10-04-2013 22:09

Mike Marandola

Re: pic: 2175 Wheel v2

What are the differences of the new version? Different type of plastic?

10-04-2013 22:14

peirvine

Re: pic: 2175 Wheel v2

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.

10-04-2013 22:18

ehochstein

Re: pic: 2175 Wheel v2

Looks like your robot is going to need some re-inspection

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.

10-04-2013 22:19

peirvine

Re: pic: 2175 Wheel v2

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.

10-04-2013 22:23

Boe

Re: pic: 2175 Wheel v2

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.

10-04-2013 22:32

ehochstein

Re: pic: 2175 Wheel v2

Coming from a team that is planning on 3D printing some wheels next year, what material were you originally using?

Glad it was approved, but they seemed a little over-engineered to me for a simple 10-point climb. Glad you guys figured something else out! Congrats on the regional win at North Star and I am looking forward to stopping by your pits at champs!

10-04-2013 22:34

Boe

Re: pic: 2175 Wheel v2

The original material if memory serves was abs m30, and the new material is Ultem about 2x stronger according to our printer friend

11-04-2013 09:59

Botwoon

Re: pic: 2175 Wheel v2

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.

11-04-2013 11:31

Chris is me

Re: pic: 2175 Wheel v2

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.

11-04-2013 11:53

thefro526

Re: pic: 2175 Wheel v2

I'd be willing to bet that the 3/8" hex shaft is also a factor in the hub wear as well. Figure a 3/8" hex shaft is transmitting the same amount of torque through a significantly smaller area on the wheel than 1/2" hex, so it should be more prone to stripping the hub out.

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.

11-04-2013 12:14

ToddF

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.

11-04-2013 15:55

Boe

Re: pic: 2175 Wheel v2

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.

11-04-2013 16:02

Aren_Hill

Re: pic: 2175 Wheel v2

I view these as a case of someone who has not yet realized the full potential of a 3D printer, my guess is you could use a fair amount less material, resulting in a lighter wheel, and also have it much more aesthetically pleasing.

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

11-04-2013 16:07

Boe

Re: pic: 2175 Wheel v2

Notice the 7 spokes But in all seriousness we knew we could do some really cool designs and there were team members that really wanted to, but we decided to play it safe for our first year doing this with such an important robot part. Expect some much cooler wheels in future years if we continue printing wheels which i personally hope we do

12-04-2013 02:11

Botwoon

Re: pic: 2175 Wheel v2

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.

12-04-2013 08:59

ToddF

Re: pic: 2175 Wheel v2

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.

12-04-2013 12:40

Botwoon

Re: pic: 2175 Wheel v2

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?

13-04-2013 00:39

nerdherdmember

Re: pic: 2175 Wheel v2

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?

13-04-2013 01:08

Botwoon

Re: pic: 2175 Wheel v2

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).

13-04-2013 01:28

nerdherdmember

Re: pic: 2175 Wheel v2

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.

13-04-2013 02:18

Botwoon

Re: pic: 2175 Wheel v2

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.

13-04-2013 18:36

Metalcrafters

Re: pic: 2175 Wheel v2

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.

14-04-2013 08:23

ToddF

Re: pic: 2175 Wheel v2

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



You can get the model here.

14-04-2013 16:38

nerdherdmember

Re: pic: 2175 Wheel v2

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?

16-04-2013 09:42

notmattlythgoe

Re: pic: 2175 Wheel v2

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

16-04-2013 10:12

ToddF

Re: pic: 2175 Wheel v2

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.