PLCs / Sensors

3 types of inspection and measurement

Munitions manufacturer gets controls and automation overhaul without interrupting production.

By Mike Bacidore, editor in chief

At the only NATO-approved munitions manufacturing location in the United States, production is hitting its stride. But a potential slump was avoided, thanks to some updated automation and an organized installation plan.

“When the global war on terrorism began, munitions supply was a huge issue of concern,” says Rod Emery, P.E., VP of operations at RedViking, designer, builder and integrator of manufacturing solutions and dynamic test systems in Plymouth, Michigan. “They were worried they wouldn’t get the munitions supply they needed. The current systems were unable to keep up with new levels of production.”

The facility’s original five lines of production equipment were built in the late 1960s and early 1970s. “The instrumentation, controls and measurement were antiquated, and the parts and technology were no longer available,” says Emery. “The machinery was constantly failing, or the measurement was calling parts bad that weren’t bad. They had too much downtime and too much scrap. The mechanics and the configuration of the machines were solid though. They just needed to be maintained. The bearings, shafts and gears were still available.”

The five production lines are responsible for producing 1.4 billion rounds of ammunition per year. When RedViking was asked to create a solution, it decided the best course was to build one new system from scratch with all new technologies and instrumentation and then prove the system before replacing the existing five lines.

Who’s on first?

The new machine created a need for high-speed, non-contact inspection technology for test and measurement. “Every 50 ms, you’re measuring a part,” says Emery. “We’re using high-speed cameras for non-contact measurement of the dimensions of the case. There was another location where we were using eddy current to look for tears or holes in the casing. We were using laser scanners to look for abrasions on the product (Figure 1).”

The first system was completed in 2010, and RedViking proved it out at its own facility. It utilized modern technology that includes Rockwell Automation ControlLogix PLCs, RSView SCADA and PowerFlex drives with SERCOS communication, along with off-line measurement instruments developed using the National Instruments LabVIEW platform. “We also included a Rockwell Automation servo system for the sample insert wheel,” says Emery. “The sample wheel is used to validate the equipment, and it’s done twice per shift. They put known samples into the sample wheel to make sure they matched. The wheel goes from zero speed to matching up to 1,200/min.”

To prove out the first system, RedViking ran tens of thousands of rounds, and defects were included to prove the system would eject defective parts. “The customer was responsible for creating the defect, so they hired a contractor,” explains Emery. “We went through the runoff. They put 20 bad parts among the tens of thousands of good parts, and we ran it and we got to the end of the line and we had one less defect than we were supposed to. They’d put permanent dye on the defects to identify all 20, and somehow we missed one of them.”

The engineers sifted through the tens of thousands of cases by hand to find the undetected one with the red dye. “It was hours,” says Emery, “but we finally found the needle in the haystack.”

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However, the case had no defect. “That particular one was supposed to have a very small hole,” explains Emery. “But the people who were supposed to put the defect in it didn’t. They missed it.”

Advance the runner

When the first newly designed machine went in, it was important to keep the lines up at all time. “We installed and did the factory-acceptance test at their location,” says Emery. “Then we began tearing down the equipment that it replaced. The inspections on the old machines were done by probes, and they weren’t able to do all of the inspections we were doing. They had eddy current, but it wasn’t covering the entire case. They were using X-ray. As each turret passed, it performed the inspection.”

The first machine was all hardwired. “There were two separate control panels—one that contained the drives and PLC and the other contained the computers and data acquisition system,” explains Emery. “When we looked at trying to streamline the installation process, we converted to a connectorized solution. We did that on the first one while it was at our facility to make the installation process quicker. It was a combination of industrial Ethernet and fiberoptic. For the discrete stuff, it was a Harding 40-pin connector.”

The first system was completed in about 40 weeks. “We built a lot of the panels and instrumentation ahead of time on the other machines, but it was about 12 weeks per machine for the refurbishment,” says Emery. “It was important for us to make sure there was not a line down. The whole time they went through this, there was never a line down. By the end, we had it down to three days for putting in the new machine and pulling out the old one.”

Once the brand-new system was installed and four of the production lines were replaced with newly equipped systems, the facility had five lines in production, which allowed for the final existing machine to be refurbished and then installed separate from the rest of the line.

“On this equipment, there are three different ways a piece will move through the line,” explains Emery. “The primary way is through the production line—continuous production and continuous inspection. Because they have had a lot of challenges to keeping the equipment running, they wouldn’t shut down production (Figure 2). They would insert a wedge into the line, so every case gets ejected into a gondola, which can be wheeled away and inserted into the equipment in a separate location. The second way is through a hopper. It puts it out and inserts it into another chain that ties into the inspection. The third method is that servo-driven sample wheel. The sixth system was not connected to a manufacturing line. It would only run in that hopper mode. These are separate pieces of equipment that are separate from the manufacturing line.”

Manufacturing Runs

The manufacturing line used three large motors, 150-200 hp, that were driving the main drive turret with only a chain connecting them. “The speed-matching was critical,” explains Emery. “If any motor was running at a different speed from the others, it would rip the chain apart. We used a SERCOS network for that kind of speed, with one motor as master. The most exciting part of that was the validation. We’d hit an e-stop to make sure it ramps down to zero speed safely and synchronously and be sure parts weren’t flying.” When RedViking modernized all of the controls and hardware, there were a lot of the same PLC and HMI riddles to track every part through the production line. “It was important to fire the eject chute quickly enough so it ejects only one part and it’s the right part,” says Emery. “The SCADA system gives all of the production awareness for how many parts and how much scrap there is.”

The final machine was installed in 2013. “The customer was able to meet its requirements and the line never went down,” says Emery. “This project helped to drive activity with our LabVIEW developments. It further defined our load-share capabilities, and some of what we learned about controls architecture and drives technology and project planning is being used for future machine development.”