Aerospace
Today, Avure is the leading fluid cell press supplier to the aerospace industry with more than 100 Flexform systems in operation at major aircraft manufacturers worldwide, including Airbus, Boeing, Bombardier, Cessna, Embraer, Alenia, British Aerospace, Aerospatial, EADS, China Aviation and Mitsubishi.
With the advent of metal airplanes after World War I, there grew an urgent need for an economical process to manufacture sheet metal parts. Mechanical stamping equipment required expensive, multi-piece tooling which could not be cost justified by the relatively small volume of airframe parts to be produced. The only other alternative was hand forming, a labor-intensive process that resulted in long lead times and inconsistent part quality.
In the late 1930s, the rubber pad forming technique was developed and subsequently adopted by a number of aircraft manufacturers. Instead of using two rigid tool halves to form a part, the upper tool was replaced with a soft rubber pad. Under sufficiently high pressure, the rubber would force a sheet metal blank to assume the shape of the lower tool surface. This concept offered the advantages of significantly lower tooling costs and improved surface finish. The process, however, had two basic limitations:
- Longer forming time than mechanical pressing. Each forming cycle required pressure buildup, which extended cycle time to several minutes.
- Insufficient pressure. Standard rubber pad equipment lacked the pressing force to form more complex parts or to achieve uniform pressure distribution over high tools. Higher tonnage models could not be cost-justified.
In the 1960s, ASEA in Sweden (now Avure) and other companies spearheaded the development of the fluid cell press. This design replaced the rubber pad with a thinner, more flexible rubber diaphragm, and a strongly reinforced press frame meant that significantly higher forming pressures could be attained at a capital cost similar to lower-pressure rubber pad presses. Beginning in the 1960s, major aerospace OEMs began to incorporate fluid cell pressing into their fabrication and assembly operations.
While some companies have retained their rubber pad presses for lower-pressure forming of simple shapes, most have adopted the advantages offered by Flexfoming: better part definition and more complex shapes due to the higher forming pressure, deeper more intricate shapes due to the flexibility of the diaphragm technology, and better productivity and capacity due to the larger forming trays that can accommodate more parts per cycle and larger parts. At high pressure, parts may also be formed to final shape in one forming operation, eliminating the need for downstream hand corrections.
