pic: 2175 Wheel v2

[Botwoon]

Originally Posted by Boe

Ill try and find the wheel at the shop tonight and upload it later. we believe the reason for the failure was because of the less then ideal shaft size causing the forces not to be distributed over a large enough area in the wheel. What size shaft do you guys use it looks like 3/4.

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.

We used 1/2" alum this year. I believe we did 7/8" in 2012 and iirc we were rolling 1" hex in 2011. I'm too lazy to embed, but here's a link to the entire 2013 assembly (4" wheel). The back end of the axle is unfinished in this photo.

[ToddF]

Originally Posted by Botwoon

We used 1/2" alum this year. I believe we did 7/8" in 2012 and iirc we were rolling 1" hex in 2011. I'm too lazy to embed, but here's a link to the entire 2013 assembly (4" wheel). The back end of the axle is unfinished in this photo.

Your wheel pictures have been a major source of inspiration for us. Out of curiosity, what is the weight of one of your 2013 wheels with the tread attached? How wide is your tread, and how is the tread holding up?

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.

[Botwoon]

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?

[nerdherdmember]

Originally Posted by Botwoon

We used 1/2" alum this year. I believe we did 7/8" in 2012 and iirc we were rolling 1" hex in 2011. I'm too lazy to embed, but here's a link to the entire 2013 assembly (4" wheel). The back end of the axle is unfinished in this photo.

Is that a 3d printed bearing block? How are you tensioning it? Does this save time/weight over an aluminum version? We on 422 are strongly considering a 3d printer for next year, and things like this make us want to take the plunge. Is this printed on something like a makerbot/reprap with ABS or PLA, or is it Ultem with some more commercial printer?

[Botwoon]

Originally Posted by nerdherdmember

Is that a 3d printed bearing block? How are you tensioning it? Does this save time/weight over an aluminum version? We on 422 are strongly considering a 3d printer for next year, and things like this make us want to take the plunge. Is this printed on something like a makerbot/reprap with ABS or PLA, or is it Ultem with some more commercial printer?

Yep, 3d printed. We print all of our parts at home out of ABS with a uprint from Dimension. It doesn't save any real time, but it saves man hours which is helpful considering the tiny team we had this year. It might take ten hours to print a couple of wheels, but all those hours are passing while we're asleep .

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).

[nerdherdmember]

Originally Posted by Botwoon

Yep, 3d printed. We print all of our parts at home out of ABS with a uprint from Dimension. It doesn't save any real time, but it saves man hours which is helpful considering the tiny team we had this year. It might take ten hours to print a couple of wheels, but all those hours are passing while we're asleep .

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).

Do you ream/bore the ABS after printing, or is the print within tolerance for a press fit already (if you press fit, you could be using the plates to hold it in place I guess)? What's the resolution/layer size of that printer? Is it comparable to the makerbot replicator 2? How do you manufacture the cam? Sorry for all the questions, seeing your robot fly off the bridge with 3d printed wheels was what really planted the seed of 3d printing in my mind last year, so being able to get responses is very nice.

[Botwoon]

Originally Posted by nerdherdmember

Do you ream/bore the ABS after printing, or is the print within tolerance for a press fit already (if you press fit, you could be using the plates to hold it in place I guess)? What's the resolution/layer size of that printer? Is it comparable to the makerbot replicator 2? How do you manufacture the cam? Sorry for all the questions, seeing your robot fly off the bridge with 3d printed wheels was what really planted the seed of 3d printing in my mind last year, so being able to get responses is very nice.

We do ream and tap after printing, but usually for a reason other than tolerances (post creation modification, tap for a screw, etc.) we don't drill, it usually results in cracks. I'll get Lucas on here in the morning to answer your more specific questions as to the printer.

The cams we machine ourselves out of aluminum on our CNC.

[Metalcrafters]

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.

[ToddF]

Here is a part you can use for testing hex tolerances for 1/2" nominal shafting.



You can get the model here.

[nerdherdmember]

Originally Posted by ToddF

Here is a part you can use for testing hex tolerances for 1/2" nominal shafting.



You can get the model here.

After looking through your picasa and thingiverse postings, would you clarify for me what constitutes removing support structure, and is "full support" an automatic option?

[notmattlythgoe]

Originally Posted by nerdherdmember

After looking through your picasa and thingiverse postings, would you clarify for me what constitutes removing support structure, and is "full support" an automatic option?

When you print many objects on a 3D printer like the Replicator, the printer needs to build up a support structure to print onto when a piece of the part would be up in the air. After the printed piece is done, this support structure needs to be removed from your part to get your finished piece. This is usually just breaking off the mesh type support system that gets printed.

Here is an example of a part with the support system still attached.
http://cdn.shopify.com/s/files/1/003...jpg?1286806837

[ToddF]

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.