Wooo the Maker Faire is a ton of fun! Lots of great stuff here. We're also right next to Mr. Jalopy, our favorite blogger and a really funny guy. We made him this sign so that he wouldn't hate us from all the noise we're making with the Shopbot.
So the PRTalpha benchtop Shopbot was kind enough to send out here for us to use at the show rocks. It's faster than the one we've got at home, and for someone that just wanted to make small stuff, like guitar bodies or signs or something it would be perfect. It's working quite well (once a fuse that worked loose in the shipping was found and set back into place!) and it's quite a draw. Several folks seem to be having the same little ephiany that we did when we first learned about them. You can see the gears turning in their heads, thinking of all the things they could make with one. Gotta say, Shopbot is really good at making accessible and affordable CNC gear for everyday folks.
The difference between the one we have at home and this one we've got at the show is that this one is an 'PRTalpha' while ours is just a 'PRT'. What this means is that the one at home is always running 'open loop' while the one here at the show can switch from 'open' to 'closed' loop on the fly when it needs to. 'Open loop' is where the computer tells the motors to move the bit a certain distance, but doesn't check that it actually moved that distance. It just trusts that it did. This means when you're doing something that's really complex, or need something to be really accurate, or cutting something really thick, you need to slow it down a bit, for otherwise it can 'loose steps', i.e. not really move as far as it thinks it did and get off register. With the Alpha, it can also run in 'closed loop' where not only does the brain tell the bit to move, it then checks to make certain it did move the right amount when it's done. This means that you don't have to worry about loosing steps when doing stuff. However, it's slower to run closed loop all the time, so the alpha switches between the two automatically depending on what you're doing. So in the end, it runs fast, yet is unlikely to loose steps. Pretty cool. Best thing is that the PRT and the PRTalpha are only different in the stepper motors that drive it and the brain, so at some point in the future when we've got the money we can 'step up' and not lose steps anymore by just swapping out those items.