Sieving Station Promotes "Cleaner" Metal Powder for 3D Printing

SIEVGEN 400-US:  Photo Credit - Farleygreene

When I worked for Nabisco, we had large robust sieves that would prepare flour being drawn from our 7-story flour towers prior to discharging into the weigh scales and mixers - several hundred pounds each batch.  The contraptions looked like very large metal boxes that shook and rotated violently to sieve the flour.  So it makes sense to me that a similar process would be recommended to pre-treat metal powders before being sintered into a 3D print.

In fact, a couple of challenges using powders in manufacturing processes are material purity and particle size. Apparently Farleygreene has introduced its SIEVGEN 400-US specifically to address these concerns for DMLS additive manufacturing.

“According to Farleygreene, when in normal use the system provides for a completely sealed and dust tight process. The feed hopper is docked into place to feed the sieve unit with a self-sealing interface and the media is introduced through an internal metering device designed to ensure the optimum screen dwell time to recover as much useable material as possible.

Oversize powder is continuously removed and ‘good’ product falls through the ultrasonically excited mesh. The screened media is filled into a receptacle locked into place on a mobile dolly to reduce manual handling as much as possible and allow the operator to move the product to where it is required.”

When you are hitting a potentially explosive metal powder with a laser, powder consistency and purity are obviously important material attributes to control.

3D Printed Titanium Vertebrae Saves Life of Cancer Patient

Credit: 3Dprint.com

Dr. Ralph Mobbs of the Sydney Spine Clinic turned to 3D printing to save the life of a patient suffering from a rare form of cancer. Drage Josevski was diagnosed with chordoma, a cancer that affects the spine.  His case was especially difficult because  the tumor was located in his top two vertebrae. Dr. Mobbs performed a landmark procedure that replaced the vertebrae with a 3D printed titanium implant. Josevski’s surgery was a success, and he is in rehabilitation to adjust to the implant. This achievement is yet another example of the possibilities 3D printing creates for the medical field.

What's the Difference Between Selective Laser Sintering (SLS) and Selective Laser Melting (SLM)

Samples of metal printed parts

What's the difference between Selective Laser Sintering (SLS) and Selective Laser Melting (SLM)?  Here's one of the better descriptions I've found that explains it:

"Selective Laser Sintering and Direct Metal Laser Sintering are essentially the same thing, with SLS used to refer to the process as applied to a variety of materials—plastics, glass, ceramics—whereas DMLS refers to the process as applied to metal alloys. But what sets sintering apart from melting or "Cusing" is that the sintering processes do not fully melt the powder, but heat it to the point that the powder can fuse together on a molecular level. And with sintering, the porosity of the material can be controlled.

Selective Laser Melting, on the other hand, can do the same as sintering--and go one further, by using the laser to achieve a full melt. Meaning the powder is not merely fused together, but is actually melted into a homogenous part. That makes melting the way to go for a monomaterial, as there's just one melting point, not the variety you'd find in an alloy. To nutshell it, if you're working with an alloy of some sort, you'll go SLS or DMLS; if you're working with say, pure titanium, you'll go with SLM."

So in lay terms, SLM is stronger because it has fewer or no voids which helps prevent part failure but is only feasible when using with a single metal powder.

RapidMade works extensively with SLS and DMLS processes.  To learn more, click here or contact us.

Original release: http://www.eurekalert.org/pub_releases/2014-06/dlnl-lrd061614.php

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Selective Inhibition Sintering Seen as Affordable Metal Printing Technology

Wrench printed by SIS (Photo Credit:  3DPrint.com)

Many consider the affordable 3D printing of metal to be a breakthrough that would allow greater adoption of additive manufacturing for end-use parts.  According to 3Dprint.com, researchers at the University of Southern California are working on a novel approach to that end:  Selective Inhibition Sintering (SIS) which inhibits powder from melting, instead using it a mold:

"Using this new technique, a machine first lays down a layer of metal powder on a print bed. At this point a commercial piezoelectric printhead deposits a liquid solution which acts an an inhibitor, preventing the metal that it is sprayed upon from melting once it’s heated. The printhead, which is similar to that found in an inkjet printer, only sprays in an area which represents the boundary of the actual print. Where this solution is sprayed, the metal clumps together and hardens.  Layer by layer, more metal powder is deposited, and more of the inhibiting agent is sprayed onto the print bed. The boundary of the object slowly is built up, with metal powder inside.  It basically becomes a mold filled with pristine metal powder. When complete the entire print is then melted at a high temperature, leaving behind a solid object encased inside the inhibitor shell, which is then easily removed."

SIS is being touted as an affordable alternative to other metal printing processes because:

• It relies on printhead technology which is seen as cheaper
• It builds only the boundary of an object and is therefore faster.
• Unused powder can still be reclaimed since the inhibitor is made from sucrose which can be dissolved in water.

While not yet perfected - part shrinkage and inhibitor application problems have occurred - researchers are encouraged by their preliminary results. 

Additive Manufacturing in Aerospace

A stainless steel bracket optimized for weight reduction (front) and the traditional cast bracket in the back.

Additive manufacturing (AM) has long been the holy grail of Aerospace OEMs like Boeing and Airbus. Where typically the costs of metal laser sintering can be prohibitive to mass producing parts, in the aerospace industry volumes are low enough and the design optimizations can easily pay for themselves in fuel and material savings. 

EADS Innovation Works recently released a study that says implementing additive manufacturing into planes and other aircraft could reduce material use up to 75% and fuel consumption up to 40%. 

Let's set aside the obvious environmental benefits for a moment. In an industry that is a slave to fuel costs and customers who always buy the lowest sticker price ticket off aggregator websites, airlines tend to get squeezed when it comes to making their margins.

Cutting just one pound of weight out of an aircraft can save over $10,000 in fuel costs every year. Not only do AM parts cut out that 75% of the material by only using structure where it is absolutely necessary, but light weight, high cost metals like titanium are now available where they were traditionally cost prohibitive, further lightening the load.

Machining titanium parts from billet generally causes up to 90% material waste versus virtually no waste from making the parts additively. Couple that with needing less material in the part design as a whole and scores of components that used to be made from stainless steel or aluminum can now be made from the valuable metal.

This is why we now hear engineers and executives dreaming about the development of printers that are large enough to manufacture entire wings. They see the value in a future where aircraft are created entirely from printed components. 

Maybe the additional payload provided by these technologies will eventually even eliminate the need for bag fees. Unlikely, but one can dream!