Volumes of production
High-volume production process.
Unit price vs. capital investment
Aluminum tooling can be very expensive but produces highly cost-effective unit parts.
Speed
The molding cycle times are typically 1 to 2 minutes, depending on the material.
Surface
The material can be colored and printed with surface patterns, and graphics can be molded into the surface. The surface is dependent on the density of the foam that you require, but all moldings will have the textured foam finish that is typical of this type of material. It is also possible to produce different color combinations within the same components, giving a mottled, multicolored effect.
Types/complexity of shape
Similar to the level of complexity that is possible with injection moldings (see p.196), but with thicker and chunkier walls.
Scale
Foam molding is a very versatile process that is capable of producing parts as small as 20 cubic millimeters up to blocks with a profile of around 3 by 6 feet.
Tolerances
Tolerances vary a little between materials, but in general it is possible to work to an accuracy of about 2 percent of the overall dimensions, with slightly higher figures for wall thicknesses.
Relevant materials
Expanded polystyrene (EPS), expanded polypropylene (EPP), and expanded polyethylene (EPE).
Typical products
Surfboards and bicycle helmets, packaging including fruit and vegetable trays, insulation blocks, head-impact protection in car headrests, bumper cores, and steering-column fillers, as well as acoustic dampening.
Similar methods
Injection molding (p.196) and reaction injection molding (RIM) (p.199).
Sustainability issues
The expansive behavior of the plastic beads reduces material use as the hollow foam structure is predominantly air. However, the extensive material preparation prior to molding is energy intensive because of heat and pressure requirements that are repeated during shape forming. The lightness in weight is beneficial during transportation of the part, but materials are not recyclable.
Further information
www.magisdesign.com
www.tuscarora.com
www.epsmolders.org
www.besto.nl
Foam Molding into Plywood Shell
Product |
chair from the Laleggera range |
Designer |
Riccardo Blumer |
Materials |
polyurethane foam and wood veneers |
Manufacturer |
Alias |
Country |
Italy |
Date |
1996 |
“Laleggera” can be literally translated as “the light one,” and this chair amply deserves this description. The new manufacturing technique that made it provides an interesting marriage of materials not commonly used together.
The constructional advantages and lightweight qualities of veneers were recognized by the makers of early aircraft, such as the Mosquito, and the structural use of thin veneers is nothing new in the manufacture of furniture. However, our interest in this engineered wood has now shifted to more innovative applications in furniture production.
The construction of one such example, the Laleggera chair (pictured), reveals a reverse type of tailoring. Starting with the thin veneers, the chair is constructed in the same way that a child might assemble a model kit, with a set of net shapes that are glued together at the edges, leaving a hollow shell with no structural integrity. To provide structural integrity, the shell is then injected with a polyurethane foam that, when cured, becomes rigid. This is an adaptation of the more conventional type of foam molding (see p.178), in which foam is injected through steam into an aluminum mold where it expands to form its own skin, and can then be removed from the mold.
The great feature of the Laleggera range of furniture and the process developed by Alias is that it takes two highly uncommon materials and methods and brings them together to produce a new functional and aesthetic feature for furniture that is disarmingly lightweight.
1 The frame for a table is formed from a two-part male and female press.
2 The formed components ready for assembly.
3 The structure of the table is made by gluing the formed components together.
4 Presses form the plywood around the table frame.
– The combination of materials creates strong but lightweight components.
– Trial and error required to achieve the full production setup.
– Limited production base.
Volumes of production
This is a unique form of production so there are no points of comparison, nevertheless the manufacturers state that more than 8,000 chairs were produced in 2005.
Unit price vs. capital investment
This information was not made available, though it is fair to assume that a certain degree of experimentation would have been required in order that the process be set up. However, the materials (a combination of cut sheet material and injected foam) could be experimented with, in a very low-tech, cost-effective manner.
Speed
Each chair requires four weeks to produce from start to finish.
Surface
The surface finish available with this type of production is totally dependent on the plywood rather than the foam core. The surface of plywood varies depending on which type of wood is selected.
Types/complexity of shape
The shapes are determined by the ability of the plywood to be cut and assembled into a hollow shell.
Scale
The table, which is the largest piece in this collection, measures 94½ by 47¼ by 28¾ inches.
Tolerances
Information not available, but it can be assumed that the tolerances are governed by the plywood and its ability to respond to injected foam.
Relevant materials
The chair uses a combination of plywood for the exterior structure and an internal structure of polyurethane foam.
Typical products
The unique nature of the process means that the only products manufactured are chairs and a table. However, there is no reason why the principle could not be extended to include other objects that require strength and lightweight properties.
Similar methods
This production method has been created by Alias in cooperation with the designer Riccardo Blumer. The manufacturers claim that there are no other production methods similar to this one. The nearest comparison contained in this book, though it produces a very different sort of product, is inflating wood (p.184).
Sustainability issues
The production process is heavily based on manual labor. The lightweight structure uses minimal materials with its thin veneer skin and air-filled foam. Any waste veneer can be recycled, while the injection of the polyurethane foam to fill the hollow structure creates no waste. The reduction in weight results in notable reductions in energy used during transportation.
Further information
www.aliasdesign.it