Building a Prusa from wiki, noticed a few problems?

Hey all,
I just recently started building my own Prusa Mendel, (with wades extruder, buddaschnozzle, and Gen7 electronics)

Forgive me if this is commonly known already, but I've come across a couple of issues with the Prusa i2, and wanted to check to make sure I wasn't missing something blindingly obvious.

First off, the BOM for vitamins on the prusa page lists an M8 grubscrew. which I cannot find used anywhere.
[reprap.org]

Also, there are 4 small springs required for the wades extruder, as well as 4 very long M3 bolts (which simply don't exist, will have to use M4's)
and 2 larger springs for use as Z axis screw preloaders, which aren't listed on the bill of materials anywhere.

Secondly, there is something wonky with the X-end motor mount. Namely, it doesn't line up at all with the pulley or the carriage, and I needed to pack it out with washers to get it to work at all.
plus it seems like the motor mount for the iteration 1 was a much better design, having the stepper hanging off the side would add a fair whack of torsion to the whole x-axis wouldn't it?
Does anyone know why this was changed?

So, am I missing something really obvious, or are there actually a few mistakes.

The grub screws would be for the small pulleys I would guess.
The long M3 bolts are as rare as hen's teeth so I too am puzzled by their use.
The "Z" springs are optional - I haven't used them or the extra nut in the extrusion but some do.
Not sure what the problem is with your X end motor without seeing a pic. Have you fitted the pulley with the teeth closest to the motor?

The M8 grub screw is for the extruder's idler. The bearing is placed on the grub screw and then is snapped into the idler. Personally, I don't see why they do it this way, you can just use a small piece of scrap M8 rod instead of searching for a comparatively expensive and exotic screw.

As far as the extruder, if you're in the States you can find really long M3s on McMaster-Carr, but personally, I recommend using this extruder: [www.thingiverse.com]. In addition to using M4s, it has a couple nice additions like a lever for reloading and a guide on the idler to keep the filament centered.

The springs for the carriage are not totally necessary; they really reduce backlash in the Z direction, but as long as you don't implement any hopping or printing parts individually (basically, you only ever go up while printing, never down) they aren't a huge deal.

Finally, with respect to the X motor, it doesn't seem to torque the system too much; there are two smooth rod and two threaded rods keeping the x carriage oriented properly, and that's more than enough to keep the carriage stable. If there's anything annoying about the version 2 carriage it's the press-fit, which requires smooth rods of perfect length, and a high quality print for the ends.

yeah after looking at it again, I figured that the M8 grub was for the idler, a fully threaded m8 bolt would have made more sense to me though, ah well.

I guess fair enough re the optional thing about the springs.

yeah I agree about the press fit issue too.

and as far as the belt and ends not lining up, turns out that was my own doofus fault.
I built my unit using linear bearings, and the place I ordered my rails and bearings from provided me with LME8UU's, because of this, the xCarriage I had bought, didn't even come close to fitting properly (as I was foolish enough to not check all the specifications correctly).
This also threw everything else out of alignment (even after a little kludging)
I'm currently in the process of getting that fixed up, so all good.

edit: I realised I might sound a little critical of the whole thing, which was not my intention, it's really all quite clever, I just had a few queries is all

Edited 2 time(s). Last edit at 02/01/2013 05:34AM by cognismith.

No problem. Don't worry about venting a bit of frustration, that's a critical part of any DIY project. I think most members agree that the documentation is not quite perfect, and probably could use a good cleaning-up.