Patent Grant
9003936
1. Technical Field
This disclosure is related, generally, to waterjet cutting systems, and, in particular, to a method and apparatus for controlling a standoff distance between a waterjet cutting head and a surface of a workpiece to be processed.
2. Description of the Related Art
Fluid jet or abrasive-fluid jet cutting systems are used for cutting a wide variety of materials, including stone, glass, ceramics and metals. In a typical fluid jet cutting system, a high-pressure fluid (e.g., water) flows through a cutting head having a cutting nozzle that directs a cutting jet onto a workpiece. The system may draw an abrasive into the high-pressure fluid jet to form an abrasive-fluid jet. The cutting nozzle may then be controllably moved across the workpiece to cut the workpiece as desired. After the fluid jet, or abrasive-fluid jet, generically referred to throughout as a “waterjet,” passes through the workpiece, the energy of the cutting jet is dissipated by a volume of water in a catcher tank. Systems for generating high-pressure waterjets are currently available, such as, for example, the Mach 4™ five-axis waterjet system manufactured by Flow International Corporation, the assignee of the present application. Other examples of waterjet cutting systems are shown and described in Flow's U.S. Pat. No. 5,643,058, which is incorporated herein by reference in its entirety.
Manipulating a waterjet in five or more axes may be useful for a variety of reasons, including, for example, cutting a three-dimensional shape. Such manipulation may also be desired to correct for cutting characteristics of the jet or for the characteristics of the cutting result. More particularly, as understood by one of ordinary skill in the relevant art, a cut produced by a waterjet has characteristics that differ from cuts produced by more traditional machining processes. These cut characteristics may include “taper” and “trailback,” as explained in more detail in Flow's U.S. Pat. No. 7,331,842, which is incorporated herein by reference in its entirety. These cut characteristics, namely taper and trailback, may or may not be acceptable, given the desired end product. Taper and trailback vary, depending upon the thickness and hardness of the workpiece and the speed of the cut. Thus, one known way to control excessive taper and/or trailback is to slow down the cutting speed of the system. Alternatively, in situations where it is desirable to minimize or eliminate taper and trailback while operating at higher cutting speeds, five-axis systems may be used to apply taper and lead angle corrections to the waterjet as it moves along a cutting path. A method and system for automated control of waterjet orientation parameters to adjust or compensate for taper angle and lead angle corrections is described in Flow's U.S. Pat. No. 6,766,216, which is incorporated herein by reference in its entirety.
To maximize the efficiency and quality of the cutting process, a standoff distance between where the waterjet exits the nozzle and a surface of the workpiece is preferably controlled. If the standoff distance is too small, the nozzle can plug during piercing, causing system shutdown and possibly damage to the workpiece. If the distance is too great, the quality and accuracy of the cut suffers. Systems for detecting and controlling such a standoff distance are known, and include, for example, direct contact type sensing systems and non-contact inductance type sensing systems. Examples of waterjet cutting systems including a sensing system for controlling a standoff distance are shown and described in Flow's U.S. Pat. Nos. 7,331,842 and 7,464,630, which are incorporated herein by reference in their entireties.
Known standoff detection systems, however, typically require direct contact sensing of the workpiece surface from which the desired standoff distance is to be maintained or positioning of a non-contact inductance type sensor proximate the surface. These types of systems therefore often include features which may limit, for example, the mobility and/or flexibility of the waterjet cutting system to traverse a workpiece in a particularly advantageous cutting path. In addition, components of these systems may be unavoidably exposed to spray-back which occurs when the waterjet first impinges on a surface of a workpiece or as the waterjet interacts with a structure beneath the workpiece during operation, thereby leading to potential wear and damage of the components.
Embodiments described herein provide waterjet cutting systems and methods particularly well adapted for processing workpieces in a highly efficient and accurate manner by providing momentary, intermittent or continuous feedback of a waterjet nozzle standoff distance. Embodiments include a cutting head having an environment control device and a measurement device integrated therewith in a particularly compact form factor or package.
In one embodiment, a cutting head for a waterjet cutting system may be summarized as including a nozzle having an orifice through which fluid passes during operation to generate a high-pressure fluid jet for processing a workpiece and an environment control device. The environment control device may be positioned to act on a surface of the workpiece at least during a measurement operation and configured to establish a measurement area on the surface of the workpiece substantially unobstructed by fluid, vapor or particulate material. The measurement device may be positioned to selectively obtain information from within the measurement area indicative of a position of a tip of the nozzle of the cutting head relative to the workpiece. The obtained information may be used to optimize a standoff distance between the tip of the nozzle and the workpiece.
The cutting head may further include a wrist manipulable in space to position and orient the nozzle relative to the workpiece, and wherein the environment control device and the measurement device are positioned on the wrist to move in unison with the nozzle. An axis of the nozzle and a rotational axis of the wrist may define a reference plane, and the measurement device may be positioned to selectively obtain information in a location offset from the reference plane.
The measurement device may be configured to selectively generate a laser beam to impinge on the surface of the workpiece within the measurement area during the measurement operation. The environment control device may be configured to selectively generate an air stream, a centerline of the air stream oriented to intersect a path of the laser beam at a position below the surface of the workpiece. A centerline of the air stream may be oriented to impinge on the surface of the workpiece within the measurement area at a position aft of a path of the laser beam and to flow across the path of the laser beam during the measurement operation. The environment control device may be configured to selectively generate an air stream such that a centerline of the air stream and a path of the laser beam define an acute angle. The environment control device may be configured to selectively generate an air stream such that a centerline of the air stream is coaxially aligned with a path of the laser beam. The laser beam may be oriented parallel to a centerline of the nozzle or may be oriented at an acute angle with respect to the centerline of the nozzle.
In other embodiments, the measurement device may be a mechanical probe that is movable to probe the surface of the workpiece within the measurement area to obtain the information indicative of the position of the tip of the nozzle of the cutting head relative to the workpiece.
In other embodiments, the cutting head may include a probe movably coupled thereto which is positioned to contact the workpiece within the measurement area at least during the measurement operation, and the measurement device may be configured to selectively generate a laser beam to impinge on a surface of the probe to obtain information indicative of the position of the tip of the nozzle of the cutting head relative to the workpiece indirectly by measuring displacements of the probe relative to the cutting head as the cutting head moves relative to the workpiece.
The cutting head may further include a shield to protect portions of the cutting head and surrounding components during operation, the environment control device passing through a portion of the shield. The environment control device may be configured to generate a vacuum to establish the measurement area beneath the shield by evacuating vapor or other obstructions from a space generally enclosed by the shield and the surface of the workpiece. The environment control device may be configured to generate an air stream to establish the measurement area beneath the shield. The environment control device may be configured to concurrently generate a positive air stream and a vacuum to establish the measurement area. The measuring device may be configured to selectively generate a laser beam that passes through a void in the shield.
The cutting head may further include a shutter mechanism configured to selectively isolate an operative portion of the measurement device from a surrounding environment of the waterjet cutting system. The shutter mechanism may include a shutter movable between an open position and a closed position, the shutter isolating the operative portion of the measurement device from the surrounding environment when in the closed position and enabling the measurement device to obtain the information indicative of the position of the tip of the nozzle of the cutting head relative to the workpiece when in the open position. The shutter may be movably coupled to a linear actuator for selectively moving the shutter between the open position and the closed position. The shutter may be a deformable member coupled to a pressure generating source for selectively transitioning the shutter between the open position and the closed position. The shutter may be positioned in a housing to selectively isolate an internal cavity of the housing from the surrounding environment, and the housing may include a passageway to route pressurized air into the internal cavity. The passageway may be oriented to route pressurized air into the internal cavity of the housing across a face of an operable portion of the measurement device. The passageway may be connected to another passageway configured to feed pressurized air to the environment control device, and, when pressurized air is fed to the environment control device to generate an air stream, pressurized air may be simultaneously fed to the internal cavity of the housing. The shutter may be positioned in a housing to selectively isolate an internal cavity of the housing from the surrounding environment, and the shutter may be biased toward the housing.
According to another embodiment, a waterjet cutting system may be summarized as including a cutting head having a nozzle with an orifice through which fluid passes during operation to generate a high-pressure fluid jet for processing a workpiece; an environment control device positioned to act on a surface of the workpiece at least during a measurement operation, the environment control device configured to establish a measurement area on the surface of the workpiece substantially unobstructed by fluid, vapor or particulate material; a measurement device positioned to selectively obtain information from within the measurement area indicative of a position of a tip of the nozzle of the cutting head relative to the workpiece; and a control system to move the cutting head relative to the workpiece, the control system operable to position the tip of the nozzle of the cutting head relative to the workpiece at a standoff distance based at least in part on the information indicative of the position of the tip of the nozzle of the cutting head obtained from the measurement device.
The measurement device may be configured to selectively generate a laser beam to impinge on the surface of the workpiece, and the control system may be configured to filter out information obtained by the laser beam from target areas of the workpiece having pre-cut kerfs and to use information indicative of the tip of the nozzle of the cutting head relative to the workpiece only from uncut target areas of the workpiece when calculating the standoff distance. The measurement device may be configured to feed the information indicative of the tip of the nozzle of the cutting head relative to the workpiece to the control system to manipulate the nozzle of the cutting head during a cutting operation based at least in part on the information. The control system may also be configured to determine whether the laser beam is impinging on a surface beyond the workpiece by comparing a measurement reading of the laser beam with an expected measurement reading.
The waterjet cutting system may further include a wrist manipulable in space to position and orient the cutting head relative to the workpiece, and the environment control device and the measurement device may be positioned on the wrist to move in unison with the cutting head. The measurement device may be configured to selectively generate a laser beam to impinge on the measurement area during the measurement operation, and the environment control device may be configured to selectively generate an air stream, a centerline of the air stream oriented to impinge on the measurement area at a position aft of a path of the laser beam and to flow across the path of the laser beam during the measurement operation.
The waterjet cutting system may further include a shield to protect portions of the cutting head and surrounding components during operation, the environment control device passing through a portion of the shield. The environment control device may be configured to generate a vacuum to establish the measurement area beneath the shield by evacuating a space generally enclosed by the shield and the surface of the workpiece. The environment control device may be configured to generate an air stream to establish the measurement area beneath the shield.
The waterjet cutting system may further include a shutter mechanism configured to selectively isolate an operative portion of the measurement device from a surrounding environment of the waterjet cutting system.
According to another embodiment, a method of operating a waterjet cutting system having a cutting head may be summarized as including activating an environment control device of the cutting head to act on a surface of a workpiece to establish a measurement area on the surface of the workpiece substantially unobstructed by fluid, vapor or particulate material; and obtaining information from within the measurement area indicative of a position of the cutting head relative to the workpiece, such as, for example, a standoff distance of a nozzle of the cutting head from the workpiece.
The method may further include optimizing a standoff distance between a tip of a nozzle the cutting head and the workpiece. Optimizing the standoff distance between the tip of the nozzle of the cutting head and the workpiece may include obtaining the information from within the measurement area indicative of the position of the cutting head intermittingly during a cutting operation, and manipulating the cutting head based at least in part on the information. Optimizing the standoff distance between the tip of the nozzle of the cutting head and the workpiece may include obtaining the information from within the measurement area indicative of the position of the cutting head continuously during a cutting operation, and manipulating the cutting head based at least in part on the information. In some embodiments, a measurement operation may be executed prior to a cutting operation to establish a desired standoff distance that is maintained during the cutting operation. In some embodiments, a measurement operation may be executed while moving along a desired cutting path prior to a cutting operation to construct a workpiece profile. This workpiece profile can be generated, for example, by sensing the surface of the workpiece continuously or intermittingly during the measurement operation and storing surface data for subsequent cutting operations. Once obtained, the workpiece profile may be used to generate movements of the cutting head relative to the workpiece to maintain the tip of the nozzle at a constant standoff distance from the surface of the workpiece. In this manner, a desired path of the tip of the nozzle corresponding to a selected standoff distance from the workpiece may be “pre-mapped” prior to cutting. During such pre-mapping, measurements may be taken with or without the environment control device acting on the workpiece surface depending on, for example, the presence of water, vapor or other obstructions.
Obtaining information from within the measurement area indicative of the position of the cutting head relative to the workpiece may include utilizing a laser beam to sense a distance between a reference point and the surface of the workpiece. Activating the environment control device coupled to the cutting head to act on the surface of the workpiece may include generating an air stream to impinge on the surface of the workpiece. Activating the environment control device coupled to the cutting head to act on the surface of the workpiece may include creating a vacuum to evacuate a space overlying the surface of the workpiece.
The method of operating a waterjet cutting system having a cutting head may further include actuating a shutter mechanism to expose the measurement area to a measurement device coupled to the cutting head prior to obtaining information from within the measurement area indicative of the position of the cutting head relative to the workpiece. The method may further include pressurizing an internal cavity that is selectively isolated by the shutter mechanism from a surrounding environment. Actuating the shutter mechanism may include energizing an actuator to move a shutter of the shutter mechanism from a closed position to an open position. Actuating the shutter mechanism may include temporarily deforming a shutter of the shutter mechanism to transition the shutter from a closed position to an open position. The method may further include routing pressurized air across a face of an operable portion of a measurement device used to obtain the information from within the measurement area. The method may further include constructing a workpiece surface profile relative to the cutting head prior to a cutting operation based at least in part on information obtained via a laser beam impinging on the surface of the workpiece within the measurement area.
The method may further include detecting an edge of the workpiece by moving the cutting head across the edge and comparing positional information obtained from a laser beam impinging on the surface of the workpiece and positional information obtained from the laser beam impinging off of the surface of the workpiece. Thereafter, the edge of the workpiece may be aligned with a coordinate axis of a coordinate system of the waterjet cutting system.
According to another embodiment, a method of operating a waterjet cutting system having a cutting head may be summarized as including activating an environment control device of the cutting head to act on a surface of a workpiece support structure to establish a measurement area on the surface of the workpiece support structure substantially unobstructed by fluid, vapor or particulate material; and obtaining information from within the measurement area indicative of a position of the cutting head relative to the workpiece support structure. The method may further include leveling the workpiece support structure based at least in part on the information obtained from within the measurement area indicative of the position of the cutting head relative to the workpiece support structure.
In the following description, certain specific details are set forth in order to provide a thorough understanding of various disclosed embodiments. However, one of ordinary skill in the relevant art will recognize that embodiments may be practiced without one or more of these specific details. In other instances, well-known structures associated with waterjet cutting systems and methods of operating the same may not be shown or described in detail to avoid unnecessarily obscuring descriptions of the embodiments. For instance, it will be appreciated by those of ordinary skill in the relevant art that a high-pressure fluid source and an abrasive source may be provided to feed high-pressure fluid and abrasives, respectively, to a cutting head of the waterjet systems described herein to facilitate, for example, high-pressure or ultrahigh-pressure abrasive waterjet cutting of workpieces. As another example, well know control systems and drive components may be integrated into the waterjet cutting system to facilitate movement of the cutting head relative to the workpiece to be processed. These systems may include drive components to manipulate the cutting head about multiple rotational and translational axes, such as, for example, as is common in five-axis abrasive waterjet cutting systems.
Unless the context requires otherwise, throughout the specification and claims which follow, the word “comprise” and variations thereof, such as, “comprises” and “comprising” are to be construed in an open, inclusive sense, that is as “including, but not limited to.”
Reference throughout this specification to “one embodiment” or “an embodiment” means that a particular feature, structure or characteristic described in connection with the embodiment is included in at least one embodiment. Thus, the appearances of the phrases “in one embodiment” or “in an embodiment” in various places throughout this specification are not necessarily all referring to the same embodiment. Furthermore, the particular features, structures, or characteristics may be combined in any suitable manner in one or more embodiments.
As used in this specification and the appended claims, the singular forms “a,” “an,” and “the” include plural referents unless the content clearly dictates otherwise. It should also be noted that the term “or” is generally employed in its sense including “and/or” unless the content clearly dictates otherwise.
Embodiments described herein provide waterjet cutting systems and methods particularly well adapted for processing workpieces in a highly efficient and accurate manner by providing momentary, intermittent or continuous feedback of a waterjet nozzle standoff distance. Embodiments include a cutting head having an environment control device and a measurement device arranged in a particularly compact form factor or package to enable highly accurate measurements to be taken prior to or during cutting operations to enable precise control of the standoff distance. As described herein, the term cutting head may refer generally to an assembly of components at a working end of the waterjet cutting machine, and may include, for example, a nozzle of the waterjet cutting system for generating a high-pressure waterjet and surrounding structures and devices coupled directly or indirectly thereto to move in unison therewith. The cutting head may also be referred to as an end effector.
The waterjet cutting system 10 further includes a bridge assembly 18 which is movable along a pair of base rails 20 and straddles the catcher tank 12. In operation, the bridge assembly 18 moves back and forth along the base rails 20 with respect to a translational axis X to position a cutting head 22 of the system 10 for processing the workpiece 14. A tool carriage 24 is movably coupled to the bridge assembly 18 to translate back and forth along another translational axis Y, which is aligned perpendicularly to the translational axis X. The tool carriage 24 is further configured to raise and lower the cutting head 22 along yet another translational axis Z to move the cutting head 22 toward and away from the workpiece 14. A manipulable forearm 30 and wrist 34 are provided intermediate the cutting head 22 and the tool carriage 24 to provide additional functionally.
More particularly, with reference to
During operation, movement of the cutting head 22 with respect to each of the translational axes X, Y, Z and rotational axes B, C may be accomplished by various conventional drive components and an appropriate control system 28 (
As shown in
With reference to
The cutting head 22 further includes a measurement device 60 for obtaining information indicative of a distance between a tip of the nozzle 40 of the cutting head 22 and the workpiece 14 to control the standoff distance 44. Information indicative of a distance between a tip of the nozzle 40 of the cutting head 22 and the workpiece 14 can include direct or indirect measurements of the location of the tip of the nozzle 40 with respect to the workpiece 14, such as, for example, the distance between a surface 15 of the workpiece 14 and the measurement device 60 or any other reference point or surface on the cutting head 22 having a known relationship to the tip of the nozzle 40.
The measurement device 60 of the illustrated embodiment is a laser displacement sensor 62 (
In some embodiments, and with reference to
Characteristics of the laser beam 64 may be analyzed by the sensor 62 to determine the distance between the sensor 62 and the workpiece surface 15 and to detect changes in said distance. For this purpose, the sensor 62 includes a detection window having a field of view 66 with which to collect data related to the impingement of the laser beam 64 on the workpiece surface 15. While the presently described sensor 62 provides particularly advantageous functionality, it is appreciated that other distance sensors and sensing technology may be used in lieu of the laser displacement sensor 62 described above.
For example, a laser auto focus device, such as, for example, the laser auto focus system available from Motion X Corporation under the trademark FocusTrac™, may be integrated into the cutting head 22 and used to gather or obtain information indicative of the distance between the cutting head 22 and the workpiece 14. This auto focus device can differentiate between “in-focus,” “above focus” and “below focus” conditions to produce a relative error signal that can be used to determine the distance between the cutting head 22 and the workpiece 14 and make adjustments to the position of the cutting head 22 to optimize the standoff distance 44. As another example, a dual laser system including two distinguishable laser beams may be provided wherein the laser beams are oriented to converge at a point when the desired standoff distance is achieved, and conversely, appear as separate features on the workpiece surface 15 when the cutting head 22 is too close or too far way. An imaging device may be used to monitor the points at which the laser beams impinge on the work surface and produce a signal that may be used to move the cutting head 22 until the laser beams converge. The aforementioned examples are not intended to be limiting. The sensor 62 may include a wide range of optical sensors, laser sensors, distance sensors, image sensors or other distance sensing technology.
Irrespective of the type of sensor 62 or sensing technology utilized, embodiments of the cutting head 22 and waterjet cutting system 10 advantageously include an environment control device 70 to condition an area on the workpiece surface 15 for accurate detection and control of the standoff distance 44. More particularly, the environment control device 70 is positioned to act on the workpiece surface 15 and establish a measurement area that is substantially unobstructed by elements of the surrounding environment, including, for example, fluid, vapor, and particulate material, such as spent abrasives. Substantially unobstructed means at least that a majority of the measurement area is uncovered by water or other obstructions and that a path from the measurement device 60 to the measurement area is essentially free of obstructions that would otherwise significantly hinder readings of the sensor 62.
With continued reference to
Further details of the cutting head 22, including the measurement device 60 and environment control device 70, are described with reference to
As further shown in
With reference to
Further details of the housing assembly 82 and shutter mechanism 92 are described with reference to
As previously discussed, the housing assembly 82 includes a cavity 80 to accommodate the sensor 62. Additionally, an aperture 111 may be provided in the housing assembly 82 for routing an electrical cable 114 (
As shown in
According to the example embodiment of the shutter mechanism 92 shown best in
The shutter 104 further includes one or more windows 140, 142 for enabling the operable or sensing portions of the sensor 62 to obtain readings through the shutter 104 when in the open position O. In the closed position C, the shutter 104 is configured to close off or substantially block the passageways 86, 90 and effectively seal the interior chamber 112 of the housing assembly 82 from the environment of the waterjet cutting system 10. To assist in sealing off the chamber 112, the shutter 104 may be biased toward the lower housing 102, such as, for example, by a biasing mechanism 146 (
With reference to
The cutting head 222 further includes a measurement device 260 for detecting the distance between the cutting head 222 and a workpiece 214 to control a standoff distance 244 of the nozzle 240 of the cutting head 222 from the workpiece 214. In the example embodiment shown in
In some embodiments, the laser beam 264 is oriented to impinge on the workpiece surface 215 beyond a perimeter of the shield 254 and relatively remote from the nozzle 240, such as, for example, beyond a radius of about six inches or more from where the axis of rotation C intersects the workpiece surface 215. In such embodiments, the obtained data may be detected further from the operational end of the nozzle 240 at a position less influenced by cutting operations. Characteristics of the laser beam 264 may be analyzed by the sensor 262 to determine the distance between the sensor 262 and the workpiece surface 215 and to detect changes in said distance. For this purpose, the sensor 262 includes a field of view 266 with which to collect data related to the impingement of the laser beam 264 on the workpiece surface 215. Again, while the presently described laser displacement sensor 262 provides particularly advantageous functionality, it is appreciated that other distance sensors and sensing technology may be used in lieu of the laser displacement sensor 262.
Irrespective of the type of sensor 262 or sensing technology utilized, embodiments of the cutting head 222 advantageously include an environment control device 270 to condition an area on the workpiece surface 215 for accurate detection and control of the standoff distance 244. More particularly, the environment control device 270 is positioned to act on the workpiece surface 215 and establish a measurement area that is substantially unobstructed by elements of the surrounding environment, including, for example, fluid, vapor and particulate material, such as spent abrasives.
According to the example embodiment shown in
Further details of the cutting head 222, including the measurement device 260 and environment control device 270, are described with reference to
As further shown in
With continued reference to
As shown best in
Further details of the housing assembly 282 and shutter mechanism 292 are described with reference to
As previously discussed the housing assembly 282 includes a cavity 280 to accommodate the sensor 262. Additionally, an aperture 311 may be provided in the housing assembly 282 for routing an electrical cable 314 (
As shown in
According to the example embodiment of the shutter mechanism 292 shown best in
When the shutter 304 is in the open position, the sensor 262 is able to obtain readings through the passageways 286, 290 in the lower housing 302. In the closed position C, the shutter 304 is configured to effectively seal the interior chamber 312 of the housing assembly 282 from the environment of the waterjet cutting system 10 and close off or substantially block the passageways 286, 290. In order to assist in sealing off the chamber 312, the sheath 305 may surround a substantial portion of the inflatable tube 318 of the shutter 304, leaving only a relatively narrow portion unsupported in a region 316 adjacent the passageways 286, 290 in the lower housing 302. In this manner, when the inflatable tube 318 is subjected to sufficient pressure, the inflatable tube 318 deforms only in this limited region 316 to block the passageways 286, 290. Accordingly, the shutter mechanism 292 provides one example of a configuration sufficient to selectively isolate the operative or sensing portions of the measurement device 260 during times when the measurement device 260 might otherwise be subjected to harsh conditions, such as during initial piercing of a workpiece with a waterjet.
The various features and aspects described herein provide waterjet cutting systems that are particularly well suited for processing workpieces in a highly accurate manner and include versatile cutting heads with compact form factors to enable, among other things, efficient cutting of workpieces having non-planar profiles.
Although embodiments are shown in the Figures in the context of processing generic plate-like workpieces, it is appreciated that the cutting heads and waterjet cutting systems incorporating the same described herein may be used to process a wide variety of workpieces having simple and complex shapes, including both planar and non-planar structures. Further, as can be appreciated from the above descriptions, the cutting heads and waterjet cutting systems described herein are specifically adapted to control the standoff distance between a cutting head nozzle and a workpiece that is being processed. This can be particularly advantageous when cutting, for example, large flat plates which typically bow over a length thereof. The systems described herein can adapt to bowing by tracing the contour of the plates with measurement devices in areas that are conditioned to be clear of obstructions during the cutting operation or prior to the cutting operation.
For example, in some embodiments, a measurement operation may be executed while moving along a desired cutting path prior to a cutting operation to construct a “workpiece profile” which represents the actual surface profile of a workpiece in the coordinate system of the waterjet cutting machine within a relatively small tolerance range. This workpiece profile can be generated, for example, by sensing the surface of the workpiece continuously or intermittingly during the measurement operation and storing surface data for subsequent cutting operations. The frequency with which measurements are taken may be adjusted to increase or decrease the relative accuracy of the workpiece profile. Once obtained, the workpiece profile may be used to generate movements of the cutting head relative to the workpiece to maintain the tip of the nozzle at a constant standoff distance from the surface of the workpiece. In this manner, a desired path of the tip of the nozzle corresponding to a selected standoff distance from the workpiece may be “pre-mapped” prior to cutting. During such pre-mapping, measurements may be taken with or without the environment control device acting on the workpiece surface depending on, for example, the presence of water, vapor or other obstructions.
In other instances, readings may be taken during a cutting operation (continuously or intermittingly) to provide highly accurate contour following while cutting is occurring. In instances where readings are taken intermittingly throughout a cutting operation, readings may be taken with greater or less frequency to manipulate the accuracy with which the standoff distance may be maintained. In other embodiments, the readings may be taken only during intervals when cutting is not occurring, such as, for example, just prior to piercing a workpiece to begin a cut or in an interval between successive cuts. Again, measurements may be taken with or without the environment control device acting on the workpiece surface depending on, for example, the presence of water, vapor or other obstructions.
Still further, although many embodiments are shown in the Figures in the context of measuring and establishing desired standoff distances with respect to a workpiece surface, it is appreciated that the cutting heads and waterjet cutting systems incorporating the same described herein may be used to generate measurement areas on the surface of a workpiece support structure from which to gather information indicative of a position of the cutting head relative to the workpiece support structure. This information can in turn be used to determine whether the workpiece support structure is level within an acceptable tolerance range and to make corrections to the same. For example, with reference to
Additionally, the cutting heads and waterjet cutting systems incorporating the same described herein may be used to detect edges of a workpiece or other features on the workpiece for various purposes. For example, according to some embodiments, a workpiece 14 may be repositioned after detecting the orientation of an edge 19 thereof with respect to a coordinate system of the waterjet cutting system, as illustrated in
As another example, similar measurement operations may be carried out to determine whether the cutting head 22 is overlying a workpiece 14 prior to initiating a cutting operation (i.e., before generating a fluid jet and piercing the workpiece 14). For example, the control system may be configured to determine whether the laser beam 64 is impinging on a surface beyond the workpiece by comparing a measurement reading of the laser beam 64 with an expected measurement reading based on, for example, the thickness of a selected workpiece for processing. When there is a significant discrepancy between a reading and the expected reading corresponding to the expected location of a workpiece surface 15, the control system may deactivate, disable or lockout the waterjet cutting system from initiating a cutting operation. Accordingly, inadvertent cutting beyond the perimeter of a workpiece 14 may be advantageously prevented.
In a similar fashion, embodiments described herein may be configured to distinguish between readings obtained from uncut target areas on a workpiece and areas that have pre-cut kerfs or other surface irregularities or characteristics. For example, for relatively planar workpieces, the measured distance between the cutting head and the workpiece should fall within a relatively small tolerance range of an expected value over the entire surface of the workpiece. Accordingly, when a reading deviates beyond this tolerance range over a relatively short distance consistent with a kerf, the operating system may treat the reading as an anomaly and disregard it. In other embodiments, the control system may store information pertaining to the location of kerfs of prior cuts and adjust a cutting path of the cutting head to avoid impinging the laser beam of the measurement device on such features. In this manner, the measurement device and control system may be configured to maintain a particularly accurate standoff distance without regard to discontinuities or irregularities in the surface of the workpiece.
Moreover, the various embodiments described above can be combined to provide further embodiments. These and other changes can be made to the embodiments in light of the above-detailed description. In general, in the following claims, the terms used should not be construed to limit the claims to the specific embodiments disclosed in the specification and the claims, but should be construed to include all possible embodiments along with the full scope of equivalents to which such claims are entitled. Accordingly, the claims are not limited by the disclosure.
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