pic: 108 Rapid Crab Prototyping
 

Re: pic: 108 Rapid Crab Prototyping
 

Out of curiousity, how quickly do the SLA machines print? I've been prototyping parts in ABS lately on a ZCorp 3D printer, but I think I've got something coming down the line that's going to be made on an SLA machine.

What are the overall dimensions of the crab module?

Re: pic: 108 Rapid Crab Prototyping
 

I actually do not know exactly how long it takes, but I always have my parts within 24 hours of submitting them. The shop that makes them also makes tons of other stuff so I am not always first priority = ( . I would guess though that it takes about 4 hours to make something large and complicated. Umm, dimensions... the overall OD of the unit is 4.5", the overall height is 9.25", the box frame is 3"X3", and all the material is 1/4" plate (eventually aluminum). Inventor's estimates its weight at just a hair under 4 pounds, including hardware.
108

Re: pic: 108 Rapid Crab Prototyping
 

Rapid Prototyping Content:
SLA machines run fairly quickly. I believe the units we used had a 1mm thickness interval, and each layer was done in a quick flash. However, I seem to recall that the cleanup of the part(s) was the most time consuming. The nylon is not very stable (due to temperature/light) so we always painted our models. That was after all the hand-sanding and detailing. Our turn-around time was a couple days.

Swerve Content:
Looks like a nice package. Is there only the single rotational bearing through the midline of the unit, or is it supported near the top as well? Also, are you making the swerve sprocket yourself, or is that an off the shelf part? Do you have an estimate cost for a full-up module? (I'd love to hear what it cost other teams to do a similar design.) I hope to see it in 2007!

BEN

Re: pic: 108 Rapid Crab Prototyping
 

wow i wish my team had the funding to be able to access a rapid prototypeing machine...we have are lucky if you can get a few things done on a bridgeport or a cnc...seeing as we dont have either of those

Re: pic: 108 Rapid Crab Prototyping
 

Right now there is only one rotational bearing in the design, however a few people have commented on the stability of that during a match so in gen2 there will be 2 bearings, one low and one high. the sprocket is off the shelf but requires serious reworking, its a 70 tooth #25 chain with a 3 inch square cut in the middle... As cost goes...hmm... I have no idea. Working the parts would be the most expensive (especially the sprocket) as everything else is a standard part. When I am done reworking the whole design, I will post it with the inventor files for all to use. My final goal is to make it 2-speed, with independent swerve per side.

Re: pic: 108 Rapid Crab Prototyping
 

Since the first time I met you (you were in 8th grade and met you at the local FLL competition), I knew you would be the right hand man for team 108 someday. I am very impressed with the design, but I do question weight. The designs you have shown me, you were using quarter inch plates (I know this particular one wasn't made for a FIRST robot), but if you do plan to make a swerve drive for next year (for FIRST), I would suggest to look at those quarter inch plate you are using and take some weight out of there. Your overall chassis design (the one you showed me) looks very good. I would suggest to post it up here asap and get inputs from others.

... now post the picture up and go back and concentrate on school work, you gotta get to MIT remember? Good luck, Evan.

Re: pic: 108 Rapid Crab Prototyping
 

our team has a Stratasys Maxum FDM machine, prints ABS plastic. its good for some things but, well, i'm a machinist and i think thats still the way to go for most stuff. not to mention you get things done a heck of a lot faster on a mill.

just what i think.

-Q

Re: pic: 108 Rapid Crab Prototyping
 

I prefer a mill, too. A small, red one sitting in our machine shop. All manual. LOL... there's 3 digital ones and 4 manual ones in K-T I think... but the only one I know how to use is the one in the robotics area and I work at K-T.

Re: pic: 108 Rapid Crab Prototyping
 

I agree, milling is the way to be, but as a prototype, this I find is cheaper. Besides, whats cooler than a crab drive that was printed and works? Obviously I wouldn't put this on a robot, it would be destroyed before you knew it, but for proof-of-concept, its great. Who knows though, one day we may see an all Lexan (or some other strong plastic) robot...how cool would that be?
108

Re: pic: 108 Rapid Crab Prototyping
 

Ahem...

http://spamrobotics.com/skins/spamin...e=history#2000

;)

Re: pic: 108 Rapid Crab Prototyping
 

and

http://www.chiefdelphi.com/media/photos/12491