In modern processing centers, inductive sensors are the components of choice for monitoring the motor
spindle clamping process. Integrated into the spindle, they must be exceptionally small and offer high
repeatability to ensure smooth tool changing at all times. Baumer offers a high-performance portfolio of
miniature sensors for the intelligent design of effective spindle solutions. This can either involve a classic
design with three switching sensors or a smart design with one measurement sensor.
Tool change in fully automated processing centers, from removal until the insertion of the new tool in the
spindle, takes less than a second. To achieve maximum system effectiveness, this process must function
with ultimate reliability. The error-free functioning of the smallest inductive sensors plays a major role in
ensuring this. For the processing center to function error-free, the machine control requires the following key
information regarding the status of the collet chuck: open and no tool clasped, closed and no tool clasped, or
closed and tool clasped. The answer to this challenge are inductive sensors. The task can be handled using
either one measurement sensor or three switching inductive sensors.
Largest portfolio, smallest sensors
In drive and clamping solutions, the sensor technology is integrated in the motor spindle. Given this confined
space, the sensors must therefore be as small as possible, yet very powerful – characteristics found in the
sensors from Baumer. The Swiss sensor manufacturer offers the market’s largest portfolio of miniature and
sub-miniature inductive sensors with micrometer measuring accuracy. One example is the inductive
proximity sensor IFRM 03 with a diameter of only 3 mm. It is available in various lengths starting at a mere
12 mm. Yet its miniature housing contains the complete evaluation electronics that are responsible for the
high-repeatability switching points as well as the precise analog measurement values. In addition, these
industrial-grade sensors are robust, EMC-stable, and comply with the protection class IP 67. The sensors
remain unaffected by heat, oily environments, and vibrations that normally occur in tooling machines. This is
where the decades of experience of Baumer in miniature sensor technology come to play.
Measuring instead of switching
Rather than detecting the three positions of the drawbar with switching sensors, an analog inductive distance
sensor offers an alternative solution. It requires a steep angle taper on the drawbar rather than a retainer.
With a steep angle taper connected to the drawbar, it is possible for the measuring sensor to detect the
position of the drawbar and thus recognize the state of the collet chuck. The distances or the respective
clamping values that are evaluated by the control can be allocated to the three positions of the bar. The use
of a measurement sensor offers a number of advantages – on the one hand, the sensor requires less space
than three individual switching sensors and also less mounting effort. On the other hand, the sensor
constantly monitors the state of the tool clamp. This makes it possible, for example, to detect when the tool
becomes loose or is not clasped centrally. This may happen if chips fall between the spindle and the tool. It
can result in damage to the tool or quality problems of the machined part. The precise sensors from Baumer
optimize the repeatability of the tool clamping. This minimizes a potential lack of concentric runout of the
used tool or detects it early on. A measuring sensor improves the reliability of the clamping system while
ensuring both the quality of the processing as well as system availability, which is reflected in increased
overall system effectiveness. This requires micrometer precision of the sensor, a detection range that is as
large as possible, and a limited temperature drift. In this regard, AlphaProx, the smallest inductive distance
sensors from Baumer, offer the highest performance on the market. The reliable measured values and high
precision ensure users a maximum reproducibility for tool tensioning. Baumer has introduced one of the
smallest distance measurement inductive sensors on the market – the inductive analog sensor IF08. This
product series has a box-shaped housing measuring 16 x 8 x 4.7 mm. Nevertheless, it contains the entire
evaluation electronics and a drilled hole for flexible mounting even in confined mounting spaces. Its
measuring distance is 2 mm with an output signal of 0 – 10 VDC.
Flexible with IO-Link
Even greater flexibility is offered by the miniature distance measurement inductive sensor of the IR06 series
with digital IO-Link interface with a housing that is only 6.5 mm thick and 46 mm long. The standardized
interface allows the easy integration of the clamping process into the control. The collected data can be
recorded and evaluated via a histogram. This allows the early detection of measurement deviations and
facilitates required error analyses. For example, the smallest changes in the process can be detected via the
vibration and addressed before the machined part is damaged. The sensor also provides additional
diagnosis data, for example, the temperature of the sensor, which the tooling machine designers can use to
indirectly recognize the heating up of the spindle. In addition, the sensor offers all the advantages of IO-Link,
such as easy parameterization and quick commissioning of a replacement sensor, by downloading the
parameters from the IO-Link master based on the parameter server function.
