Major advance in 3d printing : How do you do the same thing with Titanium?

[EzinX]

http://www.ibtimes.co.uk/carbon3d-amazing-new-3d-printing-technique-100-times-faster-using-light-oxygen-1492315

To summarize : instead of moving a print head over the entire surface one layer at a time, they use a UV sensitive plastic. The membrane they are firing the UV through is oxygen permeable, and the plastic doesn't cure where oxygen is present, create sharp boundaries between the printed regions.

This is brilliant. It eliminates most of the flaws I have seen with plastic printed parts - they have these clearly visible seams between layers, and a rough surface. Parts out of this machine are continuous, mathematically smooth contours.

It's much, much faster - printing with a 2d image means it takes a lot less time. And it's much stronger - a continuous process can be optimized for maximum mechanical strength. A "layered" process can't because there is variance in the layers.

So, how can this be done with metal? You could use several scanning beam projectors to create a 2d laser image on the metal surface. You use several so the beams overlap and create a smoother, higher resolution image. With quality optics, there would be enough beam intensity to melt metal powder.

However, how do you get new pieces of metal powder to the surface in a continuous manner? You can't have the metal in a liquid form because heating it would only make it more molten. If you try to use liquid as a carrier, you are contaminating the metal with whatever the liquid is.

The only thing that comes to mind is if the pieces of metal are extremely tiny - smaller than the wavelength of laser light - the light would diffract around them. So, in a vacuum chamber, you would be spraying this continuous mist of metal pieces towards a surface. The laser beams would shine right through the mist to the surface, continually adding features. Anyone have a better idea?

[Mazon Del]

Most super high end 'standard' type deposition printers have the striations (layers) at far too fine a level for human senses to detect. For home printers (anything less than say $10K), you are likely going with methods that would cause the striations. I myself have three printers that do this.

The primary way to look at the speed advantage of this system (which strictly speaking is actually not a new system, it's just 'new' because the patents on it expired within the last year, so now little guys and startups can suddenly sell the tech in not-million-dollar formats) is that it is producing the entire 'layer' at the same instant whereas a print-head is like moving a single pixel around.

The way you do this with metal is pretty much the way we've been doing it with metal this whole time. You have an arm (think the scanner light inside a photocopier) that sweeps across the part dropping down the fine metal dust particles of your chosen metallurgy and after the arm has swung by then really quickly a laser zap-fries the top surface in the design you want for that layer (pretty much as you described). This slightly melts the metal so that it merges with the previous layers. This method is 'fast' in that it is much faster than a print-head style printer while maintaining crazy good tolerances, but it's speed is ultimately limited to how quickly the deposition arm can make its sweeps while insuring that the powder falls in sufficient quantity over the part to guarantee coverage.

This method was actually the first used for liquid printers, except it was a spray line. Eventually they went full liquid immersion with all kinds of fancy tricks. Industry 3D printing tech is about 10-15 years of what you can snag for home tech. However, a lot of the very earliest patents are expiring which means that you can make a company based off of selling products using that tech without having to pay for royalties. Or perhaps to be more true to history, you can make a company that sells them at all. The makers of 3D printers have always been aware of how game changing their tech can become, and so they have hoarded their patents from each other as tightly as they can. Excluding some relatively rare cases, the tech never left their control over the course of the patents.

The unfortunate limitation when it comes to metal, is that unless we did something silly like using x-ray radiation that can pass through the metal (and do a converging beams style of heating) we are limited by the fact that the metal will block any attempts to melt it. Plastic (like the liquid plastic) has the advantage that you can play loads of fun molecular games with the long/short chains involved to get them to do things like cure under specialized conditions such that your UV light won't cure unnecessary plastic. Metal though, is just what it is. And what it is, is something that blocks the energy. I do believe (but I have no citations) that there have been attempts at using a relatively constant outpouring of a metal-particulate impregnated gas combined with the converging beam heating tech, but the results have not been particularly noteworthy.

I am not aware (but am not a definitive source of info on this topic) of any attempts to do the sub-wavelength particle vacuum chamber idea. However, some issues that would likely result from this can primarily be summed up as cost. Churning out the pounds of sub-wavelength metal dust is likely to be a hideously expensive proposition and I doubt any printer manufacturer worth their reputation would be willing to let their warranties cover you scooping up the old unused dust and reusing it. Too much of a chance that a given particle had been heated up just enough somehow and joined with another one, ruining the consistency of the granular size and being more likely to clog your nozzles. Plus they are price gouging jerks.

[Camacha]

This is brilliant. It eliminates most of the flaws I have seen with plastic printed parts - they have these clearly visible seams between layers, and a rough surface. Parts out of this machine are continuous, mathematically smooth contours.

The promotional story sounds great, but I am left to wonder about the accuracy of the statements and many of the traditional issues with SLA printers. This software still needs to slice the project into layers. You can get a very fine resolution, possibly one that is greater than the roughness of the material. That would make them continuous for all intents and purposes, but not mathematically so. It is, in essence, still the same process, they just upgraded and fine-tuned it.

Then there are the two classical objections to SLA:

- The resin typically is very expensive, prohibiting freely printing whatever you need. Being able to do stuff quickly is nice, but when there is another hurdle like that, it still might be in vain.

- These resins are generally of limited mechanical use. Cool for fancy trinkets, but useless if you want to make anything useful.

The last two have been, and by the looks of it still are, the big problems with SLS. Do not get me wrong, these are very exciting developments, but every printing company seems to make amazing claims.

The only thing that comes to mind is if the pieces of metal are extremely tiny - smaller than the wavelength of laser light - the light would diffract around them. So, in a vacuum chamber, you would be spraying this continuous mist of metal pieces towards a surface. The laser beams would shine right through the mist to the surface, continually adding features. Anyone have a better idea?

Though using a much more traditional approach, Renishaw makes (very, very expensive) printers that laser melt powder together. You can print in steel, titanium or other engineering grade alloys. Though there are layers, they are up to and probably well beyond the roughness traditional techniques like sand casting leave.

People wanting to improve the roughness of plastic FDM prints I fully understand, but let us not forget that pretty much all traditional techniques also leave very distinct, and sometimes very obvious, tool and production marks.

[Iskierka]

Do bear in mind also that there are a number of metals which cannot be usefully printed - particularly as they may have properties that emerge from the way they are machined. Cold-rolled, hot-rolled, cast, forged, and all sorts of other variations on steel all have different material properties, and 3D printing will only be able to produce its particular property set (which will likely be most similar to cast). Milling and other machining techniques then perform work hardening on the material, in various different ways, meaning the 3D printing won't be the be-all end-all to manufacturing metal components - for many, it will still be more desirable to cast in a mould and then perform milling as it would have traditionally been done.

Also, maximum mechanical strength in a metal can't be achieved by this method. It's not enough of an advantage to actually be bothered with in most alloys, but with inconel it certainly is, and this has to be achieved by careful cooling of molten inconel in a mould over the course of around a week, forcing the metal structure to develop as a single crystal. The resulting components are then worked as needed to produce the final properties required. None of this process can be done by 3D printing, except for mould creation, which is already done in its most common application, the manufacture of jet turbine blades. 3D printing is interesting, but won't produce a flawless crystal structure in the metal, which can be achieved with moulds.

[Kerbart]

What we need is a 3D printer that can print wax. Then you shape sand around it and cast your metal model. A complete integrated model that would take care of all the ugly stuff would be pretty awesome to have around in your average tool workshop.

[Mazon Del]

Actually, I am (in addition to my other projects T-T ) working with a group that plans to have a kickstarter up later this year for a combo self contained forge and 3D printer-mold generator. In short, you provide it with stocks of your chosen metal, a plastic (doing tests to find which is most suitable for destructive casting), sand, and the model you want. The printer then prints off the object and fills the external gaps with sand, passes it to a press as needed, which then passes it over to the forge. The contained forge gets its metal all nice and hot, then pours it. Meanwhile you are never personally exposed to the horrible heat and quite possibly bubbling metal.

[magnemoe]

What we need is a 3D printer that can print wax. Then you shape sand around it and cast your metal model. A complete integrated model that would take care of all the ugly stuff would be pretty awesome to have around in your average tool workshop.

This should be easy, if not wax some plastic who melt easy, as an fallback print the mold for the wax.

I assume this is done already then casting unique or low series items, first I thought about with 3d printers.

[Tommygun]

This should be easy, if not wax some plastic who melt easy, as an fallback print the mold for the wax.

I assume this is done already then casting unique or low series items, first I thought about with 3d printers.

They are already combining 3d printing and lost wax casting:

http://www.3dprintingcolor.com/wax-pattern-3d-printing/

And a similar technique:

http://3dtopo.com/lostPLA/

[sumghai]

If I recall correctly, in Selective Laser Sintering (SLS), rather than depositing metal powder through a nozzle, you actually have a large moving stage inside a basin of metal powder.

The laser heard would move in the XY axis, and sintered regions of each layer of metal together. Then the entire stage is lowed by a very small distance, and new powder is spread over the workpiece and the cycle begins anew until the model is complete. At the end of the process, you'd tip out the excess powder to get your model.

Obviously the problem with SLS is that you can't have completely enclosed hollow areas, because the unsintered powder will remain stuck inside them.

[Camacha]

What we need is a 3D printer that can print wax. Then you shape sand around it and cast your metal model. A complete integrated model that would take care of all the ugly stuff would be pretty awesome to have around in your average tool workshop.

They actually print jewellery this way and recently wax type filaments have become available for home type FDM printers. Pretty nifty stuff.

- - - Updated - - -

Obviously the problem with SLS is that you can't have completely enclosed hollow areas, because the unsintered powder will remain stuck inside them.

You are correct. Though you gain the capability to print parts wherever in space you want, allowing things that SLS and FDM just cannot do easily or at all. Every specific technology has pros and cons.

[Sillychris]

It might take a little fine tuning, but here is my idea:

Fire a tiny piece of metal at the target location with extreme accuracy. Upon impact, some of the kinetic energy will be converted to heating the tiny metal particle and parent metal. At the precise moment of impact, focus enough laser beams on the target area to instantly weld the metal particle. A billionth of a second later, focus precise and timed lasers on the area to instantly laser cool the weld. IT may not be fast, but you could build up 3d parts out of metal and the metal would also be amorphous.

Laser cooling is an actual thing. One of my profs does it.

[Tommygun]

It might take a little fine tuning, but here is my idea:

Fire a tiny piece of metal at the target location with extreme accuracy. Upon impact, some of the kinetic energy will be converted to heating the tiny metal particle and parent metal. At the precise moment of impact, focus enough laser beams on the target area to instantly weld the metal particle. A billionth of a second later, focus precise and timed lasers on the area to instantly laser cool the weld. IT may not be fast, but you could build up 3d parts out of metal and the metal would also be amorphous.

Laser cooling is an actual thing. One of my profs does it.

Wouldn't it be easier to combine something like a heavy duty Makerbot and a MIG welder?

[Sillychris]

Wouldn't it be easier to combine something like a heavy duty Makerbot and a MIG welder?

Your idea is more practical and near future, but it has the con of the object not appearing to materialize in thin air.

[Mazon Del]

I recently saw a video for a wonderful device made by some German machine tool company. They have a 6 degree of freedom automated milling setup that is capable of cutting parts to state of the art level precision and has the standard automated tool change system. What is new about it though is that they added a new tool that it can grab. It's a welding device. So what it ends up doing is 3D print some of the part using the welder, and once it is about to get to a spot where the printing would cause it issues with the next step, it puts the welder away and then grabs cutting tools. The cutter swings into the position/orientation needed to provide a finish to the part such that the outside surface is as precise as it could be if cut. Following this, the welder swings back into action and continues on.

They printed off a turbine (including the little fins) in their demo video. While others have pointed out metallurgy problems that cannot be overcome with this technology, it does simplify your logistics in a lot of interesting ways.

[Tommygun]

@Mazon Del

I think that could be a direction for future machine tools.

Instead of one machine just using one technique, it uses multiple ones.

We have already seen this done on modular automated assembly lines where they pass the parts back and forth between machines.

Just take it a few steps further and combine more advanced metal 3D printing, CNC type milling, sanding and welding.

You would have something like a machine shop in a box that might be able to preform most of the simple jobs that come into a machine shop for.

[Aghanim]

I think its better to use electron beam instead of laser beam. Some materials like copper are excellent in reflecting CO2 laser wavelength, so to do laser metalworking with copper, you will need to use Nd:YAG laser. But organic stuff absorb CO2 laser beam better compared with Nd:YAG laser.

As far as I know electron beam can be absorbed in every material efficiently. So a single printer can print in any meltable powder. And electron guns have higher efficiency compared to laser, even a website claimed that electron beam welding is 80-90% efficient compared to 7-10% efficiency of laser welding

The disadvantage of electron beam is X-ray production and vacuum. With plasma window its possible to only keep the electron gun at high vacuum while print head is at atmospheric pressure, and lead shielding can protect us from X-rays