Industrial Ethernet & Factory Floor Automation
五月 13, 2014
Ever since its discovery in the mid-seventies, the popularity of Ethernet has continued to increase as the standard protocol for industrial factory floor systems due to its ability to send data packets (or blocks of information) from the source to its destination quickly and efficiently.
Initially, industrial factory floor automation was developed and communicated over several different proprietary protocols including Profibus, Device Net and Modbus. While manufacturers pushed their proprietary automation protocol to market as the superior product, the customer was somewhat reluctant to lock into an industrial communication solution that restricted the components required for plant operation. At this same time, the office network, run via Ethernet, was slowly migrating to the factory floor. This transition created the need for the true "Industrial" network cable.
Factory floor automation has always presented challenges for standard office grade Ethernet cable. Automation processes require rugged connections and are subject to higher temperatures, humidity and vibration as well as harsh environments and/or chemicals. While Ethernet evolved and had the bandwidth to perform in the factory environment, the old blue PVC jacketed Ethernet cable lacked the performance to offer a permanent solution.
European based vendors began offering true Industrial Ethernet cable products with tough construction of polyurethane outer jackets combined with foil and tinned copper braid shielding. This provided a leap in technology and performance beyond current product offerings. Ethernet cable manufactures quickly realized the demand for different shielding options and jacket compounds was essential.
The significant amount of information and critical data which was being transmitted over the cables would dictate the need for enhanced cable shielding options. Because of this, the twisted pair Ethernet cable offering was developed with a standard foil shielded option. This would be vital for signal success. The foil shielded solution protected signal integrity initially with a 100% foil shielded cable. However, the foil shield could degrade overtime and reduce its effectiveness. As a result, many manufacturers were now offering a double shield consisting of foil and tinned copper braid which protected circuit integrity and assured an effective long term shielding solution.
Another component of signal integrity was the development of "bonded pairs". This design kept the twisted pairs together permanently to guarantee uniform spacing within each pair. The result would maintain consistent electrical performance throughout the cable's life. Other cable manufacturers utilized pressure extruded jackets over their twisted pairs which aimed to keep the pairs together and equalize the benefits of bonded pairs. The larger effect on the market was the emphasis put on transmitting large volumes of critical data in the harsh industrial environment by the cable manufactures.
While the shielding options enhanced signal integrity, the cable jacketing material was also becoming important for the Ethernet cable to survive outside of the office. The PVC jacketed option was a standard, however, this compound did not perform well in oily environments and was not as durable under the constant temperature swings occurring on the factory floor. As an alternative, thermoplastic elastomer (TPE) jacketed cables were developed and offered better performance and abrasion resistance than PVC. For Industrial Ethernet applications that required extreme durability, a tough polyurethane jacketed option was developed. Other unique industrial Ethernet cable options became available which included outdoor rated, direct burial rated and continuous flexing cable.
Today, there are a variety of standard off the shelf Industrial Ethernet cable options available. It is the engineer's decision to specify by basing the application on the following: environmental conditions and system life expectancy. Also, the data being transmitted over industrial Ethernet determines the integrity of its manufacturing process. While many cabling options exist, it pays to invest in the cabling of these critical circuits which will then determine the success of the manufacturing process.