A method is provided for controlling an induction welding operation. The method includes sweeping electrical current through an induction welding coil at an initial position of the induction welding coil along a weld path of a material; monitoring a response of the material to the swept electrical current using at least one electromagnetic field (EMF) sensor; calibrating an electrical current value for the induction welding operation using the monitored response; and performing the induction welding operation along the weld path using the calibrated electrical current value.

A method for joining moulded parts by electromagnetic welding. A joining inductor is moved along contact surfaces of the moulded parts, generating an electromagnetic field in an induction-sensitive component of the moulded part(s) to heat a thermally activated coupling means of the moulded part(s) to above a melting temperature of the coupling means. The strength of the electromagnetic field suitable for joining is determined by previously moving a sensing inductor along the contact plane, generating a relatively weak electromagnetic field to slightly heat the thermally activated coupling means to a sensing temperature, measuring the field strength generated by the sensing inductor in the moulded part(s), determining a discrepancy between the measured field strength of the sensing inductor and the field strength suitable for joining, and adjusting the field strength suitable for joining to close the discrepancy. A device for carrying out the method.

A method for joining moulded parts by electromagnetic welding. A joining inductor is moved along contact surfaces of the moulded parts, generating an electromagnetic field in an induction-sensitive component of the moulded part(s) to heat a thermally activated coupling means of the moulded part(s) to above a melting temperature of the coupling means. The strength of the electromagnetic field suitable for joining is determined by previously moving a sensing inductor along the contact plane, generating a relatively weak electromagnetic field to slightly heat the thermally activated coupling means to a sensing temperature, measuring the field strength generated by the sensing inductor in the moulded part(s), determining a discrepancy between the measured field strength of the sensing inductor and the field strength suitable for joining, and adjusting the field strength suitable for joining to close the discrepancy. A device for carrying out the method.

A process for packaging a product arranged on a support comprising unrolling a film, moving the film to a packaging assembly defining at its inside a packaging chamber, progressively moving a number of supports inside the packaging chamber of the packaging assembly, closing the packaging chamber with the film sheets held above the respective support, optionally causing one or both of: a gas withdrawal from the hermetically closed packaging chamber and gas injection of a gas mixture of controlled composition, heat sealing the film to said support, wherein the heat sealing uses one or more heaters having heating surfaces which are heated for discrete and short time periods only. An apparatus for performing the above process is also disclosed.

A method of joining together liner sections within a polymer-lined pipe energises an induction coil inside the pipe to spot-heat part of a circumferential interface between the liner sections. This melts and fuses the polymer material locally. The induction coil is then moved along the interface to heat other parts of the interface successively above the melting temperature. An apparatus for performing the method has a power supply for energising the induction coil and a drive system for moving the energised induction coil relative to a body of the apparatus. The apparatus may be configured as a carriage that is movable along the pipe.

A method of controlling an inductive heating circuit, having a varying load, to seal a packaging material is provided. The method comprises generating AC power of at least two frequencies on at least one inductor in the inductive heating circuit; determining of the resulting phase shift in the inductive heating circuit from the current generated at the at least two frequencies; determining the impedance of the inductive heating circuit for each of the at least two frequencies; determining a load characteristics of the inductive heating circuit based on the relationship between the determined impedance and the determined phase shift; determining an impedance operating range; and selecting an AC output frequency for an induction power generator based on the load characteristics which results in the least amount of phase shift from a set ideal value and which is associated with an impedance that is within the impedance operating range.

Systems and methods are provided for controlling welding. One embodiment is a method for controlling welding of a composite part. The method includes locating a linear fiber optic sensor along a composite part comprising a matrix of thermoplastic reinforced by fibers, measuring temperatures along the weld line via the linear fiber optic sensor, performing induction welding at the composite part along the weld line, determining a continuum of weld temperatures along the weld line, and controlling the induction welding based on the continuum of weld temperatures.

A method of controlling an inductive heating circuit, having a varying load, to seal a packaging material is provided. The method comprises generating AC power of at least two frequencies on at least one inductor in the inductive heating circuit; determining the resulting phase shift in the inductive heating circuit from the current generated at the at least two frequencies; determining the impedance of the inductive heating circuit for each of the at least two frequencies; determining a load characteristics of the inductive heating circuit based on the relationship between the determined impedance and the determined phase shift; determining an impedance operating range; and selecting an AC output frequency for an induction power generator based on the load characteristics which results in the least amount of phase shift from a set ideal value and which is associated with an impedance that is within the impedance operating range.

Applied power as a function of time is ramped up at the onset of an RF welding process in a manner that is predetermined to match source and load impedance as reflected by maximized forward power during at least the majority of the welding process. The ramp-up portion takes the form of a non-linear curve, such as an S-shaped curve, as opposed to one or more discrete steps. The applied power may then be maintained at or near that maximum required value at least a majority of the remainder of the heating portion of the welding process. The shape of the non-linear ramp-up portion of the applied power curve may be predetermined using, for example, virtual motor control using applied power as a virtual axis.

An implant for electric resistance welding of elements made of composites, with a frame of thermoplastic materials, reinforced with conductive fibres, in a flat multilayered structure with an upper and lower surface, and includes an electrically resistant layer of a flat sheet with openings, made of a conductive material, additional layers made of the frame material, one of which covers the electrically resistant layer from the top, and the other one from the bottom. The implant includes porous insulating layers made of an electrically nonconductive material, one covers the implant from the top, contacting the upper layer of the frame material, and the other covers the implant from the bottom, contacting the lower layer of the frame material. The layers are merged with each other in a flat, multilayered inset placed between the welded elements, and the electrically resistant layer has electrical connections for connecting a source of electrical current.