Heyo. My bible has been the 2009 Riobotz tutorial PDF, which goes over materials in extreme detail.
Today, Ray Billings released a video about him using FDM parts as battery holders, and during disassembly pointed out more FDM parts that are being used in the current tombstone itteration.
My question is, how do FDM or Resin print parts hold up in comparison to traditional sheet materials like cut sheet metal, polycarbonate, etc. Is there any legitimate scientifc style testing done to compare how these 3d print parts hold up under different load conditions?
Oh youāre headed down the dangerous rabbit hole of āit dependsā
Legitimate scientific testing and robots do not go hand in hand. Honestly, this hobby has too many stupid variables to get meaningful data to empirically say that X is better than Y for an exact use case. This is one of the issues I have with the Riobots guide. Itās a fantastic resource but itās written from the perspective there is a Correct Way To Robots. But I digress, Iām sure someone has tested to a degree and you can potentially get some useful information or if you are just interested in actual material science.
90-95% of what drives combat robot material themes and choices is either anecdotal or real world trial and error viewed through the lens of whatever preconceptions and design theories the builder already has (or has picked up)
There isnāt going to be a straight answer for the question of is FDM/resin going to be better than a ātraditionalā method. Honestly itās a knife that cuts both ways. People are very eager to abandon sheet material and just hit print on something that doesnāt need to be printed and isnāt any better for being produced in this way but also there is still this looming cloud that printing = weak which I can only assume is a holdover from horrible reprap pla noodle poopers of the late 00ās early 2010ās.
Heck, resin vs FDM is a whole event in itself (though with practical clear winner in FDM)
Ray is an absolute gem of the sport but part of his approach and why he does so well is because he sticks to what he knows. Heās a good 5 maybe even 10 years behind the cutting edge and that is where his strength is. He letās other people go up in smoke and hefts a lump of S7 at them with a monstrous brushed motor and power chair motors (though I think he is adapting now more than ever )
Some more specific questions would help to advise what is better for your particular uses I will say, though if you were after the Robot Materials Megadoc to flick through I hate to say one doesnāt really exist.
Thanks for the detailed response. I do agree that the exact sciences behind material engineering often donāt translate to real world benefits in situations as chaotic as combat robots sadly. I am curious about the statement about FDM being the clear winner though, with the though that resin printing has a more even surface resulting in a more consistent durability, but I lack knowledge on the topic to really give comment.
The big problem with resin printing is the materials that are available. Most printer resin is hard, and for combat robots thatās a bad thing. When your armour is hit, you want your opponentās weapon to bounce, or to pull off small pieces. If your armour is too hard it will crack instead, or worse, shatter. I fought against a resin bot once, and it cracked in half on the first hit.
This holds true even for metal - Hardox (it even has āhardā in the name!) is a popular steel for robots, but its not that hard by hardened steel standards. Hardened tool steel works out a fair bit harder, but that makes it much more prone to cracking.
There are softer resins available, but I donāt think anyone wants the cost and effort of testing them. There doesnāt seem much point when tried and tested materials are available, and you can have more fun testing a new weapon system.
Iāve got a homie whoās super into 3d printing so i will get some advise from them, but based on this I think I will stick to just trying to use some of the harder plastics since they seem to work out the best for the lighter weight classes
Ty
Weirdly, relatively soft and pliable plastics such as your HDPEās, TPUās are going to be your best bet vs engineering standard āhardā delrins, nylons and such.
Yep, seconding (re-seconding?) Harry here, you often want to use the softest material you can get away with. Too soft and your whole robot will bend (but you can get away even with that sometimes!), but too hard and itāll crack. Hardness and toughness are not the same
Iāll give you a quick rundown of the filaments i use:
PLA: Your basic printing plastic. A bit too brittle, but useable for ants
PLA-ST: A blend of PLA designed for toughness. Good for ants, and fine for internal parts at larger weights. Other ātoughā PLAs are available, not sure if anyone has tried them.
ABS: Ye olde basic printing plastic. More difficult (and stinky) to print than PLA. Itās lighter though, so can save you a bit of weight. Same properties and uses as PLA-ST
PETG: Hard. Brittle. Only suitable for internal mechanical parts that wonāt be taking shocks.
TPU: Pretty much rubber. Makes great armour. It will bend though, so you need to design around that (less of an issue for ants)
Nylon: The most āit dependsā material. Very difficult (and even more stinky) to print. Nylon is a whole family of different plastics of varying usefulness. A good nylon will work well for armour, chassis and internals for ants and beetles. A bad one is probably comparable to ABS (Iāve not tried it). Taulman 910 is considered the gold standard, but the company that makes it was bought out and shut down. Donāt bother with carbon fibre filled nylon, it makes it more likely to crack
PP: Supposedly comparable to a good nylon, but lighter. I havenāt tried using it yet myself, as itās also difficult to print. OBC is a PP variant that is easier to print, but itās expensive and hard to get hold of.
TLDR: PLA-ST or ABS for ants, and TPU if you know what you are doing. TPU armour for beetles, donāt try to print the whole thing unless you really know what you are doing
There is also ASA, which is basically ABS 2.0, less odorous and a bit easier to print (you will still need an enclosure and Iād recommend glue on the print bed for larger parts).
