Metal 3D Printing — a Dose of Reality

We have no doubt that hundreds of times a day a hacker is watching a 3D printer spew hot plastic and fantasizes about being able to print directly using metal. While metal printers are more common than ever, they are still out of reach for most people printing as a hobby. But as Mr. Spock once observed: “…you may find that having is not so pleasing a thing after all as wanting. It is not logical, but it is often true.” However, metal 3D printing has its own unique set of challenges. Texas A&M recently produced a short video explaining some of the design issues that you’ll encounter trying to make practical metal prints on an SLS (Selective Laser Melting) printer. You can see the video below.

The description says “It is more challenging to ‘metal 3D print’ a part than most people think. We’ve noticed the same even with plastic printers as friends will expect us to print the most outlandish things for them. What we like about this video is it helps to set expectations of the current state of the art so we’re not expecting far more than today’s metal printers can produce.

Among the features covered in the video are overhangs, which require supports. After removal, the surface is about like 80 grit sandpaper unless you perform further finishing. Just like plastic parts, warping and curling of large areas is a problem with metal. If you’ve ever been frustrated removing plastic support material, try having to ceramic grind metal supports off. They also use an EDM machine to cut especially tough supports, but it causes a lot of effort since it is likely to run through EDM wires and clog the filters.

We looked at recent advances in metal printing last year. We’ve seen homebrew machines that were little more than welders under computer control and we’ve seen plans by big players like HP to create metal prints, but at a steep price. Still, you can’t stop the march of 3D printing progress.

19 thoughts on “Metal 3D Printing — a Dose of Reality

    1. I’ve worked in the field, the real reason for needing supports is threefold:
      1- if you don’t have supports you weld into the underlying powder and generate a really nasty overhang
      2- large sections of overhang will warp due to thermal stresses, bowing out of the powder
      3- most importantly, the recoater (literally a blade of HSS steel or other hard metal) sweeps over the platform and will drag away anthing that isn’t tied down, or bend thin sections, or rip/scalp off small bowed sections

  1. You need support for three reasons:
    1. The melted metal creeps into the powder bed due to gravity; more or less similarly to molten plastic in FDM. This is even more prominant in heavy materials. Lighter alloys require less support and polymer SLS requires only limited or no support.
    2. Heat needs to be transfered away from the melt zone to avoid hot spots which will lead in many cases to a failed print (metal remains molten and sinks in powder bed, losing contact with subsequent layers). Supports towards the base plate help this heat transfer.
    3. The powder leveling sweeper goes back and forth at a precise height at each layer. If a solidified layer has some raised parts, it will hit the sweeper and the part will get a small shock. If the part is not sufficiently bound to the base plate (for example without a wide support base) it will be kicked out of its initial position and the print will fail quickly.

    1. Indeed.

      Sintering (joining solids together without liquifying first — just fusing adjacent beads) is also the process used for MIM (Metal Injection Molding) to turn a ‘brown’ part (plastic with metal beads) into a smaller version without the plastic, just the metal fused (sintered) together. Have people not made ‘brown’ parts with a plastic 3d printer (should be possible with filament, but at least a syringe) to then put through a sintering oven?

  2. I was able to inspect a commercially 3D printed metal part about a year and a half ago. It was a reproduction of an existing hand-forged part, both made of iron as far as I know. It was interesting because the printed part did not fit the original opposing part it should have mated with. Close inspection showed that the lower layers had “sagged” some under the weight of the upper layers of the print. It was not immediately noticeable until you looked closer and compared the original object to the printed one. This is not a problem I would have anticipated and opened my eyes to some of the difficulties in printing metal versus plastic.

  3. We have a metal printer at work (Renishaw) and use it to print functional prototype vehicle suspension parts. They guys running the printer reckon the results are a little superior to the final cast components.
    That is an industrial printer being run by dedicated operators, but indicates what can be aspired to.

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