Yes, but 10 points to Gryffindor for creativity.
We are printing a lot and I (lead mentor of team 1989) have a youtube channel that will and is reporting on our experiences. Latest video is
For this year. Lots of brackets, All gears printed in Nylon and HIPS survived and worked great, Our elevator not so much but that had mostly ābad desgnā reasons. For the off seasonā¦ Right now we are working on printing the whole frame slightly reinforced with aluminum pieces if and where needed
This year 1108 designed and used a drivetrain that used a mini-cim mounted inside the wheel. The design used Andymark steel 20dp gears for a pinion and two planets, but for a ring-gear, we actually 3-d printed gears with our Prusa Mk2S.
Initially we printed them in just PLA, but for competition we printed them in CF-20 carbon fiber.
We didnāt ever see a failure in the PLA ones, but the CF-20 was on hand and notably stiffer.
We lubed them with KOP strawberry jelly, which I think is a synthetic grease.
We only had one failure in practice, and it wasnāt in the teeth, but in a part that probably took external damage. We redesigned to thicken the part some after the failure.
Initially I had tried to get ring-gears water jetted (anchor labs) but it was expensive and took longer than printing because of the shipping. We had intended just to use the printed parts as prototype.
hereās a link to some pics of our modules in another post.
At present, we intend to expand on this idea more for next year, probably going full-swerve.
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I havenāt printed anything major important like gears etc. But they work great for making special tools, tube end caps and brackets. Iām currently printing an Anderson battery connector clip that eliminates the need to wire tie the battery plugs together. Oh and iprinted a mini Krinkle, which is the name of our robot.
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We 3D printed brackets to attach our lift cylinders to drawer sliders this year, and they worked fantastically ā from getting the dimensions right to having hex holes for keeping nuts (no wrench needed for mounting) to being able to draw it and whip off four of them overnight, it was hands-down a fantastic application for 3D printing.
I agree that COTS parts arenāt great candidates for 3D printing. Where additive manufacturing shines is rapid production of small numbers of custom widgets. This year we made those brackets and polybelt pulleys, and while we had the capability of making a lot more stuff, it was easier, faster, and usually cheaper to go with more traditional fabrication for the rest of the robot.
We did print a couple of great big 20DP gears to test some basic mechanism functionality before we went ahead and bought the real thingāand to be honest, it would have been ultimately cheaper to just buy the gears and keep them on-hand if we donāt end up using them; itās not like they go bad.
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Iām not an expert in the space, but Iāve seen success stories online in printing polycarbonate with a prusa i3.
Correct. As long as your printer has an all-metal hot end, you can print PC. And if you have a hardened nozzle, you shouldnāt have an issue with CF Nylon or other filled materials.
See below
Full metal hotend is not enough Most all metals in the stock configuration like an E3d V6 top out at about 280. If you want to go above that you got to get the copper block and a higher temp thermistor or thermocouple like the PT100. Which then might also cause problems if you have 3d printed parts like a fan shroud etc around the hotend. Recommended extrusion temp for PC is between 270 and 310 and more towards the 310. PC also likes to warp so you need a bed temp recommended around 130 and a good enclosure. This is when you want to print parts of larger size. Its possible but it will take some doing and proper preparation.
Now CF and Glass fiber with a hardened nozzle is fine but also be aware that the greater stiffness come at a price of layer adhesion and tensile strength So you get a harder part but your hook might fail sooner than with pure Nylon. Unless you have a printer that lays the whole continues fiber in like some markforged do but there is a price premium for that.
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Iām currently working on doing the same thing with my teamās robot. Right now Iām working on getting the right ratio of detail to durability to printability.
What scale is that from full-size? Do the lift parts actually slide within each other and move?
I printed a 20:1 model of our robot but made it all one solid part and printed two different configurations of it, full height/extended and low/retracted. Iād be interested in how much trial and error it took to have those thin lift parts actually slide within each other
The only material Iād consider for a gear under any sort of load is nylon (non carbon-fiber). Nylon 910 seems like a good suggestion since Taulman designed to have the best mechanical qualities they could get out of a nylon product. Iād rather have a metal gear, though. Iāve seen enough aluminum gear teeth sheared off to know that even aluminum 7075 has its limitations.
Itās hard to beat PLA as a generally useful filament. Itās cheap, emits less smelly fumes, stronger than some people seem to realize, easy to print. Since itās the most commonly printed filament, itās easiest to find resources to learn how to do it well. PLA is more resistant to bending than ABS or PETG, but also more brittle.
PLA parts will fail if theyāre designed poorly or printed poorly or asked to do more than a person can reasonably ask a plastic part to do. The specifics of how a PLA part is designed and printed and used matter a whole lot.
PLA doesnāt have to be relegated to non-structural / non-load bearing applications. Example: our teamās arm gearbox plates (https://www.thebluealliance.com/team/967) handled a 4 stage arm gearbox powered by CIM motors and also functioned as a big frame gusset between the horizontal upper frame and the vertical arm support structure. Those werenāt the weak links in the system - the aluminum frame and output shafts were the things that bent when the arm was driven back too far into the robot in a self destructive way. This robot also has plastic bumper brackets and upper frame corner gussets visible in the picture. That sounds scary to some people who are skittish about plastic, but those components are solid in the context of a frame and bumper system that is mechanically supported in multiple directions. We never had any grief with that stuff over three competitions.
I took the main cad files and reduced it to 10%. The files were still too large for my slicer program. So i took the physical measurements and designed it in Tinkercad. Believe it or not i got the elevator functional on the second design. The first design the elevator would fall out at the bottom. So i added little tabs to keep it in. This model has the drivebase and main elevator as one piece. I am currently seperating them so itās easier to print and Iāll just glue it together. I rushed the design so we could take it to Detroit. I will be refining the design to make it better. I also had aproblem with the silver filament. It didnāt extrude very well. Iām going to try Hatchbox or 3d solutech
I have said this before in other threads, but 3d printing is an amazing tool for FRC. This year every single one of our 1/2in hex hubs on our drivetrain wheels were printed with basic Hatchbox PLA. While this may not sound like a good idea, it worked very well for us. We tried it first on our practice bot, and then after seeing how well it performed, we put them into production for our comp bot. These hubs survived driving off of hab 2 every single round with no hubs breaking during any of the matches. We were blown away and will be using them again in the future.
Oh really? you printed that in one piece and still got the elevator to move? Would you mind sending me the step files for that model? I want to see what tolerances you left while still printing it in one print.
Sure. The drive base and main elevator stage were one piece. 2nd and 3rd stage were printed separately and just snapped together along with the cargo grabber. When iget home from work Iāll get in touch with you to see what you need.