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the Art of Metal Printing [message #4885] Fri, 12 June 2009 04:18 UTC Go to next message
avatar GlenG  is currently offline GlenG
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Hi all,
Lately there has been a lot of buzz about the metal print material that Shapeways has been offering. There seems to be some confusion about what this stuff is and how it is printed. I have been working as a consultant, helping to develop finishing and coloring procedures for this material and I would like to help the community understand this remarkable process and material. So here are a few basics.

1. THE PRINT PROCESS:
The printer first spreads a thin (.1mm) layer of stainless steel powder onto a build platform. An industrial print head then dispenses a liquid binder onto the first layer of metal powder. The print head moves along the X and Y axis just like an inkjet printer to describe whatever you want printed. One thin layer at a time. Once the first layer is printed the build platform moves downward (Z axis) one increment and another layer of powdered metal is spread on top of the first. There is a frame (build box)around the build platform so the unbound powder does not spill off the platform. This process is repeated until the entire object is consolidated. It takes about 10 hours for every 1" of build height! The excess (unbound powder) is now removed leaving a relatively fragile mass of powdered stainless held together with binder, think of this as green, unfired ceramic. At this point the object is only about 60% in density.

2. INTO THE FURNACE:
The next step involves a cycle through a controlled atmosphere furnace. The green print is now placed into the furnace along with a quantity of bronze powder. As the temperature rises the binders begin to vaporize. Then the bronze material begins to melt and is wicked up into the stainless mass. The temperature continues to rise to the point at which the particles of stainless fuse together (sintering). The hot mass is now approximately 85% in density. The furnace now begins it's return to room temperature. This cycle takes about 18 hours.

3. FINISHING THE GOODS
If the Gods have been smiling you now have a wonderful pile of new prints. At this stage the prints have a clean but rough surface. Print lines are obvious and the texture is unpleasant to the touch. Several options are available for surface conditioning. Just about any method employed in the metals industry can and will work. However, this metal material really is different than any others. It is a true composite of two dissimilar metals. The stainless component is quite hard. The bronze component is soft and gummy. The material is quite strong but somewhat brittle. It is much like malleable cast iron in terms of strength. Thin parts will bend a little before they snap. The good news is that it can be silver soldered with a gas torch. For removing and blending contour lines a rotary hand piece with carbide and diamond burs work best for rapid cut down. It can be milled, drilled or tapped but carbide tooling is a must. This composite is hard and abrasive stuff! It is possible to get a mirror finish but it takes a LOT of time. Small parts without a lot of surface detail or thin projecting sections can be finished in high energy centrifugal tumblers. The "Ring Poems" and "Cufflinks" are finished this way. Because this material is so hard, vibratory type finishing equipment does little more that brightening. Vibes will not remove print lines! Once you get the surface conditioned, objects can be left as is or additional coloring procedures can be carried out. Certain chemical solutions will produce nice patina finishes. Shades of brown and black are possible. However, blues and greens are almost impossible because the chemicals that color the bronze component will also corrode (rust) the stainless component. NOT pretty! I can't tell you how many tests I've run trying for a nice green patina. Although Shapeways is not offering it......... yet, the composite can be electroplated with gold or nickel.


Hope this sheds a little light on the subject. I know this material is expensive. But it really does require a whole lot more than printing with plastics. And hey, it's METAL! Unless you want to do it yourself, I think you will find that having a short run or one of a kind object cast commercially would be no less costly (probably more). The folks who make this metal printing possible are truly 21st century alchemists.


"Where the spirit does not work with the hand, there is no art."
Leonardo da Vinci
Re: the Art of Metal Printing [message #4888 is a reply to message #4885 ] Fri, 12 June 2009 07:38 UTC Go to previous messageGo to next message
avatar joris  is currently offline joris
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thanx Glen!

Joris
Re: the Art of Metal Printing [message #4907 is a reply to message #4885 ] Sun, 14 June 2009 05:31 UTC Go to previous messageGo to next message
avatar CGD  is currently offline CGD
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Can the process produce thinner items or still limited by the wall thicknes issue?

CGD
Re: the Art of Metal Printing [message #4913 is a reply to message #4907 ] Sun, 14 June 2009 18:27 UTC Go to previous messageGo to next message
avatar GlenG  is currently offline GlenG
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When printing in metal, surface details down to about .3mm can be resolved. That said, resolution of surface details should not be confused with minimum wall thickness. When designing and printing an object the term wall thickness has more to do with the average thickness of a given section. So if you are creating something like a Panzer battle tank the hull could probably be shelled out to sections 2-3 mm thick. Details like a tiny machine gun barrel projecting from the hull would almost certainly fail. But, surface details like rivet heads and panel lines would probably print well.

One of the big differences in printing metal vs. plastic is the fact that the metal goes through a green phase before it goes into the sintering furnace. Tiny projecting details are extremely fragile to the touch and will likely get broken off. There are certain tricks that can help though. For instance: when we printed the "Nose Pricker" figurine, his tail section was so thin we knew it wouldn't take the handling required to get it into the furnace so we added two tiny post supports between it's tail and body. These posts were then removed after sintering. Another troublesome print was a tree with lots of fine branches. We added a cage like lattice structure around the entire object. The cage stabilized and protected the whole object. After sintering, the cage was cut away. This extra work (and material) can add to expense but it some cases it makes all the difference between success and failure.


"Where the spirit does not work with the hand, there is no art."
Leonardo da Vinci
Re: the Art of Metal Printing [message #4926 is a reply to message #4913 ] Mon, 15 June 2009 01:43 UTC Go to previous messageGo to next message
avatar CGD  is currently offline CGD
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GlenG wrote on Sun, 14 June 2009 18:27

So if you are creating something like a Panzer battle tank the hull could probably be shelled out to sections 2-3 mm thick. Details like a tiny machine gun barrel projecting from the hull would almost certainly fail. But, surface details like rivet heads and panel lines would probably print well.



Funny that you mention that. I actually did create a tank and is printing it with plastic. Very excited to see if it can print successfully.

The reason why I asked is that the metal printing process can be used to print out the master for spin casting of these toy articles which require the master to go through high temperature and pressure. If printing the master is out of the question, than may be we can print a metal mold for casting the object.

CGD
Re: the Art of Metal Printing [message #104755 is a reply to message #4885 ] Fri, 12 December 2014 23:59 UTC Go to previous messageGo to next message
avatar umwebejo  is currently offline umwebejo
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Does anyone know the Density (kg/m3) and Elasticity/Young's Modulus (GPa) for the Shapeways Steel, Brass and Bronze ?
Re: the Art of Metal Printing [message #105117 is a reply to message #104755 ] Sat, 13 December 2014 22:17 UTC Go to previous messageGo to next message
avatar mkroeker  is currently offline mkroeker
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The value for "steel" is bound to be highly variable, as that material is sintered steel powder that is infused with liquid bronze.
For brass and bronze, which are produced by "conventional" lost wax casting from a 3d-printed wax master, you should be able
to find tabulated values for the generic compositions which are stated on the respective Materials pages as
"Shapeways' Bronze consists of 10% tin and 90% copper." and "Shapeways' Brass consists of 15% zinc, 5% tin, and 80% copper".
(And you might want to start your own topics rather than reviving a five year old thread that just happens to be somewhat related)
Re: the Art of Metal Printing [message #105384 is a reply to message #105117 ] Tue, 16 December 2014 09:54 UTC Go to previous message
avatar mygadgetlife  is currently offline mygadgetlife
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I made an observation about the stainless steel product: it has a low ferromagnetic property. That is, it is only lightly attracted to magnets. Compared to pure stainless steel (very low to zero ferromagnetism) and - for example - stainless steel cutlery (high ferromagnetism) this is pretty good.

The other steels I have appear to be plain ferromagnetic steel as the samples I have are all highly attracted to magnets.



 
   
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