Journal - Trumpf GmbH + Co. KG

Kreisel processes about five tons
of Hardox steel each month.
8 TruServices Journal 02|08
Horst Meister, graduate engineer and general manager at Kreisel (left), and
Detlef Roitsch, production manager, know when hard steel will yield under pressure.
components. Of the 60 to 70 tons of steel that
Kreisel processes each month, five to ten percent
is Hardox material. When making up the
individual chambers for these feeders they are
bent into the trough-like shape in several
steps at a TrumaBend 320. Meister says: “It
was this machine that made it at all possible to
bend thicker plate — at up to 20 millimeters.”
Wear had become too
costly “Initially we used standard dies
to bend the Hardox plates. This process
does not, however, comply with the recommendations
published by the manufacturer
of the material. As a result, fissuring and
other blemishes appeared during bending.
And above all, the dies themselves showed
extreme wear,” reports Horst Meister. It
must be remembered that the offset yield
point is five times that of “normal” tool
steel. With the Hardox 450 material, for
example, this value is about 1,200 MPa at
guaranteed hardness range of from 425 to
475 HB. Maik Lehmann, who operates the
press brake at Kreisel, experiences this time
and time again. “The material is amazingly
springy. I have to bend ten or twelve degrees
beyond what is necessary for standard plate.”
All in all, the load exerted on the dies by the
high-strength steel was so great that they
had to be replaced after bending about 100
Hardox plates. Detlef Roitsch, production
manager at Kreisel: “Initially the number of
units we turned out were not high enough to
justify the special, roller-equipped dies recommended
by the sheet metal manufacturer.
But, demand for our wear-resistant versions
rose to the point that we ultimately had to
find a solution.”
Dies for maximum hardness
levels Those were found in the
VLM die made by TRUMPF, developed especially
for bending thick plate while it
is held in position. The user
of rotating, hardened rollers
reduces the press force
required, avoids impres-
In 2008, Kreisel was recognized
with the “Saxon environment
award” for the
development of ecofriendly
technologies.