Technical

A Drool-Worthy Process for Rapid Prototyping of Metal Parts

Direct Metal Laser Sintering Meets Formula-1 – Next Up Product Prototypes?

At my house, it’s not enough to love great products and every detail of how they were made. That fact is obvious to anyone who’s seen my less-than-interested daughter hold her ears and run out of the room screaming at the first peep of conversations involving “machining” or “part line.”

Product design infatuation was clearly part of our marriage vows, along with brewing strong coffee, making soufflé, and having and holding until the end. But those who know my situation best know that a keen love of motorsport was also part of the pre-nup.

So when Formula 1 starts using a new method of rapid prototyping in metal, well, the pairing of the two topics—racing + product—seems almost cause for a celebration where I live, or at least a multi-hour discussion of the method’s potential over dinner with our equally obsessive friends.

Real Metal Parts from an Astonishing Prototyping Process (photo courtesy of 3T RPD)

Real Metal Parts from an Astonishing Prototyping Process (photo courtesy of 3T RPD)

Race Tech, a publication widely read among what must be tens of fans across the English speaking world, had an article in its January issue about Direct Metal Laser Sintering (DMLS) getting some traction with Formula-1 teams. This excerpt might pique your interest:

Advances in the latest sintering technology are likely to turn the whole design rulebook completely on its head and enable designs in metal that would have been completely impossible in earlier times. Design practices associated with traditional manufacturing—turning, milling, drilling and other techniques—could in the future no longer apply and components will be designed solely on their functionality.

To take simple example, holes could be positioned more accurately and in places where previously drill access was totally impossible. The possibilities are endless! Gone also is the concept of tolerance dimensioning because in theory, at least, every part made using DLSM [sic] is exactly the same as the previous one. The future, at least in design and manufacturing, starts here.

Metal parts without machining, casting or tooling! Parts that are functionally near-manufacturing durability and can be used for testing, assembly trials and final design validation!? I imagine this technology having a similar impact to when stereolithography (SLA) took off. Only in this case, the parts are durable, with finishing could emulate a final manufactured part, and can have details that were never possible with conventional fabrication methods.

Just to be 100% clear, they are putting these prototype parts in actual cars and using them to test.

For comparison, consider nylon sintering, called “Selective Laser Sintering” (SLS), if you are familiar with that approach. SLS for prototyping plastic parts has been around a bit longer and is a lot more accessible than metal sintering in terms of availability and cost. Nylon sintering makes durable parts, but the parts are hard to finish relative to an SLA, for example, which can be easily sanded.

Metal laser sintering, on the other hand, is made with much finer layers than its nylon cousin, which means it has a nicer surface to begin with, has greater strength in the z-axis, and—with finishing— is as cosmetically beautiful as a “real” part.

Nylon Chain Mail Part Shows How Sintering Allows Detail Not Possible with Traditional Fab Methods – This Mesh Is Constructed As All One Part, Not Put Together from Separate Rings (photo: Mindtribe)

Nylon Chain Mail Part Shows How Sintering Allows Detail Not Possible with Traditional Fab Methods – This Mesh Is Constructed As All One Part, Not Put Together from Separate Rings (photo: Mindtribe)

DMLS works by melting a powdered material layer-by-very-fine-layer with a laser. The powdered substance contains a mixture of hard and soft materials. (The composition of the powders appears to be undisclosed and proprietary.) The build platform is currently 250mm x 250mm x 215mm high (10″ x 10″ x 8.5″). At each layer, the laser melts the softer substances so that the harder, higher melting point metal is held in suspension. The fusing process has evolved to the point that it almost completely melts the entire powdered mixture. And perhaps more exciting, the alloys have evolved to include not only bronze and nickel but also different steels and even titanium.

DMLS can produce parts with comparable or better properties than casting, including tensile strength, yield strength and elongation, but it cannot yet meet tightest tolerances and surface finish requirements without secondary machining, bench work and polishing.

Metal Sintered Engine Exhaust Parts Can Be Put in a Car and Tested (photo courtesy of 3T RPD)

Metal Sintered Engine Exhaust Parts Can Be Put in a Car and Tested (photo courtesy of 3T RPD)

The DMLS machine, which is made by EOS, starts at a pricey $600K to buy, but supposedly some model shops are starting to have them. Given that the technology has only recently moved from the aerospace industry to Formula-1, that bastion of low-cost engineering prototyping (cough), most of these model makers are near the motorsport centers in Europe. Sue Burnip from 3T RPD in the UK helped me out with all of the photos of the metal parts for this blog. 3T RPD specializes in SLS and DMLS, and is one of the largest LS providers in the UK – home of several F-1 teams. (Race enthusiasts may be interested in 3T RPD case studies, including work for the Jordan-Honda team.)

Aerospace Part Made with DMLS and Secondary Finishing (photo courtesy of 3T RPD)

Aerospace Part Made with DMLS and Secondary Finishing (photo courtesy of 3T RPD)

In the SF Bay Area, I found Prototypes Plus to be the only local option for sintering, but only nylon sintering, which is interesting but not METAL.

Dylan Ternes showed Mindtribe the EOS SLS machine and some samples of nylon sintered parts, including parts made with a small percentage of carbon, glass, and aluminum. He explained that the nylon-based parts seem best suited for prototyping plastic components that are functional pieces on the inside of a product and for not the cosmetic outer enclosure. While Prototypes Plus does offer secondary processes for making the SLS parts cosmetic, the approach doesn’t lend itself to finishing the way SLAs do. Prototypes Plus plans to get a DMLS machine in the future. Dylan has personally checked them out, and he says the metal sintered parts are truly awesome. He adds that metal sintering is “really expensive” at this time.

Dylan at Prototypes Plus Discusses Laser Sintering

Dylan at Prototypes Plus Discusses Laser Sintering

Complex Part that Prototypes Plus Made with Laser Sintering (photos: MindTribe)

Complex Part that Prototypes Plus Made with Laser Sintering (photos: Mindtribe)

My colleague Lionel provided a sample part made with nylon sintering that might help bring home the truly marvelous flexibility of this approach. The spring hook, including the captured functional spring, rotatable strap feed, and other moveable features, was made as a “single part” using nylon laser sintering. This part is not brittle like an SLA would be, so it does not break in use.

Spring Hook with Functional Captured Features Made AS A SINGLE PART with Sintering

Spring Hook with Functional Captured Features Made AS A SINGLE PART with Sintering

Nylon Laser Sintered Parts Are Not Brittle Like SLAs (photos: Mindtribe)

Nylon Laser Sintered Parts Are Not Brittle Like SLAs (photos: Mindtribe)

Just to wrap, as I consider some of the metal details of products my husband has worked on, it occurs to me that metal prototyping may have taken months of quality time away from my marriage. I am sure I watched a lot of F-1 on my own in the 2006 season, in particular. Indeed, my product-consumed partner seems to salivate over the Race Tech article, and I vow to find out more about these machines and how far they are to becoming accessible – if not for the rest of us, at least for those like Apple who can afford to take the pole position for new design methods.

Dyed Nylon Sintered Hands (photo: Mindtribe)

Dyed Nylon Sintered Hands (photo: Mindtribe)