Schach makes a smart move: Sensor performance advances, sensor costs retreat

Schach makes a smart move: Sensor performance
advances, sensor costs retreat

Improved processes
at a fraction of the current costs attributable to sensors – for
Industrieservice Schach, working with SICK as a one-stop supplier is paying
dividends both technically and financially. Based in Nürtingen, Germany, the
company uses state-of-the-art sensor technology in its membrane filter winding
machines. This includes high-precision
thickness and position sensors, opto-electronic
detection and rotative displacement sensors, easy-to-integrate pressure and
temperature sensors, as well as certified safety door switches and light

Schach’s machines and plants for manufacturing tubular membranes demonstrate
just how strong an impact a broad portfolio of innovative sensors for
automation engineering and safety technology can have. “With SICK’s help, not
only were we able to identify improved technical solutions for several machine
applications, but we were also able to reduce costs attributable to sensors in
machinery by around 75 percent overall through better product selections”,
explains company owner Hans Schach. “And that’s not even factoring in the new
safety technology. What’s more, everything now comes from a single source.
Comprehensive advice is provided for all
the machinery’s automation functions, which in some cases enables significant optimisations and substantially reduces the
risks associated with delivery logistics.” For Schach, the reliability of the
sensors is another decisive advantage, since manufacturing tubular filter
elements – used for turbidity filtration in waste
water treatment or in the
production of beverages, for example – is a process that demands the very
highest standards of quality from the end product.

Industrieservice Schach: Special
mechanical engineering a forte

At Industrieservice Schach, the
design and implementation processes go hand in hand. The company’s range of
services covers everything from sealing tools, eccentric clamps, and mounting
equipment, to joining, tightness testing, and assembly machines, all the way
through to machinery and entire plants designed for spiral-wound technology. It
is in the last of these areas that the company has built up a real stock of
specialist knowledge: designing and producing plants intended for manufacturing
tubular supporting bodies made from non-woven fabrics, with membrane filter
technology in mind. At the forefront of its work is its winding machine, on
which non-woven webs from 0.1 to 0.3 millimetres
in thickness and 12 to 25 millimetres
in width can be processed in both single
and double layers. The tubular supporting body, which accommodates diameters
ranging from five to 25 millimetres,
is formed along a winding mandrel. Finely dosed, heated membrane polymer is
applied to the body and dried, and the overlapping non-woven webs are then welded ultrasonically. Following this,
the filter tube in the crosscut module is cut to a customizable basic length
using a flying saw.

“Around 380 filter tubes measuring five millimetres in diameter are inserted in bundles
inside 10″ pipes made from fibre-reinforced
plastic. This is carried out by the manufacturer of the filter elements for the
process plants”, explains Hans Schach. “It only takes a single defective tube
to stop the entire cross-flow filter module from working, and this, in turn,
leads to rejects.” That is why Schach believes it is vital to use not only
automated tube production techniques but,
also quality methods that are automated and can be documented – covering both
machine processes and the finished product. “Some examples of particularly
critical areas are keeping the thickness of non-woven material constant or
controlling pressure and temperature with precision when applying polymer”,
says Hans Schach. “In addition to the burst pressure or tensile test benches
that can potentially be integrated, various sensor types are able to provide quality assurance in the process itself.” At the same time, it is
important to deliver solutions for various detection, positioning, and
measuring tasks, which enable the machine to adapt automatically to the product
being manufactured. As a result, almost a
dozen sensors with a variety of operating principles and functions are used in the machinery.

Through thick and thin: Monitoring materials with displacement and fork

The principle of osmosis forms
the basis for filtering particles, foreign matter, and impurities out of liquid
using membrane filters. The membrane produced in the machine is semi-permeable,
meaning that it is only porous to certain substances. As the membrane carrier,
the thickness of the non-woven material (among other factors) has a bearing on
the diffusion behaviour. “In the material
infeed for the winding machine, we, therefore, monitor the non-woven material
for points where it may be thicker or thinner. This
makes it possible to cut out the damaged area in question automatically before
it reaches the winding unit.” Displacement sensors from the OD Mini product
family are used for detecting the
material thickness. They can sample the
material web with a measuring frequency of 2 kHz and a resolution of
6 µm, which means that the material thickness is very accurately monitored – and a potentially damaged area can be localised with such precision that there is
no unnecessary loss of material when it comes to cutting it out. Looking back
on the situation as it was before, Hans Schach notes: “The solution that we
previously had from another manufacturer was ten times more expensive and was
neither as precise nor as easy to integrate. Particularly in this area, optimising the product selection in line with
SICK’s application advice has really paid

In the next stage of processing,
WFM30 optical fork sensors at the sonotrodes
perform winding monitoring. Within a response time of 125 µS and with
accuracy in the sub-millimetre range,
they detect whether the material leaving the winding mandrel is being pushed
together or twisted – in other words, becoming thicker. If this happens, the
material cannot be welded by the sonotrodes and must be cut out as a damaged

Position detection for drum modules and dancer roller controls material

The winding machines from
Industrieservice Schach are capable of producing tubular membranes at a speed
of up to eight meters per minute. To enable continuous and autonomous
operation over several hours, a drum module with automated splicing is
responsible for replenishing the material as necessary. As soon as a roll of
material nears its end, this is detected by a GTB6 photoelectric proximity
sensor in a space-saving rectangular housing – thanks to background
suppression, this is a highly reliable process that is not affected by
interference stemming from the machine environment. The optical pushbutton
signal activates the splicing process. This clamps, cuts, and welds the
material webs on both rolls.

C-slot cylinder sensors from the
MZC1 product family, made from high-strength special VISTAL™ plastic, are used
for detecting the position of the clamping cylinder when it is either retracted
or extended. Hans Schach praises the ease with which these sensors can be installed and their secure fastening method:
“The sensor can be inserted into the
C-slot simply by dropping it in – without having to remove the cylinder end cap
and even in cases where the cylinder has already been installed. Not only that, but the captive eccentric screw also
guarantees that the interlocking mechanism for the MZC1 remains resistant to
shocks and vibrations in the slot.” IME12 inductive sensors, meanwhile, provide
a solution for end position monitoring and detecting the dancer roller position
in the non-woven material infeed. During the automated process of changing the
rolls and splicing the new non-woven web with the old one, the buffer module
ensures that the non-woven material infeed required over this time is delivered. “The IME12 sensors stood out due
to their space-saving, metric short variant, the option of installing them
flush in metal, plus the sensing range of four millimeters”,
says Hans Schach. “This allowed us to provide a detection solution that
delivered maximum performance with minimum space requirements.”

Rotative measuring technology for web infeed and flying saw

Non-woven webs of various widths
and material thicknesses can be processed
on the winding machines. To be used for this purpose, the angle of the non-woven
material infeed and the machine’s winding belt module must be adjusted
automatically. Single turn absolute encoders from the ACS36 product family are used for path measurement and positioning.
With their resolution of 2,979 increments, they enable modules to be adjusted
as precisely as is required to ensure optimum infeed and processing of the
non-woven webs. As well as this, the control canrecognise
the exact setting for the non-woven material infeed and winding belt even when
the machine has been switched off and back on again – with no reference run
necessary. A DBS60 incremental encoder with a friction wheel fixed to the solid
shaft is used for measuring the length of the membrane-coated supporting bodies
following ultrasonic welding. The system detects the feed speed of the finished
filter tube and controls the flying saw used for cutting the material to a
flexibly adjustable basic length.

Safe process control, safe machine operation

The speed and quality of
membrane production depend directly on
certain factors present in the process: the temperature, pressure, and dosing
of the polymer being used. Optimum
processing temperatures range between +20 °C and +60 °C, depending on
the type of polymer. The ideal value for the process in each case is monitored
using a TSP resistance thermometer. Alongside the temperature sensor, a PTB
pressure sensor – which is also compact and easy to install – is used to detect
the polymer pressure. Together with the winding machine’s special dosing principle,
this technology ensures that the end product meets consistently high processing

In both the winding machine
itself and the connected drum module, hazardous movements present a potential
risk of accidents involving people. A physical guard is used on the winding unit. The access door – providing entry to
the machine to remedy faults or
performing maintenance – is equipped with a non-contact STR1 transponder safety
switch. Thisfulfils the highest safety
requirements: SIL3 in accordance with IEC
61508 and SILCL3 in accordance with EN
62061, as well as PL e in accordance with
EN ISO 13849. What’s more, the transponder safety switch is effectively
protected against the risk of tampering thanks to its unique coding. To allow simple and ergonomic operation, a
deTec4 safety light curtain with a height of 1.35 meters is installed on the drum module; this also
meets the criteria of the aforementioned
standards. Through the use of two deflector mirrors, all three
accessible sides are monitored in a
non-contact manner. The distance between the beams used for monitoring is
30 millimetres. Not only does this
resolution ensure reliable protection for hands in the event of unauthorised access to the machine while it is
still running, but it also makes it possible to remove the non-woven material
web located between two single beams and leading through to the machine without
the safety device responding.

Membrane filter technology ready for yet more innovations

Industrieservice Schach’s
machines and complete plants used for manufacturing tubular membranes have been met with great interest in the field of waste water technology. With sensor technology
that is both innovative and deployed in intelligent ways, filter element
production is guaranteed to be not only technically efficient and
cost-effective, but also a high-quality, transparent process that can be documented. What’s more, the Nürtingen-based
company is already looking ahead to two areas that will become vital in the
future. One of these involves implementing layer thickness measurement inside
tubes, which will enable the company to provide a fully rounded quality
concept. The other will see it processing new polymers into membranes – which,
for the first time, will enable hormones and antibiotics to be filtered out of waste water along with other impurities. The
right machine technology – including the ideal sensors from both a technical
and financial perspective – is already at hand. All that remains is to adapt it
for these tasks.

Written by: Eyüp Ergün, Field Sales, SICK
Vertriebs-GmbH, Düsseldorf

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