Automation engineers often face a three-way balancing act when designing equipment, trying to maximise speed and accuracy while keeping cost at acceptable levels. Position control is no exception – high-performance systems typically rely on linear or rotary encoders to deliver the required positional accuracy, and these can be expensive, particularly when both coarse and fine positioning is needed.
Using a secondary sensor for coarse-positional control is a commonly used, although inelegant, solution to the problem. It also increases complexity and cost, while reducing the overall reliability of the system. Alternatively, designers maintain accuracy without increasing cost by reducing travel speeds during coarse positioning, increasing the cycle time. Neither approach is optimal.
Equipment manufacturers (OEMs) specifying high-speed assembly equipment with multiple linear transfers between workstations need an alternative solution. Using off-the-shelf linear stages, they require a controlled, fast approach to the critical areas and a slower, high-precision final positioning – without increasing complexity or cost. An affordable single-sensor solution is highly desirable.
Recently, a team of OEM designers specified rugged inductive sensors from the Contrinex SMART Sensor portfolio; a single sensor with IO-Link connectivity and multiple user-configurable outputs performs both the required tasks. Firstly, it initiates a controlled deceleration as the carriage of a linear stage approaches the specified workstation; it then switches to micrometre distance resolution, positioning the stage accurately and precisely.
Contrinex inductive SMART Sensors are designed with the needs of OEMs and system integrators in mind and provide an unobtrusive fit-and-forget solution. A single metal-cased M12 sensor is embedded in one of the guide rails immediately adjacent to each workstation. The sensor detects the presence of the carriage as it begins to pass overhead, triggering the deceleration and changing the sensing mode.
The sensor now operates as a high-precision distance-measurement device; its target is an inclined face on the underside of the carriage. As the carriage moves over the sensor, the distance to the inclined faces changes in direct proportion to the distance moved. With a sensing distance of up to 6mm and a dynamic resolution of ±5.5 micrometres, the sensor delivers a highly accurate 16-bit digital output, enabling the carriage position to be determined in real-time.
Once the initial set-up is completed, each sensor’s configuration is stored automatically on the local IO-Link Master; this allows plug-and-play replacement of sensors should the need arise, without any loss of functionality and without any need for recalibration. These highly versatile sensors meet designers’ needs for a highly reliable, cost-effective and non-complex solution without compromising operational performance.
PLUS Automation aims to help you make sense of sensors, helping solve applications, improve machine performance and reliability, and reduce costs using Contrinex’s exceptional Inductive, Photoelectric, Ultrasonic, RFID and Machine Safety sensors. Find more information and read other application examples go to www.PLUSAx.co.uk