Making sense of industrial sensors

Sensors are not all the same, and sensor manufacturers’ continuous investment and ingenuity have resulted in new devices that not only are smaller, faster, and higher-performing, but that help solve previously unsolvable problems.

Who cares about industrial sensors? They are the proverbial "commodity products" in the factory automation and machine-building industries. Worse yet, they are boring, simple, and all the same. Right?

While these perceptions are widespread, the technical personnel and managers who take the time to understand today's industrial sensors can advance their companies' capabilities while generating extraordinary value for their organizations.

Sensors are not all the same, and sensor manufacturers' continuous investment and ingenuity have resulted in new devices that not only are smaller, faster, and higher-performing, but that help solve previously unsolvable problems.

Common Sensor Styles

Advancements continue to be made in discrete sensing devices, vision sensors, and advanced motion products. For example, industrial Ethernet systems provide cost-effective communication options that still allow for deterministic response times.

Sensor manufacturers are incorporating many new technologies such as Ethernet, radar technology, wireless communications, and lasers into their devices. A number of object-detection and proximitylike sensors are being used in industry to address common problems.

Movement Sensors. Detecting motion, or lack of it, is not new; however, a new class of device provides a contact-free, wear-free detection method for simple motion and feed applications.

Movement sensors, or noncontact motion sensors, use a laser to detect whether an object placed in the sensor's field of view is moving. For feed applications, this means that material can be measured at any position along the process without contact.

These self-contained laser devices are virtually material-independent and immune to debris and contaminants. Advanced versions can incorporate a pixel-style camera to include direction outputs or incremental outputs for speed, distance, and velocity.

Angle Sensors. Also known as L-shaped photoelectric sensors, angle sensors typically are available with visible red light, infrared, or laser optics. They come in a number of shapes, sizes, and configurations to operate at a safe distance from any material or stamping activity (see Figure 1).

Versions with high-powered optics and contamination-detection features can work in the presence of heavy contamination such as metal shavings and grease. A flashing LED indicates when the device is seeing significant debris. Infrared versions are especially tolerant of environments with heavy pollution, dust, or debris.

Angle sensors come in a number of shapes, sizes, and configurations to operate at a safe distance from any material or stamping activity.

Angle sensors can operate for years without adjustment or replacement.

Contact Sensors. A new class of sensor provides an alternative method for part counting, part ejection, and even vibration-related applications. These ultracompact sensors are based on piezoelectricity that detects when any contact is made with the sensor, including impulses. In essence, these devices know when something "hits" them, and they register that hit by measuring frequency and amplitude.

When the sensor is mounted in an area where parts need to be detected or counted, it will register a part's initial contact and ignore subsequent contact with the same part, resulting in accurate counting. The fully enclosed devices on the market today can handle up to 100 parts per second. Timing and operation typically can be adjusted on the devices using potentiometers or self-teach buttons.

While contact sensors aren't necessarily new for part counting, this technology also can detect vibration patterns. The sensor can be tuned to operate normally at a standard operating frequency so that when the frequency increases, the sensor triggers its output (see Figure 2). This method can be used to detect machine wear and tear, bearing problems, and even an empty parts bin or hopper.

Sensors in the Transfer Die: Case Example

Ultra Tool & Manufacturing, Menomonee Falls, Wis., makes tooling and automation products. Its latest transfer system reduces material usage, driving down piece-part costs and streamlining the overall stamping process. The transfer die incorporates 28 proximity sensors to protect and monitor the press. They provide the repeatability that the company needs to guarantee operation with minimal hysteresis.

The transfer die also incorporates a laser angle sensor that provides noncontact detection of rotating targets. This high-powered sensor can operate in extreme environments, shooting through dirt and heavy coolant. For the feed application, the die incorporates a noncontact movement sensor with a small beam spot to provide accurate sensing away from the target. The movement sensor works across all desired materials, regardless of the reflectivity.

Ultra's die also employs a contact and vibration sensor to sense a change in the vibration of the tooling itself. Configured to a low vibration pattern, the sensor can detect possible mechanical failures early on to help prevent catastrophic die crashes. The company also can use vibration sensing to generate a preventive maintenance schedule based on real-world equipment operation.

Many traditional and emerging-technology sensors are available to help stamping companies solve their application challenges. Staying knowledgeable about these devices is key for stampers to ensure their equipment, systems, and businesses remain innovative and competitive.

Figure 2: Contact sensors can detect vibration patterns to identify machine wear and tear, bearing problems, and empty parts bins.