hp tooling 2020 #1

machining center
Entering a demanding market niche
HSC milling: highly productive, high-volume
production for surgical instruments
Surgical instruments are high-precision
products that are manufactured with great care,
usually in small quantities. The structures and
equipment of manufacturers specializing in these
products are therefore designed above all for a
high level of flexibility in retooling.
A separate process chain should accordingly be set up for
one-time products in large quantities. The key element is a
two-spindle machine from Schwäbische Werkzeugmaschinen
GmbH (SW) with very high repeat accuracy. An assess -
ment report.
“The requirements are high and the competition is hard
in manufacturing of precision mechanical surgical instruments,”
confirms Frank Pauschert, Regional Sales Manager
of SW, Schwäbische Werkzeugmaschinen GmbH in Waldmössingen,
Germany. His customers include a company
in this sector that has grown from modest beginnings
when it was founded in the 1980s to become a mid-sized
enterprise, with about 130 employees. Currently about
1,000 different utensils are manufactured for a wide range
of surgical applications. All instruments come complete
and ready for use. The individual parts are made of premium
biocompatible materials such as stainless steel and
are manufactured in machining processes. Despite the use
of modern NC-controlled machine tools, manual operations
make up a great deal of the manufacturing process
for these instruments, because they consist of up to 40 different
components that must be refined, surface-treated
and assembled meticulously by hand. In addition, they are
often manufactured with numerous variants. This necessitates
small batch sizes and because of that, a prime requirement
of the relevant manufacturing systems is very
flexible retooling. Due to the extraordinary diversity of
variants, there is also no way to work from stock, thereby
lowering costs by manufacturing in larger batches.
Strategy for the future:
a challenging one-time product
Since the manufacturer has not previously produced any
of its own products, it is constantly compared with the
numerous competitor products already available in terms
of price by customers, who often have great market power.
This limits profitability and with it future growth possibilities.
To safeguard the future in the long-term, a decision
was made about two years ago to enter an extremely challenging
large-scale production project: manufacturing of
a one-time tool for neurosurgery that is used so often that
hundreds of thousands of units are needed annually.
It is a type of forceps made of aluminum that can be
used to grasp tissue components while at the same time
stopping minor bleeding with electrical pulses. Minute
tubes were also integrated into each arm of the forceps
through which an irrigation fluid can be directed into the
operat ing area. Despite its straightforward appearance, the
instrument requires very time-consuming manufacturing
with numerous mechanical and manual work cycles,
all of which must meet strict quality requirements. Many
of these work cycles have to be carried out under a microscope.
Setting up the process chain requires extensive
devel opment efforts as well as investments in machines
and special equipment. Additional employees are currently
being hired and qualified for this purpose.
A machining center with the power
of a sports car
The starting point and key element of the process chain is
an automated dual-spindle BA 321 machining center from
SW. The system has a working area of 300 x 500 x 375 mm
per spindle. The spindles are equipped with an HSK A63
interface and reach speeds of up to 17,500 rpm with a chipto-chip
time of 2.5 s. The tool change system has a capacity
of from 2 x 20 to maximum 2 x 60 slots.
The automation unit consists of a supply unit for the press-drawn
sections and a drawer for depositing parts after they are separated
source: SW GmbH
This system is used to mill forceps halves made of aluminum.
It has a custom-made automation unit for supplying
material and removing milled parts. It is only intended
for a limited range of parts, but within that range
achieves productivity far beyond any other milling centers
in the plant. With its horizontal, dual-spindle design,
the new machining center delivers two completely milled
48 no. 1, 2020, March