Building a Prusa Mendel i2 instead of an i3

Hello all.
I have a Prusa i3 clone which I bought out of sheer curiosity and didnt really expect much. after a lot of fiddling I have managed to get prints which far surpass what I would have ever expected from it. I would now like to use it to print the parts so I can assemble another machine.
I have been looking at the options and the Mendel i2 caught my eye due to it not requiring a laser cut frame. Am i correct in thinking that i could print the parts and then purchase the steel rods and circuity etc and assemble from that? This would mean that the build cost would be much cheaper than if i had to outsource the frame.
What are the main differences between the i2 and the i3 from a print quality and durability perspective?
Am i correct in thinking that i could assemble a mendel for a lot less money that an i3 since i can print most of the parts?
Thanks for any possible reply's.
Dan.

Hello,

There is a good reason people aren't building the Darwins and
the Sells Mendels anymore because they are old designs and there are
better and newer models out there to be had. I think the I2 falls into this same
category. I built my I2 about 4 years ago and at that time it was what people were
building. This was before the proliferation of cheap Chinese I3's hitting the market.
The I2 was never a cheap or easy printer to build, In my opinion of course. I don't have
an I3 but I think a properly built one would be a better printer then a properly built I2, Again
only my opinion. It is improved design and why not go with it? If I were starting out today
I would pick it as the one to build. I would try to improve on the deficiencies of your I3 rather
then regressing to a earlier model. I'm not trying to dissuade you from building a I2 but am
just expressing my thoughts on the matter.

resectfully
Ray

I started with a Linear bearing Prusa 2. It's a good printer, then about a year later I made a MendalMax 1.5 with parts printed on the Prusa 2.

I started with an i3 myself.

The original prusa i3 uses many printed parts aswell, but your chinese i3 uses metal parts i suppose.

Like Shank man said above, the i2, is no longer relevant, the i3 fixed a bunch of the design issues, but the frame isn't ideal either.

I am currently finishing a Custom mendelmax 1.5 ( yes an older design then my i3) .

With the mendelmax frame you can pretty much build your printer like you want, you will always have atleast your 20 cm of print area no mather how you make your axis, on mine there is not 1 original printed piece, most of the time i reworked already reworked parts, others i made from scratch.
You could even make you're x axis verical and use linear guides per example..

Prusa i2 limits you of design, and with any printer you will build , you will want to change and improve things. if you want to do this with an i2, it would no longer look like an i2.

I am no expert, but in case you would go for a mendelmax like design, you can always pm me for advice.

Edited 3 time(s). Last edit at 09/12/2016 12:19PM by Govahnator.

I'm still running with a Prusa Mendel i2 from years ago, the frame rigidity is trash. The triangles are good for direction in the Y direction, but it's rectangular in the X direction and there's no cross bracing so when the carriage moves, it wiggles, even printing slow at 30mm it wiggles enough to cause layer alignment issues. I'll be the one to dissuade you from building one. I found it was easy to assemble. But not easy to get everything squared up.

If you still want to build one, check out my thread on getting it orthogonal here.

After rebuilds and making the machine print the best parts it can, the only thing original are the frame vertices.

I'm using the whole X assembly from the Samuel. I'd say if you were wanting to build something from scratch, in the vein of more reprappy, I'd build the Samuel.
Using these couplers modified for M5 threaded rod. And these to decouple the nut and allow me to use the M5 threaded rod without having to modify the X ends.
Using my own custom extruder mount and hot end cooling fan.
My Y axis is are custom versions of this and a this as well as height increased versions of the bearing holders which I can post if you'd like.

My next machine is going to have no threaded rod, no smooth rods, as few printed parts as possible.

A cheap plywood i3 frame is about 28 bucks on eBay, you will expend twice that getting decent rods for the i2.

I like others are moving away from smooth and threaded rods to linear rails and aluminum extrusion, getting tired of printing broken or worn out plastic parts (only my kids printers will stay cheap)

I have two i2 machines.
Works just fine. In the X-direction it indeed is a bit wobbly, but securing the Z-axis firmly to the wall it will produce prints with the same high quality as any other good reprap.
As a matter of fact I redesigned and made two i2 printers that can handle 250mm high prints.
This what I made so far with these two i2's : [www.thingiverse.com]

Chris

Thanks for all the reply's folks. Very informative indeed. I believe now that it would probably make sense for me to stick with the i3 due to having a good understanding of how it works now and also due to the steel rods costing a lot more than i would have thought. if anyone could provide information on how different frame materials compare id very much appreciate it.
Also one other thing ive been grappling with is whether to stick to the bowden design or mount the extruder directly. ive read lots of contrasting information on the subject. The main problem which i have with my prints now is blobbing and stringing. its a lot better than it was now that ive installed a fan and changed the retraction settings but i simply cant get rid of it completely. i thought that maybe direct drive extruding might help with this issue? Thanks,
Danny

Going direct drive should fix the blobbing and stringing.

I myself am thinking of going bowden though, since i have a heavy direct drive extruder and it limits my probing area..