Multipolar induction heating system

Abstract

An induction heating system for heating a working area of an electrically conductive metallic workpiece includes a current loop arrangement and at least one AC (alternating current) current source supplying AC current to the current loop arrangement. The current loop arrangement provides at least one pair of current loops with a gap therebetween. The current loop arrangement is arranged to produce a superposed magnetic field having a pre-defined geometry in the electrically conductive metallic workpiece under the gap. The superposed magnetic field induces heating in the working area.

Description

MULTIPOLAR INDUCTION HEATING SYSTEMCROSS REFERENCE TO RELATED APPLICATIONS

[0001] This application claims priority from US provisional patent application 63 / 382,912, filed November 9, 2022, which is incorporated herein by reference.FIELD OF THE INVENTION

[0002] The present invention relates to magnetic induction generally and to induction coil heating systems in particular.BACKGROUND OF THE INVENTION

[0003] Heating electrically conductive metallic materials is an important industrial process. For example, heating is utilized in surface treatment of metals (to release stress and control crystalline structure) and for melting metals, whether in bulk or locally, such as in welding.

[0004] Induction heating is a method for heating electrically conductive metallic materials, namely metals or semiconductors, which is capable of non-contact, flameless and energetically efficient heating of such electrically conductive metallic substrates.

[0005] As described in the Wikipedia article “Induction heating”, stored at https: / / en.wikipedia.org / wiki / Induction_heating, an induction coil is driven by an alternating current (AC) to produce a rapidly alternating electromagnetic field, and is suspended over an electrically conductive metallic material. The rapidly alternating magnetic field penetrates the electrically conductive metallic material, and generates electrical currents,known as eddy currents, within the electrically conductive metallic material. Such electrical currents flow through the resistance of the material, and produce a heated region of the substrate by Joule heating.

[0006] Electrical currents tend to flow on the outer surfaces of electrical conductors, a tendency known as the ‘skin effect.” Induced electrical currents act similarly, and such eddy currents described hereinabove are generated on the outer surface of electrically conductive metallic materials, under the induction coil. During induction heating, the skin effect causes the heating, caused by the induced electrical current, to be localized on the outer surface of the conductive material, under the induction coil. Any heating profile deeper within the substrate will be the result of mechanical heating of the substrate by the surface induction heating profile, rather than by electromagnetically induced heating as a result of eddy currents deeper in the material. The ‘skin effect’ is described in the Wikipedia article “Skin Effect”, stored at https: / / en.wikipedia.org / wiki / Skin_effect.

[0007] The induced electrical currents themselves generate another magnetic field, which acts to oppose the magnetic field produced by the induction coil. Hence, such magnetic fields produced by such eddy currents act to electromagnetically shield the electrically conductive metallic material from the penetrating effects of the magnetic field produced by the induction coil, which becomes limited to near the surface of the substrate. Discussion of such ‘shielding’ may be found in the Wikipedia articles “Electromagnetic shielding”, stored at https: / / en.wikipedia.org / wiki / Electromagnetic_shielding #Magnetic_shielding, and “Faraday cage” stored at https: / / en.wikipedia.org / wiki / Faraday _cage.

[0008] As a result of the abovementioned induced currents, skin effect and electromagnetic shielding, induction heating coils generate heating profiles that are localized on the surface area of electrically conductive metallic substrates, and appear to only ‘graze,’ rather than deeply penetrate the surface of such substrates.

[0009] Typically, induction heating systems comprise an inductor, typically a coil, an AC power supply, and an optional cooling system for the coil for high power, strong magnetic fields, high frequencies and high current systems and applications.

[0010] The coil geometry is matched to the desired heating application. For example, solenoid coils can be used for the heat treatment of rods, while hairpin coils can be used for flat surfaces.

[0011] Typically, the point of maximum heating of the surface is directly under or within a part or winding of the coil. Accessing the heated area typically requires removing the coil from the heated area.SUMMARY OF THE PRESENT INVENTION

[0012] According to a first aspect of the present disclosure, there is provided an induction heating system for heating a working area of an electrically conductive metallic workpiece. The induction heating system may include a current loop arrangement and at least one AC (alternating current) current source. The current loop arrangement provides at least one pair of current loops with a gap therebetween and is arranged to produce a superposed magnetic field having a pre-defined geometry in the electrically conductive metallic workpiece under the gap. The superposed magnetic field induces heating in the working area. The at least one AC (alternating current) current source supplies AC current to the current loop arrangement.

[0013] In one embodiment, the current loop arrangement may include a single coil arranged in two loops, wherein each loop is composed of one or more coil windings. In another embodiment, the current loop arrangement may include a first induction coil arranged as a first current loop and a second induction coil arranged as a second current loop. Each of the first current loop and the second current loop is composed of one or more coil windings. The current loops in the pair of current loops have opposite chiralities.

[0014] The AC current may have an amperage of at least 1KA and a frequency of at least lOOKHz.

[0015] The induction heating system may further include a cooling arrangement for cooling the current loop arrangement. The cooling arrangement include a cooling jacket. The current loop arrangement may include one or more hollow coils and the cooling arrangement may be arranged to circulate a coolant through the one or more hollow coils.

[0016] The current loop arrangement may be configured such that the current loops may be tilted with respect to the electrically conductive metallic workpiece.

[0017] The current loop arrangement may include a first pair of induction coils and a second pair of induction coils orthogonally-disposed to the first pair of induction coils. A first gap defined by the first pair of induction coils may overlap with a second gap defined by the second pair of induction coils.

[0018] The geometry of the superposed magnetic field may be one of: a circular geometry and a non-circular geometry. The geometry of the superposed magnetic field may not be a footprint of the induction coils. The geometry of the superposed magnetic field may be a function of one or more of: (1) a geometry of the current loops, (2) a geometry of the gap, (3) a tilt angle of the current loops, (4) a height of the pair of currentloops above the electrically conductive metallic workpiece; and (5) a number of coil windings in a current loop.

[0019] The profile of coil / s constituting the current loops may be one of: a circle, an oval, a spiral, and a D-shape.

[0020] The induction heating system may further include at least one power controller to control the at least one AC current source to supply relative amplitude current, relative frequency current, and relative phase current to the at least one pair of current loops. The at least one relative frequency current and the at least one relative phase current may be one of: a single discrete value, a plurality of discrete values, a plurality of continuous values, and a plurality of scanning values.

[0021] The power controller may be configured to control the power supply as a function of a height of the current loop arrangement above the electrically conductive metallic workpiece.

[0022] The induction heating system may further include one or more controllable tilt actuators for adjusting a tilt angle of at least one induction coil of the current loop arrangement. The induction heating system may further include a controllable current loop positioner for controlling a position of at least one induction coil of the current loop arrangement with respect to at least one other induction coil of the current loop arrangement and / or with respect to the electrically conductive metallic workpiece.

[0023] The induction system may further include at least one flux concentrator to concentrate a magnetic flux flowing through the at least one pair of current loops.

[0024] The induction system may further include at least one magnetic shield to diminish a magnetic flux flowing through the at least one pair of current loops.

[0025] According to another aspect of the present disclosure, there is provided a casting system for casting a metallic object by constructing a plurality of production layers forming a vertical stack, wherein production layers have mold regions and object regions defined by the mold regions. A current production layer is constructed upon a top surface of a previous production layer of the vertical stack. The system includes a mold construction system operative to construct a mold region of the current production layer, a metal deposition system operative to construct an object region of the current production layer, a build table for supporting the vertical stack of production layers, and a controller for controlling at least the mold construction system and the metal deposition system. The metal deposition system includes an induction system according to the first aspect of the present disclosure.

[0026] The metal deposition system of the casting system may be configured to deposit molten metal on the previous production layer through the gap of the induction heating system.

[0027] The controller of the casting system may be further configured to control the induction heating system so as to heat the previous production layer before molten metal deposition, during molten metal deposition or after molten metal deposition.

[0028] The casting system may further include a temperature sensor and / or a height sensor for measuring, through the gap of the induction heating system, a temperature and / or a relative height of the working area, and the controller of the casting system may be further configured to control the metal deposition system in response to readings of the temperature sensor and / or a height sensor.

[0029] According to yet another aspect of the present disclosure, there is provided a surface heating and ablation system for treating a surface of an electrically conductiveworkpiece that may include a movable surface heater, at least one sensors, and a controller, the controller may be configured to control one or more operational parameters of the surface heater in response to readings of the at least one sensor, wherein the surface heater may be a an induction heating system according to the first aspect of the present disclosure. The sensors may be a temperature sensor, a distance sensor or a camera. The one or more operational parameters of the surface heater may be one or more of: a distance of the surface heater system from the electrically conductive metallic workpiece, voltage, current amperage, current phase, and current frequency.

[0030] The surface heating system may further include a motion system for providing a relative movement along a pre-defined heating path between the surface heater and the electrically conductive workpiece, and wherein the controller may be further configured to controlling a pace of the relative movement along a pre-defined heating path in response to readings of the one or more sensors.BRIEF DESCRIPTION OF THE DRAWINGS

[0031] The subject matter regarded as the invention is particularly pointed out and distinctly claimed in the concluding portion of the specification. The invention, however, both as to organization and method of operation, together with objects, features, and advantages thereof, may best be understood by reference to the following detailed description when read with the accompanying drawings in which:

[0032] Figs. 1A and IB are front and top view schematic illustrations, respectively, of a multipole induction heater (MIH), constructed and operative according to an embodiment of the invention;

[0033] Fig. 2 A is a simulation of the magnetic field lines produced by the MIH of Figs. 1A and IB;

[0034] Fig. 2B is a simulation of the heating profile produced by the MIH of Figs. 1A and IB;

[0035] Figs. 3A and 3B are schematic illustrations of two embodiments of an arrangement of a pair of current loops with opposite chirality;

[0036] Fig. 4 is a top view schematic illustration of the MIH with two arrangements of current loop pairs according too an embodiment of the invention;

[0037] Figs. 5A and 5B are front and top view schematic illustrations, respectively, of the MIH with flux shields, according to an embodiment of the invention;

[0038] Fig. 6A is a top view schematic illustration of the MIH with elongated coils, according to an embodiment of the invention;

[0039] Fig. 6B is a top view schematic illustration of the MIH with alternate shaped coils, according to an embodiment of the invention;

[0040] Fig. 7 A is a simulation of the magnetic field lines produced by an MIH utilizing inward tilted coils, according to an embodiment of the invention;

[0041] Fig. 7B is a simulation of the heating profile produced by the MIH of Fig. 7 A;

[0042] Figs. 8A and 8B are top view schematic illustrations of the MIH using asymmetric coil tilts, according to an embodiment of the invention;

[0043] Fig. 9 is a simulation of the heating profile produced by an exemplary MIH utilizing untilted coils with similar chirality;

[0044] Fig. 10 is a schematic illustration of a multipole induction heater (MIH) system, according to an embodiment of the invention;

[0045] Fig. 11 is a front view schematic illustration of an exemplary casting system utilizing the MIH system, according to an embodiment of the invention; and

[0046] Fig. 12 is a schematic illustration of the incorporation of the MIH in a measurement system, according to an embodiment of the invention.

[0047] It will be appreciated that for simplicity and clarity of illustration, elements shown in the figures have not necessarily been drawn to scale. For example, the dimensions of some of the elements may be exaggerated relative to other elements for clarity. Further, where considered appropriate, reference numerals may be repeated among the figures to indicate corresponding or analogous elements.DETAILED DESCRIPTION OF THE PRESENT INVENTION

[0048] In the following detailed description, numerous specific details are set forth in order to provide a thorough understanding of the invention. However, it will be understood by those skilled in the art that the present invention may be practiced without these specific details. In other instances, well-known methods, procedures, and components have not been described in detail so as not to obscure the present invention.

[0049] Applicant has realized that, in induction heating systems used for localized heating, the position of the heated region is a projection, or footprint, under the induction coil. To heat an area of the substrate outside of the coil footprint requires the induction heater coil to move around the surface of the substrate.

[0050] Applicant has realized that the footprint profile of the heated region is fixed according to the design and implementation of the heating coil and its position with respect to the workpiece.

[0051] Likewise, Applicant has realized that, to gain access to the heated region after heating, for example to provide material to the heated region or to perform additional surface treatment, requires the induction heating coil to be moved out of the way.Multipole Induction Heating

[0052] Multipole induction heating using eight-figure or cloverleaf coil arrangements are known, for example for enhancing or reducing the effect of eddy currents produced by the multipoles. See, for example, US Patent Application Publication No. US20140176058A1 and the articles (1) “Figure-Eight Coils for Magnetic Stimulation” by Shoogo Ueno and Masaki Sekino published by Frontiers in Human Neuroscience, December 16, 2021, (2) “Solving the Orientation Specific Constraints in Transcranial Magnetic Stimulation by Rotating Fields” by Assaf Rotem at el., published by plos.org on Published: February 5, 2014, and (3) “Electric field depth-focality tradeoff in transcranial magnetic stimulation: simulation comparison of 50 coil designs” by Zhi-De Deng, Sarah H. Lisanby and Angel V. Peterchev, published by PMC on January 6, 2013.

[0053] Applicant has realized that by using a tilted current loop arrangement, such as a pair of tilted current loops, a heated region may be positioned under a gap between the coils.

[0054] Applicant has realized that such a pair of tilted current loops may be, for example, a pair of tilted induction coils or a pair of current loops created by a single coil.

[0055] Applicant has realized that for applications requiring high current and high frequencies (e.g., an AC current of 1 kiloampere (kA) or above, at 100 kilohertz (kHz) or above), by positioning the heated region under a gap created by the geometry of the MIH and between the arrangement of the pair of current loops, line of sight may be maintained to the heated region. Such a line of sight may be used for example to allow asensor to measure the temperature of the heated region, a height of a system element above the heating region, and / or a material to be added to the heated region without removing the induction heater and disrupting the heating or controlled cooling process.

[0056] Reference is made to Figs. 1A and IB which are front and top view schematic illustrations of a multipole induction heater (MIH) 10 according to an embodiment of the invention. Reference is also made to Fig. 2A, which is a simulation of the magnetic field lines produced by MIH 10, and to Fig. 2B which is a simulation of the heating profile produced by MIH 10.

[0057] MIH 10 comprises a current loop arrangement comprising a pair of induction coils Cl and C2 suspended a distance D above a surface or workpiece 12, each constituting a current loop. Coil Cl may be tilted by al degrees, and coil C2 may be tilted by a2 degrees relative to workpiece 12. In this embodiment, tilt angles al and a2 may be positive angles (relative to workpiece 12). Coils Cl and C2 may be separated by a gap G. Coils Cl and C2 may be connected to an AC (alternating current) power supply or power source 13 such that the phase angle between current II flowing in coil Cl, and current 12 flowing in coil C2 (shown in Fig. IB) may be adjusted. Coils Cl and C2 may also be connected to a coil cooling system (not shown).

[0058] Magnetic field MS produced by currents II and 12 in coils Cl and C2, may be divided into three components - magnetic fields MSci, MSc2, and MSCIC2. Field lines of magnetic field MSci may close upon themselves while passing only through coil Cl. Field lines of magnetic field MSc2 may close upon themselves while passing only through coil C2. When coils Cl and C2 are close enough, field lines of magnetic field MSCIC2 may pass through both coils Cl and C2. Magnetic field MSCIC2 may graze the surface of workpiece 12 (also called “work surface” 12) under gap G, generating heatedregion H3. Magnetic fields MSci and MSc2 may graze the work surface 12 and generate heated regions Hl and H2 respectively.

[0059] Applicant has realized that the profile of superposed magnetic field MSCIC2 may vary according to the phase angle between coil currents II and 12.

[0060] When current II flowing in coil Cl and current 12 flowing in coil C2 are 180 degrees out of phase, (i.e. flow in opposite directions, and are a mirror image of each other, also known as exhibiting ‘opposite chirality’), then the magnetic fields MSci and MSC2, produced by coil Cl and coil C2 respectively, may be mirror images of each other (providing angle al equals angle a2). When the two coil currents II and 12 have opposite chirality, they may form the superposed magnetic field MSCIC2 as shown in Figs. 1 A and IB. Superposed magnetic field MSCIC2 may have a maximum concentration when current II flowing in coil Cl and current 12 flowing in coil C2 are 180 degrees out of phase. Variations in magnetic field MSCIC2 strength and profile are discussed hereinbelow. Magnetic field MS may induce heating of surface 12, as indicated by heated regions H 1 , H2 and H3. Heated region H 1 may be po sitioned under the lower part of coil Cl, heated region H2 may be positioned under the lower part of coil C2, and heated region H3 may be positioned under gap G between coils Cl and C2.

[0061] In some embodiments, the heated region beneath gap G may be of interest, and other heated regions may be considered spurious or unwanted or vice-versa. In some embodiments, unwanted heated regions may be located far away from the heated region of interest, and in other embodiments nearby.

[0062] Gap G allows line of sight access to heated region H3, without removing coils Cl and C2. Such line of sight access could be used, for example, for a sensor S, suspended above gap G between coils Cl and C2, to measure the temperature of heatedregion H3. In another embodiment, a surface treatment unit may provide surface treatment to heated region H3. It will be appreciated that line of sight is not limited to ‘above’ or perpendicular to the substrate, and may be at any angle to the surface of the substrate.

[0063] It will be appreciated that prior art induction coil heating systems, especially those with a small working distance D, may require that the induction coil heater be moved in order for such a sensor or surface treatment unit to operate. It will also be appreciated that the invention is not limited by the type of unit suspended above gap G. For example, a material depositor (not shown) may be suspended above gap G to deposit material, in the form of solids (e.g., powder), liquids, gases or plasma, on top of heated region H3.

[0064] For example, the temperature of the heated region H3 may be measured by a thermal camera (not shown) through gap G along an inclined line of sight (not shown) and concurrently, new material (e.g., molten metal) may be added to the heated region H3 through gap G from above (not shown).

[0065] It will be appreciated that the geometry of heated region H3 - which is indicative of the geometry of the superimposed magnetic field - may not be a footprint of coils Cl and C2. It will also be appreciated that heated region H3 may have a dynamic geometry that changes according to changes in physical and electrical properties of the system, as explained hereinbelow.

[0066] It will also be appreciated that coils Cl and C2 may be constructed from any suitable material known in the art, such as but not limited to water cooled metal tubes, and wire wrapped coils. Coils Cl and C2 may be connected to any suitable power source13, or multiple power sources 13 known in the art. Coils Cl and C2 may be connectedto any suitable cooling system known in the art. It will also be appreciated that any coil may be implemented as a single coil with one or more coil windings, or a plurality of stacked coils. The addition of extra coil windings or coils in the x-axis (to produce pancake style coils) and / or in the y-axis (to produce solenoid coils) may change the magnetic field and subsequent heating effects.

[0067] It will also be appreciated that coils Cl and C2 may be connected in series or in parallel to a single power source 13, and may be positioned to produce the desired chirality.

[0068] It will be appreciated that inductive heating is performed with a distance D between the lowest point of a coil and the surface, and that reducing the distance D between the lowest point of the coil and the surface may increase the heating effect, and vice-versa. It will also be appreciated that, as the gap G between coils becomes smaller, the superposed magnetic field MSCIC2 may change, which may cause changes to heat profiles Hl, H2 and H3.Series Coils with Opposite Chirality

[0069] Reference is made to Fig. 3A which shows an alternative MIH, here labeled 30, comprising two coils CS1 and CS2 connected in series. Coil CS1 may be wound clockwise and CS2 may be wound counter-clockwise. A current Is may flow in opposite directions in both coils CS1 and CS2, hence producing a pair of coils with opposite chirality.

[0070] Reference is made to Fig. 3B which shows an alternative MIH, here labeled 31, comprising a single coil arranged in a single turn, multi-winding eight-figure arrangement, constituting a pair of current loops CW 1 and CW2, producing a heated region HW in work surface 12. The first windings CW1 may be wound as a clockwisewinding, and the second windings CW2 may be wound as a counter-clockwise winding. As coils CW1 and CW2 are windings of the same coil, the same current may flow through both coils CW 1 and CW2 in opposite directions in each coil, hence producing a pair of multi-winding coils with opposite chirality. It will be appreciated that in this embodiment, coils CW1 and CW2 are implemented as a stack of coils, as mentioned hereinabove.

[0071] Reference is made to Fig. 4 which shows an alternative MIH, here labeled 50, comprising a pair of coils CPI and CP2, with an additional pair of coils CP3 and CP4. Coils CP3 and CP4 may be added on an orthogonal axis O to the axis A of coils CPI and CP2. A superposed magnetic field MSCPICP2 may be produced by coil pair CPI and CP2, and a second superposed magnetic field MSCP3CP4 may be produced by coil pair CP3 and CP4. When positioned as shown in Fig. 4, superposed magnetic fields MSCPICPZ and MSCP3CP4 may themselves superpose to produce a superposed magnetic field MSCPICP2CP3CP4 which may produce a more concentrated heated region HP3 in the gap between both coil pairs, than that of a single pair of coils. For simplicity, the configuration of Fig. 4 is illustrated with 4 coils; however, the two current loop pairs configuration of Fig. 4 may be constructed by one or more coils.Reducing Spurious Heated Regions using Magnetic Flux Shields

[0072] Reference is now made to Figs. 5A and 5B which show an alternative MIH, here labeled 60, comprising current loops coil winding / s CS1 and CS2 and flux shields 62 placed over the outer edges 63 of coil winding / s CS1 and CS2. Flux shields 62 may reduce magnetic flux MScsi and MScs2, from coil winding / s CS 1 and CS2, from causing induced heated regions HS1 and HS2 below outer edges 63 of both coil winding / s CS1and CS2 respectively. As a result, unwanted or spurious heating outside of desired heated region HS3 may be diminished.

[0073] It should be noted that in a further embodiment, a combination of a magnetic flux concentrator, and / or an additional current loop pair (for example, as shown in Fig. 4), and / or a magnetic flux shields (flux shields 62 of Figs. 5A and 5B) may be implemented together to further enhance surface heating concentration and accuracy, or change heated region geometry as explained hereinbelow.Changing Heated Region Profile by Changing Coil Geometry

[0074] Reference is made to Fig. 6A which schematically shows an alternative MIH, here labeled 70, comprising coils CE1 and CE2, each of which may be extended in a direction perpendicular to the axis A connecting the centers of the coils, thus forming an extended heated region HE3. Heated region HE3 may have a non-circular shape.

[0075] Reference is made to Fig. 6B which shows an alternative MIH, here labeled 71, comprising coils CD1 and CD2, each of which may be ‘D’ shaped, giving rise to a different shape and size of heated region HD3. Many other coil shapes and geometries may be utilized. It will also be appreciated that the pairs of coils do not need to be symmetrical or have similar shapes.Changing Heated region Position and Profile Using Negative Tilt Angles

[0076] Reference is made to Fig. 7A which is a simulation of the magnetic field lines and surface temperature profiles produced by an alternative MIH, here labeled 80, and to Fig. 7B which is a heating profile produced on surface 12 by MIH 80. MIH 80 comprises a pair of coils CT1, which may have a negative tilt angle a3 with respect to the horizontal, and CT2 which also may have a negative tilt angle a4 with respect to the horizontal. A superposed magnetic field MSCTICT? may produce two heated regions HT1and HT2 (Fig. 7B), which may have diminished heating profiles (compared to heated regions produced by similar coils with positive tilt angles). It will be appreciated that by varying tilt angles al and a2, the shape of a heated region HT3, beneath and between coils CT1 and CT2, may be adjusted from a solid heated region profile like that shown in Fig. IB (for coils with a positive tilt angle as shown in Fig. 1A), to a perimeter heated region profile as shown in Fig. 7B (for coils with a negative tilt angle as shown in Fig. 7 A) with a ‘blind spot’ BS in the center of heated region HT3, where reduced induction heating may take place.

[0077] Applicant has realized that, by varying the relative coil tilts, the profile of heated region HT3 under gap G between coils CT1 and CT2 may be varied, in-situ, without changing the coil geometry. It will be appreciated that dynamically varying only coil tilt angles a3 and a4 in situ, without changing the position of coils CT1 and CT2 relative to surface 12, heated region profiles may be dynamically changed. This may be performed during heating, using coil tilt actuators (not shown).Changing Heated region Position and Profile using Asymmetric Coil Tilts

[0078] Reference is made to Fig. 8A which illustrates an alternative MIH, here labeled 90, comprising coils CMK1 and CMK2 with asymmetric coil tilts (i.e., the values of coil tilts al and a2 may be different).

[0079] In this embodiment, tilt angles al and a2 may both be positive, but not equal to one another (but it will be appreciated that in another embodiment, coil tilt al may be positive, and a2 may be negative, or vice versa), which may cause a heated region HMK3 to reposition beneath gap G, between coils CMK1 and CMK2 (as in the previous embodiment shown in Figs. 1A and IB). A superposed magnetic field MSCMKICMK2 , produced by coils CMK1 and CMK2, may be concentrated in surface 12 closer to coilCMK1, and diminished towards coil CMK2, as indicated by the shape of superposed magnetic field MSCMKICMK2 indicated in Fig. 8A. As a result of the change to superposed magnetic field MSCMKICMK2, the profile of heated region HMK3 may produce an enhanced, larger heating region closer to coil CMK1, and a diminished, smaller heating region closer to coil CMK2.

[0080] As a result, a heat profile that was rectangular shaped when symmetric coil tilts were used (such as in Fig. 1A), may become a keystone shaped heat profile HMK3 as shown in Fig. 8A. Similarly, in an alternative embodiment as shown in Fig. 8B to which reference is now made, MIH 91 comprising coils CMT1 and CMT2 may produce an oval shaped heated region when coils have symmetrical tilt angles, but may produce a tear-drop shaped heated region HMT3 when tilt angles are asymmetric. It will be appreciated that in other embodiments, asymmetric coils tilts may produce a heated region profile that may be positioned under gap G, and closer to coil CMK2 or coil CMT2, or may even split into 2 separate heated regions, depending on the original coil geometry that may be produced by coils with similar coil tilts, and the final asymmetric coil tilts used.

[0081] In an alternative embodiment, varying the relative coil currents in current loop pairs CMK1 and CMK2 (of Fig. 8A), may cause a heated region HMK3 to ‘move’ from beneath gap G, between coils CMK1 and CMK2, ‘towards’ coil CMK1, similarly to changing the relative coil tilts between them as discussed hereinabove. Heated region HMK3 may also have a heating profile in a keystone shape.

[0082] In an alternative embodiment, varying the relative coil currents in current loop pairs CMT1 and CMT2 (of Fig. 8B) may cause a heated region HMT3 to reposition from directly beneath gap G, between coils CMT1 and CMT2, to a position closer to coilCMT1, in a similar manner to changing the relative coil tilts between them, as discussed in the previous embodiment hereinabove. Heated region HMK3 may also have a heating profile in a teardrop shape.

[0083] It will be appreciated that by dynamically varying only coil tilt angles al and a2 in situ, without changing the position of coils CMT1 and CMT2 relative to surface 12, heated region profiles may be dynamically changed. This may be performed during heating, using coil tilt actuators (not shown).Changing Heated region Position and Profile by Changing Relative Coil Phase

[0084] Reference is made to Fig. 9 which is a simulation of surface temperature profiles, produced by a MIH similar to MIH 10 in Fig. 1A and comprising current loops CC1 and CC2 but with similar chirality, where coil currents in current loops CC1 and CC2 flow in similar directions.

[0085] It will be appreciated that the pair of current loops CC1 and CC2 with similar chirality, may produce a superposed magnetic field that is perpendicular to the surface, resulting in no heating in the central region BS under the gap between coils. Fig. 9 shows the resulting heated regions HCC1, HCC2 and HCC3, with ‘blind spot’ BS on surface 12, where induction heating may be reduced.

[0086] Applicant has realized that by varying the relative coil phase continuously, the heated region profile under the gap between current loops may be varied from a blind spot profile as shown in Fig. 9 when the relative phase is zero degrees, to a solid profile heated region profile as shown in Fig. 2B when relative phase is a maximum of 180 degrees, in- situ, without changing the coil geometry.

[0087] It will be appreciated that in other embodiments, coil tilts al and a2 may be nonzero values, and the resulting heated areas HCC1, HCC2 and HCC3, and ‘blind spot’ BS profiles may be different.

[0088] It will be appreciated that by dynamically varying the relative coil phase in situ, without changing the position of coils CC1 and CC2 relative to surface 12, heated region profiles may be dynamically changed. This may be performed during heating, using relative phase adjustable power supplies (not shown).Magnetic Flux Concentrators

[0089] It will be appreciated that a magnetic flux concentrator, or multiple flux concentrators, may be added to any of the abovementioned MIH embodiments 10, 30, 31, 50, 60, 70, 71, 80, 90, and 91. Any flux concentrator may be added.MIH System

[0090] Reference is made to Fig. 10 which illustrates an exemplary MIH based system 110. MIH system 110 comprises an MIH, such as any of the abovementioned MIHslO, 30, 31, 50, 60, 70, 71, 80, 90, and 91, where Fig. 10 shows MIH 10 from Fig. 1A. MIH system 110 also comprises a pair of coil tilt actuators 112 attached to coils Cl and C2, a power controller 115, a tilt controller 118, a cooling controller 119, a coil position controller 121, a workpiece position controller 122, and a gap controller 124.

[0091] Power controller 115 may independently control power source 13 to control the amplitude, the frequency, and the phase of current II supplied to coil Cl, and may independently control power source 13 to control the amplitude, the frequency, and the phase of current 12 supplied to coil C2. Tilt controller 118 may control the tilt actuators112, to achieve the desired tilt angles al and a2, applied to coils Cl and C2. Coolingcontroller 119 may control a coil cooler (not shown) that provides coolant to coils Cl and C2.

[0092] Coil position controller 121 may control the position of coils Cl and C2, in any of the three degrees of positional freedom and three degrees of rotational freedom, via coil positioner(s) (not shown), with respect to the position of workpiece 12, and hence may control the size of distance D. Workpiece position controller 122 may control the position of workpiece 12, with respect to the position of coils Cl and C2, and hence control the size of distance D. Workpiece position controller 122 may operate in any of six degrees of positional freedom. Gap controller 124 may control relative coil positioner(s) (not shown) to adjust the relative position of coils Cl and C2 with respect to one another, and hence to control the size and shape of gap G.

[0093] It will be appreciated that controllers 115, 118, 119, 121, 122, and 124 may adjust outputs in order to, for example, adjust the heated region to a desired temperature and profile; adjust the position of the current heating spot (assuming that the desired heated region is larger than the heating spot size); adjust the height of the MIH from the workpiece; or produce any other desired outcome.

[0094] It will also be appreciated that controllers 115, 118, 119, 121, 122, and 124 may adjust outputs in response to operator intervention, as well as automatically in response to, for example, temperature inputs from sensor S, power levels from power supply 13, temperature readings of the cooling water running through the coils (not shown), EM (electromagnetic) field strength and orientation, and / or measurements of distance from work surface 12.

[0095] It will be appreciated that controllers 115, 118, 119, 121, 122, and 124 may adjust outputs in a dynamic scanning and / or continuous mode during heating, as well as between static heating states.

[0096] It will be appreciated that an embodiment of MIH based system 110 may have only some or even none of the abovementioned controllers, and may maintain some or all of the abovementioned parameters fixed.Casting System

[0097] It will be appreciated that MIH system 110 may operate as a workpiece heater (surface heater) for a casting system. Fig. 11, to which reference is now made, illustrates an additive casting system 300 that may incorporate MIH system 110 as described hereinabove. An exemplary additive casting system 300 is described in PCT Patent Applications publication numbers WO2019053712A1, WO2022243921A, and W02023002468, all of which are incorporated herein by reference.

[0098] Additive casting system 300 comprises a movable mold dispensing unit 230, a movable metal deposition system 220, a build table 216, and a controller 253.

[0099] System 300 may be configured to additively produce a vertical stack of multiple production layers, one currently-produced production layer 201 after the other, on build table 216. For each currently-produced production layer 201, movable mold dispensing unit 230 moving along a mold path MP, at a working distance Wd above currently- produced production layer 201, may construct mold regions 202. Mold regions 202 include at least one cavity 203 into which the molten metal may be deposited.

[0100] Once mold region / s 202 of a production layer 201 are complete, movable deposition unit 220 may deposit molten metal 204 along a deposition path DP, at working distance Wd above currently -produced production layer 201, in working areas in objectregions 205 to be fabricated. Working distance Wd may be dictated by the height of mold region 202 of production layer 201, and may typically be 2-20mm and specifically 4- 8mm.

[0101] Movable deposition unit 220 comprises a movable molten metal deposition module 206 for depositing molten metal 204 in multiple working areas in object regions 205. One working area in the currently-produced object region in shown in Fig. 11 as heated region HR. Molten metal may be deposited as a single drop, a plurality of drops or as a stream 204. It will be appreciated that build table 216 may be moved relative to movable mold dispensing unit 230 and / or to movable deposition unit 220 along worktable path WTP.

[0102] The working area (heated region HR) may be heated prior to molten metal deposition (a process known as pre-heating), during deposition, and / or after molten metal deposition (a process known as post heating). Thus, the casting system employs area heating systems, e.g., induction heating systems.

[0103] In prior art casting systems that employ prior art induction systems for area heating, the working area receiving the molten metal to be deposited must be placed beneath the area heater for heating, and beneath the molten metal depositor for receiving the deposited molten metal. This is achieved e.g., by moving the area heater / s and molten metal depositor / s over the object region and depositing the molten metal on a specific working area once the area heater passes it.

[0104] By incorporating any of the MIH systems of the present disclosure, for example, any of the abovementioned MIH embodiments 10, 30, 31, 50, 60, 70, 71, 80, 90, and 91, the heated region HR can be heated concurrently with the deposition of molten metal into the heated region. This will enable operational flexibility. For example,the amount of heating provided to the working area may be reduced as there will be no need to compensate for the cooldown of the working area during the passage out of the area heaters and the passage in of the molten metal depositor. Further, the geometry of the superimposed magnetic field generated by the MIH - that dictates the geometry of the heated rejoin HR, may be adjusted and controlled by controlling various operational parameters of the MIH. Further still, accurate measurements, e.g., temperature measurements and height of e.g., the depositor, the MIH and additional elements above the working area can be measured concurrently with molten metal deposition.

[0105] As a non-limiting example, the casting system may be used for casting gray iron objects of small, medium and large part sizes and masses; the production layers may range in thickness from about 2 millimeters to 12, 15 and 20 millimeters. The grey iron source (e.g., a grey iron rod) may be heated to melting; and the surface of previously produced grey iron regions may be heated to melting (for example, heated to 1100-1300 C deg.); The working areas to be heated may have a length (along the deposition path) in a range of 3 to 50mm, a width equal to or larger than a diameter of the molten metal deposited by the molten metal depositor (2- 12mm), and a depth in a range of 1 to 20mm; the area heaters, realized as induction heaters, may operate at high AC current of at least 1 KA (Kilo Ampere) at a frequency of at least 100 KHz (Kilo Hertz).

[0106] Thus, according to aspects of the invention, movable deposition unit 220 further comprises MIH system 110 that may be attached or coupled to deposition module 206 so as to heat working area 212 and to produce heated region HR accessible through gap G between tilted coils C 1 and C2 of MIH system 110. It will be appreciated that gap G may provide line of sight access from above MIH system 110 to heated region HR, thereby to enable deposition module 206 to deposit molten metal 204 directly throughgap G onto heated region HR, once heated region HR is at the desired temperature and dimensions.

[0107] It will be appreciated that heated region HR may have a static or a dynamic profile, as controlled by controller 253. Controller 253 may adjust controllable aspects of MIH 110 as described hereinabove. Controllable aspects may include voltage, current, phase, tilt angle, gap, working distance of coils as described hereinabove. As such, the shape, temperature and position of heated region may be fixed or vary dynamically during heating and cooling cycles.

[0108] In the embodiment illustrated in Fig. 11, deposition unit 220 may be moved laterally across the surface of the metal in a linear or other pattern, while molten metal 204 is deposited. The motion may be in a direction parallel to the axis connecting the centers of the coils, in a perpendicular direction or in a rotational direction. MIH system 110 that is part of deposition unit 220 or otherwise coupled to deposition module 206 (for example, carried by a common motion unit, not shown), may follow the movement of deposition unit 220. It will be appreciated that deposition unit 220 may make a plurality of passes per deposition layer in, for example, a discrete, a continuous or a scanning profile.

[0109] It will be appreciated that additive casting system 300 may deposit molten metal directly onto a preheated region without overheating, and may continue heating during the deposition.

[0110] In operational scenarios involving cooling the working areas after molten metal deposition (“post-heating”), MIH system 110 may be used for post heating. Heating can be adjusted to control the cooling rate of the deposited material, thus affecting and controlling the crystalline structure into which it may form.

[0111] Movable dispensing unit 230 and movable metal deposition system 220 may be controlled (e.g., by controller 253) to deposit material (e.g., first, second, third, fourth, etc. portions) layer by layer. MIH 110 may be controlled by (e.g., by controller 253) to adjust controllable aspects of MIH 110 as described hereinabove.Surface Heating and Ablation System

[0112] It will be appreciated that MIH system 110 may operate as a workpiece heater for a metal surface heating and ablation system. Fig. 12, to which reference is now made, illustrates a surface heating and ablation system 400 that may incorporate MIH system 110 as described hereinabove.

[0113] Surface heating and ablation system 400 comprises a movable surface heater unit 420, a build table 416, and a controller 453.

[0114] System 400 may be configured to heat areas of e.g., a metallic substrate 401 positioned on build table 416, or to remove molten metal areas of metallic substrate 401, thus shaping or smoothing metallic substrate 401 as described herein below.

[0115] Surface heater unit 420 may move along a heater path HP, at a working distance Wd above metallic substrate 401, heating working areas 402. Working distance Wd may be dictated by the shape or profile of metallic substrate 401 , or some other factor. Heater unit 420 itself may move in any direction on path HP relative to build table 416 or build table 416 may move in any direction on table path TP relative to heater unit 420. Movement may be before, during or after a heating cycle and may be controlled by controller 453.

[0116] Surface heater unit 420 may comprise MIH system 110, a temperature sensor module 404, a distance sensor module 405, a camera module 406, or other sensing, measuring or controlling modules (not shown). Modules 404, 405 and 406 may be usedby controller 453 to sense and adjust any controllable aspects of MIH 110 accessible through gap G between tilted coils Cl and C2 of MIH system 110 as described hereinabove. Controllable aspects may include voltage, current, phase, tilt angle, gap, working distance of coils as described hereinabove. As such, the shape, temperature and position of heated region may be fixed or vary dynamically during heating, cooling and ablation cycles.

[0117] For example, temperature sensor 404 may be used to adjust power settings to ensure substrate 401 becomes molten and ablation occurs. Distance sensor 405 may be used by controller 453 to control Wd, to create a uniform surface as measured from sensor 405. It will be appreciated that module functionality may not be limited to sensing and measuring, and that other types of application modules may be used for other applications. For example, a laser module (not shown) may be used to add high rate deposition functionality as described in US Patent publication US 2016 / 0271732 Al, dated September 22, 2016.

[0118] It will be appreciated that heated working area 402 may have a static or a dynamic profile, as controlled by controller 253. Controller 253 may adjust controllable aspects of MIH 110, such as voltage, current, phase, tilt angle, gap, working distance of coils, as described hereinabove. As such, the shape, temperature and position of heated region 402 may be fixed or vary dynamically during heating, cooling and ablation cycles.

[0119] In the embodiment illustrated in Fig. 12, heater unit 420 may be moved laterally across the surface of an electrically conductive substrate 401 (workpiece) in a linear or other heating path pattern. The motion may be in a direction parallel to the axis connecting the centers of the coils, in a perpendicular direction or in a rotationaldirection. It will be appreciated that heater unit 420 may make a plurality of passes in, for example, a discrete, a continuous or a scanning profile.

[0120] In operational scenarios involving controlled cooling of the working areas 402 after heating or ablation (“post-heating”), MIH system 110 may be used for post heating. Heating can be adjusted to control the cooling rate, thus affecting and controlling the crystalline structure into which it may form.

[0121] For simplicity, Fig. 12 depicts a heater system movable over a stationary workpiece placed over a build table, but this is not necessarily so. A relative movement along a pre-defined heating path between the surface heater and the electrically conductive workpiece can be provided in various manners known in the art. The controller may be further configured to controlling a pace of the relative movement along a pre-defined heating path in response to readings of the one or more sensors.Foil Container Sealing System

[0122] It will be appreciated that MIH system 110 may be used for other metallic substrate heating applications, such as foil container sealing. In this embodiment, a thin metallic foil substrate may be heated, to be used to seal the opening of a bottle or other container using a weld, hot glue or other sealing method known in the art.

[0123] In this embodiment, build table 416 may be modified with, for example, a channel to position containers in the gap, under heater unit 420 and under metallic substrate 401. A cutting system (not shown) may be in the gap of heater unit 420 or another module, to cut the foil seals to a desired shape before, during or after sealing.It will be appreciated that coils used in such a system may not be energized with high currents and may use coils that are wire-wound, rather than shaped water cooled metallic tubes.

[0124] While certain features of the invention have been illustrated and described herein, many modifications, substitutions, changes, and equivalents will now occur to those of ordinary skill in the art. It is, therefore, to be understood that the appended claims are intended to cover all such modifications and changes as fall within the true spirit of the invention.

[0125] As used throughout the specification, the terms "metal" or "metallic" refers to any metals and / or mellitic alloys which are suitable for melting and casting, for example, ferrous alloys, aluminum alloys, copper alloys, nickel alloys, magnesium alloys, and the like.

[0126] Any reference in the specification to a method should be applied mutatis mutandis to a system capable of executing the method and should be applied mutatis mutandis to a non-transitory computer-readable medium that stores instructions that, once executed by a computer, result in the execution of the method. Any reference in the specification to a system should be applied mutatis mutandis to a method that may be executed by the system and should be applied mutatis mutandis to a non-transitory computer-readable medium that stores instructions that may be executed by the system.

[0127] The terms "front," "back," "top," "bottom," "over," "under", and the like in the description and in the claims, if any, are used for descriptive purposes and not necessarily for describing permanent relative positions. It is understood that the terms so used are interchangeable under appropriate circumstances such that the embodiments of the present disclosure described herein are, for example, capable of operation in other orientations than those illustrated or otherwise described herein.

[0128] The subject matter regarded as the technique of the present disclosure is particularly pointed out and distinctly claimed in the concluding portion of thespecification. The technique of the present disclosure, however, both as to organization and method of operation, together with objects, features, and advantages thereof, may best be understood by reference to the detailed description when read with the accompanying drawings.

[0129] It will be appreciated that for simplicity and clarity of illustration, elements shown in the figures have not necessarily been drawn to scale. For example, the dimensions of some of the elements may be exaggerated relative to other elements for clarity. Further, where considered appropriate, reference numerals may be repeated among the figures to indicate corresponding or analogous elements.

[0130] In the claims, any reference signs placed between parentheses shall not be construed as limiting the claim. The word 'comprising' does not exclude the presence of other elements or operations and stages than those listed in a claim. Furthermore, the terms "a" or "an," as used herein, are defined as one or more than one. Also, the use of introductory phrases such as "at least one" and "one or more" in the claims should not be construed to imply that the introduction of another claim element by the indefinite articles "a" or "an" limits any particular claim containing such introduced claim element to inventions containing only one such element, even when the same claim includes the introductory phrases "one or more" or "at least one" and indefinite articles such as "a" or "an." The same holds true for the use of definite articles. Unless stated otherwise, terms such as "first" and "second" are used to arbitrarily distinguish between the elements such terms describe. Thus, these terms are not necessarily intended to indicate temporal or other prioritization of such elements. The mere fact that certain measures are recited in mutually different claims does not indicate that a combination of these measures cannot be used to advantage.

Claims

CLAIMSWhat is claimed is:

1. An induction heating system for heating a working area of an electrically conductive metallic workpiece, the induction heating system comprising: a current loop arrangement to provide at least one pair of current loops with a gap therebetween, said current loop arrangement arranged to produce a superposed magnetic field having a pre-defined geometry in said electrically conductive metallic workpiece under said gap, said superposed magnetic field to induce heating in said working area; and at least one AC (alternating current) current source to supply AC current to said current loop arrangement.

2. The induction heating system of claim 1 wherein said current loop arrangement comprises a single coil arranged in two loops, wherein each loop is composed of one or more coil windings.

3. The induction heating system of claim 1 wherein said current loop arrangement comprises a first induction coil arranged as a first current loop and a second induction coil arranged as a second current loop, wherein each of the first current loop and the second current loop is composed of one or more coil windings.

4. The induction heating system of claim 1 wherein the current loops in said at least one pair of current loops have opposite chiralities.

5. The induction heating system of claim 1 wherein said AC current has an amperage of at least 1KA and a frequency of at least lOOKHz.

6. The induction heating system of claim 5 further comprising a cooling arrangement for cooling said current loop arrangement.

7. The induction heating system of claim 6 wherein said cooling arrangement comprises a cooling jacket.

8. The induction heating system of claim 6 wherein the current loop arrangement comprises one or more hollow coils and wherein said cooling arrangement is arranged to circulate a coolant through the one or more hollow coils.

9. The induction heating system of any of claims 1 to 8 wherein the current loops are tilted with respect to the electrically conductive metallic workpiece.

10. The induction heating system of claims 1 and 3 to 9 wherein the current loop arrangement comprises a first pair of induction coils and a second pair of induction coils orthogonally- disposed to said first pair of induction coils.

11. The induction heating system of claim 10 wherein said gap comprises a first gap defined by said first pair of induction coils and a second gap defined by said second pair of induction coils, wherein said first gap overlaps with said second gap.

12. The induction heating system of any of claims 1 to 11 wherein said geometry is one of: a circular geometry and a non-circular geometry.

13. The induction heating system of claim 10 wherein said geometry is not a footprint of said first pair of induction coils or of said second pair of induction coils.

14. The induction heating system of claim 1 wherein said geometry is a function of one or more of: (1) a geometry of said at least one pair of current loops, (2) a geometry of said gap, (3) a tilt angle of said at least one pair of current loops, (4) a height of said at least one pair of current loops above the electrically conductive metallic workpiece; and (5) a number of coil windings in one current loop of said at least one pair of current loops.

15. The induction heating system of any of claims 1 to 14 wherein a profile of each current loop of said at least one pair of current loops is one of: a circle, an oval, a spiral, and a D-shape.

16. The induction heating system of any of claims 1 to 15 further comprising at least one power controller to control said at least one AC current source to supply relative amplitude current, relative frequency current, and relative phase current to said at least one pair of current loops.

17. The induction heating system of claim 16, wherein said at least one relative frequency current is one of: a single discrete value, a plurality of discrete values, a plurality of continuous values, and a plurality of scanning values.

18. The induction heating system of claim 16, wherein said at least one relative phase current is one of: a single discrete value, a plurality of discrete values, a plurality of continuous values, and a plurality of scanning values.

19. The induction heating system of claim 16 wherein said power controller is configured to control said power supply as a function of a height of said current loop arrangement above the electrically conductive metallic workpiece.

20. The induction heating system of any of claims 1 to 19 further comprising one or more controllable tilt actuators for adjusting a tilt angle of at least one induction coil of said current loop arrangement.

21. The induction heating system of any of claims 1 to 20 further comprising a controllable current loop positioner for controlling a position of at least one induction coil of said current loop arrangement with respect to at least one other induction coil of said current loop arrangement and / or with respect to the electrically conductive metallic workpiece.

22. The induction system of any of claims 1 to 21 further comprising at least one flux concentrator to concentrate a magnetic flux flowing through said at least one pair of current loops.

23. The induction system of any of claims 1 to 22 further comprising at least one magnetic shield to diminish a magnetic flux flowing through said at least one pair of current loops.

24. A casting system for casting a metallic object by constructing a plurality of production layers forming a vertical stack, wherein the production layers have mold regions, wherein the production layers have object regions defined by the mold regions, and wherein a current production layer is constructed upon a top surface of a previous production layer of the vertical stack, the system comprising: a mold construction system operative to construct a mold region of the current production layer; a metal deposition system operative to construct an object region of the current production layer;a build table for supporting the vertical stack of production layers; and a controller for controlling at least the mold construction system and the metal deposition system, wherein the metal deposition system comprises an induction system according to any of claims 1 to 23.

25. The casting system according to claim 24 wherein the metal deposition system is configured to deposit molten metal on the previous production layer through said gap of the induction heating system.

26. The casting system according to claim 24 wherein the controller is further configured to control the induction heating system so as to heat the previous production layer before molten metal deposition, during molten metal deposition or after molten metal deposition.

27. The casting system according to claim 24 further comprising a temperature sensor and / or a height sensor for measuring, through said gap of the induction heating system, a temperature and / or a relative height of said working area, and wherein the controller is further configured to control the metal deposition system in response to readings of said temperature sensor and / or said height sensor.

28. A surface heating and ablation system for treating a surface of an electrically conductive workpiece, comprising a movable surface heater, at least one sensors, and a controller, said controller is configured to control one or more operational parameters of said surface heater in response to readings of said at least one sensor, wherein the surface heater is an induction heating system according to any of claims 1 to 23.

29. The surface heating system of claim 28 wherein said at least one sensor is a temperature sensor, a distance sensor or a camera.

30. The surface heating system of claim 28 wherein the one or more operational parameters of said surface heater are from among a group consisting of: a distance of the surface heater system from the electrically conductive metallic workpiece, voltage, current amperage, current phase, and current frequency.

31. The surface heating system of claim 28 further comprising a motion system for providing a relative movement along a pre-defined heating path between said surface heater and said electrically conductive workpiece, and wherein the controller is further configured to controlling a pace of said relative movement along a pre-defined heating path in response to readings of the one or more sensors.

Images