Sandia National Laboratories has been busy and inventive lately, taking a whole new approach to 3D printing recently with the creation of a telescope. Now the lab is looking at the testing of 3D printed parts. Sandia has created a six-sided work cell that resembles a circular desk, with a commercial robot at its center that conducts testing to rapidly determine the performance and properties of 3D printed parts. The modular, scalable and flexible system is called Alinstante, Spanish for “in an instant.”
The system is the result of Sandia materials scientist Brad Boyce’s work, which began in the spring of 2015. Boyce was working on a project to improve the qualification of custom 3D printed parts.
“In traditional manufacturing of metals, there’s a lot of experience and finesse in process control to produce metals with uniform properties,” he said. “When we went to laser manufacturing we had to take a step back and rethink qualification.”
Boyce had already developed a machine for high-throughput tensile testing, but he realized that he needed a more flexible general solution, so he began working with Sandia’s robotics group.
“Once we committed ourselves to automation, we realized that the barriers could be overcome. Yes, we invested some time and money, but the real challenge was getting ourselves out of the mindset of ‘business as usual’ to understanding that we need a faster solution,” Boyce said.
The hexagonal work cell has six petal-like work stations that surround the robot in the center. Each work station can have a different commercial or custom testing system, and they can be swapped in and out depending on the kind of work required. Multiple work stations can also be combined in a honeycomb-like structure. The design of the work cell was led by Sandia mechanical engineer Ross Burchard, who explored many different configurations before deciding on the hexagon.
“My challenge was: How do you come up with a work cell with one robot and multiple testing stations that’s also modular and scalable?” Burchard said.
Burchard and his team used off-the-shelf hardware wherever possible to save money when building the work station. In addition to the hexagonal floor plate and the pedestal for the robot, safety light curtains were installed wherever a person might interact with the robot. If a person reaches into the work cell, or if a robotic arm reaches out of it, the light beam is broken and the robot automatically stops, as Tim Blada, the roboticist who is leading the design of the software interface, underscores as a safety feature.
“Safety is always our No. 1 concern. Every line of code we write, every piece of mechanical fixturing we do, is always safety first,” he said. “‘How is this safe? Can I do this without risking any injuries?’”
By the end of this summer, Blada hopes to have a user interface that will allow anyone to place their parts on a tray in the parts rack, select a few tests and automatically receive their data in a process that doesn’t require every user to be an expert. He also wants the software architecture to be modular so that new modules and tests can be easily added.
The Alinstante prototype has only two testing stations and a rack where users can place their parts. The first station is a structured light scanner that can convert a scan into a 3D model for direct quantitative comparison to the original intended design. The second is a load frame for testing physical properties, such as tensile and compression testing. Next, the team wants to add a laser-induced breakdown spectrometer, which could determine the batch-to-batch consistency in the chemical composition of parts in a minimally destructive manner.
“Sandia has testing labs that can perform all of these tests; however, it takes a few weeks to schedule each of them, which can add up to one or two months of testing,” said Burchard. “Alinstante can reduce the scheduling burden for the testing, greatly speeding up the turnaround time.”
The system can also reduce human error and produce more consistent, reproducible data than humans can.
“Right now, Alinstante is really just scratching the surface of what it could be,” said Boyce. “We could integrate the printer, processing systems — such as a heat-treat oven or a grinder — and many other post-processing tests.”
Additional tests that the team may add to Alinstante include x-ray tomography, corrosion testing and density measurements. They are currently looking for partners to support the development of new modules.
Blada is interested in testing the endurance of the new machine.
“In theory you could run this thing forever, if you had enough parts,” he said.
Meanwhile, Boyce is interested in using Alinstante for rapid materials discovery and for foundational advances in alloy performance and reliability. The machine already has plenty of benefits, however, as he said:
“Friday afternoon you tell the 3D printer ‘I want you to print this part 10 different ways and then go test each one.’ You come to come back Monday morning and Alinstante tells you which process was the best. Let the robot do all the logistics work and get the human out of the loop except for making the important engineering decisions.”
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[Source/Images: Sandia National Laboratories]