Is a metal 3D printed part a sinter?

I've used a helium sniffer on some metal 3D printed part done by the DMLS method. It's a small part with a pipefitting on each end, and some internal geometry. I could detect some helium on the outside of the part, but I don't know if it leaks through the wall of the part, or if it leaks around the swaged pipefitting and "sticks" to the surface of the part.

Does anybody know if a 3D printed part is a sinter or if it is gasproof?

DMLS stands for "Direct Metal Laser Sintering"

JNieman said:

DMLS stands for "Direct Metal Laser Sintering"

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Yah, like duh. Are the parts actually porous? If so, can they be made nonporous? I assume among the people on this forum who has access to a printer like this, maybe a couple deal in the gaseous realm.

jeuhrn said:

Are the parts actually porous? If so, can they be made nonporous?

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DMLS is a bit of an old term nowdays as the laser really welds the powder to each layer. EOS still uses the term because they originally invented the process.

That said, the layers are still not 100% solidified unless the parts get HIPed (Hot Isostatic Press) afterward.

https://en.wikipedia.org/wiki/Hot_isostatic_pressing

Philabuster said:

DMLS is a bit of an old term nowdays as the laser really welds the powder to each layer. EOS still uses the term because they originally invented the process.

That said, the layers are still not 100% solidified unless the parts get HIPed (Hot Isostatic Press) afterward.

https://en.wikipedia.org/wiki/Hot_isostatic_pressing

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Exactly what I needed! Thanks!

Futher to previous..
I suspect it wont hold helium (or hydrogen) no matter what.

Both gases are really slipperty.

Air at moderate pressure ..sure.

Just another thought, there could be cracks due to internal stress. I've had problems with well-hidden cracks, pariticularly at sudden changes of section. Haven't had any obvious porosity problems in my pressure vessel parts, but they're only holding air.

Sounds like Philabuster got things covered though.

DMLS process

jeuhrn said:

I've used a helium sniffer on some metal 3D printed part done by the DMLS method. It's a small part with a pipefitting on each end, and some internal geometry. I could detect some helium on the outside of the part, but I don't know if it leaks through the wall of the part, or if it leaks around the swaged pipefitting and "sticks" to the surface of the part.

Does anybody know if a 3D printed part is a sinter or if it is gasproof?

Click to expand...

There was an early DMLS vendor (can't remember their name) who promoted the process for short run injection molding tooling. Their process was to print the part, set it on a block of copper, run the whole thing in a non-oxidizing furnace whereby the copper melted and infused (by capillary action) the sintered structure. A bit of polishing on the mold surface and you were good to go. High speed machining and aluminum mold alloys kind of killed that one for short run tools since I don't see or read much about the process anymore. It would however create the "helium gas tight" structure that you are interested it and might be worthwhile for complex geometries that lend themselves to printing vs. 3-5 axis machining.

jeuhrn said:

Yah, like duh. Are the parts actually porous? If so, can they be made nonporous? I assume among the people on this forum who has access to a printer like this, maybe a couple deal in the gaseous realm.

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I didn't mean to come off sarcastic or speak to you as if you were ignorant. I just couldn't tell if you were very unaware of "3d printing" methods or if you were looking for very specific needs. I've put time into writing out detailed and long-winded posts with experience and references/examples only to find out the person just wanted to see a one-word answer to a simple question. So I didn't want to waste my time. I'm selfish like that, I guess

I don't know about the "Hot Isostatic Pressing" - no experience there but it sounds pretty effective.

I do know that some carbon steels can be, essentially, annealed afterwards to reduce stresses that may induce internal cracking and also has the benefit of reducing porosity, but still is only going to be in the 95-97% range. I haven't had to deal with pressurized parts. Our concerns with porosity has been surface quality after machining. "Post-Printing Heat-Treatment" has been helpful. Whoever you contract to do the manufacturing, or whoever sells the machine, will likely have good information on options and expected results.