Flexibility Is Key to Automated Welding

Figure 1: A standards-based, industry-accepted communication solution of EtherNet/IP and IO-Link provided the flexibility, speed, information handling and ease of use for CenterLine’s updated FlexFast welding machines.

Challenging Customer Demands

In the process of updating our popular FlexFast welding machines (Figure 1), our company identified several requirements for increased flexibility and performance. Because the FlexFast's unique modular design is used for applications ranging from advanced fastener (nut & stud) welding to other resistance-welding applications, the versatility of the equipment needed to be supported by a controls architecture that was just as flexible.

In operation, a programmable servo axis moves the fixture that holds the part or parts in place to an operating area where a similarly programmed motion profile places the parts (nuts, studs) to be welded in position, and moves the welding electrodes in place to execute the welds based on the programmed "recipe" in the controlling PLC.

The design update was required to satisfy an expanding, globally competitive market, and to meet the demands of a growing customer base. To extend the flexibility of the machine, CenterLine needed an I/O and controls design that provided a common platform, allowed for a growing variety of tooling, and enabled its machines to interface with many different controller brands regardless of customer specifications.

"We were looking for a globally available platform that would be fast, flexible and provide the features that would satisfy the needs of our international customers," says Simon Britton, controls technologist at CenterLine. "When we evaluated various solutions, we decided to move away from DeviceNet and considered an Ethernet/IO-Link solution.

Controls manager Scott Pittl says that DeviceNet didn't give the Flexfast the update speeds it needed. "There's a lot of analog information, such as VeriFast electrode information that measures the position of the welding pin and the position of the upper electrode, passing through the network from devices," he explains. "All of this is needed quickly and precisely to make a ‘weld proceed' and ‘weld complete' decision."

Unique ID Manages Fixtures

A main hurdle with Ethernet was how to handle the analog signals effectively. IO-Link was a solution that had the proper signal resolution we were seeking, as well as being very competitively priced and accepted internationally. That particular value proposition made it easy for us to select IO-Link.

The new FlexFast design also demanded a controls architecture that could easily integrate new automation components with minimal concern. "The need to integrate new components on the machine quickly and easily is critical to addressing ongoing changes in production needs that this equipment is expected to satisfy," Britton adds. "For example, one challenge was that standard mechanical components and custom controls affect how the tooling fixture that holds the part is configured (Figure 2). IO-Link allowed us to standardize many tooling fixture elements and run manufacturing in batches, which resulted in improving the modularity of the overall platform at an improved cost and faster turnaround time."

IO-Link gives us the possibility to assign a unique engineering ID number to each fixture. With IO-Link, we can call it that number, and even with multiples of the same fixture, we can identify them individually with a memory-accessed node address on the fixture. We couldn't do that with DeviceNet.

To realize these objectives, CenterLine partnered with Balluff, a global sensor, networking and RFID component supplier. This enabled CenterLine to use a distributed modular I/O solution that incorporates IO-Link technology. IO-Link is a universal, vendor-neutral standard designed to make it easy to integrate automation components into any control architecture. 

There's a high level of acceptance of Balluff in our industry and Balluff has been very proactive in supporting our needs, so it was the logical IO-Link supplier for us. By specifying Balluff's I/O hubs with built-in identification data, CenterLine was able to operate multiple tooling fixtures with the same standard machine.

"This was possible with our old DeviceNet solution, but it only could be effectively applied on one machine at a time; in other words, one machine, several tooling plate fixtures, since the available identification format wasn't large or versatile enough to allow us to track individual tooling from design all the way through the equipment build," Pittl explains.

"Essentially, we now can identify every single tooling plate uniquely without duplication, and that information can be written to the tooling block control to identify every single tool on a project accurately, regardless of machine. This makes it possible for us to move tooling across different machines. Since the ID is generated in engineering during design, it's maintained all through our other business systems, so we can accurately track it all the way through a project and into the installation environment. It's as if the tooling has a fingerprint."

This increased the flexibility and intelligence of the equipment without increasing the overall cost of the machine. Moreover, it enabled CenterLine to accurately track interchangeable tools to ensure proper machine setup.

Essentially, IO-Link allowed CenterLine to have a common control architecture while easily integrating a wide variety of sensing and control components. "IO-Link supports the versatility of our product line, and the new design streamlines the design of the equipment while reducing cycle time and increasing machine throughput," CenterLine product engineer Adam Waites says.

A Significant Improvement

Figure 2: With IO-Link, CenterLine can identify each welding fixture with a unique number and, even with multiples of the same fixture, can identify them individually with a memory-accessed node address on the fixture.

"It's important to mention that the improvements in configuring the systems have been significant," Waites adds. "In the past, an average machine could take up to a day to configure. With IO-Link, we tend to do it in about two hours. On large programs this is a very visible savings, and also helps us maintain consistent practices." 

Of particular importance is that IO-Link talks to any fieldbus. "Whether our customer uses EtherNet/IP, DeviceNet, Profibus or Profinet, we don't have to worry about platform standards," Britton adds. "Whatever they require, we've been able to accommodate using various masters that Balluff provided that connect to each of these protocols and drop down to IO-Link."

Gateway to Ethernet

IO-Link operates in a similar manner to a gateway for most fieldbus protocols," adds Will Healy, networking marketing manager for Balluff. "Or a simpler realization is a master/slave relationship. The IO-Link master is a slave on the Ethernet I/O network, and acts as a master to the individual IO-Link slave devices. The data from the devices appears on the fieldbus as a maximum of 32 bytes input and 32 bytes output. Thus the data is easily realized to the controller and then can be communicated via the controller to the ERP or CMM systems. Add-on instructions (AOIs) or function blocks are used by the engineering software to integrate the bitmap into usable, data-like switch points, measurements or diagnostics."

By integrating IO-Link components into its machine, CenterLine was able to fulfill its need for increased flexibility and improved cycle time. "We saved up to a second per weld by making these changes, with half of that saving coming directly from IO-Link integration and half from mechanical improvements we made to the equipment and our change to Ethernet," says CenterLine's Pittl. "By facilitating and improving the processing of the analog signals at the weld point, we realized up to one second per weld cycle time improvement all at a reduced implementation cost." 

Remote Is Better

Could this machine be connected with a centralized I/O system rather than distributed via the I/O blocks? Yes, a centralized I/O system could have been used in this application, but we think that comes with a set of problems. Centralized I/O requires greater wiring efforts, has fewer diagnostics, less intelligence and ultimately might be a greater risk for us and our customers. 

"The benefit of a modular decentralized solution is seen in a setup like CenterLine's," Balluff's Healy states. "With multiple tool changes, a centralized I/O system can be a struggle to wire and configure on tool changes. With a centralized I/O system, large multi-conductor connectors are used, and these require regular maintenance or replacement. And, if someone forgets to disconnect it before removing a tool, a significant amount of downtime can occur for repair of the tool and machine."

The Road Ahead

Now that CenterLine has integrated IO-Link into its machines, our future designs can quickly and easily take advantage of the value of other IO-Link technologies such as the Smart Light stack light and valve manifold control. The company also uses the remote IO-Link solution on some of its other automated systems, and has realized similar benefits.

New Kid on the Block

IO-Link is relatively new to North America, compared with Europe, for example, and we sometimes see some resistance to its use, but when we demonstrate the benefits, we have been able to sell it. The biggest hurdle was that customers did not have spare I/O blocks, so we included spares in many of our proposals. Our company believes that IO-Link is ready to handle expanding requirements for years to come.

"IO-Link does not replace a digital fieldbus. In fact, IO-Link can be thought of as enhancing existing fieldbus and Ethernet technologies," says Jason Dias, head of quality and technical support for Balluff Canada. "IO-Link makes use of the current controls architecture, and delivers more functionality, diagnostics and intelligence—all in a more cost-effective and easy to implement package."

What our company offers today could be very different from what we offer in the future. IO-Link being an open standard allows for new devices to be implemented at the customer's request.

At some point, CenterLine will start to make better use of the remote diagnostics and troubleshooting capabilities for its installed machines. IO-Link devices provide a diverse selection of diagnostic data from operational status to maintenance required. In addition, the IO-Link master stores all of the configuration data of slave devices, and can reprogram a replacement to a broken part automatically. This means a basic maintenance technician can replace a complex device as easy as a prox switch without a manual or instruction. This reduces the number of service calls to the machine builder.