Have you ever looked in a jewelry store window and wondered at the patience
of the goldsmiths responsible for crafting gold chains? Every link perfect,
thousands of links in all sizes and patterns, right down to the finest sub-millimeter
gauge of wire. As you might have suspected, handmade chain is now the realm of
the custom jeweler. Most chains today are made by machine. And the true
craft is in the design and manufacture of the machine that will make perfect
chain from precious metal all day, every day.
Such a machine, or rather range of machines, is designed and built by Sisma.
Based in the community of Schio in northern Italy, close to the traditional
Italian goldsmithing center of Vicenza, Sisma design and manufacture a
comprehensive range of machines for the production of precious metal chains of
all descriptions. The privately held company is about to celebrate 40 prosperous
years of operation.
Whatever your fascination with machines, there is something rather special
about a machine that can tie knots. When you consider the complexity of the
chains that Sisma machines can produce – every link perfect and made at
blinding speed, this equipment is right up there with the best of them.
Most of Sisma’s jewelry machines make a variety of different types of chain
from gold and silver wire. The smallest wire gauge used is 0.12 mm (less than a
hairs’ breadth) which is an incredibly thin piece of gold wire used to make
the very finest gold chain. Other machines such as the diamond ice lathe and pin
and link form/fixers, provide automated and semi-automated finishing operations
for manufacturing jewelry around the world.
Sisma manufactures more than 30 different kinds of jewelry machines from its
factory and ships over 800 machines every year. All machines are designed
entirely with CADKEY. To perform consistently and reliably at high production
rates these machines are built to very high precision. Computer-aided design and
manufacturing was introduced at Sisma in 1986. CADKEY has been the principal CAD
system in use since 1993.
Sisma design uses CADKEY to design machine parts and
assemblies.
Over 300 instruments are used to check and monitor the precision and
operation of machines during and after manufacture. The management and
calibration of the measuring instruments alone is a significant role in the
success of the business. The heart and soul of a chain-making machine are the
jaws that grip and manipulate the wire and the cams that actuate the movements.
The hardened steel jaws are precision cut with EDM machines. The EDM tools are
made on high precision Swiss CNC equipment installed specifically for this
purpose. The cams are precision ground on a multi-pallet Hauser CNC grinder (see
movie). VisiCAM is used to create tool paths from CADKEY drawings.
High-speed milling of cams for Sisma machines.
There are 80 PCs throughout the organization and while only a few are
involved in design activities, all are networked and have access to the custom
in-house QA system that is fundamental to the business.
Networked PCs have online access to the company’s 25,000+ CADKEY drawings.
Each PC is equipped with CADKEY viewer to access drawings to check details and
produce hardcopy output if required. The company employs 120 people (40 in
production) and more than 30 sub-contractors. Staff development is a high
priority within Sisma, with up to 8% of work-time spent on on-going staff
training. Says technical director Arfeo Canaglia, "It is very important
that everyone is doing the same thing and using the same tools". A high
importance is also put on understanding the operations and needs of other
departments, such as, marketing, design, production
and service. This also makes up a good proportion of the training
time.
The 12-person Sisma design department creates new machine designs and is also
responsible for prototype construction. Both 3D and 2D documents are used in the
design process. Machine design time can be as little as 200 hours or as many as
7000 hours. An important reason for using 3D is fast, accurate access to mass, centre of gravity
and other derived engineering data essential for balancing machine components for high
speed and high performance operation.
All electrical and electronic design is conducted in-house. Out-sourced
subcontractors complete the specialized electronic component development and
production using OrCAD and ECAD software.
Traditional-style 2D annotated drawings are still a vital part of the company
information store. They are used in manufacturing and are the only way that
surface finishes and tolerances can be communicated to the production people.
Perhaps surprisingly, no kinematic or FEA design tools are used in Sisma’s
design office. I say perhaps because I got the feeling that the Sisma team know
these machines inside out. I suspect that they could easily design a high-speed
precision machine with a burnt stick and a sheet of butcher’s paper! But
seriously, it goes to illustrate that at Sisma, figuring the complexities of
each machine and its workings is the domain of real people. CAD is used as an
aid to tedious calculation and as a documentation system that integrates very
well with the company’s internal communication and quality assurance system.
In addition to jewelry machines, Sisma has also begun to design and
manufacture large flat-bed knitting machines.
Unocad's Ivano Ambrosini and Sisma t
echnical director Arfeo Canaglia
inspect the precision bed of a
Sisma knitting machine. Unocad is the Italian distributor of CADKEY and
maintains a close relationship with Sisma.
Knitting machines now account for
15% of Sisma’s business and this share continues to grow. Knitting machines
are also very complex and require precision manufacturing for a reliable and
high performance working life. This area of design and manufacture complements
the machinery business and draws on Sisma’s strengths of high quality,
high precision machine manufacturing.
