Diversity in factory automation

This blog was originally posted on the Innovating Automation Blog.

Biodiversity is beneficial not only in biological ecosystems, but in industrial factory automation as well. Diversity helps to limit the effects of unpredictable events.

Typically, in factory automation a control unit collects data from sensors, analyzes this data and, according to its programmed instruction, triggers actuators to a defined operation. In most cases, a single-channel structure consisting of sensor, logic and output perfectly fulfills the application requirements. Yet in some cases two-channel structures are preferred to increase the reliability of the control concept.

Clamping control at machine tool spindles

spindle-position-control

To monitor clamping positions of tools in machine tool spindles, several options are possible: Sensors with binary output (e.g. PNP normally open) or sensors with continuous output (e.g. 0..10V or IO-Link) may be installed. The clamping process in many spindles is controlled with hydraulic actuators. This means the clamping force can be controlled by using pressure sensors which control the applied hydraulic pressure in the clamping cylinder.

The combined usage of both position and pressure sensors controls the clamping status in a better manner than using only one sensor principle. Typically, there are three clamping situations: 1) unclamped 2) clamped without object 3) clamped with object. In tooling spindles, the clamped position is usually achieved by using springs which force the mechanics to hold and clamp the object when no pressure is applied. A pneumatic or hydraulic actuator allows the worker to unclamp the object by providing force to overcome the spring load. Without hydraulic or pneumatic pressure, the clamped position should be detected by the position sensor. When enough pressure is being built up, after a short delay, the unclamped position should be achieved. Otherwise something must be wrong.

The advantage of diversity

By using two different sensor principles (in this case pressure sensing and position sensing) the risk of so-called common cause failures is reduced. The probability of concurrent effects of environmental impact on the different sensors is diminished, thereby increasing the detection rate of failures. The machine control can immediately react if the signals of pressure and position sensors do not match, simplifying monitoring of the clamping process.

The Evolution of RFID in Metalworking

RFID – A key technology in modern production

It’s not just IIoT that has focused attention on RFID as a central component of automation. As a key technology, radio frequency identification has been long established in production. The inductive operating principle guarantees ruggedness and resistance to environmental stress factors. This makes the system highly reliable in function and operation. With unlimited read/write cycles and real-time communication, RFID has become indispensable. The beginnings for the industrial use of RFID go far back. RFID was first successfully used on machine tools in the mid-1980’s. Since the usage of RFID tags on cutting tool holders has been internationally standardized (ISO 7388 for SK shanks, ISO12164 for HSK shanks), there has been strong growth of RFID usage in cutting tool management.

Cutting tool in tool taper with RFID chip

Track-and-trace of workpieces

Modern manufacturing with a wide bandwidth of batch sizes and ever compressed production times demands maximum transparency. This is the only way to meet the high requirements for flexibility and quality, and to minimize costs. Not only do the tools need to be optimally managed, but also the finished parts and materials used must be unambiguously recognized and assigned.

Workpiece tracking with RFID on pallet system

RFID frequencies LF and HF – both RFID worlds come together

In terms of data transmission for cutting tool identification, established systems have settled on LF (Low Frequency), as this band has proven to be especially robust and reliable in metal surroundings. Data is read with LF at a frequency of 455 kHz and written at 70 kHz.

When it comes to intralogistics and tracking of workpieces, HF (High Frequency) has become the standard in recent years. This is because HF systems with a working frequency of 13.56 MHz offer greater traverse speeds and a more generous read/write distance.

As a result, RFID processor units have been introduced that offer frequency-independent application. By using two different read-/write heads (one for tool identification and one for track-and-trace of workpieces) that each interface to a single processor unit, the communication to the control system is achieved in an economical manner.

RFID processor for both tool identification and workpiece tracking

New Hybrid Read-Write Head

Industrial equipment is designed for a working life of 20 years or even more. Therefore, in production you often find machines which were designed in the last century next to new machines that were installed when the production capacity was enlarged. In such a brown field factory you have the coexistence of proven technology and modern innovative equipment. For the topic of industrial RFID, it means that both low frequency and high frequency RFID tags are used. To use both the existing infrastructure and to introduce modern and innovative equipment, RFID read/write heads have been recently developed with LF and HF technology in one housing. It does not matter whether a LF RFID tag or a HF RFID tag approaches the RFID head. The system will automatically detect whether the tag uses LF or HF technology and will start to communicate in the right frequency.

This hybrid read-write head adds flexibility to the machine tools and tool setters as you can use the entire inventory of your cutting tools and tool holders.

RFID Tool ID tag ready for the Cloud

The classical concept of data storage in Tool ID is a decentralized data storage, which means that all relevant data (tool dimensions, tool usage time, machining data, etc.) of a tool/tool holder is stored on the RFID tag which is mounted on the single tool holder. The reliability and availability of this concept data has been proven for more than 25 years now.

With the Internet of Things IIOT, the concept of cloud computing is trendy. All — tool setter, machine tool and tool stock systems — are connected to the cloud and exchange data. In this case only an identifier is needed to move and receive the data to and from the cloud. For this type of data management Tool ID tags with the standard (DIN 69873) size diameter 10 x 4,5 mm are available now in a cost effective version with a 32 Byte memory.

Evergreen – more modern than ever: RFID Tool ID in Metalworking

Learn more about the Evolution of RFID in Metalworking from true experts at www.balluff.com  or at  Balluff events worldwide