... from www.positek.com
An additional option to the Series 2000 gauge roll offered
by Sasib Food & Beverage is a motorised roller gap adjustment
which greatly reduces the amount of fiddly adjustment needed
to ensure a consistent dough sheet thickness and which also
permits the gap to be automatically adjusted for different dough
products.
Sasib Food and Beverage manufactures a wide range of baking
machines for producing food products from flat sheet dough such
as crisps and biscuits. During the continuous process, gauge
rollers form the dough into a flat sheet of the correct thickness
before the biscuit shapes are formed, cut out and baked. The
control of the thickness of the dough sheet is important for
the quality and standards of the finished product.
At the heart of this new refinement is the Positek P103 Linear
Inductive Position Sensor mounted at each set of the paired
gauge rolls. The sensor measures the gap between the rolls and
relays the information to the PLC. The adoption of the Positek
LIPS® sensor in preference to the older LVDT sensors has
saved the manufacturer both time and money according to Geoff
Speak, Electrical Manager for Sasib's Food & Beverage Machinery
Division, because the P103 comes ready-calibrated. The sensor
is now operating on a number of sites throughout the world.
The sensor has a flange mounting which provides a well-defined
reference face for mounting with two easily accessible mounting
holes. The sensor is supplied by Positek calibrated to within
+/- 0.25% of the overall range both for the slope and the offset
of the output. The flange is used as the reference when it is
calibrated. When installing the sensor it requires only mechanical
adjustment by a Vernier screw incorporated into the roller mechanism
to take account of mechanical tolerances in the mechanism; installation
and commissioning is now a much speedier and less complicated
operation than it was in the days of the LVDT sensors which
needed careful and long winded electrical calibration.
The internally-integrated Positek sensors permit further simplification
of the new Sasib gauge roll because the output is a loop powered
two-wire 4-20mA format. The older LVDT sensors needed a special
electronics module separated from the sensor to convert the
output to mA and to avoid the voltage drop which would otherwise
occur over the often considerable distances between the sensor
and the PLC. The old electronic module needed to be wired up
with the sensor with multiple connections. The Positek sensor
has just 2 connections to make resulting in quicker installation.
A further advantage of the LIPS® sensor derives from its
fully linear response over the entire mechanical range. The
sensor provides a linear response to within +/- 0.5% of the
travel. This means that not only is there no longer the need
to incorporate adjustments in the PLC to correct the non-linearity
of the LVDT response but also that the same sensor units can
be used for a much wider range of dough sheet thicknesses -
and hence product lines. As well as the good linearity, the
Positek sensor has a very short body length compared to the
travel which helps to save space in the application.
The P103 sensor is a standard sensor with a small special modification
requested by Sasib. It incorporates technology developed by
Positek and used in its other displacement sensor products.
This PIPS® technology is based on inductive coils and uses
a unique custom integrated circuit to produce an accurate analogue
output signal. Several versions of the P103 sensor are supplied
for different gauge roll travels from 10mm up to 50mm.
