System Description; Measurement Principle; General Hints For Process Security - Roland R1000 Series Manual

B0048191 / Rev. 1.5

3 System description

Flexible manufacturing systems in sheet metal processing require automated and reliable double
sheet control systems in order to safeguard presses and other processing machinery against
damage due to multiple sheets. This applies not only to steel but also to aluminum and other non-
ferrous metals as well as non-magnetic stainless-steel (austenite), materials as they are
increasingly being used in automotive applications. In addition, the production of so-called
"Tailor Welded Blanks" (TWB) has created complex manufacturing systems with special
requirements regarding automated double sheet control systems.
The Double Sheet Detector UDK20 was specifically developed for this technical environment. The
special feature of the system is the ability to monitor ferrous and non-ferrous materials with one
sensor only - the PW42AGS.
A system for one measuring point consists of the following three components:
•
Control unit
•
Sensor PW42AGS for ferrous and non-ferrous materials
•
Sensor cable
3.1

Measurement principle

The Double Sheet Detector UDK20 combines the electromagnetic and eddy current measurement
principles. It monitors the sheet thickness from one side only and in the case of steel does exert
forces only during measurement. A change of the sheet thickness causes a change of the
inductance. The control unit calculates the sheet thickness resulting from this change. Based on
the predetermined thresholds 0-sheet, 1-sheet, or 2-sheets of output signals are generated.
3.2

General hints for process security

The process security of the system is influenced by the following factors:
• the stability of the measuring values
• the setting of under-gauge threshold and over-gauge threshold
• the evaluation of the status signals
Stable measuring conditions will result in stable measuring results. For measuring procedures with
single-sided contacting sensors the air gap between sensor and material surface is a decisive
criterion.
Air gaps varying from measurement to measurement will cause varying measuring results.
Basically, such situations are bad, since in such cases the user is inclined to decrease the under-
gauge threshold and to increase the over-gauge threshold. On doing so, the user puts up with the
drastically increasing risk of not detecting a double sheet.
The following external factors decisively influence the stability of measuring results and need to be
considered for operation of a double sheet detector:
• the air gap between sensor and material surface
• the magnetical characteristics of the material
• the tolerance in material thickness
ROLAND ELECTRONIC GmbH · Otto-Maurer-Str. 17 · DE 75210 Keltern · Phone +49 (0)7236-9392-0 · Fax +49 (0)7236-9392-33
Double Sheet Detector R1000 series UDK20
with integrated fieldbus interface
Manual
System description
21