Open-source metal 3D printer | Hacker News Reader

Open-source metal 3D printer

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64 pointsemrgx44 comments

Sadly I can't find any images or videos of the product of the device. The site has a couple of videos showing it throwing sparks, but that's about it.

Agreed -- the fact that they don't show a single finished item tells me that the quality of the printed part must be extremely bad.

Why you assume that? Is not like they are trying to sell it to you..

Otherwise seems like a very interesting project.

Because perhaps it's just me, but the printed part is the most interesting part of a new 3D material. Just a glance at it lets me know the possibilities for the device, in initial printing resolution and finish quality. So not including it seems like they're hiding it for some reason.

Thanks to jeffmcjunkin above for linking to an image of a printed part. It certainly looks better than I anticipated.

It is extremely bad. See the actual paper, where they show one part and its CAD model.

http://ieeexplore.ieee.org/stamp/stamp.jsp?tp=&arnumber=6678...

There's only a vague resemblance between model and part. No way could you use that sprocket. Not only are the edges rough, it has voids. You could grind or machine down down rough edges, but voids make the process worthless even for making blanks. That's about what you'd expect with MIG welding. Welding just isn't a good way to make smooth surfaces.

The low-end 3D printer people tend to obsess on the problems of building a 3-axis motion system (a completely solved problem in CNC machines) and gloss over the problems of what's happening at the weld point. The common extruder-type printers are trying to weld a hot thing to a cold thing, which never works very well. (In soldering, that creates cold solder joints. In welding, it creates bad welds.) Heating the bed plate helps a little, but once the thing being built is more than a few cm high, the build plate isn't accomplishing much. That's why most taller objects made with low-end 3D printers fail.

There's a plastic welding technique that's been in use since the 1950s that works reliably. (http://www.professionalplastics.com/WELDER). Not only is the welding rod heated, the target area is heated with hot air. This produces a solid, reliable weld. I've suggested doing something similar for extruder-type 3D printers, using small lasers (2-5 watts) to preheat the target area just ahead of the extruder. So far nobody has done that.

Heating things with a laser is not quite as easy as you might think. Different materials will absorb different wavelengths of light at different rates. So for example a 1um laser might not heat white polyethylene enough while it would melt black ABS. Hot air has the advantage that it is always a consistent temperature regardless of the material.

Use a laser diode pulsed with pulse width modulation, at perhaps 1KHz, duty cycle < 80%. During the off period, view the hot area with two photodiodes behind different-wavelength IR filters. The ratio between the outputs gives you the temperature. Go closed loop on temperature.

That's a pretty glaring omission. I imagine the prints look pretty awful, but it a neat idea. In the normal use a wire feed welder the arc (bright sparky part) would be uniform to create a bead. From what I saw in the videos they are using a "bad" welding technique that would build up the instead of penetrate the metal. They will need to replace/control the wire feeder and the voltage of the welder in order to better results.

There's a few different ways to do 3D printed metal, but this looks different then them.

Prometal, for example, has a process that's very similar to SLA or SLS, but with a stainless steel powder instead of resin. They then infuse it with bronze, using capillary action to do the work. You end up with pretty solid parts.

The hackaday article [1] has an image of a printed piece, which helps give an idea of the resolution

[1] http://hackaday.com/2013/12/07/a-rostock-welding-3d-printer/

This page has a photo of a sprocket from the machine: http://motherboard.vice.com/blog/you-can-now-3d-print-with-m...

This is a nice first step and all, but there are a number of challenges here. The irregular sparking and popping noises imply that the metal laid down will also be irregular. This uses a regular MIG welder as the print head, and MIG welding only allows you to lay so fine of a bead. Large welds tend to be brittle due to internal stresses, voids, and the like.

The more successful commercial metal 3D printers build parts a thin layer at a time. A fine metal powder is sintered on each layer using a laser. This technique is called Direct Metal Laser Sintering (DMLS).

https://www.academia.edu/5327317/A_Low-Cost_Open-Source_Meta...

It's so cool that it's an inverse delta! Sadly this is probably because they had to find a way to circumvent patents.

Its open-source. Maybe patents don't apply? They're not selling anything.

Patents still apply to open source, even if they are not selling anything.

How does that work? Genuinely curious - can a patent holder force someone to un-publish source code?

A court can order someone to stop publishing source code and to pay damages for illegally distributed material.

In the related field of copyright, courts have been known to order the destruction of books, fake watches, etc.

That's pretty much what happened when a Dutch developer tried to publish source code emulating what the Shazam song-recognition app did: https://www.techdirt.com/articles/20100708/04230710128.shtml

In the USA if you knowingly violate a patent you will be responsible for triple damages. For software that would be 3X the revenue generated. This is true even if the violator does not charge - because the person with the patent is still suffering damages (lost revenue). So practically they can force you to remove it if they can show damages - which wouldn't be that hard to show in the Shazam example.

Inducement, etc

See, e.g., http://www.law.cornell.edu/wex/inducement_of_infringement

I think individuals can create projects for personal use which use a patent so long as its only for personal use and is not used commercially or sold.

False. This is a common misconception. There is also no "academic exemption" to patent infringement.

I agree that GP is dangerously wrong about noncommercial use in general, but doesn't the research exemption[1] muddy the waters a little?

[1] http://en.wikipedia.org/wiki/Research_exemption

No. It is very very limited.

"Patents do not prevent "making". They prevent making for another's use. One can make and use anything (well, anything legal, I'm not talking about devices which are themselves illegal)." - Mike McCarty

Patents are for commercial use. This is just publishing the details of construction - anybody can make and use such a device for their personal use, despite any patents that exist.

That is true in the USA. In the UK, for example, there is an academic exemption. Practically there would be very little damages that could be shown by infringing a patent once in a lab.

Wait wait, what? When you file for a patent, you make your invention known. In detail. With plans. That's public. The idea being that if somebody uses your designs, they pay you a reasonable licensing fee.

These are just plans. Even if they incorporate patented designs, those designs are public knowledge. It's the use and implementation of those designs that's restricted.

Am I missing something?

Yes. Anyone building or using one of these would be open to a patent suit (if it violates any patents). There is no patent equivilant to "fair use".

>Anyone building //

In the UKPA Section 60(5)(a), (b) says:

An act which, apart from this subsection, would constitute an infringement of a patent for an invention shall not do so if - (a) it is done privately and for purposes which are not commercial; (b) it is done for experimental purposes relating to the subject-matter of the invention; ...

There are other clauses too, for example allowing farmers to use the products of plants they've acquired lawfully.

35 USC 271 has some very limited exceptions too (research related to pharmaceuticals is one IIRC).

It's funny that in the US there is such liberty for copyright but patents seem to be locked down relative to other jurisdictions. I assume you're talking about USA, no one ever seems to note despite it being crucial in discussions of law.

Not necessarily. Tilting the substrate platform lets you build more complex shapes without support material.

I have a delta 3d printer and I'm having a hard time imagining how this would work... Do you have an example?

Looking closer, this doesn't apply here. The Stewart platform allows 6 degrees of freedom, with useful amounts of tilt. The inverted delta used here is 3 axis.

Additive manufacturing pretty much always needs some sort of leveling phase to cope with z-axis irregularities. Without that you can't hold tolerance. Furthermore without support material you're limited in what you can build.

Looking at the pictures this seems like it makes metallic blobs approximating the shape. I suppose if you have a CNC to post-process it into something closer that may be fine. It'd be nicer to do the machining on the fly, but with the width of the material deposition it looks like it would drip down the sides if you did that.

With this design you might but you can get good essentially flat layers using the same essential process. There are existing commercial machines that use metal welding to do mixed additive and subtractive manufacturing. It's really a question of getting the welder dialed in so it creates a smooth enough surface. The weld will also fill into the small inconsistencies in height better than filament.

https://www.youtube.com/watch?v=s9IdZ2pI5dA

Perhaps manufacturing processes like laser sintering or 3D printing with a MIG welder have not become mainstream because traditional metalworking processes like casting, turning, and milling are so much faster and much more repeatable. Let me know when this thing can hold tolerances of +/- 0.0001". We'll probably have a cure for cancer by then.

Metal can be a tricky material to work with. It takes a lot of force manipulate. If you don't know what you are doing, you can very easily get seriously injured or even killed. To me, it would seem much more rational to try to build low-cost milling and turning centers that are small enough to move into a house without taking out the walls and simple enough to maintain where you don't need to have certified mechanics come every time you crash it. You're still going to have to make a considerable investment of time to learn how to safely and properly operate it, but that seems much more realistic scenario than emailing a file to grandma, having her put on her sunglasses, then pressing "Print," followed by 6 hours of sparks flying.

Don't get me wrong, I'm sure there are applications for additive metal manufacturing processes, but I believe that the cases where they are the best solution are few and far between.

I think your bar is a bit high. Standard milling tolerences are almost 50x higher than what you state. Casting is much worse. The point is that additive printing won't take over the metal world any time soon but it does have some advantages. Try to machine a hollow sphere for example. There are plenty of shapes that can't be traditionally machined.

Yes, milling to 0.0001in tolerance is rare, although possible on some machines. 0.001in is not unusual, though. This 3D printer, from the pictures, seems to be delivering about 0.2in. That's worse than sand casting. Still worse, some of the errors are in the void direction, undersize. If this thing consistently produced a good solid metal blank, ready for finish machining, it could substitute for having a foundry for small jobs. But it's not even that good.

There are very good, but expensive 3D printers that print excellent metal parts. Check out Space-X's 3D printed rocket engine for the new Dragon spacecraft. Shapeways can now do small steel parts for $10 + $5/cc with reasonable tolerances. 3D printing of metal works now. This welder thing, not so much.

I'd rather see this used as an robot-welder than a "3D printer". At least enclose this in an argon chamber dammit!

How about something like SHIP2? They print the shape in the green and compress it using gas. This allows 3D printing of Inconel in shapes that require almost no machining after production.

[0] http://www.summitmaterials.com/near-net-shape/