12/09/2019 | sme.org | By Scott Fosdick, Head of Sales, Marketing, Business Development and Communications, GF Machining Solutions
Additive manufacturing (AM) once was called “rapid prototyping.” Its earliest forms made prototype parts—and nothing else. However, manufacturers were intrigued by the prospect of using it to make cost-effective metal parts in production. That day is here.
Speed is an Issue. Generally, laying down a bed of metal powder and sintering to make a part a single laser-beam-diameter in thickness at a time, layer by layer, is just not as fast as milling or turning. Lack of speed limits AM to complex parts or specific, expensive materials where it is more practical than cutting and joining.
Developers are working on making AM faster. Beginning with a single laser, now some machines use four or more. Developers are optimizing the beam and its movement across the powder bed. In addition to laser speed, developers are researching the temperature a given metal powder actually sinters under a laser beam to further speed up the process.
To do more, they need a broader scope.
Optimize the System
Production cost per part isn’t based only on how fast the metal is cut—or, in this case, is sintered—but on the efficiency of the entire system. The system needs to optimize material delivery and post-processing as well as build speeds. Today, many additive manufacturing equipment developers put their energy almost exclusively in how to speed up the printing process, with little thought to the system.
Some companies get it. For example, our DMP Flex 350 printer uses a powder cartridge system like those used by office laser printers. Operators can reload the powders of the same materials in about 30 minutes and switch materials in two or three hours—a process that in most systems takes two or three days. The same machine deposits the powder onto the bed bidirectionally, almost doubling its speed.
AM with Metal Cutting
Another twist—post-production processes in metal additive almost always include metal subtraction. Nearly all AM metal parts require secondary operations, whether they be high-speed milling, grinding, EDM, or something else.
There tends to be a common assumption in manufacturing that one either cuts or prints a part. If additive takes off, subtractive technologies may be under threat of eventual elimination from the production floor. The truth is, additive and subtractive technologies are, and will continue to be, complementary to one another.
Certainly, metal removal will be influenced by metal printing. For example, as additive scales up in production, efficient high-speed machining to finish a near-net shape printed part will become a more sought-after capability than the ability to remove metal and rough out a part at lower speeds. This will be reflected in the offerings of metal cutting machine makers.
And one can expect new products to be developed that better compliment the printing process. For example, the AgieCharmilles CUT AM 500, introduced this September at EMO Hannover, is a horizontal wire EDM specifically designed for removing metal additive parts from their build plates. Its swivel axis rotates the build plate to immerse the plate and parts upside-down in a dielectric solution. That orientation allows the parts to be cut from the plate without pressure on the EDM wire and fall softly into a catch basket. It is a subtractive metal machine that aids the processing of metal additive parts.
Manufacturers can expect to see many more innovations in the future with new subtractive machining use cases.