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Taking the fastener out of fastening.

There is a quiet revolution that has been going on for some time in fastening. It has taken the riveting, hammering, pressing, peening, rolling, welding, and coldheading out of a host of joining operations for products ranging from miniature electronic assemblies to 1 1/2" solid steel stock.

It's called orbital headforming by process developer Taumel Assembly Systems, which some years ago had also developed another joining method, the orbital riveting process, to replace the centuries-old method of heading rivets by impact. Taumel chose to sell the orbital riveting patent, which is characterized by a rosette pattern traced by the tool and point peening contact with the workpiece. The company pursued development of the orbital headforming technology, which has since grown into a major manufacturing fastening and assembly technique.

The variety of products that can be joined or finished with the orbital headformeer range from the fragile and miniature to heavy and large. In fact, Taumel's Orbital Headforming equipment and tooling has been used to swage and seal the end of a D-sized battery casing or flare out a 3" dia aluminum tube and do it on the same machine. In onee field application, a Taumel orbital headformer has been used to thermo-mechanically form tenons on turbine rotors in a reblading operation service offered by IMO Industries Deltex Service Div, Houston, which replaced hand peening of an inductively heated component.

The one requisite for using orbital headforming is that the forming and joining material be malleable. The Taumel Orbital Headforming machines can flare, flange, join and swage, as well as assemble pins, studs, shafts, axles, and hubs. They can work on just about any malleable material and will not fracture delicate parts made from ceramics, phenolics, glass, or carbon.

How the process works

Orbital headforming depends on constant line contact of a forming tool, under pressure, with a malleable material that is formed into a traditional head shape or into a formed edge required to accept an enclosure or cap. The Taumel system employs an orbital head (chuck) to hold a forming tool at a constant angle. The tool orbits the workpiece like the sweep of a radar screen but does not spin.

As the tool follows its orbital path with its long axis parallel to the wall of an imaginary inverted cone, the tip of the tool presses on the workpiece on a radial line emanating from its center. With all the pressure applied on this line, a flowing were of material is formed ahead of the orbiting tool to produce the desired shape.

The material has time to flow properly because only a minute quantity is displaced during each revolution and, as friction is minimal, no tearing of the workpiece occurs. The result is a clean, polished, non-porous surfacee on the formed material with no measurable changee in molecular structure.

The Taumel Orbital Headforming process relies on precisely controlled dwell-times and tool force (pressure) to obtain formed rivet heads and other shapes. Electric motors drive the orbital movement of the toolholder noiselessly, and pressure for head forming is generated by either air or hydraulic cylinders. Pressures range from zero to 32,000 lb in the largest of its 24 machines. Machine selection depends on the material and the total surface area of the part to be formed.

The Taumel system allows precision control so that any required degree of tension or resistance can be built into joints as they are formed. Because pressure and dwell-time are precisely adjustable, join performance can be carefully controlled. When firm immovable joints are required, high pressure is used to expand the shank of the rivet to fill the bore while the head is being formed. When smoothly operating sliding or swinging joints are needed, the rivet heads must be formed without deforming the shaft. Low pressure with slightly longer dwell-times are used to form heads and allow the shafts to retain their shape for unimpeded movement within the bore. Even very thin gage stock can be processed in this way.

Tooling and combinations

Standard tools are used to form the most common types of heads, including taper heads, button heads, and flat heads in all malleable materials of all diameters and sections, including square, hexagonal, and rectangular stock. Other tools are available to form hollow that heads, hollow bead heads, conical heads, externally closed heads and caulked heads. Custom tools can be manufactured for special applications such as fastening in confined spaces or in deep recesses beneath an obstruction.

Fixturing is minimal with only the simplest fixturing needed to ensure that workpieces are correctly positioned. The vibration-free, non-spinning motion of the tool puts smoothly sustained pressure on the workpiece, so that expensive, bulky jigs and time-consuming clamping are not normally required. Superior rivet heads are claimed to be formed with only one-tenth the force of an impact press, for example.

When a number of operations need to be performed simultaneously, multi-spindle orbital heads can handle many different fixtures--all of different heights (or even recessed in cavities)--during one machinee cycle. This allows the user to complete, in one step, a single part which requires multiple operations or alternatively process a number of separate parts at the same time. Tools of different lengths can be combined on the same plate and can be placed on centers as close as 3/16" to each other. The largest machine can support a tooling plate that is 20" across.

For more complex assembly systems such as those needed to form many different parts in sequence or for high production control of a number of workstations, automatic dial feed systems and CNC automated control of dwell-times and heading pressures are available. Modular units that will operate in any position--vertically, horizontally, at any angle, and even upside down--mounted as opposing pairs for simultaneous headforming both ends of a shaft or mounted on special frames for deep-recess forming applications, such as working on 40-ft trailer construction.

For more information on Taumell orbital headforming, circle 289.

Sheet metal joined sans fasteners

A production process for joining metals that uses a combination of drawing and forming techniques that is easy on the surface finish of the joing material is promising to solve some environmental problems associated with spot welding, according to developer, TOX Corp, Addison, IL.

Called TOX, the system is compatible in connecting almost any type of sheet metal, including sandwiched layers or varying thickness layers separated by foil or paper. The TOX system can replace spot welding, riveting, bolting, self-piercing fasteners, and brazing in many applications. It doesn't produce sharp edges and burrs, which are susceptible to rust, and does not mar painted metal surfaces.

An appliance manufacturer has replaced spot welding of uncoated, coldrolled steel with TOX and eliminated the need to go through expensive degreasing stages prior to painting the finished housings. The washing machine manufacturer is using pre-painted sheet metal that is first cut to length and then fed through a roll forming machine. After punching and forming, the parts pass through five TOX stations, and the housings are joined by 11 TOX guns with 88 TOX joints.

Benefits of the TOX joining system include producing a joint with extremely high shear and pull strengths, with outstanding fatigue strength under dynamic loads with minimal notch effect, and with increased material joint strength in cold forming. Because burrs and chips are eliminated, a leakproof joint that will not damage is formed. Even galvanized reinforcements can be joined to pre-painted housings.

As a result, the washing machine manufacturer was able to eliminate its entire degreasing and painting lines, eliminate handling of solvents and chemicals as well as the costs of containing toxic fumes related to spot welding, and lower the cost per joint to about one-third of the cost of spot welding.

The recently introduced TOX Handgun, Model CHH-04, is a portable version of the sheet metal joining system. The TOX Handgun utilizes a pneumo-hydraulic TOX booster as the power source that operates on shop air and boosts the pressure over an internal, self-contained oil system. The output force is controlled by means of a pressure switch connected to the oil system. When the required force is reached, the switch sends a signal to the directional valve to retract the tools. This particular TOX Handgun delivers up to four tons of force with 90 psi supply air pressure.

Typical applications include appliances, heating ducts, and automotive. The process is particularly applicable to manufacturers using prepainted sheet metal due to strict emission requirements recently imposed by the Federal EPA.

For more information on the TOX process, circle 290.
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Copyright 1992 Gale, Cengage Learning. All rights reserved.

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Title Annotation:orbital headforming
Publication:Tooling & Production
Date:Sep 1, 1992
Previous Article:Flexible gaging for flexible manufacturing.
Next Article:CAD/CAM software boosts CNC productivity.

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