Best of Both Worlds: Turning Performance

The technology is not intended to produce most parts, but a hybrid machine, which combines additive manufacturing and subtractive machining, can save a significant amount of time and money — when the application is appropriate.

DMG Mori USA reduced processing time by 80% when it switched from making ma chine drawbars with the traditional method to a hybrid approach, said Lennart Tasche, engineering manager for the Hoffman Estates, Illinois-based machine tool builder. “The core of the drawbar is still manufactured like it always has been, but instead of a complicated process of adding a hard facing material to the drawbar, we now do that in the same ma chine by switching to our laser head and de positing that second material that’s required for the necessary wear resistance.”

DMG Mori offers four hybrid 5-axis CNC machines with laser-based directed energy deposition (DED) through a powder nozzle: Lasertec 65, Lasertec 125, Lasertec 3000 and Lasertec 6600 DED hybrids. The first two are milling machines, with the number for each indicating the table diameter in centimeters, Tasche said. The other two machines are turning centers.

The Lasertec 3000 DED hybrid is for producing parts up to 670 mm × 932 mm (26.38″ × 36.69″) in diameter at B-axis 180° or up to 400 mm × 1,321 mm (15.75″ × 52.01″) at B-axis 90°. It can be ordered with an extended bed to double the length for even larger parts, he added. The Lasertec 6600 DED hybrid handles workpieces up to 1,010 mm × 3,702 mm (39.76″ × 145.75″) in diameter.

The turning machines have an A and B spindle and an upper and lower turret with live tooling, and the laser head is loaded into the upper turret, Tasche noted. “The two spindles can run independently from each other.”

Repairing parts is a major application for the hybrid machines, he said, with other significant ones being the creation of internal cooling channels, cladding and depositing coatings. For example, a die with a worn wear surface is repaired by machining off a thin layer of the worn material, then cladded via 3D printing with either the same material or an advanced material and finish machined to bring the die back to its original shape. “All of that,” Tasche said, “in one machine without having to bring the part from one ma chine to another and reposition it and fixture it.”

Typically, he added, the thickness of a deposited layer is about 1 mm (0.039″) that is adjustable with parameter settings, but an additive technology is available to re duce the thickness to about 0.1 mm (0.004″) when coating rotary items.

More than One Metal

A standard DED hybrid machine comes with two hoppers for storing powder, enabling users to load two materials into the machine, Tasche said. That arrangement enables mold and die makers, for instance, to produce a part with a copper core that’s finished with steel. “We can really get the best of both worlds of having a long-lasting mold with good heat transfer.”

Not only can one metal be placed on top of another, he added, but a gradual transition between the two metals can occur. An application might require starting with 100% deposition of one powder, and then slowly reducing it to 75%, and depositing a second material for the remaining 25% before transitioning to a 50/50 composition. That’s followed by depositing 25% of the first material and 75% of the second, then finishing with 100% deposition of the second powder.

If more than two metals must be printed, a special hybrid machine can be ordered with more than two hoppers, Tasche said. Another option is to print with two hoppers, and, when the machine is printing the second metal, exchange the hopper for the first metal with a hopper containing a third metal powder. “You pretty much have un limited material combinations in that machine.”

DMG Mori does not produce the powders but uses a supplier network to provide them to its hybrid machine customers, he noted. Nonetheless, a customer can purchase powder from any supplier. Because powder quality is critical to effective 3D printing, the machine builder offers powder testing at a laboratory that quantifies various qualities of a powder, such as particle size distribution, flowability and humidity. “In general, powder quality is nothing that will ever harm the machine. It’s just something that you want to keep an eye on for successful printing.”