Old production machines don't have to retire when they start to become less productive not when modern automation systems can give them a new lease on life. That's one of the messages that emerged from last week's Siemens Automation Summit in Orlando, FL.
Modernization has become one of the top issues facing manufacturers, according to Raj Batra, vice president of Siemens' Motion Control and Automation business. "At one point or another, manufacturers have to grapple with how to upgrade their production machines," he says.
A couple presentations at the event underscored this point. One involved the use of modern networking technology to eliminate failing slip ring on one of Osram Sylvania's light bulb machines. The other detailed Owens-Illinois' on-going migration from costly customized motion control systems to off-the-shelf drive-based controls for its glass forming lines. Here's a closer look at both applications:
Reliable Light Bulb Line
Osram Sylvania's upgrade project involved one of the exhaust turret that evacuates air from the light bulbs during the production process. According to Roger Girard, an Osram Sylvania staff engineer, the exhaust machine's slip ring, which carried all the signal communication between the turret's I/O and a nearby PLC, had become troublesome over the years. "In the mornings, it didn't always want to start up," he recalls. And it during the rest of the day, it was causing downtime due to failed RS-485 communications and unreliable signal commutation. "Slip rings do degrade over time," Girard says, pointing out that this system had been in use since the mid-80's.
Osram Sylvania engineers decided to do something about this degraded slip ring during the plant's week-long maintenance shut-down in April. Rather than simply install a new slip ring, though, they revamped the communications architecture using wireless industrial Ethernet (Profinet).
"Going wireless" drastically simplified the communications with the turret's 140 solenoids and 40 pressure switches, Girard explains. The old system, which was based on an STD bus, featured a variety of on-turret controls, including a CPU and I/O cards. In all, the slip ring had to handle 17 different control signals plus power, Girard says.
The new control system removed lots of the communications complexity. It consists of a master Siemens S7 300 PLC installed in an existing cabinet next to the machine. All that goes on the turret now are a wireless interface module and two PROFIBUS I/O racks, which were placed inside the previous STD bus boxes. All the communications between the PLC and the turret-based I/O now take place wirelessly over PROFINET via Siemens Scalance access points. The wireless system did retain the old slip ring but only to provide the 24 VDC power to the new I/O racks. "We eliminated 15 control layers with the new architecture," Girard says.
And they eliminated some long term cost from operating the machine even though the wireless system appears to be more expensive at first glance. Girard estimates that the cost of just replacing the slip ring would have been about $35,000 versus about $100,000 for the wireless architecture. But the wireless figures represent a one-time charge that includes engineering, while slip rings each have to be replaced as they wear out. A few slip ring replacements, and that $100,000 starts to look like a bargain.
The savings become even more pronounced when you consider downtime. Girard estimates that the potential downtime costs from slip ring failures are roughly $140,000 versus just $5,000 to fix problems with the wireless network.
"Just replacing a slip ring doesn't address the underlying problem of the STD bus, which is 80's technology," says Girard.
Better Bottle Forming
Owens-Illinois (O-I), the big supplier of glass packaging, likewise adopted more modern technology when it upgraded the motion control architecture it uses for its glass forming machines. These machines typically have seven different mechanisms to deliver glass, form it and take the bottles away.
O-I uses both servo- and inverter-driven mechanisms for any given motion task, depending on the precision and production requirements of the bottle. "Most machines have a mixture of servo and inverter-driven mechanisms. Some machines use one or another," explains Tom Green, an engineering manager in the company's R&D group.
On some machines, for example, the needles that feed the glass into the forming machine have a servo configuration in which their motion can be individually controlled with electronic cams. On other machines, a single inverter-driven motor runs a mechanical cam that raises and lowers the needles in unison. The same goes for other mechanisms such as one that distributes gobs of glass into different forming stations and the one that pushed finished bottles into an annealing station.
Faced with the expense of maintaining two motor control systems, O-I engineers recently began shopping for a motion control architecture that would accommodate both the servo and inverter mechanisms while keeping costs down. As Green explains, O-I had previously been using many custom components including its own circuit boards, in-house software and modified off-the-shelf motion hardware. "With a custom system you fight obsolescence all the time, and that's a big cost," he says.
After evaluating a handful of motion control offerings from different vendors, O-I picked Siemens' Simotion platform because it allowed the same drive-based control technology to be applied to both the servo and inverter systems. "The award went to Siemens mostly for this reason. It's something that the other vendors struggled with," says Green.
Simotion also met what Green considers a unique constellation of functional requirements, which is one reason O-I had gone the custom route in the past. These include changing cam motions without interrupting the forming process and keeping inverter-driven mechanisms synchronized without the use of motor feedback devices. The software that handles both these tasks was developed with Siemens' help. "It's the first time we let an outsider get involved with our software," Green notes.
O-I engineers also wanted scaleable cabinet design that would adapt to O-I's individual forming lines, which differ in axis count depending on the number of stations and how many bottles each station handles at once. "As an R&D engineer, I don't want to get involved every time we order a cabinet," he says.
A host of other miscellaneous requirement had to be met too. These included support for resolvers, position based I/O, master timing signal scaling and Ethernet communications to a center server using a custom protocol carried over from some of O-I's legacy systems.
O-I engineers first prototyped the Simotion system on the loaders that feed the glass into the line's annealing station. With alternating electronic cam motions and tight timing considerations, this three-axis system is one of the more difficult motion control tasks on the line, according to Green. After the success with that system, O-I's engineering team developed Simotion controls for two of the seven system on the the forming line. "We're currently working on additional applications using the Simotion platform," Green says.