Rapid Prototyping Speeds Deployment of Stronger, Safer MRAP

May 18, 2010
Mine-Resistant Ambush Protected (MRAP) vehicles are improving the standard of safety for soldiers in combat zones, and a prototyping firm is helping to accelerate these vehicles from design to deployment.
Using multiple production processes, as well as its design and engineering expertise, 3-Dimensional Services Group was able to create these parts quickly and assemble them into a completed door-assist module for the Navistar Defense MaxxPro MRAP, one of the new breed of vehicles that are providing higher levels of protection for military personnel.

The powerful, and heavily armored, troop carrier called the MRAP (for “mine-resistant ambush protected” vehicle) won’t win any prizes for style, though the people who ride in it don’t mind a bit. That’s because thanks to a V-shaped hull that deflects the force of explosions beneath it, and its outer shell of thick steel plate, it has brought U.S. soldiers and Marines an unmatched level of protection against explosives and small arms fire. Once the effectiveness of these vehicles in saving lives and preventing injuries became obvious, the U.S. Dept. of Defense rushed to increase the number of them available for deployment to combat zones. In May 2007, Secretary of Defense Robert Gates declared that the acquisition of MRAPs was the DoD’s highest priority.

Among the companies charged with supplying these vehicles is Navistar Defense. Navistar and its suppliers had to move quickly to fill the DoD’s order. The work of developing new components for this evolving family of vehicles had to be done rapidly and it had to be done right. Navistar Defense supplier Inteva, a manufacturer of door systems, was tasked with producing a new door-assist module for the Navistar Defense MaxxPro MRAP, as well as the heavier MaxxPro Plus and MaxxPro Dash models. The module assures that the vehicle’s 2,000-lb armored door with its air-assisted hydraulics opens in case of an accident or emergency. It also prevents the door from accidentally closing on a person.

As a partner in this vital work Inteva chose 3-Dimensional Services Group, a firm that specializes in design, engineering and analysis, in-house tool construction, and complete build of prototype first-off parts and low-to-medium volume production runs. Its use of advanced process methods, manufacturing technologies and staff talents means that prototype parts—not just models—are typically provided up to 70% faster than conventionally equipped prototype shops are able to offer.

The door-assist module is a complex part and 3-Dimensional Services was tasked with creating 63 components in all. These included the base plate, two latching components designed to be mounted to the body inside the door skin, hinges which are, similarly, covered by the door skin, side rods, and slider blocks.

An array of production processes
To create this complex part an array of production processes were required. Forming was used to produce the angle supports for slide system. Welding, both manual and robotic, was employed: manual welding for the module’s handles, levers, and angle supports, while the main base plate and close out brackets were robotically welded. Plastic injection molding, using tough, metal-like Delrin (Polyoxymethylene) as well as Sanaprene thermal plastic elastomer was used to make the wedges and handle covers.

Laser cutting and CNC machining were primary operations used on nearly all of the module’s metal components. Materials included A36 stainless, high strength/low alloy steel and, for the hinges, CNC 1045 steel. Fortunately, 3-Dimensional Services was able to bring both a high degree of staff expertise and a virtual arsenal of equipment to bear in each of these areas.

“Our lasers—both 3- and 5-axis—can cut through thick armor plate or slice through thin sheet metal, all with amazingly tight tolerances,” notes Mike Brabandt, Senior Sales Engineer for 3-Dimensional Services Group. The 3-axis laser cutting systems excel in speed, accuracy and flexibility, while the 5-axis systems are ideal for cutting complex contours and shapes, and 3-Dimensional has designed, developed and produced needed laser systems in house, including an ultra high-speed unit with cutting speeds up to 50,000 mm per minute.

In terms of machining 3-Dimensional Services has over 40 CNC machining centers along with 75 knee mills and lathes, and the ability to machine steels hardened to 60 Rockwell at feed rates of up to 20,000 mm per minute, as well as machine and finish grind with machining centers that provide a 40,000-rpm spindle with 30,000-mm per minute feed rate. Thus, neither machining capacity nor machining expertise was an issue when it came to processing the metal components for the door-assist module.

Seven-day turnaround
Capabilities like these allowed 3-Dimensional Services to complete the prototype in a mere seven days. Four design iterations followed, and all were successfully performed over the course of a single month thanks in large measure to the size and capabilities of 3-Dimensional Service design and engineering department, which boasts over 30 high-speed CAD terminals and employs nearly all major CAD/CAM packages, including CATIA, Delcam, Mastercam, Unigraphics, SolidWorks and ProE.

The final design of the MRAP door modules called for components to be zinc yellow chromate-plated for superior corrosion resistance, and for the module to be CARC (chemical agent resistant coating) painted. CARC, which is typically used on today’s U.S. military vehicles, is a polyurethane paint that provides superior durability, extends service life for military vehicles and equipment, provides surfaces with superior resistance to chemical warfare agent penetration, and greatly simplifies decontamination.

3-Dimensional Services moved swiftly to commence limited-run production of the approved door-assist module design, making 300 to 400 per month for an eventual total of 2500 units. According to Mike Brabandt, successfully completing a demanding prototyping challenge is always a professionally rewarding experience, but in the case of the MRAP door-assist module it was something more.

“We know how important these modules, and the vehicles they’re a part of, are for the safety of our troops, so we’re gratified that we were able to work closely with Inteva to make this happen.”

The 3-Dimensional Services Group, consisting of 3-Dimensional Services, Urgent Plastic Services, and Urgent Design & Manufacturing, provides rapid prototyping services that encompass virtually all relevant processes, including injection molding and casting, stamping, machining, robotic and manual welding, laser cutting and welding, waterjet, hydroforming, tube bending, vibration welding, casting and pattern fabrication, RIM tooling, SLA, LOM and SLS rapid prototyping, and assembly.

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