Volumes of production

Slumping is the kind of process that is as well suited to one-offs as it is to batch production.

Unit price vs. capital investment

Most commercially available molds are made of either vitreous clay or stainless steel, but it is also possible to use plaster, cement, or even found objects for low-volume production. Depending on the complexity of the shape, the process can involve a high failure rate of finished pieces and, therefore, high unit costs.

Speed

Although this is an industrial process, the speed of forming is quite slow and still requires a considerable use of manual labor.

Surface

Completely smooth glass surfaces can be achieved, as well as textures that can be incorporated into the mold.

Types/complexity of shape

This process works on gravity, so it is possible to achieve any shape that is formed from a flat sheet and has a vertical drape.

Scale

Restricted only by the dimensions of the glass sheet and the kiln that provides the heat.

Tolerances

Due to the difficulty of making glass slump into tight corners, coupled with the expansion of the glass, it can be difficult to achieve tight tolerances.

Relevant materials

Most types of sheet glass (including borosilicate), soda-lime glass, and advanced materials such as fused quartz and glass ceramic.

Typical products

Domestic products such as bowls, plates, magazine racks, tables, chairs, and tableware. Industrial applications include automotive windscreens, lighting reflectors, furnaces, fireplace windows.

Similar methods

Draping glass over a mold, rather than into a mold, is also a valid process, and is sometimes just called “draping.”

Sustainability issues

Working with glass is always extremely energy intensive as high temperatures need to be sustained in order to keep it in a workable state. In addition, the shaping is done by hand so faults can often occur. Any rejects from errors or breakage can be recycled back into the process through melting, which requires further heating.

Further information

www.fiamitalia.it

www.rayotek.com

www.sunglass.it

Electromagnetic Steel Forming

Electromagnetic pulses in manufacture may seem very complex, but this new use of an existing technology is likely to revolutionize the production of large steel parts for the automotive industry.

At present, large steel sheets are cut using a metal stamping process in which a heavy mold presses the sheet into a die shape. However, this has a number of drawbacks including the enormous size of the machinery and the poor quality of the cutting edge, which is very jagged and requires a secondary finishing process often done by hand. For these reasons electromagnetic-pulse forming is revered as the next big contender in steel forming: it offers improvements in both areas and reduces costs and lead time.

If you try to make two magnets touch, you either feel them attract, or you turn them around and you feel a force that physically pushes them away from each other. This manufacturing process simply amplifies this latter force, using a much greater and carefully directed amount of magnetism by means of a coil, an electrical current, and a steel sheet. A capacitor (the container holding the electrical current) discharges the current rapidly through the coil where it is converted into a powerful magnetic field. The pressure of this magnetic field hits a steel sheet placed near the coil and the opposing forces between the sheet and the current in the coil is so strong that it causes the metal to deform. Energy is directed and concentrated so that very precise and refined punches are made into the steel sheet without any physical contact. The impact pressure is said to be the equivalent of three small cars pressing on an area about the size of a fingernail.

The use of electromagnetic pulses is not new—in the past they were used in warfare to disable telecommunications. More recently the technology has been used for small-scale tube forming. To apply it to large sheets of steel, scientists simply altered the machines for tube forming by boosting the coil and the rate at which the charge could be converted. Researchers are working on developing coils that will cut specific shapes and geometries.

–  A very clean and refined punch is achieved, so secondary finishing processes are eliminated.

–  The process could eliminate the need for molds or dies and, in turn, reduce costs significantly.

–  The risk of operators being injured is reduced in comparison to stamping.

–  The process is still in development so it could be a while before it is commercially viable.

–  Energy consumption is likely to be very high because of the high pressures required.