by increasing the coupling, or using two turns in series (electrically) on rivets are driven at once by the action of the press. This can be obtained by using more power, or time, Hot efficiently. wrenches. manually held against the locating pin. In some situations, coaxial leads may be necessary (450 kHz and To correctly machine a part, it must be held in a fixturing setup that guarantees through the clamping dies after the welding current is applied. machines may be used for delicate assembly operations. Machine screws usually are inserted into tapped holes, but of the proper washer in each assembly and prevent the loss of washers during The properties of the inductor should be kept as close as possible without touching. to material thickness and clinch allowance. welds are required. to drive the fasteners. off any dirt or oxides. Promote heat dissipation from the weld line. A heat barrier of As is the case with most joining processes, good tooling and fixtures cannot These machines are available to perform: These machines vary in sizes from small bench to large floor models. 51, a bushing, bracket, and shell are joined together with a ring-staking throat of the welding machine. assembly work. T-bolts are square-headed bolts machining centers, except that the cutting tables do not normally contain The coil need only be formed to surround the weld joints and properly place the weld in the location. 6, determine the proper weld backing bars for the weld joints in (6.4 mm) and greater can be tolerated. Studs are cylindrical rods It should be noted that, in some cases, the filler metal may wet and flow increasing its temperature. are inserted prior to the operation. No contact is needed with the workpiece to create a welded assembly (FIG. needed to operate industrial lasers and the damaging characteristics of the Excessive pressure in driving is produced. The flow of alternating FIG. must be made regarding frequency, power density, heating time, and inductor suitable machining allowance or post-heat treatment must be considered. The means of distinguishing (0.8-mm) length clinch easily when struck by the contoured riveting tool. However, the design should take into consideration the Often, several parts may be joined mechanically and welding done out of the fixture. .5-1.5 kW/in.^2 (279-837 kJ/cm^2 ) of surface area. clearance for cutting media below the piece-part. The fixtures for this process must provide support, alignment, FIG. The tooling must hold the work pieces in correct relationship during joining, The leads to the inductor should be kept as short as possible and close Other means of locating include solder at a predetermined rate (FIG. This is more prevalent with to the coil axially instead of radially (FIG. The intensity of the magnetic field in which In practice, it would be necessary to Large diameters may be heated efficiently with low frequency. even in part, should be minimized as best as possible to limit the amount and fixture components can be used. may be machined to match the part. The sticks are loaded manually Backup bars may irregularly shaped sections where efficiency is not too important, gaps of Eighth Edition. .25 in. 28. A dye in as preheating and post-weld heat treating. nonmetals. 1. flow of current, is related only to the frequency: D = depth, in. Bear in mind that stationary parts of the fix ture and work are affected FIG. design should al low sufficient room between the worktable and focusing optic and the solidifying weld metal provides the path of least resistance. The tooling material must be stable at the intended process temperatures. 42. Power density and heating time are closely related to the design of the It is said that an imperfect fixture is required to make a perfect part. (b) cap screw; (c) stud. At times, mechanical joining may be considered as the tooling method heating obtained with conventional electric heaters. Many workpieces can be held for Closed-circuit TV is used to monitor the operation. as illustrated in FIG. The design also permits making welds in a horizontal position. work. pins and sheet holders (FIG. kW/in.^2(558 kJ/cm^2 ) is recommended. Simple parts may be properly located or positioned in a fixture visually. The process must account for the differences in the coefficients of thermal Simple nesting fixture with work in place. There should be no problem with electrical matching to the proper power source. 39 shows the sequence of a punching and riveting operation used in gas welding. a riveting die fixture. emitted light to the eye and skin, great care must be taken when performing The shanks of cap screws are not fully threaded to their heads. These cross-supports are held in position by a square or Tip area is a function of the workpiece material This necessitates tack welding the fixtured parts at V-blocks, adjustable clamps, rest buttons and pads, spring plungers, and Cap screws are manufactured to close dimensional 49 illustrates the parts and clinching dies of the retaining-ring assembly. utilized optical scanners that followed a paper template or digital tape Typical types of distortion occurring during welding. They are available with Conventional methods of adhesive curing include convection This process will produce a better weld for to minimize heat loss while providing sufficient support and locating points. foil seam, magnetic force, percussion, friction, thermo-pres sure, diffusion and that excessive driving pressure is avoided. the deformation pressure. or-for ID heating-be adjacent to the surface to be heated. Heat-activated (Class IB) and film adhesives (Class V) require heat to DVDs, Fixture Design (19 minutes) also relates directly to this section's 24. [joules]) may be required. prevent rapid heat dissipation from the weld area. 6. These machines deliver materials to be welded, the fixturing, or other weld-related processing such good fixture welds. 5. The total power required will depend on the above value and kilowatts or assembly to a required depth to provide a brazed joint. (cooler underlying metal) and heat flow by conduction. of the small focused laser beam diameter. For 400 F solder, convert to kilowatt seconds by multiplying by 100. The hole may have been drilled in both pieces prior to mating. rivet, holding a bucking bar against the end of the rivet, then cycling fixtures are constructed to support the material to be cut, allowing for Partial nest-type workholding fixture for assembly of a cabinet. hole in the components, into which a screw is to be inserted. Tooling may be required to hold parts in correct relationship to one another After hardening, the contour must be highly polished. Typical assemblies using threaded fasteners: (a) bolt and nut; FIG. FIG. Delayed-tack adhesives (Class IV) are heat activated to produce a tackiness Soldering filler metals melt below 842 F (450 C) and 30) or round mandrel. This gap or loop is an intense magnetic field, within which (4.8 mm) in diameter. As shown in FIG. operations: oxy flame, plasma-arc, and laser. They are made with slotted, recessed, or wrenching heads in various head Stamped nuts are made with integral Backing bars with provisions for (a) directed gas flow, (b) diffused Figure A. FIG. Materials Park, OH: American FIG. The turns can be held tightly on the surface or wound 43. Another function of tooling is to assist and control The complexity of an assembly joined in this manner is limited by the number caused by welding brings the parts into the correct relationship to each maintenance. The shape may be flat (reflecting the contour of positioned between electrodes that exert heavy pressure, conduct the current, to permit use of an internal induction-heating coil. The welding-electrode tip size directly affects the size carrying the current, or from separate insulated connections to a water supply. 46 provides examples of staple nomenclature. To accomplish this, large fixture masses should not be placed close to the 3. induction brazing may require significant tooling/fixture design and development. One of the simplest fixtures for gas welding is the gravity type shown in The flat clinch is formed by an upward movement of the clinching die, folding The factors of coil design essentially are the same 24). instance, hand soldering often requires no special tooling at all, while content. in the hole, and torque a nut onto the bolt. such as ceramic, stainless steels, and titanium, which are not as easily metals. FIG. Mechanical joining ordinarily does not involve changes in composition a flat bearing surface. nuts usually are limited to light duty and special assemblies. of a large transport plane. The peening and spinning C-clamps hold the workpieces to steel support bars. 1983-1997. If the shape of the workpiece will not support itself in an upright or convenient bolts are usually square (as sheared). arms or knees containing electrodes and the base of the machine that houses placed in a standard hydraulic or mechanical press. mirror. ferrous metal and hinder stud removal. on the lower anvil. heat is developed entirely from the resistance effect of the current. the surface finds itself should be as uniform as possible. Adjustment should be provided for electrode wear. a definite location, or position, with respect to a part's datum points or The number of inductors used at one time is, of course, influenced by production Both rivets and eyelets are available commercially in .03-in. (resistance is high). The material to be cut is placed on water tables. Welds expand during the welding process and then contract during cooling. standardization efforts have made most threaded fasteners interchangeable. or nibs on some screws increase locking action and minimize thread stripout. in the invisible, infrared region. of surface area to volume. The washer is placed on the For thick material, use (.25-2.00 in. but also in many cases, either accelerate or retard the flow of heat. Some fixturing is used on plasma-arc and oxy-flame machining centers. This design eliminates excess fixture material from the weld area FIG. The following procedure is recommended (using (mm). the number of turns in an inductor. in the flame path of a fixed torch while a feed mechanism introduces wire FIG. are sometimes used with nuts. Pneumatic hammers (rivet Fitting-up bolts have A significant CTE mismatch between the fixture and the workpiece may lead aircraft sections while thousands of holes are pierced and rivets driven. are tightened by turning their mating nuts. for soft solder and epoxies to 2,100 F (1,149 C) for cop per. workpiece. FIG. FIG. If a single-turn inductor is Welding electrodes should be easily and quickly replaceable. rivets should be 50-70% of the shank diameter to prevent buckling and ensure They produce mating threads in wood or other resilient of the filler metal. gas metal-arc welding (GMAW) (also known as metal inert-gas-shielded arc Magnetic flux in induction heating. lower end of the feed track locates the rivet directly above the pin locator. Tapping screws are Threaded fasteners are used for a wide variety of applications, and the enable tailoring the weld by adding filler material to match the desired Estimate the surface area of the joint. The workpiece to it. by riveting include stationary, portable, and self-contained (riveting die or accelerating the cure. The adhesive would penetrate the bar serves to provide shielding to the backside of the weld and pull affect the clinch diameter. and cooling techniques. of an automatic eyelet-setting machine in loading and clinching positions. 36). 53. Inductor formed on a rectangular mandrel. lead to weld cracking since the residual stresses want to relieve themselves For light) or infrared radiation (wavelengths longer than visible light) to create the screw threads closely, with no clearances necessary. Because of their basic design, it is possible Workpiece with simple fixturing for arc welding operations. the pressure increases to 5,000 lbf/in.^2 (34.5 MPa) for the rivet upsetting Captive screws remain attached to panels extends beyond the combined thickness of the assembly before the rivet or highly polished. transformer, the primary being the inductor that generally surrounds the (Type D was formerly prevent their movement due to alternate heating and cooling. but distort after removal from the fixture. not needed and access is required from only one side. the many types of rivets commonly used. If a fix ture acts as a chill for one part of the joint, this may result For thin sheets (up to .250 in. if a welding positioner is used. to create the strongest possible bond. into the pores of the wood for some distance, and the work piece edges would in load-carrying applications, especially when disassembly and reassembly punch. MI: Society of Manufacturing Engineers. For motor generators, iron laminations are used. to this moisture, tooling must be made of non-rusting material. or solid copper that has been drilled out or machined to provide water passages. may result in: bulging of the edge of the piece being riveted; buckling or other distortion, particularly if thin material is used; and/or. Use of mechanical force for these on one side of the assembly. in their holes. position, a simple nesting fixture may be required. during the cutting operation. The strips are wound together and metals or the process atmosphere unfavorably. the addition of a magnetic material in the throat increases impedance and If a corner of a workpiece overheats, Major fixture design objectives, some basic and others special, include: holding the part in the required position for the welding process; providing proper heat control of the weld zone; providing suitable clamping to reduce distortion; providing channels and outlets for welding atmosphere; providing access for the welding process; providing for ease of operation, including part loading and unloading; the workpiece so the holes are conveniently positioned, and it should support types of welding. by capillary action. Other popular joining techniques include ultrasonic, high-frequency resistance, material is added, with the edges losing their identity in a homogeneous Thus, two workpieces may be bolted together to ensure alignment during subsequent material with laser processing, lower thermally induced stresses (low distortion) inserted. whereas the motor-generator sets (1-10 kHz) can operate into either multi-turn FIG. a suitable mandrel. Positive location is desirable as the shape of the workpiece becomes complex of the surfaces to be joined must be considered as well as the properties Some common shapes are shown in FIG. a joint on or near its end. Sequence of punching and riveting operations. Then they are placed into staplers. styles and with spaced (course) inch or metric threads. Standard types of electrode face or nose shapes. Plural components (Class 1A) can cure at room temperature, but heating in creased life, the design must provide sufficient strength with adequate is no need for other operations such as punching or drilling prior to fastening. For many applications, concern. be made of copper, stainless steel (used for tungsten inert gas), titanium, FIG. job. are illustrated in FIG. FIG. with prongs formed to engage mating threads. to be assembled. high-current transformer; (3) primary coils; (4) tap switch; (5) welding From the Fundamentals of Tool Design video series, which comprises nine Workholding examines the principles and concepts inherent to all workholding. applications could induce unwanted strains and deformations. components. can be adjacent to the work for more uniform heating. They are usually the transformer. Combined spot and ring-staking punch. necks on the shanks below the heads to prevent the fasteners from rotating adjustment, or improper fuel-gas selection. Joining processes generally fall into two classes: physical and mechanical. The flux also covers and protects the area by shielding Automation typically locates the anticipated Clinch allowance is the space caused by the part of a rivet or eyelet that For 1,600 F brazing material, convert to kilowatt seconds by multiplying Because laser energy is delivered to the workpiece without mechanical force, Use all heavier material. flux must be taken into consideration). surfaces through the application of heat or pressure, or both. For 2,000 F brazing material, convert to kilowatt seconds by multiplying an inductor formed on a square (FIG. FIG. or not. The riveting process is extremely varied-it may be This power loss may sometimes be used to advantage, however. The fixture design principles are the same as described previously. This method has several limitations, that are high enough, possess adequate hot strength, and not react with base The principal advantage of adhesive bonding is improved just to locate the parts in relationship to each other; the welder can find wide inductor can be made of .25 x 1.00 in. cap screws are available for applications having head clearance problems. as is the selection of frequency, power density, and heating time. The depth, D, increases with temperature. The heat is conducted into the adhesive, initiating required. The assembled parts are placed in location in the riveting die, and all edge of one member to flow either inward or outward around the other parts. usually is obtained by introducing a flux that cleans, dissolves, and floats 13 illustrates the principle of indirect welding, which is ordinarily As each notch for heating such an area is shown in FIG. Underhead serrations expansion (CTE) of tooling and fixtures relative to that of the parts being Pressure-sensitive adhesives (Class VI), just as the name implies, include Temperatures can range from a few hundred degrees characteristics. the kilowatt rating of the equipment by the surface area of each part in accidental defocusing of the laser beam. Nesting fixture for brazing with an external inductor. methods for high- and low-volume parts; machining center workholding; and to a stationary-type rivet unit or machine. 47 illustrates the In manual welding, it is sufficient For high-quantity production It also is used heat out of the weld. FIG. Protect the root of the weld from the atmosphere. Power lost by unintentional heating of fixture die. Rivet diameters vary from .015-5.000 in. FIG. The purpose of the inductor is to set up a magnetic flux pattern inverted and another 10 screws are driven to fasten the other shield. FIG. and machining centers and lathes. 38 shows a hydraulic riveting yoke.). A simple backup part tolerance is required for weld joint gap and vertical mismatch because forces, with some setscrews providing additional resistance to rotation by A solid-type inductor is preferred because of its greater rigidity. 31. The optimal joint clearance is by tape control or CNC. temperature variation and excessive parts abuse during baking. weld. The fixture also must establish the exact height 39 illustrated the sequence of operations. beneath the driver and the machine is cycled to insert and drive one screw. rectangular container into which the drop-outs fall. If the leads are not a continuation or part of the inductor and a brazed This spot- and ring-staking punch (FIG. of Computer-Aided Manufacturing. fasteners. Inductor with C-shaped laminations added. workpiece together while inserting the bolt and adding and tightening the (NC) and computer-numerically controlled (CNC) machines. Each process will require individual variations to the general Clamping pressure should not deform the The inductor design is integral to the success of any induction-heating workpiece. Workholders or fixtures used to hold and locate workpieces being assembled Coils can be attached by studs (preferably If the external coil Resistance welding is self-holding and locating, but it requires two parallel Keep all magnetic materials, particularly ferrous materials, out of the illustrates the elements of a resistance-welding machine. When there are large changes in diameter in the section to be heated, the 28. the same as ring staking except that three or more equally spaced chisel workpiece acting as a secondary. riveting (both produce similar outcomes) as it does not require drilling Certain design considerations apply to fixtures for resistance welding. 15. Regardless of the material used in the induction-brazing process, the inductor be no wider than the bore diameter; for greater coverage, multi turn inductors Assembly showing series-welded joint. 4. welding [MIG]), to create greater depths of penetration. bonding material to flow. passage of large amounts of electric current and applied pressure. Small stationary machines have a spring-loaded pin locator in the rivet 9 used where the welding current must pass through the side or ends of parts

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