WiFi on the plant floor
Interested in implementing a wireless communications network on your production line, on the plant floor, or even expanding the network outside the manufacturing walls? Manufacturers have three key wireless elements to consider, and what may be a surprising solution: WiFi, that ubiquitous IEEE 802.11 standard popping up in cafes and airport terminals across the U.S. Trends include:
1) Control oriented wireless communication is at the core of the production environment. Control over wireless links addresses the need to talk to I/O untethered. A multitude of applications demand the mobility and flexibility of wireless control, including automated guided vehicles (AGVs), gantrys, turrets and others.
2) Manufacturers are taking advantage of the growing ability to monitor and evaluate each machine or operation wirelessly, inside or outside the plant.
3) The merger of manufacturing and IT environments means that office technologies can be used and improved on with manufacturing environment advancements. One of these is VoIP (voice over Internet protocol) over two-way radio.
How WiFi works
A WiFi installation exists as a subnet attached to the enterprise-level network. It has a star-network topology with a wireless access point (WAP) at its center and an unspecified number of nodes each linked to the WAP via two-way digital radio.
When a data terminal equipment (DTE) device, such as a handheld computer, enters the WAP’s coverage area, it attempts to connect to the wireless network. Networks can be secure (only DTEs carrying proper authentication codes can join) or open (any DTE can join). Depending on conditions, links can be reliable to roughly 30 m of the WAP indoors and somewhat farther outdoors.
Specific features can ensure I/O application performance. Point coordinated function (PCF), for instance, can create deterministic-like performance over wireless by polling, which is when the access point scans clients in a defined time.
Antenna technologies, including R-coax cable (see below), can communicate with devices that move along a track. The Volkswagen plant in Emden, Germany, uses R-coax cable in critical radio system environments found in mobile screwing stations. Client DTEs communicate reliably with the plant’s control system and assembly line server there.
|Wireless can bring together office and industrial domains into a comprehensive wireless architecture, providing plant wide connectivity for solving the needs of both IT and automation|
Another company, CAMotion, uses wireless communication to control its overhead gantry robot systems used in food- and material-handling applications. Gantry systems use one network for standard and safety data. A safety rated wireless network communicates over Siemens Scalence W wireless access points, helping reduce cabling costs up to 30%, shortening installation time, and simplifying startup.
Bear Island Division of the White Birch Paper Co. sought ways to improve manufacturing processes and find cost savings and efficiencies. At the mill’s remote scale house, truckloads of wood chips, whole-tree-length wood, and chemicals are weighed as they enter and exit the plant.
For years, unplanned telephone line interruptions had plagued the scale house’s telephone connection to the company’s network server. Industrial-grade wireless LAN technology helped eliminate unplanned downtime at the station and reduced labor costs.
An in-bound scale automatically weighs entering trucks and their contents while drivers scan a ticket into the automation system. Information is wirelessly communicated from a directional antenna mounted on the exterior of the facility to an access point at the mill’s servers 1,000 yards away. Replacing phone lines with the rugged wireless LAN system delivered $150,000 in annual savings.
Mt. Olive, NC —Mt. Olive Pickle Co. Inc., the largest privately held pickle company in the U.S., is using voice over Internet protocol (VoIP) technology. Mt. Olive also makes heavy use of electronic data interchange (EDI) technology, using it to receive more than 90% of orders from retail customers and to send invoices to about 80% of customers. So when the new advanced ship notice (ASN) EDI format was emerging, Mt. Olive knew it had to upgrade its warehouse management system accordingly.
|Mt. Olive Pickle’s 3-year ROI for its wireless network investment|
|Reduction in IT support||$51,000|
|Reduction in assets||$45,000|
|Elimination of paper system for maintenance||$1M|
|Reduction in downtime||$2M|
|Savings in automation support & programming||$150,000|
|Source: Mt. Olive Pickle and Siemens Energy and Automation|
|Jeremy Bryant is automation market network specialist with Siemens Energy and Automation.|
|R-coax cable is lossy, meaning slots in the outer conductor allow it to “leak” RF power along the cabin’s length|
R-coax cables make good antennas
R-coax cables are radiating cables that function as special antennas for the Siemens’ Scalance W WAPs in applications needing complex radio-coverage patterns. The cables’ design creates a defined, cone-shaped radio frequency radiation pattern along the cable. The radiating cables are therefore perfectly suitable for use in environments with complex radio coverage and in any type of track vehicle. The cables were specially designed for the WiFi frequency bands around 2.4 GHz and 5 GHz.
Openings in the outer coaxial conductor permit penetration and emission of radio waves. This elongated radiation pattern is ideal for areas with complex radio coverage (tunnels, channels and elevator shafts) where “unlimited” mobility is not of decisive importance, but where a mechanically wear-free, low-maintenance solution is required to ensure reliable data transmission, such as conveyor systems, robots, rail-mounted vehicles, overhead conveyors, and AGV systems.