plasma cutting and weld preparation 2D machine is generally required in a metals service center even if the service center a beam machine like the Python-X, but the present embodiments allow for elimination of specialty beam processing machines. One gantry machine can process all long steel products, from flat plate to pipe, as well as sections like I-beams. It can also cut metal fabrics (U.S. Pat. No. 9,952,581) and cambered beams and other non-structural long product like ARMCO, rail and bulb flat (
(89) Essential Innovations in Detail
(90) Apart from the complete redesign of the bevel drive system to make it taller, narrower, rounded, lighter, more stable and with greater depth for cutting between flanges, it is the individual critical developments inside the computer control which make the processing of unclamped beams possible.
(91) Real Time Transformation for Four or More Synchronous Machine Axes
(92) In plate cutting machines, only a 2-axis simultaneous control is required, smoothing moving in X and Y simultaneously. For plasma cutting with a pantograph, the tilt and swivel of the torch generally works independently mechanically of X and Y. This means tilting in A and/or C poses no requirement to move the machine in X or Y to keep the torch tip stationary. So, a machine smooth in X and Y can smoothly change A and C at any time. For general plate cutting applications there is very little Z movement—just enough to compensate for surface irregularities of plate—and it is essentially a two axis X and an independent two axis torch application.
(93) A pantograph produces much higher quality of cut in plasma applications as coupled axes mean moving a 1-ton machine smoothly and quickly over very short distances take time and delays will create unacceptable marks on the plasma cut surface, especially when cutting smooth curves. So, the independent pantograph produces smooth cutting on sloped surfaces, especially curved surfaces and in corners. The pantograph also does not rotate the torch very much, where others such as the Messer Greisham Planetary motion creates a substantial rotation, making centering of the torch critical.
(94) In cutting long product, major surfaces are also vertical and sloped as with Angle (
(95) Also, while it might be presumed by casual readers that the Buccella bevel head (U.S. Pat. No. 9,687,933) and many similar systems can move synchronously in XYZAC, that is unlikely and perhaps impossible given the Burny brand Z-axis control used. Certainly, Buccella teaches nothing about synchronous movement in Z and height control is still independent from the NC control and Z-axis information is not part of the NC program.
(96) While our machine superficially resembles existing flatbed plate cutters, it is capable of complex movements not considered by existing flatbed plate cutters. This permits the required torch extension which allows processing of beams.
(97) For cutting pipe and to keep the torch square to the curved surface at all times you need five synchronous axes, XYZAC. Note that when sawing in a fixed YZ plane across a pipe, you only need four axes. For angled cuts, you need the entire five axes synchronous which is not a limitation for the invention. In some countries the sale of synchronous five axis cutting technology is restricted by law. This means pipe cutting is restricted legally in some countries to square cutting and not mitered cuts or simultaneous weld preparation of pipe.
(98) The great impact of using 4-5 axes and mathematical transformations in real time, setting our machine apart from simple 2D plate processors such as Buccella (U.S. Pat. No. 9,687,933), is that extending the torch past the focal point was simple. While this created complexity in the coupling of all axes the solution was mathematically straight forward. While this was not previously elaborated, compensation required only the extension of the previous transformation formula 2.2.2.1 with the torch extension vector in 2.2.2.2.
(99) It is important to note that Kerf compensation or cut width compensation and circular interpolation is also included in the calculations so that separate NC kerf compensation is not needed.
(100) The mathematics of the transformation are detailed in the next section.
(101) Real Time Conversion of the Axis Position XYZAC (
(102) In addition to rotation around the rotation axis 315, the pantograph permits rotation of the torch tip around a tilt axis 335 perpendicular to the rotation axis 315. V and W are internal mechanical pantograph axes and affect movements shown as V and W in
(103) The coupling between is due to the circular drive for the tilt axis in that rotating the twist axis also implies a large change in the tilt axis with a 3:1 gearbox ratio. The tilt axis is perpendicular to the twist or rotation axis.
(104) To derive the pantograph axes from the programming axes AC you require
(105) 2.2.2.2 Transformation formulae from programming axes AC to pantograph axes αβ
(106) α=atan((cosδsinAsinC+sinδcosA)/ (−sinδsinAsinC+cosδcosA)) β=acos(√(−sinδsinAsinC+cosδcosA).sup.2+(cosδsinAsinC+sinδcosA).sup.2))
(107) All this is computed in real time while the cutting head is moving. This is done through a direct module connected to the real-time system so that the VW movements are synchronous with the XYZ movements. Only a high-speed CPU with a floating-point processor is capable of this performance.
(108) The Mathematics of Extending the Torch Past the Focal Point.
(109) As in shown below, a pantograph is only one of many ways in which a plasma cutting torch can be held but it has the distinct advantage of allowing tilt in any direction without movement in XYZ and without requiring the machine to be moved simultaneously.
(110) Kinematically decoupling XYZ movement from AC movement is preferred for quality of weld prepared cutting on near flat horizontal plate. However, manufacturers who use a pantograph typically require the cutting point of the plasma head (
(111) Such manufacturers can convert programming axes A (Tilt or Azimuth) and C (Rotation) into the internal pantograph angles α and β by a simple lookup table. This table is created just once by measurement or modelling, usually with a tilt limit of 45 degrees. This is the technique used by Buccella. This table approach avoids completely the need for high speed real time computation but also totally prevents the use of torch past the focal point. For Buccella the table incidentally prevents the rotation past 45 degrees as the table is limited to 45 degrees. The Buccella head is also limited by software and mechanical stops to 45 degrees. This is reasonable for plate processing but any of these restrictions make the invention unusable for beam processing, despite superficial similarities in appearance.
(112) As can be seen in
(113) The other aspect which prevents normal pantographs from extending the torch is the degree of high speed computation required. Consider
(114) 2.2.3.1 Torch extension unit vectors for projection length T components Tx, Ty, Tz
(115) Tx=cosδsinAcosC−sinδcosA Ty=sinAsinC Tz=sinδsinAcosC+cosδcosA
Where δ is the tilt of the pantograph from the X axis.
(116) Extending the torch beyond the focal point means that any change in A or C produces a large and immediate change in XYZ required to maintain the torch at a same location over a workpiece. All the five axes are coupled requiring synchronous movement in all five axes because of a torch tilt. In most cases on a single plane, only four axes are required. Such computation requires high speed computation with only the few millisecond time slices of a high speed real time system; in our system the computations of X, Y, and Z offsets required to maintain the extended torch at desired locations over the workpiece are performed by firmware 164 on controller 135 in real time as the torch is rotated in the rotation axis or tilted in the tilt axis, using floating point arithmetic in a high speed processor of controller 135; these offsets are applied immediately to keep the tip of the torch at desired X, Y, and Z locations as determined for desired cuts as determined from a laser map of the beam, the ideal shape of the beam, and desired locations of cuts relative to actual ends of the beam. The pseudo real time slice systems of the major control manufacturers such as Microsoft Window Embedded are not only too slow but offer no facilities to include such mathematics in the computation of axis positions in real time.
(117) Creating many surfaces in 3D from individual laser derived cross sections.
(118) When processing beams we must know in each case what is on the bed, knowing all points on all surfaces to millimeter precision. Consider in plate cutting we only had one large flat near horizontal surface, now there are many surfaces. The NC program was only in X and Y as Z was largely irrelevant for general cutting. Consider also in the invention that we cannot imply position from work cell. The beam to be processed is sitting untouched at a position on the bed.
(119) Firstly, we must know what the beam is from the long products shown in
(120) Eleven laser scans across the beam allow us firstly to locate this beam on the bed and determine points by measuring them as illustrated in
(121) Any of the points on a surface can be mapped relative to the desired XYZ position on the ideal beam and from the reference datum used for the program, say distance from the top flange, the bottom flange or the centerline. Then, as shown in
(122) As shown in
(123) 2.3 Closed Sections Including Pipe
(124) Closed hollow sections, such as pipe, presents a different problem as, unlike the Python-X, we cannot get under the beam. The low-cost solution is to flip 180-degrees and rescan; for product like purlins (
(125) Most pipe cutters use 2D controls and rotate the pipe, using the Y axis as a rotary axis. This means real problems though because pipes are long and invariably not straight and heavy and have to be supported. The whole setup gets very expensive and complex again. In the invention pipe processing is easy and cut to length very fast. A series of cuts on the top, a 180-degree roll and the severing cuts on the bottom. No additional cost.
(126) 2.4 Extension to Non-Straight Product
(127) There is the interesting possibility of drilling and sawing precambered beams not covered by DSTV. It can however be done by our system and that opens a new class of cutting where long products can be formed as needed before processing.
(128) One big application is in preparing truck chassis rails which could be processed after forming, or even after assembly, by driving the chassis under the gantry of the machine. This would save a great deal of time and prevent the current process of cutting the web to order for the many penetrations required by each customer and then welding on the flanges. Preformed extruded beams could be processed in minutes.
(129) Minimizing Movement from Heat Expansion
(130) The actual sequence of cutting without restraints raises questions about heat induced movement in cutting. This can sometimes be solved by changing cutting paths, as in sequences illustrated in
(131) There is always the possibility of using light restraint or mechanical clamping in these cases, at no great expense. While there is currently no provision in the scanning for movement after scanning including the movement from heat expansion. There is always the possibility of additional scans and checks.
(132) Described herein are methods and systems for processing long products (cross-sections of which can in
(133)
(134) Gantry 150 supports a plasma bevel head 127, which in turn holds a plasma cutting torch 125. In this illustrative example, angle iron pieces 162 are used to support the beam 160 so that the torch 125 can to cut the bottom of beam flanges (not numbered)
(135) Operation of the system of
(136) In an embodiment, the plasma torch 125 may cut at its tip (e.g., cone 503,
(137) As also described above, conventional XY plate processing machines control Z-axis movement, if any, by an independent Torch Height Control (THC) In such conventional systems, a controller (e.g., NC controller 135) serves only to turn on and off the THC system. Such conventional systems, unlike the present embodiment, are strictly 2-axis XY machines although an additional 2 axes may be added for beveling. According to the present example, however, additional Z-axis movement along back plate 124 is directly controlled by the same computer (i.e., NC controller 135) as the X- and Y-axes 120, 122. According to the present embodiments, therefore, synchronous control is achieved along all three X-, Y-, and Z-axes and with tilt axes A, C. Older controls have two synchronous axes XY and the additional bevel axes when available are likely to be simultaneous rather than synchronous. The difference is what happens on a scale of a few milliseconds or synchronous rather than hundreds of milliseconds of simultaneous. To the human eye these are synonymous but to high speed plasma cutting the difference can be dramatic and unacceptable.
(138) Our machine provides 4 or more axes synchronous movement of axes XYZAC as shown in
(139) Collectively, these axes are positioned to control the cutting tip (i.e., cone 503) of the plasma torch 125, and cutting point can then be approximately 8-12 mm from the point of the brass cone 503
(140)
(141) With reference to both
(142) In practice any given shape can have different names locally, and the I beam 200 may itself be described by its center piece, or web 205, and its flanges 210
(143) For even such defined shapes, the web height and flange width, as well as the overall material thickness, can vary, as can also the weight per meter. Thus, for a given physical space, the strength and weight of the beam can vary in practice, and/or according to the requirements of the designer. For purposes of the present embodiments though, the discussion presumes that the shape of the beam is nearly constant over its length but the present embodiments can operate successfully even where the shape is not constant over the length of the beam. The present embodiments may also be utilized in cases where beams are fabricated from cut and welded flat plate and not hot rolled, in addition to product where the cross section can vary down the product's length.
(144) Referring to
(145) The beam 160 should be supported above the slats (i.e., angle iron pieces 162) on the plate cutting bed 142. In this example, the angle iron pieces 162 allow the beam 160 to be raised above the bed 142 by a distance (e.g., element 560,
(146) In an embodiment, the NC control 135 can examine the processing NC program for each beam that may require patterns of drilled holes, and/or other operations at specific points along the length of the beam 160. In this case the NC controller 135 is further able to calculate precisely where support is both needed and/or best utilized, and optimally where the support will avoid collisions with the torch holder operating on the flanges.
(147) In an embodiment, support placement information can be manually entered into the NC program or automatically calculated by the NC controller 135.
(148) The NC controller 135 may also read programming requirements in a beam specific language for beam processing, such as DSTV, discussed above, and convert the requirements into a sequence of XYZAC movements. This elaborate and mathematical process integrates laser scans giving surface and edges of an actual beam with the formal shape of the beam and its expected nominal parameters, and ultimately creates a beam specific NC program for each beam and dependent on exactly how it is presented on the machine and where it is located and all faults, twists, bends and other variations from ideal.
(149) According to this example, the controller 135 converts a requirement to cutoff at a specific distance into a series of head movements, which achieves the same effect as an operation using a saw.
(150) In addition to DSTV, the present inventor contemplates that the present embodiments may be utilized using other developed file formats which provide portability from machine to machine, including the inventor's proprietary FPV file output format of the FastPIPE™ program and the FBV file output of the FastBEAM™ program. Such additional programming file formats convey the results to be achieved by the controller regardless of bends and other variations. As cutting beams involves so many surfaces and the shape is so highly variable at a millimeter level, the final coordinate NC program cannot be prepared beforehand as is traditional in NC programming. An individual program must be written in situ for each beam as it is presented. The ability to read and interpret files including FBV, FPV, DSTV and create a piece specific NC program eliminates all commercially known controls in the general gantry NC control business.
(151) Whether provided to the NC controller 135 externally or calculated by the NC controller itself, the NC program that guides the torch 125 may include XYZAC positions that guide the torch cutting point (i.e., element 315 or 325 of
(152)
(153) In this example, the 3 axis pantograph bevel head (e.g., bevel head 127,
(154)
(155) For the bevel head 127 to achieve maximum accuracy in plate beveling, the torch tip is positioned at the focal point 310. In this position #1, both C and A can be varied while the machine is stationary, i.e. without changes in X, Y or Z.
(156) New position #2 is at 315 and allows much more clearance from flanges and to prevent collisions as can be seen in
(157)
(158) The X- and Y-axes correspond to the physical axis rails 120, 122, respectively, shown on the gantry system illustrated in
(159) Formal torch axes AC corresponding to the azimuth and rotation of the torch plane correspond to the concepts of longitude and latitude. The mechanical axes are quite different and shown in
(160)
(161) The main axis of the pantograph is the X axis. The rotation around the X axis of the pantograph is measured in the YZ plane. The pantograph axes of α and β are notional and relate to the pantograph system alone. Axis β corresponds to the folding and unfolding of the pantograph and axis α corresponds to the twisting of the main arm of the pantograph. Both axes describe the departure of a vertical plasma torch along the Z axis and a is measured in the XZ plane while β is in the YZ plane. These axes XYZ would be identical to the machine axes of
(162) The mechanical axes UV are shown notionally in
(163) Pantograph values α and β are themselves calculated from programming axes AC through equations 2.2.2.2.
(164)
(165) Under the Power Automation (PA) open system architecture [4300], the mathematical connections between the axes are programmed inside a .DLL [4301] which is conceptually embedded inside the PA real time system. Power Automation's CNC Interpreter and Interpolator processes will regularly call the compile cycle .DLL program at the beginning of each of their respective cycles.
(166) It all happens very quickly. The CNC Interpolator has a cycle time of only 4 milliseconds. So, every 4 milliseconds it will execute codes inside the DLL along with other tasks.
(167) In each cycle, FastCAM compile cycle DLL will perform the following:
(168) Read data from CNC Interpolator's Target Axes positions table.
(169) Perform the AC to VW Transformation (Equations 2.2.2.1 & 2.2.2.2) takes the A axis and C Axis target position to calculate the corresponding V and W axis target positions. It then writes the calculated desired V and W positions back to the CNC Interpolator table where the motion control takes this as an objective for these mechanical axes. See also
(170) ACXYZ Torch Extension Compensation takes the A axis and C Axis target positions, as well as the Torch Extension Value [4305] in the DLL to calculate the additional compensations to the final XYZ axes positions required to keep the cutting torch tip at a desired XYZ position. (Ref: equation 2.2.3.1) given that the torch has been extended past the focal point by the extension value (4305). See as well
(171)
(172) This figure illustrates the need to update, and narrow, the entire drivebox in 530 (
(173)
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(177) In this example, elements 604 represent circular bolt holes ideally of adequate roundness and smoothness. There is no known standard for taper but as the taper is under 4 degrees on relatively thin material it is not of any consequence. The standard does reject holes which have roughness over 1/16.sup.th inch but the melting process of the plasma covers that and if the torch does not leave a mark on entry or exit, the holes will be acceptable. This is more about abrasion as in principle the load is carried entirely by the fully tensioned bolt and washers and not by the side of the bolt.
(178) So, holes 604 must be smooth and straight, within tolerances, for practical use in the field of art. General cutouts or penetrations 606, on the other hand are arbitrary shapes in the beam, and which may be placed for making a standard beam lighter, and/or to allow other pipes, beams, or plumbing to penetrate the beam, often without touching the beam.
(179) When assembling a bolted beam structure, welding is common, but most cutting is simply to avoid contact between adjacent beams. Two classes of such cuts are illustrated in
(180) According to the present embodiments, however, a plasma torch can also line mark the beam 600, a low amperage plasma using Argon which leaves only a surface mark or scratch, as shown by element 607, and/or mark the beam 600 with lettering 608 to identify or instruct in assembly. Additionally, a plasma torch utilized according to the present systems and methods with more power is also capable of gouging the beam 600 to produce a deeper mark in the surface, which may be desirable similarly to elements 607 and 608, but will still be visible even after the beam 600 is painted.
(181) According to the present embodiments, a plasma torch can be used to perform all of the drilling, penetration, sawing, coping, mitering, and cutoff functions of conventional full-functioned universal beamline machines and systems, but with significantly better flexibility, lower expense, and lower weight than such conventional machines. Systems and methods according to the present embodiments are further capable of producing line marks text on long products, which conventionally must be performed by separate hard stamping.
(182) Many other operations may be performed according to the present embodiments, which not shown in
(183)
(184) Example 750 illustrates a case where a twist in the web can travel down the length of the beam. In addition to these examples, long products are also known in the field to be delivered, prior to processing, with significant variations in width, height and twist, with all sections of the long product potentially having variations in thickness as well. This is notwithstanding distortions, bends and deformations which occur during handling.
(185) Such variations are typically tiny and can be measured in millimeters. Twist and camber down the length of the beam at approximately 1/500 to 1/1000 of product length is quite acceptable and hardly noticeable. Such dimensions may not seem significant at first glance, until it is considered that, for a 10-meter beam (which can be common in the field), such variations may add up to 10 mm (1 cm) over the product length. When cutting with a plasma torch this means the torch is off position by 10 mm which can either mean a damaging collision with the beam, or that the torch is so far away it does not work. This historically was a slightly smaller problem with drills which were much longer than needed.
(186) Additionally, all the potential dimensional variations may occur in a single product, thereby adding up to even more significant problems over the product length that would not be significant for conventional NC operation of plate material alone. An NC program, even after creation, must still allow for correction of actual measured distances. Reference points in the material should be chosen according to the use to which the holes are to be put. Unlike all other metal processing, holes always reference edges in the material as the cross section is built for purpose but variable.
(187) For example, if the flanges of a beam are to form a floor in a building, it is necessary to specify bolt hole distances from the top flange. Conversely, if a bottom flange is to form a flat roof, hole positions must be referenced to the bottom flange. For column formation, the center of the beam will be used despite variations in width. The position of the center of the beam or web is determined in each case by measurement across the beam at that point along the beam.
(188) When assembling bolted structures, the distance between bolt holes is critical, since the beams themselves generally do not touch each other. The clearance features such as copes and miters are not significant in assembly as they only prevent collision between beams and other beams or columns. Hole patterns however must be exactly located relative to a datum which varies according to the use of the beam.
(189) Such examples are not intended to be exhaustive, but the examples to provide illustrative explanation of how fixed NC programs, as typically run used a gantry NC plasma cutter, will not be adaptable to beam processing. Beams are almost never perfect in all dimensions as presented to processing.
(190) In structural applications, apart from the bolt holes, miters, copes, cutouts, and end cuts described above, the actual cut shapes are not as critical for dimensioning tolerances as are the edges of the beams, their relative positions and thickness.
(191) Unlike a robotic beam processor using a fixed work cell and moving beam, the universal systems and methods of the present embodiments can also act as a full-size plate processor, including multi pass weld preparation, as well as cut and drill beams; this may significantly change the degree of automation available in structural steel construction, as thus reduce the cost and speed of building, worldwide.
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(201) FCHMI is the FastCAM Human Machine Interface. The operator initiates the scan through the Human Machine Interface. This software conducts the 11 survey scans and collects the results. The survey is the first step.
(202) After the survey is complete the final points are passed from the FCHMI to FastBEAMx via an ActiveX engine, SurvX.exe which writes the points to a file. Later another instance of SurvX.exe is used by FastBEAM-X to read and interpret the same data.
(203) FastBEAMx is the software which generates the final NC code for the specific beam from three sources, including the laser scan results, the ideal shape of the long product, and the desired locations of holes relative to sides and ends of the long product.
(204) The file data.ini (1220) connects scan system 1200 to NC system FastBEAMx (1210) and each uses its own instance of SurvX.exe to read and write the data.ini (1220) file.
(205) Each Instance of Survey Data Transfer:
(206) The sequence to generate NC code is: 1. Start the laser-scan survey. 2. When the scan completes, we have the Data Points calculated and stored in memory of FastCAM Human Machine Interface Software (FCHMI). 3. FCHMI (1200) initializes a write function using an instance of SurvX.exe (1202)—an activeX engine—to write out the FCHMI Internal Survey data arrays (1201) into a file data.ini (1220), according to the format in SurvX.exe 4. FCHMI starts/launches program FastBEAMx (1210) via passing a specific command line to Window Shell. (1230) 5. FastBEAMx when it is launched, firstly retrieves data and fill its Internal Survey Data arrays (1211) by using a read function from its instance of SurvX.exe (1212) to read from the same data.ini file (1220) 6. The survey data is thus transferred from FCHMI to FastBEAMx. FastBEAMx is ready to proceed to its next task of making CNC files according to the survey data, the ideal shape of the long product, and a file containing locations of holes, penetrations, miters, and copes relative to ends and sides of the long product. FastBEAMx must determine all the reference data this specific beam and calculate the precise position of holes, slots, penetrations, cutoff, marking and copes. The final NC program generated is then specific to this beam in this location at this time.
(207)
(208) There are three distinct files which are needed to generate NC data
(209) 1. The original .DSTV or .FBV file which contains the work to be done on the beam in a parametric form for an ideal beam.
(210) 2. A catalog which defines the nominal shape and sizes to be expected for an ideal cross section of the beam to be cut. This is needed as the reference points differ for each shape as seen from
(211) 3. The Data.ini created in
(212) The combination of the ideal dimensions from the catalog (1305) are compared the real dimensions at each of 11 cross sectional surveys to establish the surfaces which form the H beam at all points between and including the measured 11 slices.
(213) This 3D multi surface model (as distinct from the single surface model of U.S. Pat. No. 9,539,664) is then combined with the desired parametric definition of the desired processing to create the CNC program to process the beam.
(214) This is the process of specifying a part we need cut even from a paper drawing all the way to generating the required CNC file that will instruct the cutting machine to make the correct cuts.
(215) Beginning 1301 perhaps from a drawing of the part use 1302 the desktop FastBEAM software to construct a model of the part and save it as an .FBX file. This is a proprietary parametric beam file format specifically created for beam processing. German industry standard DSTV files may also be imported and then converted to .FBX files. At the machine the stock material is placed 1303 on the bed and the operator selects 1304 the FBX file for processing and specifies 1306 a start origin point to start a survey scan according to the material to be cut.
(216) The FBX file includes parametric data for the cutting including the nominal description of the beam. We can then interrogate FastBEAM Catalog file (1305) and extract the product material's ideal dimensions to assist in conducting the Product Survey. Each Product Survey looks for different shape specific control points as in
(217) 4. (1307)—Survey Scan with the vertical Laser Range finder on the product material is carried out. In the scan we continually save the machine's XYZ co-ordinates and distance to the beam as data points. There are of course bad points, missing points and zero points, which is part of the smoothing process not detailed here. At the end of a single survey scan across the material, we have a large collection of (X, Y, Z, LASERREADING) data points, the data points representing surfaces and edges of the long product.
(218) 5. (1308), (1309)—Using developed software algorithms to clean, smooth and interpret the large data collection we arrive at a small set of (X, Y, Z) points to represent the co-ordinates of the top surface of the product material and the control points of
(219) 6. (1310)—Apply the processing requests to the precise shape as determined from all the survey. These are naturally in the coordinates of the cutting machine. In effect the cutting machine now knows precisely where the real part is located on the cutting bed and its exact shape.
(220) 7. (1313)—with the exact shape of all surface of the scanned beam, the desired processing is calculated in the coordinates and passes for the actual beam on the machine. Allowance for cutting width or kerf must be made. Also, circles are no longer available as a movement function, so all arcs and circles must be cut as small movements in XYZAC.
(221) So, a CNC file is then generated ready for the cutting machine controller to process and cut the specific beam as required. The individual cutting or marking passes are created as streams of movements which consist of XYZAC blocks in absolute coordinates. The torch is kept a fixed distance from the beam surface without height controls of any sort. All scanning and processing occurs without touching the beam.
(222)
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(224) Then the part is flipped and the final cut bottom cut is from 1 to 3. The difference with the sequence in
(225)
(226) In cutting A then B then C there is minimum movement and the part is completely and quickly severed in the order of a minute. Note that in this case the torch must tilt substantially past horizontal.
(227) This section illustrates that the invention can be used for a large range of ‘Long Products’ which include but a are not limited to structural products or beams.
(228)
(229) Changes may be made in the above methods and systems without departing from the scope hereof. It should thus be noted that the matter contained in the above description or shown in the accompanying drawings should be interpreted as illustrative and not in a limiting sense. The following claims are intended to cover all generic and specific features described herein, as well as all statements of the scope of the present method and system, which, as a matter of language, might be said to fall therebetween.