Abstract: An apparatus and method are provided for surface treating the inside surfaces of hollow or three dimensional plastic objects. While the invention will be described with respect to plastic objects, it will be understood that other objects having a high dielectric strength, such as ceramics, cardboard, paper and wood, may be similarly treated. The surface treating is effected by selectively directing a high voltage plasma field to a selected interior surface of the object to enhance adhesion of various glues, inks and the like. The plasma field is generated in the interior of a tunnel directed into an opening of the hollow portion of the object to be treated. A specially designed electrode is supported from the opening to direct in a controlled manner the field to the selected interior area of the object to be treated. The electrode is supported from a high dielectric shield covering a central area of the opening to direct the plasma field around the shield to a laterally extending electrode below the shield.

Abstract: A mat of reinforcement material, such as glass fiber reinforcement material, is manufactured by forming a layer of continuous strand or chopped fibers on a conveyor belt and conveying the layer along a defined path. At a location downstream of the application of the layer, the layer of fibers is coated with a binder in the range of 2.0-10.0 weight percent, either a microwave-sensitive binder or an ultraviolet-sensitive, binder and the binder-coated layer is fed into a radiation tunnel which includes a compression stage and a curing stage. In this radiation tunnel, the binder-coated layer is compressed to a desired density-thickness ratio and cured, the compression and curing occurring in stages, and the resulting mat is taken from the conveyor belt and wound up for storage.

Abstract: A system and method for constructing a three-dimensional object (10) from a design created on a CAD machine (14) is disclosed which includes a support (B) which may be indexed along two coordinate axes (X, Y) and a movable dispensing head (A) which indexes along a Z-axis. A fluent material (54) is dispensed or extruded from head (A) and as it is dispensed, the fluent material is subjected to a treatment by treatment sources (D) which cause the fluent material to transform into a fixed solidified state in the form of a three-dimensional object. Fluent material (54) may be a polymeric material which is solidified by an energy beam of ultraviolet light (56) upon dispensing. A shield (E) is provided to shield the dispensing head (A) and strand of material (54) so that the material is treated at the proper time and location to cause it to solidify properly to form the three-dimensional object. In accordance with the method, indexing takes place in desired steps so a dimensionally accurate object is formed.

Abstract: An apparatus for high frequency molding plastic material using a mold made of a conventional material for applying this technique, e.g. a silicone elastomer or like material. The mold is kept locked shut while the shaped plastic material is cooling by the effect of a pressure reduction set up inside the mold after the high frequency electric field has been applied.

Abstract: A molding device a molding machine with both fixed and movable side molds and which has cavities for molding a product. An injection cylinder injects resin into the cavities and a mold driving control performs the opening and closing operations of the molds. During the molding cycle, the cavities are heated by a high frequency heating system consisting of a coil, oscillation control section for inducing high frequency oscillation to the coil during the opening of the mold and stopping the high frequency oscillation during the closing of the molds. A mold temperature detector having a temperature sensor measures the temperatures of the molds and a temperature control initiates the circulating of a cooling medium within a circulating pathway which is provided within the molds.

Abstract: An apparatus and a method for correcting for drift in production of objects by stereolithography is disclosed. A beam sensor comprising a pinhole in a plate and a photodector behind the pinhole is used to obtain the apparent position of the beam at calibration time and subsequently. A comparison between the prior and present apparent position of the sensor is made in order to determine a drift error correction term to be used to compensate for drift and thereby improve the accuracy and pointing repeatability of the scanning mechanism.

Abstract: A method and apparatus for selectively sintering a layer of powder to produce a part comprising a plurality of sintered layers. The apparatus includes a computer controlling a laser to direct the laser energy onto the powder to produce a sintered mass. The computer either determines or is programmed with the boundaries of the desired cross-sectional regions of the part. For each cross-section, the aim of the laser beam is scanned over a layer of powder and the beam is switched on to sinter only the powder within the boundaries of the cross-section. Powder is applied and successive layers sintered until a completed part is formed. Preferably, the powder is deposited to the target area of the laser and attains high bulk density during sintering.

Abstract: Apparatus for the manufacture of individual small lenses, which may have gradient indices of refraction. The apparatus includes a pedestal having a conduit therein and an end surface the perimeter of which may be circular or elliptical. The perimeter is defined by a sharp edge. The pedestal is supported with the end surface horizontal and facing downwards. The intersection of the conduit and the surface, also defined by a sharp edge, forms an orifice through which at least one of the liquid monomers for forming the lens is fed. Gradient index small lenses are formed by suspending a first monomer from the horizontal end surface of the pedestal and then, via the orifice, introducing the second monomer at a rate which equals the rate of inter-diffusion of the second monomer into the first monomer. Alternatively, both monomers are both fed, in mixed condition, through the orifice in continuously varying proportions. The monomer(s) are cured in the pendant condition.

Abstract: A system responsive to coordinate information for automatically providing a three-dimensional physical model of a desired geometry and comprising apparatus for selectably solidifying a solidifiable material on a sequential layer by layer basis characterized in that following selectable solidification of a given layer, the non-solidified portions thereof are removed and replaced by a removable support material which is not solidifiable under the same conditions as the solidifiable material.

Abstract: A method and apparatus for selectively depositing a layer of material from a gas phase to produce a part comprising a plurality of deposited layers. The apparatus includes a computer controlling a directed energy beam, such as a laser, to direct the laser energy into a chamber substantially containing the gas phase to preferably produce photodecomposition or thermal decomposition of the gas phase and selectively deposit material within the boundaries of the desired cross-sectional regions of the part. For each cross section, the aim of the laser beam is scanned over a target area and the beam is switched on to deposit material within the boundaries of the cross-section. Each subsequent layer is joined to the immediately preceding layer to produce a part comprising a plurality of joined layers. In an alternate embodiment of the present invention, a gas phase is condensed on a surface and a laser beam is used to selectively evaporate, transform, activate or decompose material in each layer.

Abstract: An integral three-dimensional object is formed from a photohardenable liquid composition containing radiation deflecting matter.

Abstract: A three-dimensional object formed from a photohardenable composition containing deflecting matter of core-shell polymers. A preferred material for the polymeric core is crosslinked to an extent to be nonswellable and insoluble in solvent for noncrosslinked polymer material while the shell polymer has no pendant acid groups.

Abstract: A plurality of holders, each capable of holding a rod of raw material, and a single handler are equipped within a chamber which is adapted to be evacuated. An operator positions one of the holders at a location where it is opposite to a rotary shaft capable of driving the rod of raw material for rotation at a high speed. The operator then secures the rod held by the holder to the free end of the rotary shaft by handling the holder. A rod of raw material which has become consumed by granulation is separated from the rotary shaft by the handler which is operated by the operator. A fresh holder is then positioned at a location where it is opposite to the rotary shaft, and a rod of raw material which is held thereby is then secured to the rotary shaft.

Abstract: A method and apparatus for manufacturing one phase of a silica crucible including controlling the filling of a hollow mold of cylindrical shape, which rotates about its vertical axis, with grains of crystallized quartz. The grains of material are continuously introduced into the mold and are deposited on or near the lateral wall face of the mold in the form of a cylindrical layer, E, of internal radius R. A beam of light is directed to form a luminous spot on the summit of the layer from the commencement of its formation and the radial displacement of the spot on the layer is observed. The height at which the grains are introduced and the height of the trajectory of the luminous beam are modified as a function of the position of the luminous spot relative to determined reference points.

Abstract: A method and apparatus for selectively sintering a layer of powder to produce a part comprising a plurality of sintered layers. The apparatus includes a computer controlling a laser to direct the laser energy onto the powder to produce a sintered mass. The computer either determines or is programmed with the boundaries of the desired cross-sectional regions of the part. For each cross-section, the aim of the laser beam is scanned over a layer of powder and the beam is switched on to sinter only the powder within the boundaries of the cross-section. Powder is applied and successive layers sintered until a completed part is formed. Preferably, the powder comprises a plurality of materials having different dissociation or bonding temperatures. The powder preferably comprises blended or coated materials.

Abstract: An improved stereolithographic process is provided in which the formation of a thin walled three-dimensional object in a reservoir of liquid ultraviolet-curable ethylenically unsaturated material using a support is positioned immediately beneath the upper surface of the liquid reservoir with that upper surface being exposed to ultraviolet light in a pattern to solidify the liquid at and near the upper surface in a series of cross-sections of the desired three-dimensional object, one atop the other. In this way there is formed a series of superposed layers which adhere to one another to build the desired three-dimensional object within the liquid reservoir. The improvement comprises, stopping the exposure at any portion of the surface in the formation of said layers and then repeating the exposure at least once again in the production of each surface layer so that the strength and solvent resistance of the formed object are increased and its distortion is minimized.

Abstract: An improved stereolithographic system which produces a three-dimensional object from a heat curable fluid medium which is capable of solidification when subjected to heat includes a computer-aided design controller, a container, an elevator platform and a first servo mechanism which incrementally drives the elevator platform in response to the output signals. The improved stereolithographic system also includes an elongated carrier which is movably coupled to the container, a second servo mechanism which incrementally drives the elongated carrier along the two side walls of the container in response to the output signals, a plurality of spot-sources of heat and a switching network. Each spot-source of heat may be individually switched on and is serially disposed on and fixedly coupled to the bottom surface of the elongated carrier on the bottom surface adjacent to the designated working surface. The switching network individually switches on each spot-source of heat in response to each set of output signals.

Abstract: An apparatus for roll forming of thermoplastic material is provided which employs a pair of rollers having forming surfaces thereon, the pair of rollers defining a gap through which the thermoplastic material is to be passed during the forming operation, the thermoplastic material being dielectrically heated to a softening temperature as it passes between the rollers by a radio frequency electromagnetic field produced between the rollers by activating a radio frequency generator or oscillator which is electrically connected to one of the rollers, the rollers each having conductive portions between which the electromagnetic field is produced.

Abstract: A method and apparatus for selectively sintering a layer of powder to produce a part comprising a plurality of sintered layers. The apparatus includes a computer controlling a laser to direct the laser energy onto the powder to produce a sintered mass. The computer either determines or is programmed with the boundaries of the desired cross-sectional regions of the part. For each cross-section, the aim of the laser beam is scanned over a layer of powder and the beam is switched on to sinter only the powder within the boundaries of the cross-section. Powder is applied and successive layers sintered until a completed part is formed. Preferably, the powder is deposited to the target area of the laser and attains high bulk density during sintering.

Abstract: Forming an optical fiber so as to have a relatively constant bend loss characteristic includes apparatus for continuously bending the optical fiber downstream from a preform from which it is drawn and continuously detecting light withdrawn from the fiber at the bend so created to determine the fiber bend loss characteristic, the fiber bend loss characteristic being maintained constant by using feedback control to vary a drawing speed of the fiber and hence a diameter of a core of the fiber.

Abstract: The irradiation apparatus for the photopolymerization of plastic embedding masses for histological preparations has a preparation support located in a housing and a plurality of irradiation lamps, with one lamp above and one lamp below the preparation support forming one lamp pair. In order to cure photopolymerizable embedding masses in a manner that does not harm the embedded preparations or specimens, and in particular to avoid an abrupt rise in the reaction heat, and so that a small number of irradiation lamps is sufficient, the preparation support is a rotary support plate having a plurality of light pervious preparation holding means located about its outer circumference, and the lamps are positioned such that in operation, the holding means sequentially pass in between the lamps of each lamp pair, and the centers of the holding means are located on a circle that is concentric with the axis of rotation of the support plate.

Abstract: A method of molding a polymeric containing article by exposing the article to ultraviolet radiation and a substantially uniform pressure. The method includes placing the precursor article within a pressure vessel and substantially filling the vessel with a solid, flowable, polymer medium that is substantially ultraviolet transparent under pressure. The polymer medium is pressurized so as to produce a substantially, uniform predetermined pressure on the surface of the article and the article is exposed to ultraviolet radiation that passes through the polymer medium to cure the article. Alternatively, the polymeric article may be passed through the medium containing vessel during exposure to ultraviolet radiation and a substantially uniform pressure.

Abstract: An improved method of forming three-dimensional objects comprises irradiating an uncured photopolymer by emitting an effective amount of photopolymer solidifying radiation directly into a desired area inside of uncured photopolymer using an immersed radiation guide. The radiation is emitted through a material which leaves the irradiated surface capable of further cross-linking so that when an adjacent area is irradiated, it will adhere thereto. Repeating the irradiation for all areas in desired sequence, any three-dimensional object can be made; depending on the size of the emitted beam and the amount of emitted energy, objects can be formed point by point, post by post, area by area or layer by layer.

Abstract: An automated system is provided for selectively separating resin pellets having a gel count below a specified maximum from pellets having a gel count above the specified maximum, while the pellets are flowing in a pneumatic conveyor. The separation is based on an essentially continuous measurement in which a laser beam is utilized to detect the number of gels in a film made from pellets withdrawn as a sample stream from the main pellet stream. In response to the gel count measurement, a control signal is established that is utilized to manipulate a diverter valve located in the pneumatic conveyor, which diverts pastic pellet flow between a preferred storage means storing pellets having a low gel count and a secondary storage means for storing pellets having a higher gel count.

Abstract: A process and apparatus for producing plastic-bound propellant powders and explosives in crystalline form, with the apparatus including an extruder comprising a casing with a feed opening, optionally a solvent supply opening and one or two extruder shafts with kneading and conveying segments. For processing the plastic binders, which polymerize photochemically or under X-rays, a casing section transparent for the rays is provided, with polymerization within the extruder being initiated by UV/VIS or X-radiation sources arranged around it and the radiation intensity and/or the wavelength of the radiation are controlled as a function of the pressure difference over a given path in a compression zone of the extruder, in such a manner that the propellant or explosive strand or strands leave the extruder in a dimensionally stable and cuttable manner.

Abstract: A process for the manufacture of shaped bodies from silicon granulates for producing silicon melts includes first incipiently melting silicon grains on their surfaces, so that they bond with their neighbors in the process and, after solidifying, form a porous compound shaped body which only then may be melted completely. Such compound shaped bodies can be manufactured continuously or semi-continuously and converted without difficulty by a subsequent step into the molten state. An apparatus for producing shaped bodies is also provided which preferably employs an electron beam, to supply energy to incipiently melt the granulate.

Abstract: There are disclosed an apparatus and method of forming magnetic recording media having surfaces thereof replicated while being in the process of being cured.

Abstract: A process for producing a surface-embossed, deep-drawn article suitable for an interior finish or lining of a motor vehicle, for example, starts with a partially-crystalline polymeric material, i.e., one having crystallites, in film form. The film-form material is heated to a temperature below the melting point of its crystallites an surface embossed. The embossed material is then cooled and crosslinked. The crosslinking is preferably done by irradiating the cooled material with a high-energy beam such as an accelerated electron beam, for example. The cooled and crosslinked material is then reheated, this time to a temperature above the melting point of its crystallites, and deep drawn into the shape of the article.

Abstract: Bulk production of carbon fibers by a spinning process incorporating the exposure of the fibers to a level of electron plasma to achieve the curing to carbonization stage as desired. Fibers are also broken into shorter lengths for particular uses.

Abstract: A press apparatus for magnetic injection molding machines in which only the portion of a movable table in close contact with a lower metal mold is made ferromagnetic material and the other portion of the movable table is made of non-magnetic material, thereby fully utilizing the magnetic flux generated by magnetic coils with high efficiency and reducing the magnetic resistance of the magnetic circuit.

Abstract: A device for orienting magnetic particles contained in a magnetic layer on a disc-shaped magnetic recording medium along the circumference of the recording medium. The magnetic layer is provided on a substrate. The orientation is effected by a magnetic field developed by a pair of permanent magnets and which the recording medium traverses during rotation. The permanent magnets are individually shaped flat and arranged to oppose each other at their pole-faces which are common in polarity. A trailing edge of each magnet located with respect to relative movement of the rotating recording medium extends and aligns with the radius of the recording medium.

Abstract: A system for generating three-dimensional objects by creating a cross-sectional pattern of the object to be formed at a selected surface of a fluid medium capable of altering its physical state in response to appropriate synergistic stimulation by impinging radiation, particle bombardment or chemical reaction, successive adjacent laminae, representing corresponding successive adjacent cross-sections of the object, being automatically formed and integrated together to provide a step-wise laminar buildup of the desired object, whereby a three-dimensional object is formed and drawn from a substantially planar surface of the fluid medium during the forming process.

Abstract: A corona treater includes an active electrode which has one or more insulated electrode elements slidably supported by an insulating track. A contact spring connects each electrode element to a conductive electrode bar embedded in the track, and sheet material to be treated is fed through a treatment zone created between an active discharge surface on each electrode element and a bare metal roller electrode.

Abstract: The invention concerns a method and an apparatus for manufacturing a contact lens, through molding within water-tight molds. The polymerization of lenses is insured by arranging a number of molds within one or several sealed metallic chambers (9) constituting a resonant cavity of a unique mode for an ultra high frequency wave; these molds are positioned in an area of the cavity where the electromagnetic field approximately of ultra high frequency waves is homogeneous, and are distributed so that the amounts of basic composition to be polymerized act as a load fitted to the inside of said cavity.

Abstract: The end face of an optical fiber is urged against the highly polished surface of a disk as a laser beam is directed toward the disk to heat the end face above its softening temperature and cause it to conform to the contour and finish of the highly polished surface. A termination ferrule may be simultaneously mounted on the fiber optic cable with a heat bonding agent, using as a heat source either the laser beam or an auxiliary heat source. A hand-held, gun-type unit with a built-in disk and triggered laser can be used to polish and terminate optical fibers in the field.

Abstract: A centrifugal pelletizer has a hollow electrically and thermally conductive rotor with a series of orifices along its outer rim portion for centrifugally powering strands of heated thermoplastic material from a body of said material in a flowable state within the interior of the rotor. A knife mounted on the frame adjacent the rotor orifices severs the strands into pellets of a predetermined length. A molten material feed tube with fins therein at the exit end to divide the flow extends into a rotor housing to direct flow in a uniform manner to an axially opposite impeller on the rotor and control mechanism, sensitive to the temperature of the rotor adjacent the orifices, controls the supply of current to electromagnets, which have a peripheral magnetic flux conducting plate system extending to and forming a part of the housing creating a flux field which is interrupted by the spinning rotor to induce currents in the rotor which heat it according to the temperature sensed.

Abstract: Apparatus and method for curing sheet rubber by radiation of microwave energy. The sheet rubber is wrapped around a metal cylinder forming a roll with a layer or liner of microwave transparent material separating the adjacent rubber layers. The ends of the roll are shielded from microwave energy by metal disks which support the cylinder. The disks sit between rollers of a roller conveyor which is activated to provide the result of rotating the roll for uniform heating in a microwave field.

Abstract: A method of and a device for high-precision moulding of transparent objects is described. Before the object assumes its final shape, a radiation beam is passed through the moulds of a moulding device and the material contained therein, and the intensity distribution of the radiation spot formed by the beam is compared with a reference, thereby enabling the moulds to be aligned very accurately, so that high-quality products can be manufactured.

Abstract: This relates to the heating of polyethylene terephthalate by way of RF energy. It has been found that if polyethylene terephthalate articles are passed through a radio frequency energy field, the molecules thereof will become excited and rapid heating will result. This heating is particularly useful in the heating of preforms prior to the blow molding thereof and by varying the configuration and relationship of electrodes, controlled heating of the preforms may be effected with it being possible to have a controlled temperature differential along the length of the preform or other article so heated.

Abstract: Particleboard is manufactured by scattering an endless mat of chip and binder material on a series of overlapped mat carriers 17 moving on a forming conveyor 2 beneath a scattering station 1. A cut-off saw 5 is then used to separate the endless mat into mat sections 18 each of which is mounted on a respective mat carrier 17. The overlap between the mat carriers is eliminated and the laden mat carriers are removed from the forming conveyor 2 by an accelerating conveyor 6 which simultaneously operates as an intermediate store and a feed unit for a single storey press 8 arranged immediately after the accelerating conveyor 6. The accelerating conveyor 6 introduces the laden mat carrier into the inlet to the press from where it is transported into the press by internal transport devices of the press. After the mat section has been pressed to form a particleboard a pair of driven rollers 9 extract the mat carrier from the press and feed it towards a separating wedge 10.

Abstract: A uniform thin replica film of a specimen for electron microscopy having a high resolution power such as approximately 1 A is presented. This uniform thin replica film is directly prepared on the specimen by a plasma polymerization technique by depositing organic monomer vapors on a specimen placed on a negative electrode in a high vacuum atmosphere. The deposition is carried out by applying a discharge voltage of from 0.5 to 3 K.V.D.C. between a pair of positive and negative electrodes for 1 to 15 minutes to effect a glow discharge under the conditions of a current density of the glow discharge of from 0.1 and 2 mA/cm.sup.2 and a gas pressure of from 1 to 10.sup.-2 Torr in the system.

Abstract: This device comprises an applicator in which the micro-waves are generated. Inside this applicator is disposed a tubular enclosure, preferably coaxial, made from a material inert to the micro-waves which is connected to means for generating a relative vacuum or treatment gas atmosphere. This enclosure is sealed and comprises means allowing the objects to be treated to enter therein or leave therefrom while ensuring the continuity of the seal.

Abstract: High-purity metal powder is made by the electron beam melting of a starting material in rod form in a vacuum wherein the molten metal is momentarily caught on a spinning plate rotating at high speed and flung therefrom and thereafter solidified by cooling. The metal on the spinning plate is bombarded with an electron beam that is so focused and periodically deflected that its focal spot is many times smaller than the diameter of the spinning plate. The beam deflection between the rotational center of the spinning plate and its marginal area is performed such that the spinning plate is scanned in a zone that extends radially of the axis of rotation of the spinning plate and is small in relation to its diameter. Cooling of the metal particles to the point of solidification is accomplished by radiation loss.

Abstract: A method and apparatus for substantially instantaneous liquid molding of an article utilizing a radiation curable liquid composition and a forming mold transparent to the through passage of radiation so that radiation curing of the liquid composition is effected during the molding thereof.

Abstract: A three-dimensional flow molding process and associated molding apparatus for making plastic parts or pieces utilizing a radio frequency heating field and means for applying constant pressure, along with an even temperature gradient, to the plastic part. In the process two metallic mold halves are joined clamping therebetween an imprinted diaphragm having the plastic on one side thereof between the diaphragm and one of the mold halves. In one version which may be preferred in constructing planar (two-dimensional) pieces or parts, pressure is applied directly by closing the mold halves and the diaphragm has a constant thickness therealong to provide even heating of the plastic that is being molded. In another version of the invention preferably for molding three-dimensional parts, a liquid conductor, such as mercury, or a sodium or graphite solution extends about the other side of the diaphragm in a space provided in one of the mold halves.

Abstract: The invention is a process for manufacturing an irradiation cross-linked molded article by utilization of molding apparatus wherein at least a portion of the molding apparatus is separable and capable of withstanding irradiation.

Abstract: Particleboard made from particles in the form of chips or fibers or the like is made by distributing a mass of chip material onto an endless belt conveyer system. The mass of material is subsequently passed to a precompressor, a high frequency preheating device, a further press and a finishing press. The unheated further press serves to reduce the thickness of the material to substantially that of the finished board prior to its consolidation by temperature and pressure in the finishing press. A further endless belt contacts the surface of the material and runs through the precompressor, the high frequency heating device and the further press and serves to counteract any tendency of the chip material to expand after leaving the precompressor. This endless belt additionally yields a number of other significant advantages, in particular a reduction of loss of heat from the material prior to reaching the finishing press.

Abstract: Method and apparatus for producing small hollow spheres of glass, metal or plastic, wherein the sphere material is mixed with or contains as part of the composition a blowing agent which decomposes at high temperature (T.gtoreq.600.degree. C.). As the temperature is quickly raised, the blowing agent decomposes and the resulting gas expands from within, thus forming a hollow sphere of controllable thickness. The thus produced hollow spheres (20 to 10.sup.3 .mu.m) have a variety of application, and are particularly useful in the fabrication of targets for laser implosion such as neutron sources, laser fusion physics studies, and laser initiated fusion power plants.

Abstract: An integral blow-moulding machine heats and extrudes plastic parisons having variable wall thicknesses directly between the opened half moulds of a continuously rotating ferris wheel type blow moulder. The parisons are severed and thereupon grasped by hydraulically closed half moulds. An electric discharge device is adapted to softening part or all of the parison during extrusion. Air injection is performed using a conventional extensible injection needle. After blowing the half moulds are hydraulically opened while the blown object is held by pneumatic grippers. During the extraction procedure the flash is removed from top and bottom of the blow moulded object by hydraulically operated means.

Abstract: Apparatus for use with a pair of thermoplastic strips of the type illustrated in U.S. Pat. No. 3,608,177 wherein one strip is formed with studs longitudinally spaced at intervals and a second strip apertured and counterbored at the same intervals is used to bind sheets apertured at the same intervals at locations spaced inward from one marginal edge is described. A pressure bar is first manually moved to operative position and a handle compresses the strips together by exerting a controlled force on the pressure bar. The handle then initiates movement of a support for a knife consisting of a length of metallic ribbon material having spaced horizontal stretches in horizontal alignment with excess stud lengths of the first strip projecting through the second strip, the ribbon being under tension to hold such stretches taut. As the support moves toward the studs a current is passed through the ribbon, heating it so that the ribbon functions to cut off the excess stud length slightly below the second strip.