New technique improves finishing time for 3D-printed machine parts

A 3D-printed part is mounted in the CNC machine after finishing work; the touch probe is preparing to take automated measurements. Brandon McConnell, NC State University

Researchers from North Carolina State University, Raleigh, N.C., have demonstrated a technique that enables manufacturers that use metal 3D printing technologies to conduct automated quality control of parts during the finishing process. It allows manufacturers to identify flaws without having to remove the parts from the machine.

“One of the reasons people are attracted to 3D printing and other additive manufacturing technologies is that these technologies allow users to quickly replace critical machine components that are otherwise difficult to make outside of a factory,” said Brandon McConnell, co-corresponding author of a paper on the work. “And additive manufacturing tools can do this as needed, rather than dealing with supply chains that can have long wait times. That usually means using 3D printing to create small batches of machine parts on demand.”

After a metal machine part is printed, it requires finishing and has to be measured to ensure the part meets critical tolerances. Currently, that involves taking a part out of the machine, measuring it, and then putting it back in the machine to make modest adjustments.

“This may need to be done repeatedly and can take a significant amount of time,” said McConnell. “Our work here expedites that process.”

The researchers have now integrated 3D printing, automated machining, laser scanning, and touch probe measuring technologies with related software to create a largely automated system.

Here’s how it works.

When a manufacturer needs to make a specific part, it pulls up a software file that includes the measurements of the desired part. A 3D printer uses this file to print the part, which includes metal support structures. The part is then mounted in the CNC finishing machine using the support structure. At this point, lasers scan the mounted part to establish its dimensions. A software program then uses these dimensions and the desired critical tolerances to guide the finishing machine. As this process moves forward, the machine orients the part so that it can be measured by a touch-sensitive robotic probe that ensures the part’s dimensions are within the necessary parameters.

To test the performance of the new approach, researchers manufactured a machine part using conventional 3D printing and finishing techniques, and then manufactured the same part using their new process.

“We were able to finish the part in 200 minutes using conventional techniques; we were able to finish the same part in 133 minutes using our new technique,” said McConnell.

The paper, “Automatic Feature Based Inspection and Qualification for Additively Manufactured Parts with Critical Tolerances,” was published in the International Journal of Manufacturing Technology and Management.