johnridley | First Thingiverse thing posted

I installed the printed knee joint replacement in the dome tent this afternoon and it works perfectly. I uploaded it as my first object to Thingiverse.com
Dome tent knee joint replacement by jridley - Thingiverse

+4 by Elle Plato, dermot dobson, Mike Bakula, Bob Trembley
Bill Higgins's profile photo
Bill Higgins - It is so cool that you have acquired such a machine and that you are already making something useful with it.
Moshe Yudkowsky - I'm really looking forward to the day when anyone can print any sort of deadly weapon. This will utterly transform the relationship between citizen and state in repressive societies.
Todd Johnson - Very cool!
Elle Plato - Most excellent.
John Ridley - +Moshe Yudkowsky Well, knives are already perfectly possible; this stuff is pretty tough and you could print something really nasty. Current guns probably require something non-printed at least for the barrel and receiver because current printing technology uses thermoplastics.

Within the 3D printing community, the RepRap project is as much social as it is technological; there's a real push to try to make the printers accessible to everyone. One of the popular printing materials is polylactic acid, which is made from plant starch; the hope is that even in a 3rd world country the plastic could be made from essentially plant waste material. It's also biodegradable so failures and products no longer needed can be composted - I've heard that small objects break down in an active compost heap in less than a year.
John Ridley - I should point out that I bought the kit (for $825) because I did not have any experience with the field at all and had nobody to go to for help. Given the slight amount of knowledge that I've gained now, I'd probably try to build from scratch in the future. The electronics can be bought as either a simple kit for about $160 or assembled for $200. Apart from that you need 5 stepper motors, a set of printed parts, some microswitches, some skateboard bearings, and a power supply, all of which can be bought on eBay, and a bunch of hardware store stuff - nuts and bolts and threaded rod, a little wood plus some smooth rod which can be gotten from McMaster Carr or local industrial supply. The only thing I'd definitely go custom on is the hotend - $75 from MakerGear. This is the extruder nozzle, the thermal barrier, and the heatcore that heats up the extruder nozzle, and the thermistor for temperature control.

About $450 would probably do it on the DIY route.
Bob Trembley - Awesome... Keep posting... Sam and I very nearly have Constance convinced into getting one! :P
Moshe Yudkowsky - You know, the first time I read "knee joint" I was thinking "human body part."
John Ridley - +Bob Trembley if you decide to go for it I'd be happy to help you - I'll print you a set of parts for cost and help you get started. You can probably reproduce what I've got here for < $400 with a basically free set of printed parts from me. A set of sanguinololu electronics ready to rock is about $160 on eBay, $70 or so for motors and belts and bearings, $70 for a hotend, a couple boxes of nuts and screws and some threaded rod, 6 pieces of tool rod and you're there.

You are talking about a couple of solid days to build though. Just buying a plastruder for $170 would probably save some frustration, though again I could just be projecting my own ignorance. I should probably try printing my own extruder to get a feel for how hard it is. Maybe it's not that bad. A printed extruder is more like $30 instead of $170 since it's just a couple of bearings, a bolt and a motor plus the printed parts.
Elle Plato - At some point I want to get into 3D printing, but I have too much going on right now. This is really cool though John!
John Ridley - I'm planning on doing a completely from-scratch build now that I have a working unit built from a kit. Then I'll have the ability to help others make one as cheaply as possible, plus have the added egoboo of having a unit built completely from stuff scrounged out of Lowes and eBay.
Moshe Yudkowsky - I sincerely hope you're documenting all this.
John Ridley - There's already pretty good documentation on the RepRap wiki. I've been given collaboration rights on the MakerGear Google Doc and I'll be working on that.
I have another 3 or 4 hours work to do to finalize the assembly of this printer; right now it has a lot of loose wires just hanging, and it doesn't have the proper power supplies yet, then I plan to do a more complete doc. I did a bunch of doc up on the GT Wiki before I got the kit and I'll be working on that as well.