Pressing sheet metal parts with complicated geometry, fine surfaces and narrow tolerances is usually a complicated process requiring expensive tools. That is, unless you use hydroforming with pressure dome. German metal former Walter Förster discovered the potential of this relatively simple method of making the impossible possible and therefore purchased a 400-ton AP&T press with associated pressure dome.
Walter Förster, 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 AP&T, the company will be able to take on more assignments that it previously had to turn down.
Sees great potential
“We didn’t have any concrete customer orders when we decided to purchase
the equipment, but I’m not worried. When our customers learn of our new
expanded capacity, we will have much more to do,” says Walter Förster’s
Volker Rohrbeck, assistent to the technical management team.
Small series more efficiently
Walter Förster 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.
“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,” says Volker Rohrbeck.
Fluid and mechanics working together
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.
Reduces tool cost
Since the punch is the forming tool, tool cost is extremely 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.
“The impossible becomes possible and with tool cost just a fraction of what
it used to be, a world of extremely cost-effective, small series
manufacturing of parts with complicated geometry opens up,” says Magnus
Svenningsson, AP&T’s key account manager for Walter Förster.
Best for both form and the environment
If the pressure dome is the heart of the process, then the associated HMU
unit is its brain. It is here that the counterpressure in the dome’s liquid
is generated and regulated. It is even possible to precharge the pressure
for optimal cycle times. AP&T’s solution is unique since 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, which is used in other
pressure dome designs on the market. It is also environmentally friendly
since the pressed part is easier to wash and the need to handle large
quantities of oil is eliminated.
Good experiences with AP&T
Back in 2001, Walter Förster purchased a hydraulic press from AP&T.
Even then, they were interested in hydroforming with pressure dome. Over
the years, they have been very pleased with their AP&T press and the
service and support provided by AP&T. During this time, they evaluated
other forming methods, such as standard hydroforming, and decided that it
was too costly for the applications in question. Despite this, it was a
challenge to order the equipment.
“For us, hydroforming with pressure dome was completely new technology.
But, we trusted AP&T and now know that we made the right
decision.”
“We will support the technology Walter Förster invested in an will also
support development of the forming method in the future,” says Michael
Hunger, AP&T sales manager for the German market.
“Our biggest problem in this context is that AP&T is punctual with its
deliveries but we haven't managed to completely set up the premises where
the equipment will be installed,” concludes Volker Rohrbeck.
