Watercutting in Wartime
US Marines deploy waterjet cutting for in-theater rapid response repair
To deal with aggressors ranging from regular troops to ragtag insurgents, in venues from crowded cities to trackless mountains, the Pentagon is developing smaller, more flexible fighting forces built to rapidly adapt to continuing change. With defense spending under increasing scrutiny, efficiency and cost control are concurrent concerns.
Focused on rapid response since its founding, the US Marine Corps has deployed Marine Expeditionary Units to trouble spots around the world for more than 200 years. The Corps’ flexibility depends on its support operations, including such services as in-theater repair and fabrication units that provide immediate machining and welding capability.
In line with trends towards increased speed and efficiency, the Corps recently added advanced abrasive waterjet technology to its on-site metalworking arsenal. Abrasive waterjet machines precisely cut a wide range of materials of various thicknesses, from advanced composites to exotic alloys to traditional metals, while generating no heat and providing a cut edge smooth enough for immediate use in many situations. Low cutting forces minimize workpiece-clamping issues, and CNC programming enables quick adaptation of the process to small-part runs and rapid modifications required to meet changing combat environments.
Camp Leatherneck Deployment
The Marines’ first in-theater use of waterjet technology took place in Camp Leatherneck in Helmand Province, Afghanistan, before the recent troop drawdowns began. According to Gunnery Sergeant Charles Thompson, who commanded the repair and fabrication unit when the waterjet machine arrived overseas, the idea to deploy waterjet technology to the war zone arose during the development of deployable CNC lathes and mills.
The shop Thompson ran at Camp LeJeune prior to deployment to Afghanistan had a waterjet machine, and according to him “some of the guys came up with the idea of a deployable waterjet. Like a CNC lathe, the waterjet is not inherently mobile, but obviously you can do it. The waterjet we used in Afghanistan was almost a proof-of-concept kind of thing.” The idea, he said, was to “provide as much flexibility as possible in machining and fabrication to give combat commanders more options on what can be done. That became a huge force multiplier for us.”
The machine sent to Afghanistan was an Omax Mobile JetMachining Center, a portable system ideal for applications in mining, oil exploration, large ships and even high-rise construction. The model 2652 sent overseas can handle a maximum-size sheet workpiece of approximately 54 × 42" (1.4 × 1.1 m), and 8" (203-mm) thick. Engineered to be quickly and easily moved, the machine was mounted on an epoxy-coated platform featuring lifting eyes, tie-down rings, and flooring consisting of rubberized, non-skid, antifungal material. The system is transportable in a standard shipping container.
Local Water Issues
At Camp Leatherneck, the machine sat on a cement pad under a tent. A water container to feed the machine was filled daily. “The available water was bad for the machine and destroyed a lot of filters,” Thompson said, “If ever in the same situation, a lot of the technicians have suggested a secondary water filter or maybe some kind of totally self-contained system that we wouldn’t have to refill. We didn’t have time to look into something like that, but if I had six months to get ready that is probably something I would explore.”
In abrasive waterjet machining, proper water treatment is critical because it influences the longevity of certain critical machine components, such as the nozzle orifice, on/off valves, seals, check valves and plungers. In order to maintain the high-quality cutting of an abrasive waterjet, it is important to take water contaminants, hardness and temperature into consideration.
The machine proved to be extremely useful. “I could run it 24 hours a day,” Thompson said, “because as you go through combat operations, equipment breaks. And, the waterjet gave us a lot of flexibility logistically to fabricate parts right there, in-theater 10 miles from where they would be used. The machine saved a lot of time and repair costs.”
The machine’s flexibility helped coalition forces counter ongoing changes in enemy tactics. When combat commanders needed different tools to overcome new threats, “They were able to come in and talk to us about what they’d like to do. We would design something on the spot, cut it and give it back to them within an hour,” Thompson said. “They would test it and come back and say, ‘We want 200 of them’ or ‘Hey, tweak this, and then give us 200 of them.’ Because we had almost unlimited fabrication capability with our waterjet, CNC machines and mobile welding shop, we were able to change almost as fast as the enemy. The Intelli-MAX Software Suite on the Omax machine automates most of the programming and tool setup work, which made it extremely easy for my guys to use. They literally could have a prototype done within hours.”
The Hook Brings You Back
A simple but important example of tools conceived to overcome uncommon threats were devices called grappling hooks. Troops dragged the ground with the hooks to find trip wires for improvised explosive devices (IEDs). Unit commanders developed ideas for the best hook configurations to overcome certain types of IED, and the Omax waterjet cut the hooks on site. “Infantry and operators safely find the trip wires without losing their legs,” Thompson said.
An ongoing project involved reinforcement of the frames of heavy-duty M870 trailers. Over 40' (12-m) long and capable of handling a 40-ton (36.3-t) payload, the trailers provided crucial mobility for equipment and supplies. However, they were designed for highway use and, Thompson said, “The terrain was so bad in Afghanistan, and it was destroying parts of the trailers. We had to essentially invent a way to reinforce the I-beams.” Without the use of waterjet technology, the project would have involved plasma-cutting reinforcement plates from stock then finish-grinding them before they were welded between the webs of the beams—a process that would have been extremely time- and cost-consuming. The cutting, grinding and welding could have taken two to three days. Use of the waterjet eliminated several steps in the finishing process, saving significant time and money. The waterjet machine could cut four plates in an hour and a half, then the plates were welded onto the trailer with no further finishing. Downtime was greatly reduced and “We didn’t have to replace the trailers and were able to continue to move stuff around in a very kinetic environment,” Thompson said.
For some projects, waterjet cutting was the only truly viable option. For an upgrade of the MTVR (Medium Tactical Vehicle Replacement) all-wheel-drive all-terrain vehicle, the shop processed approximately 300 armor plates, for the most part, cutting holes for cables. “Armor plating by its nature is very tough. We wouldn’t have been able to cut it on our CNC mill,” Thompson said. To have the heavy plates manufactured in the United States and shipped to Afghanistan would have been unreasonably slow and expensive.
The waterjet machine typically handled workpieces up to 3/8" (9.5-mm) thick, but some parts were cut from 2" (51-mm) square stock. Materials were mainly steel plate and aluminum, but the shop also machined 2000 titanium washers for a V-22 Osprey tilt-rotor aircraft. Waterjet performance on titanium, Thompson said, was “awesome, better than trying to mill it. The only problem with the washers was that they were so small we would lose them down in the tank.”
Learning on the Job
In general, achieving quick response limits the amount of time available to get a job done. As troops rotated in and out of the war zone, time for training in machine operation was minimal or nonexistent. Gunnery Sergeant Anthony Lashley followed Thompson in command of the welding and fabrication unit at Camp Leatherneck. Although he was very familiar with manual and CNC lathes and mills, Lashley had no prior experience with waterjet machining. “I had no official training, and had a lot of reservations about it,” he said. However, he “learned on the job, in just a few days.” Regarding programming, he said, “In a week, I had it down. I found it to be one of the easier machines to use. You don’t have to put in any code. Once you get the dimensions, what you draw is what it is going to be cut.”
According to Thompson, the isolation of the combat zone presented a challenge like no other. “Afghanistan is far away from everything. I think the only place farther we could have gone is the moon. You can’t just order something on Amazon and it shows up. It must go through some pretty unstable places, and there is no infrastructure. The only thing I think we could have done better when introducing the waterjet was prepping for the supplies for the machine, such as repair parts and the like.” However, he said, “When we did have a problem with the machine, Omax flew a guy over.” Although the service technician’s trip to the base was difficult, Thompson said, “He was still a pro once he arrived. In 10 days, the technician taught the person running the machine more than he probably learned the entire time before.”
As part of the drawdown, the mobile machine was sent back to the United States where it continues its active duty at the Marines’ Camp Pendleton. Thompson concluded saying that “right until the time Lashley and his guys boxed the machine up and sent it home from Afghanistan that thing was running and making us parts fast.” ✈
Article edited by Yearbook Editor Michael Anderson from information provided by Omax Corp.
This article was first published in the 2013 edition of the Aerospace & Defense Manufacturing Yearbook.
Published Date : 10/14/2013