I agree with @Shane_Graber , it’s possible you could utilize existing X carriage setup of the i3 that way. Save yourself a lot of extra work, and allow modifications to the design to span multiple printers.
I plan on making those revisions, though it might require the top z cross brace to be longer.
Don’t be afraid to let plastic hang out a little. Look at the upper Z mounts on the i3 and you’ll see what I’m talking about. They hang pretty far off the machine, with far less support than yours has, and they work beautifully.
I agree with @ThantiK about the amount of extrusion on the y axis. You could do something smart with some makerslide ( http://store.makerslide.com) and design a really neat machine. You should also think about maximising the x travel by spacing the z rods at the extemeties of the machine.
Why do we (repraps) use two motors on the z axis? Couldn’t we use one dual shaft motor and belt drive the second threaded rod? This would drastically reduce the cost of the machine.
@Daniel_Wood because a geared Z axis was used in the sells mendel, and people learned their lessons with that. Belting is just a pain in the ass to route, takes up room that could be used for mounting electronics, etc, and think about the costs: If you want a nicely functioning Z axis, you’ve gotta buy a manufactured pulley, belt, probably a bearing or two. It ends up being almost as much as just buying a second stepper motor.
What about one z motor mounted horizontally using dual shafts and driving the z axis a using worm drive arrangement?
The ORD bot has a makerslide based y axis. Might be worth a peek. Excited to see an extruded i3 design. Pesky water jet cut aluminum plates!
I’m using these specific extrusions because I have them, and I have enough to make a printer. The ones I have are 1 inch extrusions which I found very few printers for. But fear not, I am designing it to be parametric.
Kill the 1" “feet” on the corners of the frame and use 1020 t-slot instead. Makes for a lot less to bolt on. Also there’s no reason for that cross-piece in the bottom-center of the frame either.
As far as the feet go…printed feet imho. And @Shane_Graber , she’s using this because it’s the extrusion she has. There’s really no leeway for 1020 in the design.
FWIW if you want to make it compatible with the Prusa i3, I’d highly recommend making modifications to the Prusa i3 Single_Plate plastic parts instead of redesigning them. All of the dimensions are already there. Really, you could easily reuse the z-motor-lower and z-upper pieces along with the complete X-axis parts and the y-belt-holder and the y-carriage. The y-carriage can easily be laser cut from wood. Your t-slot extrusion does away with the y-corner parts. The only two remaining pieces you’d need are the y-motor and y-idler parts. Then there’s however you decide to attach the t-slots to each other…
put it on a conveyor belt somehow…now that would be cool.
The fun is to design it, not to hack around in others code. I would however consider trying to design it so that metal does not touch metal. That is what I currently work on in my extrusion printer. Thinking it could eliminate some noise. I would also consider rounding of corners on plastic parts for smoother printing / taking advantage of acceleration.
FWIW having designed my own Prusa i3 variant (a completely laser cuttable i3 - source coming eventually: http://www.flickr.com/photos/sbgraber/8440575244/in/set-72157632677580692/), I found it much quicker (and easier) to work off his parts than systematically iterate through my own design to eventually make them work. Also, one of the criteria for this project is to make the t-slot i3 compatible, which means lining up the z-axis with the x-axis motor, idler, and carriage along with making the y-carriage usable with a Prusa i3 y-carriage. FYI you can buy just the y-carriage from http://shop.seemecnc.com/Prusa-i3-Frames_c17.htm. Just email them and ask them for only the y-carriage and they can laser cut you one.
Thanks for the tip @Tom_Oyvind_Hogstad inevitably there will be metel on metal on this design, I might use some off the shelf parts to really make the connection solid.
The feet could easily be printed, my own solution will be to cutoff 4 pieces and rotate them sideways, they’ll be exactly the height I need.
I plan on re-using the smooth rods from my prusa i2, so I am taking that into consideration.