3D Metal Printing Takes a Page from Carbon Fiber Printing

Over the course of the last month or so, Come and Make It blog has shown some carbon fiber reinforced plastic parts he's been printing with (what I understand to be) a pretty typical desktop-class plastic printer.  The "secret sauce" here is that the plastic has chopped, small pieces of carbon fiber in it.  In a way, it's creating a carbon fiber/plastic composite similar to glass-filled plastics.  Scores of fiberglass boats were made with a mix of chopped fiberglass and plastic resin sprayed onto a mold to create the interior.  The resulting plastic is stronger than plain plastic, but not as strong as laid up cloth.  Laid up cloth can use equal-sized threads in both directions and be equally strong in both directions, or have one direction with heavier threads than the other so that it ends up stronger in the direction the heavier strands run.  The printed, chopped-carbon fiber parts will be weaker than parts made from either type of laid-up cloth, but stronger than plastic.  Continuous carbon fiber printed in plastic is becoming available and will be stronger, yet.

Markforged, a 3D printer company founded by MIT aerospace engineer Greg Mark, has raised the bar on this technology by producing printers that produce chopped carbon fiber-filled plastics(called their Onyx process), printers that produce continuous carbon fiber-filled plastics, and is now going for metal printing with what they describe as their Atomic Diffusion Additive Manufacturing, or ADAM process.  It's a metal powder-filled plastic fiber similar to the chopped carbon fiber approach:

Greg Mark unveiled the company’s Metal X desktop printer , which, once it becomes available in September, will print in a variety of metals including 17-4 stainless steel, 303 stainless steel, 6061 aluminum, 7075 aluminum, A-2 tool steel, D-2 tool steel, IN alloy (Inconel) 625 and titanium Ti-6Al-4V. The printer speeds up production with rapid sintering using a microwave furnace, a process that becomes highly reliable when the printer is following consistent instructions. Designs are printed in metal powder surrounded by plastic, the plastic is dissolved and the metal is sintered, leaving behind a strong metal part.

The link in that description is a short overview; a better overview video is here.

In the first, shorter, video, Greg Mark says, “If you can afford a half million or million dollar metal printer - buy one.  This is for the rest of us”.  Further reading will show you that the Metal-X printer will be just under $100,000.  That doesn't include the cost of the “microwave furnace” to sinter the parts and I have no data on what that will cost, but I'd be confident predicting it's significant.  Definitely not my idea of something for the home market, but something corporations might be interested in.  The hope of metal additive manufacturing (3D printing) is that it will lower the cost of manufacturing, but it's still out of the class of the machining (or subtractive manufacturing) infrastructure that has been the backbone of industry since the industrial revolution.  Let me gloss over the differences and relative strengths vs. weaknesses between additive and subtractive manufacturing to just point at price.  For quite a bit less than $30,000, a company can buy a very capable subtractive manufacturing station (Haas CNC Milling machine).  I've heard numbers suggesting a fully tricked out machining center is in the range of $50,000.  On the other hand, if the work envelope and rest of the work flow supports it, a rather competent Tormach machine can be had for under $10,000.

Design News points out:

Few manufacturers are discussing replacing traditional production methods for parts with AM techniques, as it would simply be too expensive. For plastics 3D printing will probably never beat the speed and volume capacity of injection molding. (However, using AM to create the molds will lead to more rapid product innovation with plastics by eliminating the single biggest bottleneck in the injection molding process.)
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Earlier this year, CEO Greg Mark told the audience at CES that the future of metal 3D printing is in print farms. The Metal X printer was created as an affordable ($99,500 is the current price tag) standalone shop printer, but the company sees a vision of fleets of these printers operating in tandem.

“Our Metal X printer is the first step in this direction,” (Marketing VP Cynthia) Gumbert told Design News. “It’s not in the same category of the large-format metal printers that form a high-end, expensive niche that only larger manufacturers can afford. Parallelization is the key to scaling volume, rather than a different, faster type of print process. We’ve always been about getting a near-final or finished piece right off the printer that can be sintered with very little post-processing, and ADAM is generating extremely high-quality parts.”

There are thousands of small contract machine shops that will produce a company's designs for them to compete with these printer farms.  I think the only way the printer farm vision gets a foothold is doing the techniques that Additive manufacturing does better than subtractive.  Manufacturing and machining in general just keeps getting better.  The 1/3 to 1/10 reduction in price to go with a more conventional machining center instead of metal AM is a very big disadvantage for the metal printers to overcome.  It might encourage designers to redesign parts to take advantage of the cheaper machining process rather than go to the more expensive metal printers.