3D Printed Metal vs CNC Machined - How Strong?

How does 3D printed metal compare to CNC machined metal? Or what about carbon fibre nylon? Let's find out! The one tonne Print Buster 3000 test rig is back in action to answer more questions about the strength of 3D prints. This time around, we start with a number of PLA FDM prints before looking at Onyx FR carbon FDM and then on to Sintered Laser Melting (SLM) 3D printed metals and finally CNC'd metals. Which will be strongest, and how strong will it be?

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#3dprinting #cnc #strength

[bluerider]

The "heat treat" you did likely did nothing, if anything softened the parts. Heat treating steel requires specific temperatures and specific times for cooling to create the proper grain structure. It's followed by an annealing process to dial back the hardness to a specific number.

I would recommend redoing those tests and obtaining pieces that have been properly heat treated to a specific hardness.

I was surprised on the 3d printed part strength.

[Personnenenparle]

The kg/time graph is not really useful. Kg/elongation would give way more info on the stiffness

[BLenz-]

I understand you are doing your best, but . . . .
As someone who works in materials testing, testing a single sample really isn't enough to draw many conclusions. You could just have a bad sample.
AND, tensile test samples are SUPER sensitive to stress risers. Grooves or pits too small to see can be a stress riser and weaken a sample A LOT. I suspect that's why your CNC samples gave weaker strengths than the printed ones. Have you looked to see how the CNC samples compared to published material strengths?

Also, how are you calculating your elongation? I feel like if I can see it visually, it has to be more than 1.2%.

[simp-slayer]

I hope we get consumer-grade metal printers soon.

[kmyerslp]

Grain direction in some of the cnc materials plays a big part too. The titanium looks like it was perpendicular to the test load. The break seemed like it too.

[joshuadelisle]

I don't know if anyone has mentioned this but it matters which way on the plate the part was machined from. There is an elongated grain structure from the rolling process. I tested this in my nail making video as I was making nails from sheared material and the strength drastically differs from 90 degrees on the original plate. Cheers J

[xenon]

It's nice seeing that characteristic stress-strain profile for the steel, even with the 3d printed one. It would be interesting if you could somehow constantly increase the load instead of pumping the jack.

[GRBtutorials]

It’d be interesting if you could test metal cast from 3D prints, as that’s a DIY way of “3D printing” metal. Maybe a collab?

[desmond-hawkins]

Great tests! I don't think it was mentioned, but I assume the 3D printing process built these pieces "flat", right? I mean as opposed to "standing" like they are on the test rig. A major source of weakness in 3D prints is at the interface between layers, so I don't see how these parts could be this strong if the layers were horizontal when the piece is being stretched. By the way, it would be interesting to also compute the tensile strength you observed in Mpa (as Stefan from CNC Kitchen does), and compare these values to the ones reported by PCBWay. For example, they claim 560 Mpa for 316L stainless, 330 Mpa for aluminum, and 600 Mpa for titanium – all tensile strength numbers.

[germanrcbashing]

Well I didn’t expect to see that result… thanks for showing this👍

[alexeytsybyshev]

6:24 This is definitely way higher than 500 C. Based on my limited experience melting brass and the glow, I would say the middle part is at least 900 degrees

[jeanladoire]

Depending on what "tool steel" you had, you could have heat treated it to triple its performances (i don't mean annealing it as a heat treat, i mean hardening and tempering). Heat it to cherry red, and not any hotter or under that, drop in water, and then make its surface shine again with sandpaper or a stone, you just want to see the metal underneath. Then, with the torch, slowly heat it back up until the steel starts taking tempering colors. Reach an electric blue, avoid going above that too much, and below that will just be too brittle. Flame tempering is kind of a crude way of tempering usual carbon steel, but that's how it was done before. That being said, it's not pushing the material to its best capabilities, you'd need a tempering furnace for that.

[RobGadeke]

Very interesting results here
Curious what the cross sectional area of the test piece is? Could be more useful to have the numbers in MPa.
An idea for a future video could be comparing the metals at varying infill levels to high performing plastics (peek, ultem...) For strength:weight and strength:volume comparisons

[electrosync]

The results were a little surprising! Any ideas for a future strength test video?

[McRootbeer]

How much were the different parts? It would be interesting to see which printed material gets you the most strength per dollar.

[helpmeimconfused]

How did you measure the % elongation? I don't see any strain gauge nor was it explained in the video. Kg/time doesn't really tell us anything other than saying we can progressively load this specific part for this long before it breaks. Also, that's not ASTM D638 dogbone standard so you can't really say that the test has been "standardized". Pedantic, I know. But there's a fine difference between doing something that resembles a standardized test and doing an actual standardized test; I understand you're constrained by your test rig but I must point this out.

Cool results though. I'd like to see an improvement in the experimental setup and eventually see an actual stress strain curve.

[apollolux]

Does metal, especially CNC or forged/hammered metal, have "directional grain/layers" like wood and FDM 3D-printed plastic does? If so, would that significantly affect tensile strength to the degree that plastic is affected or is it not noticeable enough, and is it not possible to ask a fabrication shop to CNC certain metal parts along a certain axis of the sheet if it is?

[seanpolke]

Using Newtons as your unit for force is more helpful, instead of a static mass substitute (kg). You can still describe the static equivalent but then also show how dynamic forces can be huge, compared to the masses used. A very important lesson.

[DaRealdioactiveMan]

Your „heat treatment“ was interesting. Rest of the video: awesome 👍

[milspectoothpick]

Most common alloys are not suitable for 3D printing, like 6061. The 3D printed aluminum part was most likely a much different alloy but cool to see they can be just as strong as a machined part these days.