3D Printing Materials

A friend of a friend has one. He uses ABS and PLA.

He can bridge spans by laying down a bridge of ABS. The PLA has a lower melting temp and won't stick well to the ABS. After done and cool he snaps off the ABS from the PLA and has features that would seem like they were suspended in mid air during fabrication.

I can see the prototyping application, but can it print using materials that can actually be used. like a replacement auto part (metal)?

There may be some limited applications for final parts in very small quantities. Normally it is only good for prototypes. The friend of a friend uses it to prototype parts before having tooling made for custom aluminum extrusions.

I don't know exact numbers but it appears to lay down a bead a few thousandths wide. I think he said it runs about 5 inches a minute. A part about the size and complexity of a cell phone is about a 8 hour run. Useless for high volume production. Great for finishing up a CAD design at the end of the day and having a mechanical mock-up on your desk in the morning.

That's been my general interpretation of the grand majority of the 3D printing developments thus far. Incredible accuracy and detail, but it takes quite a long while and is highly impractical as an actual production piece.

When you think of the grand scale of things, it's kind of amazing that we can just put in a digital model and create something with a snap of our fingers (and some patience). The future can be pretty amazing sometimes

There are a number of businesses that allow you to upload designs online and receive the 3d print from a wide selection of materials.

Here is one such site, highlighting titanium printing. The prices and times listed are not modest, but lower than I previously expected.

Much in line with your thinking, it seems Ford is not using 3d printing for metal surrogate parts on test vehicles prior to production.

I have a use for 3D printing to produce a variant of a geometry which, quite frankly, I have no idea how to mass-produce, and by other, faster means. Mathematically the object is called a Menger Sponge. In my application the voids are filled with a material having a different density. The first image is a cutaway view:

How to mass-produce this geometry using two different materials? Anyone?

So are you saying you are able to produce an acceptable model of the portion made of one density of material on a 3d printer? To what resolution?

I think what he has pictured, in one material, is "easy," but it would be a pretty involved drawing. But I think I have read that printing in different materials is possible, but I don't know how to do it.

A drawing is unnecessary as its description can be easily encoded as a simple recursive procedure. Notice the exact same pattern repeats at ever smaller scales. Once you've described it at one scale, you've described it for all. It is a fractal in that it is self-similar; mathematically-ideal Menger Sponges recurse indefinitely and so look identical at any magnification up to infinity. Physical M.S.s have interesting (and very surprising) properties which haven't been adequately explored... :)

Of course physical models cannot 'recurse indefinitely'.

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You specified: ' the minimum feature size is around 100-130 microns (approx. 0.005" on average).'

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This means it can't be expected to have infinite surface area.

I suspect you are (despite what the others say) one of the sharpest tools in the shed, so I doubt this idea previously eluded you.

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If you care to expound, I'm curious what other properties you are interested in that might show up in a physical model.

I have not made a model of this on a 3D printer. Insofar as resolution goes? How is resolution specified when it comes to 3D printing? 3D 'pixels'/mm? I can say with confidence that the minimum feature size is around 100-130 microns (approx. 0.005" on average).

My main question is: How does a 3D printer print over a void?

In other words, say I were fabricating a simple box shape - a cube - and that I've already printed the floor and sides. How to print the top? There is nothing there to support the material to be printed.

As you can see from the cutaway view in my previous post that this shape is essentially nothing but boxes!

I've given more thought on how to print the second material, the one having the different density. Solution: I wouldn't print it at all, provided the second material is available in liquid form. Rather, I would saturate the printed shape with the liquid to which a catalyst/hardener has been added, and leave it to cure. The problem with this approach is of course the formation of bubbles which would have to be removed, but this isn't a show-stopper by any means.

The biggest technical hurdle that I can see at the moment (having no experience whatsoever with 3D printing myself) is how to print over a void, as mentioned.

Thoughts, anyone?

Depending on the material (strength and speed it becomes stable/rigid), on solution could be to print the model with one vertex as the lowest point.

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This way the printer never has to attempt to print a completely horizontal unsupported span.

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Reducing pressure prior to adding your second lower density material as a fluid would help to minimize bubbles. Some (good good good) vibrations might help as well.

Yes, I can see how that would work for a cube shape, but what if you wanted to make this pattern in, say, large or continuous sheets? You're kind of stuck with the 'printing over a hole' problem in this case methinks. One possible solution is to use a low-power blue or UV laser to 'write' the pattern on the surface of a liquid bath of polymer which cross-links where the light hits it. Then lower the pattern into the bath just enough so the liquid covers it again and write your next layer, and repeat. For patterns containing closed voids you'd have to provide some means of draining the unwritten polymer and sealing the voids back up but the M.S. pattern doesn't contain such voids, fortunately.

Since you are interested in filling the empty space with a different material. it seems like large continuous sheets could be printed with a different print head for each material, so that each layer is a solid sheet when printed.

Then either continue printing the next composite sheet on top, or stack, align and somehow attach laminate sheets?

Assuming that printing can be done in two different materials, hows about filling the void spaces with some material that will support the desired material just above until it hardens, and which can later be melted or dissolved out?

I have a similar wonderment. Since I am involved with antique vehicles, I wonder when they will be able to print parts with the strength to function in use. I'm sure they can do "cosmetic" parts now, but I would like to see "strength" parts be available. One-off manufacturing would be fine, which suits the printing techniques. But getting a .stl computer file would require a digitizer of some sort.

Any comments?

I think this used to be called "Stereolithography," but now is better known as "additive manufacturing."

Check out the 2nd link in comment #5. It addresses that question.

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Also, a suitable 3d model can be generated from multiple pictures taken from an ordinary digital camera with available software like this.

3D printers are going to be the tool of the future. Currently, they are making replacement body parts with a 3D printer. Here is and article of a replacement jaw made of titanium and coated with an artificial bone material - search on techhive.com and search for 3D Printers Now Print Human Body Parts.

I also heard about a printer called an MMX Bio Printer by NovoGen which prints actual cells - see organovo.com I believe this has been around since 2010 or so. Absolutely fascinating and maybe a bit eerie; can we someday create clones?

In the not too distant future, we may be buying products at the store that were made with a 3D printer. We will order something from home (or mobile) and pick it up at our local Wal Mart when it's ready.

For instance, you can order a new office desk on your iPhone, the store will print it and you pick up the parts with instructions and you assemble it at home - like we do with Sauter desks. Instead of a huge retail space, the stores will have rows and rows of 3D printers, each one spitting out an item made from a specific material. The parts will be moved to an area where they will be combined with other parts and assembled or delivered as a bunch of parts.

Reminds me of the old Service Merchandise - order your items and wait for it to come down the conveyor belt.

I worked for 3D Systems when they started publicly offering their first StereoLithography system. There was just one photopolymer available at the time but development into photopolymers with different characteristics soon started.

Copycat systems quickly developed that used paper and sintered materials like graphite.

My home machine uses ABS or PLA and could be adapted to various foodstuffs (like chocolate or icing) if I was so inclined.

There's a whole lot of development going on with bio-engineered parts.

Hooker