Technological lead

There is a technological shift going on out on the shop floor that is allowing machines to communicate directly with corporate information systems, generating big benefits for companies by increasing their operational efficiency. Applications are available that provide real-time machine monitoring, acquisition of Overall Equipment Effectiveness (OEE) metrics, dynamic computer-aided machining, automatic synchronization of part programs, DNC, work order scheduling, and central control of machine operations.

Why make the leap?

The Internet has changed how the world gets its information: it’s all about easy access. Manufacturing machines that communicate via serial ports run the risk of being not connected to the information highway and consequently being an unproductive asset. If these machines could be refurbished with advanced communications technology, a company could avoid spending millions on new machines. Furthermore, extracting operational information from all its machines, both new and old, would permit a company to optimize its manufacturing processes. Companies that have moved to the Ethernet report a significant improvement in efficiency and cost savings.

The evolution of CNC communications

The first NC and CNC machine tools were programmed by hand directly on the control. Thereafter, machines were loaded with a punched Mylar tape that allowed the running and storage of programs. In the late 1980s and early 1990s, CNC machines with RS232 serial ports for communications with computers appeared. Programs were stored on a PC, backed up or called up remotely, and easier to manage. Older machines were converted from tape to serial port communication by a Behind the Tape Reader (BTR), which converted the tape format to RS232 serial format and allowed controls without a serial port to connect to a PC. Some CNC controls (such as the Fanuc 6) had both serial and parallel ports but still required a BTR to drip feed in Direct DNC mode. Nevertheless, this approach was so successful that many of these controls and machines are currently still in use.

One way to upgrade older CNC equipment is to install a PC at every machine, a solution adopted by many shop floors today. This approach solves the main weakness of RS232 serial port technology, which is the length of the cables required. The longer the cable, the slower the Baud rate (2400), and the greater the risk of damaging interference. Flow control issues and other cable interactions can lead to data loss. However, the harsh environmental conditions of some shops can cause PC failures that interrupt operations. Maintaining large numbers of PCs on the shop floor is time consuming, costly, has inherent security concerns, and requires IT personnel.

These issues have been solved in two ways. The first approach is to use a single PC with one port DNC software working through manual switch boxes. This option is cheap to set up but more costly over the long term due to inefficiency and uncertain reliability. Time is wasted in finding the program, setting up the switch, and walking back and forth from the machine to the PC. In some small shops, where program changes are infrequent, operators must locate supervisors to make the transfer. The second approach is to use a single PC with multiple port serial cards. This solution simplifies the communications protocol but is risky because only one PC is involved. All cables lead to one location, and the malfunction of any part of an interface card, power supply, PC hardware or OS means that the entire system goes down. A further disadvantage of the multiple port serial card solution is the length of the serial cables (perhaps hundreds of feet long) that may be required to connect the PC to the CNC. Such extended cable lengths frequently require a lower baud rate to ensure data reliability, resulting in increased program load times that reduce machine runtime availability.

Today, such problems can be solved using the Ethernet. The newest CNC machines are equipped with TCI/IP Ethernet ports, and some of these machines can use FTP servers such that external DNC software is not required for basic file transfer. It is thus common to find in one shop different machines using different communication systems. This multiplicity creates a management issue for plant personnel because more than one system must be maintained.

A solution is to convert older RS232 serial CNC controls to Ethernet and wireless Ethernet connections. However, older serial port-based DNC software often requires additional drivers that can interfere with data integrity and connectivity. In addition, many serial-to-Ethernet conversions are jury-rigged using off-the-shelf components that were not designed with CNC equipment and shop floor conditions in mind, and may require power from 110 volt sources that are not always present in the CNC cabinet. These ad hoc solutions thus produce high failure rates in the field.

Benefits of ethernet conversion

Complete and purpose-designed tools that convert serial port to Ethernet communications have several immediate advantages over older technologies:

•The CNC becomes an individual node on the corporate network and is not directly connected to a PC.

•The network infrastructure can include standard off-the-shelf switches and routers.

•Standard Ethernet cables are used instead of expensive proprietary RS232 cables; cable length becomes irrelevant and surge damage is a concern of the past.

•Data transfers occur at the maximum speed of the CNC control’s ability to receive data.

•Data transmission is secure.

•The PC or server that hosts the DNC software only needs to see the TCP/IP address of the CNC machine. If that PC or server or network fails, any other PC or laptop with the appropriate software back-up can assume the DNC server role with little or no delay.

•There is no single point of failure that will shut down the shop DNC network. A laptop can connect to the CNC if necessary.

•Newer PCs and laptops do not have RS232 ports but all have Ethernet connections.

•The hardware is not control-dependent and is easily reinstalled on new machinery.

In almost all cases, the conversion of serial port to Ethernet communication instantly increases speed, reliability and productivity. For example by increasing the Baud rate from 2400 to 9600, program transfer time is reduced by 75 per cent. This time savings alone often repays the conversion cost.

Automating the network: DNC and direct DNC

An example of a device that connects serial ports to the Ethernet is Memex Automation’s Mx1053 Universal Network Interface (UNI) with the accompanying Ax2200HS product. The Mx1053 UNI configures access to the Ethernet for the serial ports of older machines as well as for many new machines that only have RS232 serial ports. The Mx1053 UNI is shop-hardened, not control-specific, and will operate with any CNC RS232 serial port. Forward-thinking companies like Goodrich Aerospace have used the Mx1053 UNI for several years. Similarly, Halliburton, the world’s second largest oil field service company, has adopted this technology for their CNC machines.

The Mx1100E UNI is a BTR version that facilitates Ethernet conversion for tape reader-based CNC controls that are still in service. Although these machines are easily configured with older serial-only DNC software (such as NetDNC), new heights of integration are achieved when the Mx1100E and AxDNC software are used. This new advanced DNC program not only handles traditional serial communications but also has built-in functionality for TCP/IP-based controls. For those newer controls that use FTP, AxDNC has a built-in FTP client that automatically synchronizes with the main server. AxDNC has an additional advantage over the freeware that is commonly used for FTP transfers: the AxDNC allows security-controlled user access so that management can restrict operator access to specific folders and functions. The result is a shop environment in which one application serves all the equipment and is secure, simple to use, and easy to maintain and back up.

Automating the automation: advanced OEE and machine monitoring

The increase in speed and data flow volume facilitated by Ethernet use allows manufacturers to upgrade their information exchange and retrieval. Two crucial areas are OEE metrics and real-time machine event monitoring.

An example of a device that tracks these parameters is Memex’s Ax9150 Universal Machine Interface (UMI) with optional I/O boards, including the Ax650 CNC interface board and the Ax750 Fanuc interface I/O link board. These devices streamline DNC communications while gathering pertinent data directly from the machines. Unlike a software solution, the Ax9150 UMI does not depend on inserted D-Print commands or other program manipulation. Through its I/O links, the Ax9150 UMI collects data in real-time directly and electrically from the CNC. These data can then be fed to OEE, ERP, MTConnect and OPC-compliant software programs to provide a complete picture to management of the machine’s operations and usage. During drip feed, the G-Code is read and interpreted as it is being run by the control.

Automation of data collection and reporting eliminates tedious and inaccurate manual data entry of machine events. Production planning ERP software (such as that from JobBoss, Baan or SAP) can be integrated with the CNC directly in a two-way bi-synchronous link. The data flow can also be adapted to the needs of customized software and databases that are unique to individual manufacturers.

Actual experience in the field has shown that use of the Ax9150 UMI allows manufacturers to manage assets more effectively such that productivity gains of 5-20 per cent are achieved. With the current economy and competitive global environment, every avenue of efficiency improvement and cost reduction must be accessed. A major aerospace manufacturer, Héroux Devtek, has taken this philosophy to heart and has recently instituted a corporate roll-out of a totally integrated OEE + DNC solution from Memex for all its machines at all its plants. This group has already seen benefits from real-time alerting, centralized scheduling, program control and accurate reporting that have significantly increased their overall operational efficiency.

Today’s manufacturing environment demands an increased flow of data and information that legacy serial communication software and hardware simply cannot supply. Migrating from serial ports to the Ethernet is the solution. Conversion to Ethernet communication is cost-effective, has a short ROI period, and provides the easiest path to reliable shop floor information and increased operational efficiency.

Manufacturers with an eye on the bottom line should look at this technological leap to maximize the utility of their most valuable assets, their shop floor machines. The added-value provided by Ethernet technology will ensure a competitive edge and a successful business in today’s global environment. CM

Graham Young is the technical sales manager at Memex Automation Inc., Burlington, ON.

www.memex.ca