| Important Updates
phone number is:
Customized Machines with Software CNC
Medium-sized induction-hardening company relies exclusively on software CNC for
new machines and retrofits. Stemmermann GmbH in Radevormwald, Germany
specializes in the fields of induction heating and building inductors. Well-known
companies from the automotive, aerospace, tool and mechanical engineering industries
rely on the company’s know-how. The open software CNC from MDSI plays a
major role in the reliable delivery and quality of the mainly mass-produced parts.
In recent years, Stemmermann GmbH has used the enormous flexibility offered
by OpenCNC for the customized construction of several new machines, and
retrofitting the existing machines with the software CNC is also planned. Finally,
OpenCNC will control the complete networked machinery, thus ensuring better
With its specialist knowledge in the field of induction heating, Stemmermann GmbH
contributes to the general feeling of safety. The parts, which are mass-hardened,
must resist extreme stress, for example during rudder setting in an Airbus
airplane or in shock absorber piston rods. In addition, 18 employees produce
several million parts per year in two shifts. Since the start of production in
1974, the company, now managed by the second generation of the family, has
acquired extensive know how in processing sintered steel.
Everyday production is characterized by short-term, high volume orders which
are often collected on the same day. This requires considerable flexibility in
production planning as well as in use of the individual machines. In the year
2000, a full order book made the company think about expanding their manufacturing
capacity, but a borrowed test machine with controls from a well-known manufacturer
could not convince the team responsible at Stemmermann. "Our staff found the
controls particularly inconvenient to use", remembers managing director Dirk
Stemmermann. "The controls were also inflexible, awkward to program and the
operation was not clear for the workers."
"Due to its flexibility, OpenCNC allows the customizated
building of machines."
Solution For Old And New Machines
Thanks to retrofits with OpenCNC, even several older machines
reach a high level of productivity.
The open software CNC from MDSI seemed to be a suitable solution. OpenCNC
offered not only the required flexibility with respect to building new machines
but also the chance of increasing the performance of some older machines by up
to 20 percent with retrofits. The concept of an open-architecture software CNC
allowed the affordable building and customizing of new machines to the exact
production needs of Stemmermann GmbH. The use of standard PCs and other
standardized hardware components means that the company is largely
independent of any one controls supplier, especially in the long run.
"Previously, the mechanical life of our machines mostly outlived that of
the controls", explains Dirk Stemmermann. "So any repairs or spare
parts required for the controls soon incurred considerable costs."
Here the managing director saw one of the strengths of OpenCNC, as standard
components can be replaced relatively easily in the event of repairs or if
more powerful new hardware becomes available. And the software itself
can also increase machine productivity as new versions can be installed at
Network Ease Of Use
In the medium term, OpenCNC offers Stemmermann GmbH the option of using the
same control on all machines. The targeted networking of the machines, a
central requirement for connection to order processing, could be implemented
using standard PCs under Windows, resulting in more transparent and flexible
Another argument for OpenCNC was the fact that the Windows-based user
interface can easily be customized to the users’ needs. Relevant input and
display fields are centrally and clearly presented. The system even ensures
easy integration of additional masks, e.g. for displaying the values of a
Christian Schlomann, an MDSI integrator based in Düsseldorf, Germany, was
responsible for the design and construction of the controls, including
electrical planning for the new machines. Performance requirements
included short generator heating times of up to 0.2 seconds with a resolution
of 0.5 milliseconds. The machine with four interpolated axes should be flexibly
usable for a wide range of parts. Another requirement was an angular
resolution of 0.00025 degrees at a speed of up to 600 revolutions per minute.
"For Stemmermann, we decided to use PROFIBUS together with Wago bus clamps,
so that we could utilize the soft PLC integrated in OpenCNC to achieve the highest
possible flexibility, standardization and openness for future extensions",
explains Christian Schlomann, managing director of the engineering firm Schlomann.
"All digital and analog inputs and even the temperature sensor and the power
feedback from the generator run via PROFIBUS."
Another indication of the flexibility of OpenCNC is the fact that the automatic
feeders are partly also controlled by the CNC software. For quality assurance,
all relevant process data is logged and saved on an SQL server. Because OpenCNC is
integrated in the corporate network, machine logs with diagnostics data can be
viewed on any office PC.
A positioning repeat accuracy of 0.01 millimeters with coupling distances of
0.2 millimeters and hardening times with a resolution of 0.5 milliseconds
ensure high process precision.
Tailor-Made At An Affordable Price
The development and construction of the first machine took three months.
"The delivery period for a ready-made machine would have been six to
eight months, plus the time required for the necessary customizations
here at the company”, says Dirk Stemmermann. "The bids that came
in were considerably more expensive and the machines wouldn’t have been as
universal for use with our wide range of parts. With OpenCNC, on the other
hand, we have machines which are tailored exactly to our needs."
The good experiences Stemmermann GmbH has had with OpenCNC have prompted
the company to use the software CNC on a new kind of machine with a
dual-frequency generator. With 100 kilowatts of power at a frequency of
200 to 250 kilohertz and 200 kilowatts at 20 kilohertz, it enables
contour-accurate hardening, for example of gear-wheels, while shortening
the heating process from 2.8 to between 0.2 and 0.5 seconds. "With
this new machine generation, we are entering new territory together",
says Christian Schlomann. "But we are convinced that the flexibility
of OpenCNC will 125 ill also be helpful here and that we will be able to
realize this ambitious project." As the possibilities of reducing
auxiliary process times have been exhausted, the dramatic shortening of
the heating process means an enormous increase in productivity.
"The new machines running OpenCNC are tailored exactly
to the needs of Stemmermann GmbH."
Through the use of OpenCNC from MDSI on all machines, Stemmermann GmbH has
not only increased its planning stability. The wide range of parts which can
be produced on each machine with OpenCNC, in combination with the connection
of the software CNC to capacity planning, has greatly improved the flexibility in
production planning as well as the company’s delivery reliability. The desired
further growth of the company has become more calculable as the cost and
performance of additional machines are known. Any employee can work on any machine,
and this is also true for new employees as the user-friendly controls require
minimal training. "Even repairs and the associated downtimes are less
frightening with OpenCNC”, says Dirk Stemmermann. "The software itself
cannot break and we can replace most of the standard hardware components