Stainless filament

[Seadog]

I just skimmed the pdf, does the furnace need an inert gas ?

It's a vacuum furnace - $100,000

 

[Erie Fred]

I think the high end ones use a vacuum furnace.
I don't see why you couldn't use the same methods as heat treating high tolerance parts, ie, inert gas purge or encasement methods?

There is a bunch of powdered metals plants nearby in St. Mary's Pa.
They all have large tanks of Liquid Hydrogen & Nitrogen for the sintering furnaces.
Some have added the metal injection molding process to their capabilities.

I would suggest that heat treating and sintering, while both thermal process's,
are not interchangeable.

 

[Erie Fred]

I’ve got a few items, made in silver and sintered, that my wife made. Used silver clay ‘putty’ - dried and then popped in the kiln at a suitable temperature. I suppose 3D printing is just an extension, to the art, with at least reproducible results.

Were these arts & crafts items ?
(carvings etc.)
Or parts with specific dimensions that need to be held ?

 

[hotponyshoes]

There is a bunch of powdered metals plants nearby in St. Mary's Pa.
They all have large tanks of Liquid Hydrogen & Nitrogen for the sintering furnaces.
Some have added the metal injection molding process to their capabilities.

I would suggest that heat treating and sintering, while both thermal process's,
are not interchangeable.

I didn't mean that you could use the same process, just that (at a hobby level at least) you could use the same equipment.

It must be possible to print this stuff in your shed otherwise what's the point of it?
No use me paying £200 for a roll of filament because I can print it in a £300 printer if I then need to spend £50,000 on a furnace to finish the part.

 

[Erie Fred]

I didn't mean that you could use the same process, just that (at a hobby level at least) you could use the same equipment.

It must be possible to print this stuff in your shed otherwise what's the point of it?
No use me paying £200 for a roll of filament because I can print it in a £300 printer if I then need to spend £50,000 on a furnace to finish the part.

I'm thinking that it will all fall down into a pile of melted mush if the $100k furnace isn't used.

I think the process controls are pretty stringent to get the binder out, the particles
of SS knitted properly, and at the right times.

 

[Seadog]

The part that he sintered took 12 hours in the furnace after being frozen in a freeze dryer for several hours.

 

[Dozzer]

I didn't mean that you could use the same process, just that (at a hobby level at least) you could use the same equipment.

It must be possible to print this stuff in your shed otherwise what's the point of it?
No use me paying £200 for a roll of filament because I can print it in a £300 printer if I then need to spend £50,000 on a furnace to finish the part.

The 3D metal printing has been about for quite a few years, there was a Siemens network of companies that would do the Green sintering for you, its not cheap, but its just a follow on from the older MIM tech
Now BASF have a network of companies that will do the sintering, most of the filament suppliers can recommend someone.
https://evo3d.co.uk/pages/sintering-and-debinding

We have used it to prototyped exhaust manifold in stainless as they are slightly better final density than the laser sintered parts.
The main downside is the filament is very brittle and a total PITA to work with.

 

[hotponyshoes]

I'm thinking that it will all fall down into a pile of melted mush if the $100k furnace isn't used.

I think the process controls are pretty stringent to get the binder out, the particles
of SS knitted properly, and at the right times.

I can't see how an expensive furnace can stop it falling down any better than a cheap one?
A vacuum furnace will remove any out-gassing and possibly any traces of the binding agent.
But an inert purge should also flush out gasses and I'd guess the filament is designed not to produce any negative gasses anyway?
Lost casting filament is already available that leaves virtually no ash and the 99% pure metal I've seen mentioned seems believable enough.

Process control instructions are pretty strict, you would at least want a kiln with a programmable controller and have your temperature control fairly well sorted for accuracy.
I'm not sure how important it would be to have perfectly even heating and even temp rise and so on?
It would make sense that everything would need to be 100% perfect yet, on the other hand, you can print odd shape parts. So if you have a part with a 50mm thick lump and a 1mm feature that won't heat up evenly in a 100k furnace so what shouldn't matter if a budget furnace has a bit of wobble during the ramp phase?

 

[Erie Fred]

I can't see how an expensive furnace can stop it falling down any better than a cheap one?
A vacuum furnace will remove any out-gassing and possibly any traces of the binding agent.
But an inert purge should also flush out gasses and I'd guess the filament is designed not to produce any negative gasses anyway?
Lost casting filament is already available that leaves virtually no ash and the 99% pure metal I've seen mentioned seems believable enough.

Process control instructions are pretty strict, you would at least want a kiln with a programmable controller and have your temperature control fairly well sorted for accuracy.
I'm not sure how important it would be to have perfectly even heating and even temp rise and so on?
It would make sense that everything would need to be 100% perfect yet, on the other hand, you can print odd shape parts. So if you have a part with a 50mm thick lump and a 1mm feature that won't heat up evenly in a 100k furnace so what shouldn't matter if a budget furnace has a bit of wobble during the ramp phase?

I know what I don't know.

Put parts in a hot furnace ?
Maybe furnace needs to be cold, ramp up to a holding temp, pull vacuum, wait
a few hours to degass, ramp up more, burn off, hold.
Ramp up again slow/fast to knit.

I do not know.

I do know that it's not just buying a propane weed burner
and pointing it into a pile of firebricks either.

And as pointed out above, I would not risk the high priced filament
on guessing games.

 

[Dozzer]

I can't see how an expensive furnace can stop it falling down any better than a cheap one?
A vacuum furnace will remove any out-gassing and possibly any traces of the binding agent.
But an inert purge should also flush out gasses and I'd guess the filament is designed not to produce any negative gasses anyway?
Lost casting filament is already available that leaves virtually no ash and the 99% pure metal I've seen mentioned seems believable enough.

Process control instructions are pretty strict, you would at least want a kiln with a programmable controller and have your temperature control fairly well sorted for accuracy.
I'm not sure how important it would be to have perfectly even heating and even temp rise and so on?
It would make sense that everything would need to be 100% perfect yet, on the other hand, you can print odd shape parts. So if you have a part with a 50mm thick lump and a 1mm feature that won't heat up evenly in a 100k furnace so what shouldn't matter if a budget furnace has a bit of wobble during the ramp phase?

When you design your parts, just like you would for normal plastic 3D printing, you design in supports, but mainly you try and make them easy to mill/saw/file off.
A lot of the Cylinder deactivation valve train components are MIM and its an almost identical process of debinding and then sintering and lets you design/create complex components that would be to small/complicated to be machined even on a bar fed CNC

 

[hotponyshoes]

I’ve got a few items, made in silver and sintered, that my wife made. Used silver clay ‘putty’ - dried and then popped in the kiln at a suitable temperature. I suppose 3D printing is just an extension, to the art, with at least reproducible results.

You don't need anything other than heat for silver as it doesn't react with oxygen when heated.
Stainless does so you'll need something to get the air out of the kiln for sintering

 

[Seadog]

Watch the video. All is explained.

 

[hotponyshoes]

When you design your parts, just like you would for normal plastic 3D printing, you design in supports, but mainly you try and make them easy to mill/saw/file off.
A lot of the Cylinder deactivation valve train components are MIM and its an almost identical process of debinding and then sintering and lets you design/create complex components that would be to small/complicated to be machined even on a bar fed CNC

That makes sense.
I guess you would have to put in supports to print it anyway so you just print on a raft, take it off the printer complete with the supports and pop it into the kiln?
Then trim and finish like a cast part?


So what stops everything (including the supports) falling apart once the temperature is high enough to burn off the binder but not yet high enough to fuse the metal powder?

Or does the binder actually turn into something else rather than just burn away?

 

[Dozzer]

@hotponyshoes this is a company we used to work with about 20 years ago on fiber optic terminations, we could get better than 0.05mm accuracy on some parts
its MIM but most of the principals are the same.

 

[hotponyshoes]

Watch the video. All is explained.

Just had a quick look at the video but that looks more like he's using the powder and casting like I mentioned earlier rather than printing directly with stainless filament as mentioned in the first post of this thread?

 

[Dozzer]

That makes sense.
I guess you would have to put in supports to print it anyway so you just print on a raft, take it off the printer complete with the supports and pop it into the kiln?
Then trim and finish like a cast part?


So what stops everything (including the supports) falling apart once the temperature is high enough to burn off the binder but not yet high enough to fuse the metal powder?

Or does the binder actually turn into something else rather than just burn away?

If i remember correctly from my visit with to the factory (its been 20+ years since i dealt with it, so im a bit rusty.) , the filament/moulding putty has different binders/fluxes that bond at different temps. when the part has been debinded from its green stage, its called a brown part, and that is the most fragile stage, (yes they lose a few) but there are low temp solders holding it together,
for the high volume parts the developed ceramic (macor) nests they would support the part but allow shrinkage.
You can get other metals other than just stainless.

 

[Seadog]

Just had a quick look at the video but that looks more like he's using the powder and casting like I mentioned earlier rather than printing directly with stainless filament as mentioned in the first post of this thread?

Correct.

 

[Dozzer]

 

[hotponyshoes]

@hotponyshoes this is a company we used to work with about 20 years ago on fiber optic terminations, we could get better than 0.05mm accuracy on some parts
its MIM but most of the principals are the same.

I'll have a watch tonight

I'm not looking for sub 1mm accuracy.
I've got 2 parts I'd like to make. But I don't actually 'need' these parts, I'd just 'like' to have them.
316l stainless would be a suitable material.
They don't have any small features, don't need precision, don't need mirror polish, but they have compound curves on all axis.

To make these traditionally (material removal) I'd need to start with an oversize piece of stock because of the curves.
Using only the tools I have, I'd spend £40 on the bar stock, maybe another £20 on cutting/grinding consumables and probably best part of a day cutting them out and shaping them up. Not got the time and I probably wouldn't be happy if they were not a well-matched pair.

Next option would be to sit on the sofa and draw them out in cad.
Then send the drawings out for machining.
Probably pushing £200?
Then spend a couple of hours fettling them up when I get them back.
That's the sort of thing I'd do as a birthday present to myself as they'll last me for life.

Or, I Draw them, print them in filament I already have, clean them up and send them off to somewhere that will cast them in 316. That might be more of an issue, plenty of online places offering 5 axis cnc machining by just uploading the drawing for a quote.
Casting foundries seem to be a little bit harder to find and work with..

Or, I spend the £200 on a roll of stainless filament, use the drawing I would have to do anyway, print it out, stick it in the oven.
I'd have to get a programmable controller and fit it to the kiln but that's a job that needs doing anyway.
I'd make those as a test run so I could offset the roll of filament against my tax as I could then print parts for work use.

The parts I use at work are fairly easy to make anyway but the neighbours would probably be happier if I wasn't running an angle grinder at 10pm on a Wednesday night!

 

[hotponyshoes]

You can get other metals other than just stainless.

I've seen them, quite a range including tool steel.
One of the horseshoe manafactures I do a bit of work with has 3d printed custom shape copper coils for induction heaters.
Not sure what process that was as they were all done remotely from the drawings but they would certainly have the interest and the budget to bring that in-house.