Volumes of production
Still in its developmental stage, PulshapingTM, like conventional pultrusion (see p.99), is potentially a high-volume production process.
Unit price vs. capital investment
PulshapingTM is a fairly costly process and is not suited to small production runs. Economic quantities are in excess of 6,500 linear feet.
Speed
Typically 1½–3 feet per minute for the continuous pultrusion part of the process, plus an additional 1–3 minutes for reshaping cycles.
Surface
As in pultrusion, the surface finish can be controlled to a slight degree of variation, depending on the reinforcement and polymer. Due to the ability of the process to allow manipulation of form along the cross-section surface, features such as dimples and projections can be designed into the product in the reshaped segment.
Types/complexity of shape
This process is highly versatile because of its ability to produce a variety of cross-sectional shapes.
Scale
Ideally suited to long products, more than 6 feet.
Tolerances
Very fine tolerances.
Relevant materials
Thermosetting resins with glass, carbon, or aramid fiber.
Typical products
Components such as handles for large tools, which typically require the main body to be straight, with end features to be produced in separate processes, can be made in one go with PulshapingTM.
Similar methods
There is nothing really similar to this process in the sense that similar methods, such as extrusion (p.96) and pultrusion (p.99), do not allow for manipulation of the cross-section.
Sustainability issues
As with pultrusion, parts can be produced with thin wall-thicknesses as a result of fiber reinforcement, to minimize material use while optimizing strength. The combination of materials makes the composite nonrecyclable.
Further information
www.pultrusiondynamics.com
Roll Forming
Product |
Apple iMac aluminum stand |
Designer |
Apple Design Studio |
Materials |
aluminum |
Date |
2004 |
The aluminum stand for this iMac illustrates, in a discreet way, Apple’s achievement in exercising extremely tight control over the manufacturing of their products. The achievement here is in being able to bend such a thick piece of aluminum without any tearing of the material at its widest radius, which would normally be associated with this thickness of material at this scale.
Roll forming can be used to produce continuous lengths of anything from simple shapes in a single operation to quite complex profiles that require a number of passes through different rollers, from square sections to round shapes and from folded flanges to box sections.
In simple terms, roll forming involves passing a continuous sheet of metal, plastic, or even glass, over or through a series of at least two shaped rollers. Feeding the sheet in a straight line between the rollers forces the material to bend into the required profile. The bending occurs progressively over the series of rollers, in a process that may require up to about 25 different rollers, depending on the complexity of the profile. Roll forming can be achieved either as a cold forming process or with heat. In the case of glass, the sheet passes through the rollers as a molten ribbon.
1 A very crude setup, but this shows a flat strip of metal fed into rollers to be bent into a fairly shallow radius.
2 As the distance between rollers is closed for this second pass through the rollers, so a curve with a tighter radius is achieved.
– Flexible in terms of finished length.
– Limited to an unvariable thickness of material.
Volumes of production
High-volume mass-production.
Unit price vs. capital investment
Setup and tooling costs are high, which is why the process is suited to mass-production. It is, however, possible for small prototypes to be produced in a small workshop, depending on the complexity of the shape.
Speed
Production speeds are typically 1,000 to 2,000 feet per hour for a medium-sized manufacturer, depending on the complexity of the profile and the gauge of the material. Larger manufacturers can often go faster, but minimum quantities and lengths apply.
Surface
Other operations, such as punching and embossing, can be incorporated into the process to allow for surface details.
Types/complexity of shape
Long lengths of the same profile, which can be quite elaborate.
Scale
For mass-produced components the standard depth is approximately 4 inches, but it is possible to produce extremely large pieces, as demonstrated by the famous monumental curved steel structures by the artist Richard Serra. In theory, the only thing that dictates the length is the physical size of the manufacturing plant.
Tolerances
Vary between ± 1/500 and ± 1/25 inch, depending on the thickness of the sheet.
Relevant materials
Roll forming is almost exclusively used for forming metals, but it is also a useful process for glass and plastics, albeit on a much smaller scale.
Typical products
Automotive parts, architectural profiles, window and picture frames, and guides for sliding doors and curtain rods. In the case of glass, the process is employed to make U-shaped glass profiles that are used in architectural glazing.
Similar methods
For metalwork, similar methods include sheet-metal forming (p.50) and extrusion (p.96), both of which also provide long lengths of a profiled shape.
Sustainability issues
Roll forming is a straightforward heatless process that produces little waste material and has a fairly quick cycle rate that minimizes energy consumption. However, when using metals roll forming can in some cases cause microcracks and thinning, so sufficient testing should be carried out prior to production.
Further information
www.graphicmetal.com
www.crsauk.com
www.pma.org
www.britishmetalforming.com
www.steelsections.co.uk
www.corusgroup.com
Rotary Swaging AKA Radial Forming
with stationary-spindle and flat swaging
The original-diameter material is fed into a rotating steel die (1). This hammers the material into shape with a series of backers (2), which hit the rollers as the piece rotates. The hammering takes place when the backers pass over a series of rollers (3). Simple centrifugal forces allow the backers to recede from the die before once again being pushed forward as they pass over the rollers.
To explain this process in very simple terms, rotary swaging is used to alter the diameter of a range of metal tubing, rods, and wires. The process involves the original material being fed through a series of rotating steel dies, which form the material to the required profile (which is always symmetrical and round). As they are rotating, the dies perform a hammering action at a rate of up to approximately 1,000 hits per minute, basically battering the work piece into shape.
Other forms of rotary swaging include stationary-spindle swaging, which is used to form nonround parts. Flat swaging is used to reduce the overall thickness of sheet metal.
– A large range of symmetrical profiles can be formed.
– Because no metal is removed, the process is economical in its use of material.
– It is possible to achieve a fine degree of dimensional control of both the inside and outside surfaces.
– Working the material hardens it, thus increasing its strength.
– Rotary swaging is limited to forming round, symmetrical shapes (stationary-spindle swaging, however, can achieve nonround shapes, including squares and triangles).
– Reduction of diameter tends to be easier at the ends than at the middle of the tubing.