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pic: 2175 Wheel v2
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What are the differences of the new version? Different type of plastic?
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Yes, the black wheel is made of Altem, a stronger 3D print material. We ran into the problem that after 2 regionals we wore the hex out on the wheels, so we asked our friend to make us some stronger wheels.
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Did your pneumatic arms ever get approved up in Duluth? I was the inspector that didn't actually do much because we were waiting on a ruling from the LRI. |
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Yes, they did get approved, but we decided not to use them... We made passive climbers that were able to be actuated for North Star. A lot simpler and safer.
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The new wheels also have a stronger printing pattern around the hub. We did not start noticing wear on the origanal wheels until after a regional and a half. We also are using a much smaller hex shaft then we wanted (3/8) we ended up having to use this size shaft because all of the half inch bearings were out of stock.
Yes we got them approved, but ended up not using them because they would have crushed our new shooter we had installed. We added a passive ten point climber that actuated up for north star and it worked beautifully. |
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The original material if memory serves was abs m30, and the new material is Ultem about 2x stronger according to our printer friend
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Could you send me a picture of the worn out hubs you're describing?
Glad to see 3D printed wheels are working for you guys, in at least some extent. I think they've got the potential to open up custom wheels for a lot of teams that may have not had that option available before. |
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I would be VERY careful with those 3/8" drive shafts supporting cantilevered wheels. Have plenty of spares ready and check them every match, and make sure they are a strong material (7075 AL or a nice, strong steel alloy).
Otherwise, neat wheels. |
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Also, for those of you that are curious, ABS M30* has an tensile strength of ~5,200PSI and Ultem* 9085 has a tensile strength of ~10,400 PSI. *Assuming that these materials are being printed using a Fortus Printer.... AFAIK it's the only machine that uses both of these materials. |
Re: pic: 2175 Wheel v2
Since our season ended, we have been doing some experimentation with 3D printed wheels, too. Here are a couple of our results:
More pics here: https://picasaweb.google.com/1099928...eelDevelopment The latest version has the spokes as internal structure, with fairings on the outer surfaces. We'll print some graphics or lettering on the outer fairing in a contrasting color. Fun experiments, but we were so happy with our Colsons this year that we'll probably go that route again, unless there is a compelling reason to switch. |
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Also the 3/8 shaft is steel (not sure the exact alloy) and they have held up through 2 regionals plus practice in the shop, i dont expect to see any failures from them, but we have two spare drive sides that we can scavenge off of if they start to fail. |
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Let your imagination run wild, I always have to re-jump the hurdle when I cad something I know will only be 3D printed, as past experience has taught me to CAD for whatever machining capabilities I've had at hand. 3D printers only recently joined this list, and its been fun. go crazy, you're allowed to |
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At some point, we are going to have to make a decision about whether the benefits of printing wheels is worth the time it takes. Right now, we're just playing, to see what is possible. |
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Fully assembled, the wheel weighs 130 grams (.286 lbs). We use the 1" wide wedge top tread that Andymark sells. They changed the rubber compound they're using, and it seems a lot tougher than the kind they sold last year. We did two events on the same set, and they really don't look any different now than they did on bag day. Granted, we're only running 4 cims in a drivetrain that wasn't geared nearly as high as a lot of robots out there.
I'm looking at new options for tread attachment personally. What kind of glue did you guys use for your wheels? |
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The ABS portion of the bearing block is captured with two long screws between the two plates, and the frame tube is captured between the two plates. Tensioning is accomplished using that cam sitting next to it on the table (the cam is bolted onto the frame tube next to the block, rotating it either pushes the bearing block outwards or allows it space to move inwards). |
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The cams we machine ourselves out of aluminum on our CNC. |
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The uPrint only has one res .010, we pay close attention to how the part is grown in relation to the loads we think we see in our parts.
We also try not to run any maching ops on the part as it stresses the parts and creates cracks, we do not clean up the hex with a broach. So we run test parts to look for best fit. For the hex we printed a small ring with the hex with different tolerances. We do this with any part requiring a mating surface. Plus it's quick the test pieces usually print in 10-20 min. Our bot jumping the bridge was a big deal for us. It proved that our plastic drive train parts could handle the unexpected. Plus it was just darn cool. I have no experience with the other brands on the market so I can not compare. I have found printing parts saves us time, effort and weight , but we know expect failure so we try to print spares. But have had to use many. |
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Here is a part you can use for testing hex tolerances for 1/2" nominal shafting.
![]() You can get the model here. |
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Here is an example of a part with the support system still attached. http://cdn.shopify.com/s/files/1/003...jpg?1286806837 |
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The software we use to go from STL files to the X3G files that are used by the Replicator is "ReplicatorG" with the Sail Fish modification.
http://www.makerbot.com/sailfish/install/ Sailfish firmware adds velocity profiling to the Replicator, so it prints faster and with better quality. If you have two nozzles (we do), it also adds "ditto printing", which allows printing from both nozzles simultaneously. This lets you print two parts at once, if they are smaller than the spacing between the nozzles. The options for rafts and support structure in ReplicatorG are tricky and finicky. Unfortunately, they don't always work as advertised, and you need to experiment with the settings and part orientation to get things to work right. The software uses the last settings as the default for the next part, so in that sense, it is "automatic", but I believe the installed default was with rafts and support structure turned off. |
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