A surprising analysis of strength: comparing 3D printed metal with CNC milling.


In a fascinating analysis conducted by YouTube channel electrosync, a surprising comparison was made between 3D printed metal and CNC milling. The test focused on tensile strength and included various materials in both 3D printed and CNC milled forms. The results were unexpected, to say the least.

To establish a baseline, pull-tests were conducted on a standard coupon made of PLA (a type of polymer). The PLA fractured at a load level of 55kg, with an elongation of 0.3%. Different variations of infill were attempted, which slightly increased the strength of the part.

The testing then progressed to stronger materials such as Markforged’s Onyx FR with continuous carbon fiber. As anticipated, these materials exhibited increased strength compared to PLA. Electrosync tested different types of Onyx FR and found them to have varying, yet significantly strong results.

Next came the analysis of 3D printed metals. Electrosync obtained these metal parts through an unnamed service bureau that used the SLM (Selective Laser Melting) process. Aluminum, stainless steel, tool steel, and even titanium were tested. Unsurprisingly, these metals proved to be much stronger than PLA or reinforced polymer materials.

The testing then shifted to CNC milled parts, which were cut by a service bureau using CNC milling equipment. The results were unexpected, as the CNC’d parts showed slightly less strength compared to their 3D printed equivalents. This raises the question: how could 3D printed parts be stronger than CNC milled parts?

The prevailing assumption is that layer-by-layer production in 3D printing would result in less strength due to the possibility of layer delamination. However, this was not the case in electrosync’s testing. Each CNC’d part proved to be slightly weaker than its 3D printed counterpart using the same testing equipment and procedures.

The video by electrosync does not provide an explanation for this surprising outcome, leaving us to speculate on the reasons behind it. My speculation is that the crystalline microstructure of the materials might play a significant role. It is possible that the metal chunk used for CNC milling cooled from the outside-in, leading to a potentially different microstructure throughout the material. On the other hand, the SLM printed metal coupons would have a very consistent microstructure since the conditions during printing are identical for each layer. Metal 3D printer operators even go to great lengths to fine-tune parameters like speeds, energy, and temperatures to achieve the best possible microstructure.

What implications does this have? One possibility is that this newfound knowledge could enable the use of smaller and lighter weight parts in certain applications by opting for 3D printing over CNC milling. Another potential outcome is that this could be a glimpse into the future, where 3D printed parts consistently outperform conventionally made parts in terms of strength. If that were the case, we could expect to see a significant increase in the adoption of 3D printers.

Overall, this analysis presents a thought-provoking finding that challenges our assumptions about the strength of 3D printed parts compared to CNC milled parts. It opens up new possibilities in various industries and hints at the potential of a future dominated by 3D printing.

Original source


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