Page 17 - 3D Metal Printing Fall 2017

Educated AM Customers 3D
than just making parts. Its goal is to sup- port its AM customers in their efforts to make smart, informed AM-business deci- sions. So, before CTC ever started printing parts, it provided customers, beginning in 2008, with engineering and design sup- port for AM components. The AM team helped them, for example, develop pro- cedures for testing their materials and builds, seeding defects and identifying the correct nondestructive-testing tech- niques to find those defects.
“We perform a lot of work for the U.S. government’s prime contrac- tors,” Altergott tells 3D Metal Printing. “Teaching them how
to buy AM parts is our pri-
mary concern, especially
when it comes to qualifying
AM as a replacement for
other manufacturing processes. Many of these companies, in fact, have
their own AM machines. We
find ourselves helping them understand where the AM processes make sense, and where conventional manufacturing still is preferred.”
Prototyping and Internal R&D
Most 3D metal printing performed on CTC’s SLM machine supports prototype projects for customers; it also uses the machine for internal R&D projects. “This includes,” says Sabo, “conducting design- of-experiments projects to develop parameter databases, to understand what parameters impact build quality and sur- face finish, to study powder recyclability, and to examine post-processing tech- niques. We’ve learned a lot from these types of projects in the last 3 years.”
Examples of lessons learned, per Sabo: How to adjust powder-feed parameters to accommodate post-process machin- ing, and how to develop and adjust the path of the laser as it melts (“or welds,” says Sabo) the powder to optimize build quality.
“We’ve looked extensively at laser-path
parameters to determine where to deposit successive beads, how much to overlap the beads and how wide to make the beads,” he explains. “Defining the hatch spacing, width and overlap, in addition to beam power, are critical parameters to understand and optimize. We know, for example, that if we weld too hot or travel too slowly, the weld scavenges powder from in front of the laser beam and glob- ules of metal can form—an undesirable condition.”
Another noteworthy lesson-learned, this one from a project for an outside cus- tomer: The post-build heattreating process and procedure can markedly affect the strength and shape of the part, particularly true with larger parts.
“On one recent project,” Sabo explains, “we were developing builds that initially
Long before Ken Sabo and the rest of the CTC AM team decided to make a decisive move into metal AM for repair and rebuild work, it acquired, in 2014, this SLM laser
powder-bed machine. CTC uses the machine mostly for customer-part
builds (65 percent), as well as for internal R&D projects. Sabo expects to add a second laser powder-bed machine
to the ranks by year-end.
exhibited high strength but unacceptably low ductility. We investigated various heat- treating procedures, recognizing that not all powders react the same to AM and subsequent processing, including heat- treatment. Performance of 17-4 PH stain- less-steel powders, for example, is sensitive to powder-grain structure, powder-size distribution and the atomization process used to produce the powder. Thus, tighter controls are needed during powder pro- duction and use for AM than for other processes, such as thermal spraying.”
Project Examples
In addition to internal R&D and pro- totype efforts, CTC’s AM team also sup- ports LRIP (low-rate initial-production) activities for its customers. These projects, averaging small part runs of 500 to 1000 typically, also can, as they grow in scope and revenue generation, lead to work for
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