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Walter Foster has utilised a 400-ton AP and T press with associated pressure dome to press sheet metal parts with complicated geometry, fine surfaces and narrow tolerances through hydroforming.

Walter Forster, situated outside of Hamburg, manufactures metal parts in series ranging from one part to one million.

The company has several important customers in the medical-technical industry, where they manufacture very short series from 100 to 500 parts per year.

In these series, narrow tolerances and a high degree of surface fineness are important parameters.

With the new equipment from APandT, the company will be able to take on more assignments that it previously had to turn down.

Walter Forster decided to acquire a hydroforming press with pressure dome as a means of expanding its service offering and to be able to develop the pressure dome and forming technology.

Volker Rohrbeck, assistant to the technical management team at Walter Foster, said: ‘We will be able to manufacture small series of complex parts in just a few production steps.

‘We will also save money on tool manufacturing and be able to attract new customers.’ The principle of hydroforming with pressure dome is that a punch presses in the sheet blank in a fluid-filled chamber – the pressure dome.

The liquid is at an extremely high pressure – up to 900 bar.

The blank is then pressed against the punch with uniform force and forms itself to it.

Since it is liquid that presses the blank against the punch, the part acquires an extremely fine, scratch-free surface.

It also makes it possible to meet extremely narrow tolerances.

Since the punch is the forming tool, tool cost is low compared to other forming methods.

Since the liquid presses against the punch at right angles, it is possible to form parts that cannot be formed in conventional drawing operations in which press force only has one direction.

If the pressure dome is the heart of the process, then the associated HMU unit is its brain.

It is here that the counter-pressure in the dome’s liquid is generated and regulated.

It is even possible to pre-charge the pressure for optimal cycle times.

In AP and T’s solution, the liquid used is water with an infusion of lubricant.

Water is less pliable than oil and is therefore better suited to forming than oil.

It is also environmentally friendly since the pressed part is easier to wash and the need to handle large quantities of oil is eliminated.

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