3-D Printed Pelvis Holding Up After 3 Years

An anonymous reader writes "Here's a neat story out of Britain, with good news about long-term success for the patient involved, and for others who might benefit from similar procedures: three years ago, surgeon Craig Gerrand successfully printed and implanted an artificial pelvis (actually, about half of one) into a patient suffering from a rare form of cancer. Other techniques were ruled out, because the patient would be losing so much bone. So, after careful scanning, additive printing with titanium was used to create the replacement: 'In order to create the 3-D printed pelvis, the surgeons took scans of the man's pelvis to take exact measurements of how much 3-D printed bone needed to be produced and passed it along to Stanmore Implants. The company used the scans to create a titanium 3-D replacement, by fusing layers of titanium together and then coating it with a mineral that would allow the remaining bone cells to attach.' Now, three years after the procedure, the printed pelvis is holding up just fine, and the patient is able to walk with a cane."

Re:Not plastic, titanium

[ubergeek2009]

Selective Laser Sintering metal printing although much stronger than typical Fused Deposition Modeling is nowhere near as strong or tough as cast and treated metal components. It has it's place and this is one, but SLS is not great everywhere.

Re:Not plastic, titanium

[drinkypoo]

Wiki quote: "Unlike some metal sintering techniques, the parts are fully dense, void-free, and extremely strong."

Bah. Sintered metal parts are usually both of those first two things. But the parts have an inferior failure mode (and are more likely to fail) when compared to forged due to the fine grain structure, as opposed to a large interlocking grain structure. Large grains are like legos and small grains are like sand. The large grains interlock, the small grains don't.

Re:And how much would that cost in America?

[ElementOfDestruction]

I know I'm feeding a troll, but that's a really great argument. Justifying the backbreaking expense of keeping oneself alive against the cost of fuel in two countries. I suppose if you consider the far more efficient vehicles, the vastly reduced amount of driving required, and the great public transport alternatives the argument kind of doesn't seem as brilliant. But I'm just splitting hairs I suppose.

Re:Not plastic, titanium

[drinkypoo]

Forging is what creates the large, interlocking grain structure. No forging, no large interlocking grains. You do get some benefits from sintering, like extreme regularity. Thus, even though the failure mode is less desirable, you can more reasonably engineer out failure because you have a better expectation of how the part will behave. The only problem is that ounce for ounce it won't behave as well as forged+machined, so you're either going to throw more material at the problem, or you're going to have to do more design work and then use more costly manufacturing processes. There are inexpensive sintering processes which are not substantially different in most ways from casting plastic, and even without incremental deposition techniques you get secondary benefits which also reduce cost like being able to crack the caps off conn rods instead of machining them to match. By combining deposition modeling you can also create shapes which you can't reasonably cast, which makes using sintered metal practical; you can throw more metal at the problem where necessary to increase durability and strength lost by using sintered metal as opposed to forged, but you can also reduce metal in places you couldn't with casting, without machining it away.

I am also not an expert on this subject, but I've been doing a lot of reading on it recently.