Miniature sensors for effective tool change

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 centre 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 is inductive sensors; either one measurement sensor or three switching inductive 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 sensors from Baumer. For example, the miniature housing if the IFRM 03 inductive proximity sensor – with a diameter of only 3mm and lengths starting at just 12mm – contains the complete evaluation electronics responsible for the high-repeatability switching points as well as the precise analogue 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.

Measuring instead of switching

Rather than detecting the three positions of the drawbar with switching sensors, an analogue 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 recognise 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 measurement sensor requires less space than three individual switching sensors and also less mounting effort. It also constantly monitors the state of the tool clamp making it possible, for example, to detect when the tool becomes loose or is not clasped centrally.

Baumer's precise sensors optimise the repeatability of the tool clamping, minimising a potential lack of concentric runout of the used tool or detecting 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, are reported to offer the highest performance on the market. The reliable measured values and high precision enble maximum reproducibility for tool tensioning. Baumer has introduced one of the smallest distance measurement inductive sensors on the market – the inductive analogue 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 2mm 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 6.5mm thick and 46mm long.

The standardised 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.