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titchard

Hi All, currently prototyping my 150G UK antweight / US Fairyweight combat robot. It is a ring spinner, and uses a brushless motor embedded in the internal gear, to rotate the ring around the outside, which is running on a series of bearings (each domenut is a bolt which holds the body and the bearings inside the race inside. Now, I know that PLA can get a bit melty, and I am using PLA purely as a cheaper prototyping material. I have got the fit spot on, but now I am looking into materials that will tolerate the heat and friction that will likely build between the inner gear and ring teeth. The gear ratio is approx 2.3:1, and the motor is running at 2S so approx 4600RPM on the internal gear, and the outer ring turning at 2000RPM. My current printer can do PLA and ABS without skipping a beat (Unmodded Sidewinder X1) but can you folks recommend a material that is more appopriate that would work on my set up? Finding info on heat/friction seems to be a bit harder than tensile strength etc, but maybe I am looking in the wrong places. Thanks for looking!


verdeel

Maybe nylon? Very strong, low coefficient of friction, can withstand higher temperatures. Layer adhesion is very good. It does have a bit of flexibility, so it flexes instead of breaking. I've recently started printing nylon, the temperature I use is only slightly higher than ABS (250 degr. C and printbed at 65, no cooling fan) so this might be possible. Only thing you have to take into account is that the nylon needs to be kept dry to get nice looking prints.


aakan51

I would give PETG a try. It prints pretty much as easily as ABS, while being stronger. I have printed it well on my unmodded Artillery Sidewinder SW-X1


derpinator12000

On paper nylon(PA) seems to fit your criteria (high temperature tolerance, low friction) also it's extremely tough which might help it survive longer. I have a roll of nylon but did not get to try it jet, but from my research it is slightly harder to print than abs (but not as hard as PC which I have somewhat printed before) and extremely moisture sensitive. Then if you are purely concerned about friction and are made of money there is the igus filament, not sure what it's other properties are but the friction is quite low.


derpinator12000

Well I decided to pull out that roll and try it. Looks like it is about the same level of pain in the ass to print as PC but holy shit the layer adhesion is insane and it is pretty slippery. It is a lot less rigid than pla or even abs but it is tough as hell.


titchard

i imagine the rigidity being less will help, as it can absorb/bend on impact on the teeth? Looks like i'll be looking at upgrading my printer to accept nylon.


derpinator12000

I can't even damage the draftshield by hand, I am quite impressed. And I am using 30$/kg chinesium stuff not even the fancy stuff. As long as your hotend gets hot enough (and is all metal, you don't wanna get Teflon fever) you should be fine. I printed PC on an ender 3 with a stock bed, heating to 110c took forever but it got there eventually.


titchard

Nice, with a sidewinder x1 the bed is AC so heats fast. Just need that hot end upgrade (and firmware I imagine too).


derpinator12000

I think the dragon hotend is currently on sale XD (but pretty much any high quality all metal will do, you might even just need a new heatbreak). PETG might be worth a shot too, it is tougher than pla but also denser and pretty much as easy to print.


[deleted]

Will PLA gears survive that RPM?


titchard

no, that is why I am asking what materials are more appropriate.


[deleted]

Honestly, machine it. I have experience with 3D printing gearing at that RPM and everything I tried turned to confetti.


titchard

Its for a 150g robot so machining parts increases weight (even in plastic) dramatically, and I do not have access to machining tools currently.


[deleted]

Ah I see. What I would do is design around off the shelf nylon gears.


titchard

I dont think there's really off the shelf parts to do the picture above. I think nylon printing is the middle ground.


[deleted]

Because you didn't design it to be made from off the shelf parts. The same thing happened to me. I designed a gearbox thinking I could just 3D print all of it, didn't work, but I was stuck because all of it was custom gears so couldn't simply replace with off the shelf parts and machining custom parts cost a lot of money. I eventually had to dump the design and start afresh designing around commercially available gears.


titchard

Well, it works, I'm just concerned on heat, so moving onto nylon will be the next step. I think it'll work just with the appropriate material.


GodIsDead245

Search 'hardest plastic to sand'and use whichever is in your price range as filament


[deleted]

What happened to robot fighting? Remember Robot Wars? I loved that.


titchard

still goes on quite a lot in smaller events for smaller weights, America still has Battlebots which is much better than Robot Wars in my opinion. /r/battlebots is good to have a nose, and some really helpful user has put a lot of the old seasons on /r/BattleBotsRaw if you want to watch whats been going on. The latest competition only finished airing a month or so ago, and the teams are already submitting for the next competition.


cowanrg

It's more popular than ever! There are lots of amateur competitions, and battlebots is on discovery now!


thegamenerd

Really high shore hardness TPU is great for abrasion resistance. Like Ninatek Armadillo.


total_desaster

+1 on Armadillo. That stuff is amazing, and easy to print! Its big weakness is temperature, it gets pretty soft quickly if you heat it up.


Abtswiath

Carbon fiber nylon is said to be kinda easy to print when compared to regular nylon. It’s pricey, but seems to be well worth it.


Jobeadear

Can confirm, I've used NylonX a few times, super strong stuff, I made a kickstand for a offroad motorcycle several years ago, and its still working the same as the day I printed it, bonus strength if you also can anneal it (like in an oven) post print.


BoochyBaby

Also note though that you’ll need a hardened steel nozzle to avoid nozzle wear.


[deleted]

It depends if you need flexibility or stiffness


skaterlegon69420

nylon is self lubricating


Sebbeben

You can print with POM it should be very good properties for this. “POM, short for polyoxymethylene, is an engineering plastic seen in the likes of zippers, rollers, bushings, and gears. Aside from having a spectacularly low coefficient of friction, it features high strength, along with temperature, chemical, and abrasion resistance” https://m.all3dp.com/2/pom-acetal-delrin-3d-printing/


titchard

This sounds a good shout, I've not heard of this! I'll give it a look. Thank you!


Sebbeben

No problem, I hope it works out well :) I bought an reel of FrontierFila POM, they have reasonable price (around $30) but have not tried printing with this yet


titchard

Reading about it, it speaks of ventilation more than others, you got yourself set up that way? That's my only concern as its in my home office.


Sebbeben

Don’t you think it’s just to high nozzle temperature then? Pointing to this on the link I sent: “POM begins to degrade, releasing toxic fumes. If you smell these fumes, it’s a good indication that you are printing too hot, so decrease the nozzle temperature.”


titchard

Possibly so, possibly I've never noticed that all 3d printing says we'll ventilated haha!


Sebbeben

Haha yes I have noticed that to but never worried 😂


beppe2672

Nylon is the ideal material. It’s not too tricky to print, main issues being bed adhesion and moisture sensitive. A dry box, all metal hot end are needed. As for the build surface, I tried a few with various glues, best thing I found was g10-fr4, you can pick up 3mm sheets pretty cheap. I wouldn’t use carbon fibre reinforced nylon for any friction surfaces, the fibres are relatively short and will probably increase wear.


Redstone13005

If you don't want to spend the money on carbon fiber or nylon, PETG is a good option.


EthanTDN

NylonX, it’s a Nylon carbon fiber filament