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Pjotr, titanium 3D printed pen

Since 1998

RapidPRO Innalox

Created wherever needed, modified if better

About a decade ago the U.S. Army introduced the Mobile Parts Hospital (MPH). The name derives from the Mobile Army Surgical Hospital (MASH) that is well known because of an identically named film and television series. The MPH’s purpose is to create spare parts on-site or to reproduce parts after being adapted to particular local needs. So a copy of a part is created right after the original has failed. And no parts are kept in stock preventing the Army from moving around tons of ready to use expensive spare parts (unless short-term failures are expected).

The U.S. Army Forces Command (FORSCOM) had already found that trucks and weapon systems are quite often unavailable due to malfunction of simple small parts. With the MPH the Army does not depend on huge local stocks anymore. Local stocks are particular impractical in case of operations in rural areas located at the other side of the planet. Also gathering new parts by plain is not a desirable route because of local security conditions, the weather and costs.

Complementary
Therefore the U.S. Army has put several manufacturing processes into a single container: a machining center and a '3D printer' (for ‘additive manufacturing’ or AM). Both are considered complementary. For some types of parts machining is the best technique and for others it is 3D printing. In most cases a combination of both is best, taking advantage of the power of 3D printing to create complex shapes in a single process, and the power of machining to finish the printed surface more accurately. Note that even steel and titanium can be printed in 3D having very fair material properties (the density of the material is close to 100%). However the surface quality of printed objects is rather poor and sometimes some deformation may occur. This can be remedied by machining their surfaces after they have been printed.

Machine gun
The creation of components near to where they are used can become more beneficial if they get optimized for local needs instead of ‘standard’ products sent by the MoD located ‘back home’. Not only does this concept include advantages with respect of the local availability of components, but also changes can be applied to the geometry and material for better usability. One of the American examples relates to a lever in a machinegun: the modified version made locally turned out to be more effective than the original part. Modifying parts like this is like doing updates on software.
One can 3D scan existing parts locally to get a digital model for printing (or milling) and modify them if appropriate. One can also download all relevant data if available.

MPH.jpg

Timothy Gelios, Mobile Parts Hospital site lead, Kevin Lewis, machinist and Maj. Ardis Ikstrum, 1st Bn., 402nd AFSB special projects officer, look at replacement parts fabricated at the MPH located at Joint Base Balad. In 2008, the MPH team produced 11,000 parts for pieces of equipment ranging from M-16s to 118,000-pound Rough Terrain Container Handlers (source: US Army).

Frigates
The U.S. Army has gained good results using the MPH. Meanwhile, a second generation of the system has been introduced by the U.S. Air Force and Navy. In the case of the U.S. Navy there are MPHs on some frigates.
Next to machining there is 'selective laser melting (SLM, also called 'laser engineered net shaping’ or LENS) and 'laser cladding’. Laser cladding results in a rougher surface than SLM does. In contrast laser cladding is capable of adding metal locally, including surfaces of existing objects like eroded areas. For example the wheels of the Leopard 2 A6 main battle tank being revitalized by laser cladding. This project aimed at doing that on-site with the wheels still attached to the tank. However recently - after nearly two centuries - NL heavy cavalry was ended including this research project initiated by SOLide.

Rein van der Mast MSc (1969) is using AM since '97. He publishes in several Dutch and English / international journals, consults companies in the field modern production methods and is involved in research projects related to new applications of AM. Three years ago he tried to interest the Dutch Defence Material Organisation (DMO) through Mr. De Vries, then Secretary of State. Unfortunately and to his unbelief the management of DMO informed him that availability of spare parts was of no concern to the MoD.

He strongly believes that the MPH holds many advantages in offshore and shipping. A vessel located on open seas is like a frigate of the U.S. Navy. Printing large parts may take many hours. Getting them there by air many more. And again, by creating parts locally one can optimize their geometry etc.