Patent Application
20220234138
Laser cutting heads use a laser beam to perform cutting operations on sheets of different materials (typically, different types of metals and metallic compounds). The laser cutting process requires precise control of the cutting head and requires particular control of the gap between the tip of the cutting head's nozzle (where the laser beam exits) and the surface of the material being cut (referred to at times as the “workpiece”). For this purpose, the laser cutting head uses optics and sensors for controlling the cutting process.
In general terms, the laser cutting head converts the energy of a high-power laser source (typically a CO2 or YAG laser) into a laser beam able to cut through (sever) a metal sheet in a precise, controlled manner. The cutting head may pass the beam through a series of lenses and may use optical fibers as the guiding path for the beam. The cutting head focuses the beam to a spot size desired for the cutting process, and the focused beam is directed through a nozzle of the cutting head and toward the sheet of material to be cut.
A companion gas (typically nitrogen or oxygen and referred to at times as a cutting or process gas) can also be delivered to the surface of the sheet along with the laser beam. The gas functions either to assist in the melting process (e.g., “oxy-fuel burning process”) or to help blow molten material away from the workpiece. Although the cutting gas used during lasing process can blow material outward concentrically away from the nozzle, the nozzle needs to be positioned at a particular standoff from the workpiece to achieve proper cutting and to avoid molten material contaminating the nozzle and the cutting head.
A wide variety of laser cutting heads are manufactured for different purposes. Each type of cutting head requires the ability to adjust, control, and monitor the gap between the tip of the nozzle and the workpiece's surface. One typical system for monitoring (and controlling) this gap is based upon a measured capacitance between the nozzle tip and the workpiece (with the air gap between the two serving as the dielectric for the capacitor). To function properly, both the nozzle tip and the workpiece need to be conductive and connected to a voltage source of a measurement system.
Numerous types of nozzles are used on the laser cutting heads. These nozzles are typically composed of metal, such as copper, and have a passage therethrough for delivery of the focused laser beam and the cutting gas. Nozzles can include one or more component layers. The outward shape of the nozzle as well as any internal profiles of the through-passage can vary from nozzle to nozzle depending on the implementation and their use.
During customary use, the nozzle can become worn and contaminated, requiring replacement. During bevel cutting at acute angles, features associated with the nozzle may interfere with sensor measurements to control the standoff or gap of the nozzle from the workpiece. At very acute angles, existing arrangements of nozzles and adapters may not prevent contamination from interfering with the optics and sensing of the laser cutting head.
The subject matter of the present disclosure is directed to overcoming, or at least reducing the effects of, one or more of the problems set forth above.
An apparatus disclosed herein is used to connect a nozzle to a laser cutting head. The head has a sensor assembly for capacitive sensing, an opening for communicating a laser process, and an orifice for communicating a purge gas. The apparatus comprises a conductive adapter and a cover. The conductive adapter has first and second ends and has a first passage for communicating with the laser process from the opening. The first end is affixable to the sensor assembly, and the second end is affixable to the nozzle. The conductive adapter has a collar disposed thereabout, and the collar defines one or more second passages therethrough. The cover is configured to position between the head and the collar and is configured to enclose a space communicating the purge gas from the orifice to the one or more second passages of the collar.
A laser cutting head disclosed herein uses a nozzle to deliver a laser process. The head comprises a housing, a conductive adapter, and a cover. The housing has a sensor assembly for capacitive sensing, an opening for communicating the laser process, and an orifice for communicating a purge gas. The conductive adapter has first and second ends and has a first passage for communicating with the laser beam of the opening. The first end is affixed to the sensor assembly, and the second end is affixed to the nozzle. The conductive adapter has a collar disposed thereabout, and the collar defines one or more second passages therethrough. The cover is disposed between the end of the housing and the collar and encloses a space communicating the purge gas from the orifice to the one or more flow passages of the collar.
The foregoing summary is not intended to summarize each potential embodiment or every aspect of the present disclosure.
To protect the internal optics inside the housing 32, the head 30 may include a cover slide cartridge 34 that holds a replaceable cover slide. This cover slide acts as a transparent window between the interior of the housing 32 (having the internal optics) and the external environment (exposed to the lasing process). Removal and replacement of the cartridge 34 can be made through an access door in the side of the head 30. The nozzle attachment 50 also protects the laser cutting head 30 in ways disclosed below.
In general, the laser cutting head 30 can be used with a gantry assembly, a robotic arm, or other apparatus so the head 30 can be moved relative to a workpiece. For example,
In general, the laser cutting system 10 includes a control system 12 that controls operation of the various components, namely the robotic arm 20, cutting head 30, etc. The system 10 likewise includes a measurement system 14, which in the present example is used with the control system 12 to measure the standoff or gap of the cutting nozzle 120 from the workpiece WP to facilitate the cutting operation.
Depending on the shape of the workpiece WP and the cuts to be made, the head 30 can be manipulated by the robotic arm 20 at various angles and orientations relative to the workpiece WP. During the lasing process, components of the nozzle attachment 50 can sense the distance of the nozzle 120 from the workpiece WP. This is achieved using capacitance between the nozzle 120 and the workpiece WP, with the air gap between them providing the dielectric. This sensed capacitance allows the positioning of the head 30 to be controlled relative to the workpiece WP to achieve the desired lasing.
As expected, heat from the lasing process damages the nozzle 120 during use. Additionally, the lasing process can produce debris, cast off, splatter, blow back, etc. that can damage the nozzle 120 and can diminish the capacitive sensing of the head 30. Features of the nozzle attachment 50 of the present disclosure can help mitigate the damage to the nozzle 120 and can protect the capacitive sensing.
At very acute angles of the head 30, such as shown in
Depending on the laser process, different nozzles may be used on the nozzle attachment 50. For example,
Briefly,
Turning now to more details,
The head 30 includes a housing 32 having an end, which can include an end plate 38 from which the laser beam (B), the process or cutting gas (G), and the purge gas (P) can pass. The laser beam (B) and the process gas (G) pass from the interior of the housing 32 through an opening 36 and then through the sensor assembly 60, while the purge gas (P) can pass from elsewhere in the housing 32 through a pathway or other opening 35, which is only schematically shown. Components of the sensor assembly 60 are affixed to the end of the housing 30, and the cap or fixture 52 covers the assembly 60 on the end of the housing 30. The conductive adapter 110 is attached to the sensor assembly 60, and the cover or girdle 130 is disposed between the sensor assembly 60 and the conductive adapter 110. Finally, the nozzle 120 is attached to the conductive adapter 110.
The cap 52 functions as an outer protective element for the sensor assembly 60, protecting the assembly 60 from exposure to other manufacturing/fabrication elements that may damage the assembly 60 or otherwise disrupt its operation. As shown in detail, the cap 52, which can be conical, has a large circumferential end that can thread to the end plate 38 fit against a retaining ring 70 used between the sensor assembly 60 and the base plate 38. A plurality of gaskets can be used to seal the arrangement against external influences, as well as to prevent intrusion of the purge gas (P).
The nozzle attachment 50 has an orifice 54 from which some of the purge gas (P) passes. For example, an annular space 54 is provided between a lip of the cap 52 and the outer edge of the sensing assembly 60. Purge gas (P) can pass out of this annular space 54 toward the end of the adapter 110 and nozzle 120 for the purposes disclosed herein.
For its part, the sensor assembly 60 has a ceramic body 62 and a conductive holder 66. The ceramic body 62 has a first passage 64 through which the laser beam (B) and any process gas (G) can pass. The conductive holder 66 is disposed in the first passage 64. The sensor assembly 60 can further include a conductive grounding shield 72 disposed about the ceramic body 62. As discussed in more detail below, the conductive holder 66 and the conductive grounded shield 72 are connected in electrical communication with a voltage and a ground respectively.
The conductive adapter 110 has first and second ends 114, 116 with a second passage 112 through which the laser beam (B) and any process gas (G) can pass. The first end 114 is configured to affix to the conductive holder 66, while the second end 116 defines a receptacle into which the nozzle 120 is affixable. For example, the first end 114 can include external threading that threads into the conductive holder 66. The receptacle 116 can define internal threading to which the nozzle 120 threads. For its part, the nozzle 120 defines a passage 122 that extends therethrough from end 126 to end 124 for passage of the laser beam (B) and process gas (P).
The conductive adapter 110 has a collar 115 disposed thereabout, and the cover 130 is disposed between the sensor assembly 60 and the collar 115. As shown, the cover 130 can have a conical shape having a large circumferential edge configured to engage the cap 52 and having a small circumferential edge configured to engage the collar 115 of the conductive adapter 110. The conductive adapter 110 can include a gasket seal 117 disposed about the collar 115 to sealably engage the cover 130.
The collar 115 defines one or more gas flow passages 118 therethrough from one side to the other for passage of some of the purge gas (P) as noted herein. In this way, the cover 130 encloses an internal space 55 communicating the purge gas (P) from the orifice 54 to the one or more flow passages 118 of the collar 115. One or more exits of the one or more flow passages 118 in the collar 115 are thereby preferably disposed directly adjacent the nozzle 120, which can increase the cooling of the nozzle 120 and prolong its operational life.
As will be appreciated, the adapter 110 with its flow passages 118 can assist in the ejection of the purge gas (F), which can effectively prevent debris from reaching components of the head 30 and the nozzle attachment 50. The adapter 110 with its flow passages 118 also controls the diffusion area and size of the purge gas' stream, which can be tailored to the cutting operation to be performed.
As will be appreciated, the cutting nozzle 120 can assist in the ejection of the cutting or process gas (G) used in the cutting operation. The size of the nozzle's aperture 124 may be selected based on the thickness of the material to be cut. The nozzle 120 helps prevent the molten material from the workpiece reaching back into the laser head 30 so that internal components of the laser head 30 can be protected. The nozzle 120 also provide a capacitance signal for use in adjusting the standoff of the lasing head 30 by its adjustment system to maintain a stable lasing operation.
In some arrangements, the internal shape of the laser head nozzle 120 can direct the flow and pressure of the process gas (G). A single layer nozzle 120 can be used in melting cutting where nitrogen may be used as an auxiliary gas to cut stainless steel and aluminum plate. A double-layer nozzle 120 can be used with oxygen as an auxiliary gas for cutting carbon steel. Typically, the nozzle 120 is conical in shape and can have a single layer or multiple layers. For example, a double-layer nozzle can have an inner core to increase the velocity of the process gas (G), which has a number of advantages. The nozzle aperture 124 and the nozzle's thickness is configured for the implementation at hand.
Turning now to details of the sensor assembly 60 used for sensing the stand-off of the nozzle 120 from a workpiece, the cylindrical ceramic body 62 is used as a base element of the sensor assembly 60. The ceramic material of the body 62 is insulative. Electrical connections between the laser cutting head nozzle 120 and an external measurement system (14) can be sintered to the outside of (or embedded within) cylindrical ceramic body 62. In this manner, the electrical connections are permanently fixed in place and prevented from moving (even in the presence of “high g” conditions) and are able to function properly in the presence of high temperatures.
These electrical connections can include: a pair of electrical conductors (wires) 82, 86, the conductive holder 66, the outer cylindrical shield 72 (also conductive), and a socket connector 65. The conductive adapter 110 and the nozzle 120 engage with conductive holder 68. Together, these direct the laser beam (B) and any process gas (G) out of the cutting head 30 toward the workpiece.
The socket connector 65 can be a coaxial cable connector, including a central conductor and an outer ground conductor (with insulating material disposed between them). One wire 86 is used to conduct an electrical signal (voltage) along the central conductor to the conductive holder 66, which is itself formed of a conductive material (for example, stainless steel). In assembling the laser cutting head 30, the adapter 110 is threaded into the conductive holder 66 (in particular, screwed in place by the mating threads), and the nozzle 120 is threaded into the adapter 110. As a result, the nozzle 120 is electrified by virtue of the connections established through wire 86 and threaded holder 66.
The other wire 82 is positioned within the ceramic body 62 to create the conduction path between for the outer ground or shield 72. This outer shield 72 takes the form of a sleeve that is designed to slip over and contact the outer surface of cylindrical ceramic body 62. The shield 72 is permanently fixed in place around ceramic body 62 and is preferably formed of stainless steel.
The combination of the conductive holder 66, the ceramic body 62, and the shield 72 provides the connection arrangement for energizing the attached nozzle 120, minimizing problems with internal interference and parasitic induction that would otherwise affect the capacitive measurements performed by the associated measurement system 14. In addition to the cap 52, the cover 130 used in conjunction with the collar 115 and the seal 117 of the adapter 110 protects these components of the sensing assembly 60 during operations, while still allowing the head 30 to be used at small acute angles as noted herein.
As already noted, for example, the conical cap 52 having a large circumferential end attached to the end 38 of the housing 30 and having a small circumferential end defining the annular gap 54 about the ceramic body 62 for the passage of the purge gas (P). A circumference of the collar 115 of the conductive adapter 110 lies within a conical angle (A) extending from a tip of the nozzle 120 to the large circumferential end of the conical cap 52. This configuration allows the head 30 to be positioned at small acute angles relative to a workpiece during lasing operations, as previously noted with respect to
As can be seen, should any molten debris or the like be able to reach the annular gap 54, the contamination can obstruct the flow of purge gas (P) from the head 30. Moreover, any molten debris or the other contamination reaching the sensor assembly 60 may interrupt its sensing capabilities. To that end, the cover 130, the collar 115 of the adapter 110, the seal 117, and the other features protect the gap 54 and the sensor assembly 60. Moreover, the directed purge gas (P) can actively cool the nozzle 120, which prevents overheating/wear. The purge gas (P) can also be used as a curtain (shielding) for the cutting gas (G) stream.
For instance,
Turning to another configuration,
As shown, the nozzle 120′ extends beyond the collar 115 of the adapter 110. To allow the purge gas (P) to flow from the flow passages 118, side chamfers 119 can be defined in the side of the collar 115. The purge gas (P) from the flow passages 118 can escape outside the sides of the adapter 110 and can still achieve the purposes of cooling the nozzle 120′ and creating additional shielding.
For example,
An alternative configuration of the nozzle attachment 50 is shown in
As disclosed herein, the nozzle attachment 50 can relieve problems during bevel cutting operations that may be encountered during operation. The nozzle attachment 50 can prevent contamination from getting inside the sensor assembly 60 and can produce the cooling effect with the purge gas (P) for cooling down the nozzle 120. The adapter 110 and cover 130 are configured to not impact the capacitive sensor assembly 60 and system (14) of the cutting head 30. Moreover, the attachment 50 has a modular design so the attachment 50 can be used with a number of different nozzle types.
The foregoing description of preferred and other embodiments is not intended to limit or restrict the scope or applicability of the inventive concepts conceived of by the Applicants. It will be appreciated with the benefit of the present disclosure that features described above in accordance with any embodiment or aspect of the disclosed subject matter can be utilized, either alone or in combination, with any other described feature, in any other embodiment or aspect of the disclosed subject matter.
In exchange for disclosing the inventive concepts contained herein, the Applicants desire all patent rights afforded by the appended claims. Therefore, it is intended that the appended claims include all modifications and alterations to the full extent that they come within the scope of the following claims or the equivalents thereof.
