EuroWire September 2017

70 / 100

Technical article
September 2017 68
New stretch-bend-levelling
line for very thin copper
strips is energy efficient
and operates with minimal
tolerances
By Volker Lüdecke, Burghardt + Schmidt GmbH, Remchingen, Germany
Flatness requirements for metal strips
have increased steadily in recent years.
At the same time there is a trend –
particularly in the electronics industry
– towards increasingly thinner materials.
Here, quality improvements through
stretch-bend-levelling facilitate further
processing considerably. As a result,
for example, dimensional accuracy is
increased in the stamping process and
thinner surface coatings can be achieved.
Hence, the cutting and levelling machine
specialist Burghardt + Schmidt GmbH
(B+S) developed an innovative solution
for the levelling of extremely thin copper
strips for a Chinese manufacturer. The line
is suited for all alloys of the material as
well as for phosphor bronze, and allows
strips just 30µm thick to be processed with
minimal tolerances. Depending on the
starting material, flatnesses down to one
I-unit can be achieved.
The client in China manufactures parts
for the electronics industry that need to
satisfy exacting requirements with regard
to surface quality as well as flatness
or dimensional accuracy. In this case,
extremely thin metal strips are used.
At a plant to be redesigned, these are to be
prepared for further processing. The aim of
the new purchase was to keep the shape
tolerance within tight limits during the
stamping process. This is vitally important
in regard to the automated assembly of
electronic components. Besides flatness,
the client also defined exclusion criteria
relating to the surface quality. This means
that the optical density of the end product
should not be changed through the
processing.
“Given the clearly recognisable trend
for ever thinner strips, the B+S lines
constantly reach their control limits. Due
to customer requirements as well as the
results of corresponding market analyses,
we have therefore pressed ahead with
basic developments for some time. These
generally allow the levelling of metal
strips that are just 20µm thick,” said Volker
Lüdecke, technical manager at B+S.
The concept presented and the company’s
extensive experience in stretch-bend-
levelling were ultimately the decisive
factors in winning the contract from China.
Cassette with 8mm
levelling rollers
For the build-up of tension, the line has
four rollers on the braking side, ie, in front
of the levelling machine. Around these
rollers runs the metal strip. Together
with the decoiler, they generate the back
▲ ▲ Since the old lines noticeably reached their control limits when it comes to the processing of very thin materials,
Burghardt + Schmidt has developed a new stretch-bend-levelling line. This allows the levelling of copper strips with
thicknesses of as little as 20µm and the achievement of evennesses down to one I-unit, depending on the starting
flatness
All photographs courtesy of Burghardt + Schmidt GmbH