Controls News 13
16
Main theme: Lean automation |
Technology
A Collection of bus
connectors/electronic slices
as «self-build control device»
from the panel manufacturer.
They «save» on backplanes and casings.
The DIN rail must look after that.
The DIN mounting rail is the backbone of «self-build automa-
tion devices» from the control panel manufacturer. It must be
obtained from the electronics manufacturer, which in practice is
almost never done. The rail, as the backbone, must not be bent, but
no one notices this at the time of inspection. When the mounting
tension of initial acceptance subsides, some rather worrying effects
and problems arise and their causes are difficult to pinpoint.
The manufacturer delivers building blocks, or mod-
ules, a special high-grade DIN rail mounting and a
comprehensive manual for assembly and operation.
The core of this homemade «self-build controller»
is the DIN rail. Everything else is built onto it. In me-
chanical and electrical terms, it is both the backbone
and also the Achilles’ heel of the system. The largest
manufacturer of slice kits for self-build controllers
stipulates in the operating instructions for each slice
that the DIN-rail must be obtained from the manu-
facturer, or alternatively that the cabinet must be
removed by the manufacturer’s engineer, because
otherwise the whole system is not CE-compliant. The
same applies, of course, to every modification made
during the life cycle.
If these very restrictive conditions and
46
pages of assembly instructions are
not followed, CE compliance is lost!
In addition to the manual for
all the slices, there are
46
pages of information
to increase reliability.
Front image: Tangle of
cables in a slice-type control
system. Horribly complex and
error-prone when it comes to
servicing.
The Achilles’heel
of the system:
the ground connection
of individual bus
terminals on slice.
DIN-Rail
Attention:
The components are not resistant
against materials with seeping and insulating
properties, e.g. Silicones, triglycerides (found in
some hand creams). If it cannot be ruled out that
these substances might seep into the component
environment, the component should be installed
in an enclosure that is resistant. Generally speak-
ing, clean tools and materials should be used
when handling the aforementioned materials
When there are electrical faults and failures due to I/
Os, dedicated controllers again have definite draw-
backs. Instead of one I/O module, the entire device
including CPUmust be replaced. This requires service
personnel with specialist knowledge, carries a higher
possibility of error and costs more. When the replace-
ment device is not fully compatible in terms of func-
tionality and programming, software engineering is
required. The smallest thing can turn into a major
project requiring qualified specialist personnel and
long shutdown periods. Anything but «lean».
«
Self-build» control devices are not lean as
there are multiple opportunities for error, un-
clear responsibility and too much small print.
How can you win the control panel manufacturer as a
sales partner when dealing with investors and opera-
tors? That is the question asked by many electronics
manufacturers.
The answer: Hand over some added value and much
of the responsibility to the control panel builder. That
reduces the cost of materials in his calculations. At
the same time, he gains access to the lucrative af-
tersales business. To service this kind of «non-lean»
technology, his own specific technical qualification is
needed, for which he is well paid. In practice, these
are the home-made control units, which consist of
horizontally arranged slices of electronics.
It is such a simple and profitable model that there is
now a vast array of products on the market that quali-
fied electrical specialists eagerly recommend to op-
erators, investors and planners.
The target audience believe they are buying control
and automation equipment. But there is no mention
of this on the manufacturer’s page. There people can
read about bus terminals, intelligent bus cou-
plers and I/O systems – but the word «PLC» is
deliberately avoided. That would require de-
livery of a proper device, meeting the relevant
quality standards for PLC equipment (IEC 61131-2).
But such a device only exists in the eyes of the ex-
pectant beholder – nowhere else.
What is the technology behind these «Made by the
panel manufacturer» automation devices, and what
are the implications in terms of achieving the aims of
lean automation?
You save on a backplane and module carriers. With
qualified, careful electrical specialists for assembly
and innovative contact technology,
you can save on the cost of a
robust, solid casing and ex-
pensive plugs.
The DIN rail becomes
the backbone of the
«
self-build automation
device».
