Volumes of production

From one piece to millions of pieces.

Unit price vs. capital investment

Investment costs of designing prototype productions and for manufacture are high. However, savings on materials, storage, and transportation, and the elimination of secondary fixing processes make the process cheaper overall.

Speed

Origami features are dependent on the available punch, laser, or stamping speeds. Folding is complete in seconds.

Surface

Not applicable.

Types/complexity of shape

Suitable for a range of thicknesses from 1/100 inch to the limit of any cutting equipment.

Tolerances

Alternative methods of forming in metal can produce stack-up errors related to maintaining dimensional tolerance. Industrial Origami maintains the level of accuracy of the machine that originally applied the lancing.

Relevant materials

The process has been predominantly used with sheet metals but it could be applied to any number of materials, including plastics and composites.

Typical products

Currently the main applications are for engendering components such as automotive chassis systems, solar mounting systems, packaging, cooktops, and built-in ovens.

Similar methods

Superforming aluminum (p.70), press forming (p.59).

Sustainability issues

The sheets are stamped in flat pieces so can be transported flat-packed and folded on arrival. This reduces the space needed during transportation, which could potentially allow for greater effectiveness of energy use. Additionally, there is a significant reduction in materials consumption as many joints and fixtures are incorporated into the fold design. As with any sheet-cutting process there is a high degree of waste materials; however these can potentially be recycled.

Further information

www.industrialorigami.com

Thermoforming

including vacuum, pressure, drape, and p lug-assisted forming

Product	chocolate-box tray
Materials	Plantic biodegradable polymer
Date	2005

There are few better examples of thermoforming than a chocolate-box tray. The individual shapes of the chocolates are evidence of the shape of the mold that is used to form the trays.

Thermoforming is one of the most common methods of producing plastic components and any art undergraduate will have used a vacuum-forming machine. Vacuum forming is one of the few plastic-forming methods that is as accessible to school and college students as it is to large-scale industrial production. It is also one the easiest methods of production to comprehend, and if you have ever seen the process in operation you will understand why.

The basic materials needed for this process are a thermoplastic sheet and a former. Because the pressures employed are low, the former can be made of wood, aluminum, or other inexpensive materials. The former is the exact shape of the part required and is placed at the center of a table, which can be raised and dropped. The rigid plastic sheet is heated under a series of convection bars similar to a domestic oven, until the plastic is soft, pliable, and saggy. At this point, the former is raised on its bed, pushing into the soft sheet, and a vacuum is applied. This sucks the air out from below and pulls the plastic onto the former. Once the plastic has “hugged” the former and cooled slightly, it can be removed for post finishing.

Other types of thermoforming include pressure forming, which works in the opposite way to vacuum forming by forcing the material into the mold. Drape forming, as the name suggests, consists of draping a sheet of heated plastic over a male mold, where it is mechanically stretched, allowing the sheet to remain close to its original thickness. Plug-assisted forming uses plugs to prestretch the plastic before the vacuum is introduced. Again, this allows for greater control over the material thickness.

1 The former (in this case a simple wooden shape for a college project) is placed on the bed.

2 Once the bed has been lowered, the plastic sheet is placed on top, ready to be clamped by the metal frame.

3 The heater is lowered onto the plastic sheet.

4 A vacuum is applied to form the shape.

–  Equally suitable for small or large production runs.

–  Low pressure, so tooling can be fairly cheap.

–  Suitable for in-mold decoration.

–  Multiple parts can be made using a single multi-former.

–  Requires a secondary process to trim the sheet.

–  No vertical sides on the finished part; draft angles are a must.

–  Can have undercuts, but these need special tooling.

Volumes of production

Suitable for model-makers’ prototype work and one-offs, but also for large-scale production.

Unit price vs. capital investment

Formers can be made from a range of materials, depending on the number of components that is required. The ease of machining and its wear resistance makes aluminum suitable for large production runs. Epoxy resins are used as a cheap alternative to aluminum, but anything can be used, including MDF, plaster, wood, and even modeling clay, which is excellent for vacuum-forming shapes with undercuts, because you can pick it out afterward.

Speed

Bathtubs can be made at a rate of one every five minutes. Beyond this, speed is difficult to estimate, because multi-mold formers can rapidly speed up the process, and, besides this, the thickness of the material affects the time it takes to heat up sufficiently.

Surface

Vacuum forming picks up surface details very well, so the surface finish of the mold is reflected in the surface finish on the part.

Types/complexity of shape

You will need draft angles, because undercuts are impossible to achieve with standard tooling.

Scale

A 6½ by 6½-foot aperture is standard, but it can be even bigger.

Tolerances

Varies, depending on size of the formed piece. As a guide, a forming of less than 6 inches will hold a tolerance of 1/70 inch.

Relevant materials

Most thermoplastics that are supplied as sheets. Typical examples include polystyrene, ABS (acrylonitrile butadiene styrene), acrylics, and polycarbonates.

Typical products

Canoes, bathtubs, packaging, furniture, interior car trim, and shower pans.

Similar methods

Superforming aluminum (p.70) and inflating metal (p.76).

Sustainability issues

The low pressure and moderate temperatures employed during processing, along with fast cycle times, ensure that energy consumption is low. However, additional processing is required to trim the excess material and this produces a significant amount of waste plastic. Further heat is needed for these scraps to be melted down and recycled. The nature of the shapes that are thermoformed means components can be nested during transportation, saving on bulk.

Further information

www.formech.com

www.thermoformingdivision.com

www.bpf.co.uk

www.rpc-group.com

Explosive Forming

AKA High-Energy-Rate Forming

Product	Desert Storm architectura l panels
Materials	coil-coated aluminum
Manufacturer	3D– Metal Forming BV
Country	The Netherlands
Date	1998

These architectural panels show the scale of panels and the complex patterns that can be achieved with explosive forming.

Can you imagine the fun in discovering this process? In a way it reminds me of the British TV-show character Mr. Bean, who decided to paint his living can of paint. However unlikely, explosive forming is actually an established method of forming metal sheet or tube. It is also another great example of a process that demonstrates the lateral thinking used by engineers to pursue new methods of making things.

The first use of explosive forming was documented in 1888, when it was employed in the forming of plate engravings. The First and Second World Wars provided an intense period of development, as a result of which explosive forming became a major process for manufacturing missile nose cones in the 1950s. Today, explosive forming exists in two forms —“standoff,” in which the explosive is positioned at a distance from the metal, either in the open air or submersed in water or oil, and “contact forming,” in which the explosive is in direct contact with the metal.

In simple terms, the sheet or tube is placed in a vacuum-sealed die cavity, which is in turn placed under water (unless it is the open-air method). A charge is placed over the sheet and detonated, sending shockwaves through the water and rapidly forcing the material into the die cavity.

Although this image does not show the close-up workings of the process, it does give some indication of the scale and the sealed, pressurized environment in which the explosive forming takes place.

–  It is possible to achieve precise tolerances.

–  Cost-effective tooling compared to alternatives.

–  Can reduce the number of operations in the manufacturing process, including welding, due to its ability to form complex parts.

–  Limited number of manufacturers.

–  Must adhere to strict safety regulations.