Iteration 2 Building Help

Okay...I'm lost, confused and frustrated.

Working on the Prusa Mendel iteration 2 (as the subject line tells you) and things aren't lining up anymore. From the page http://reprap.org/wiki/Prusa_Mendel I see that I need the following rods:

Threaded (all M8):
6x370mm (for the frame triangles)
4x294mm (bottom front and back)
3x440mm (2 on top - hold Z-axis motors, 1 on bottom)
2x210mm (coupled to Z-axis motor shafts)

Smooth (all 8mm):
2x350mm (Z-axis)
2x405mm (Y-axis)
2x420mm (X-axis)

I also have the plastic parts shown on the same page, printed in ABS.

From this, the X-axis will use the two 420mm smooth rods and will sit parallel to two of the 440mm rods. But after having done this the hex nut columns don't align vertically with the Z-axis motor shafts - the idler and motor mount are separated too much.

So something is wrong...by my thinking, I can either:
1 - get new threaded rods, longer to replace the 440mm and 294mm rods
2 - get new smooth rods, smaller to replace the 420mm rods
3 - drill through the other end of the idler or motor mount and slide the rods through to adjust for fit

Has anyone else run into this problem? Are there any other suggestions? Drilling through one of the two plastic parts would be easiest, but would there be a reason to not do that?

Hi,

I built a V2 using a kit from MakerFarm.

Here is a link to Colin's intructions: [docs.google.com]

For the MakerFarm kit, the distance between the triangles should be 240mm and the 440mm rod sticks out at the top quite a ways on both sides. He lists the x-axis rod lengths as 384mm so you may want to adjust the distance between the triangles to 276mm. There should be enough excess of the 440mm rods to handle this increase just fine.

Hope this helps.

KDog

KDog, I'll give that a shot tomorrow and see what comes of it. If my bottom threaded rods are long enough to handle that much distance then this could work...

Hi All,
I am building a kit (not MakerFarm's) and I've arrived at exactly the same point. I was just about to a "me too" reply when I found that pushing REALLY hard on the X assembly I was able to squeeze out what appears to be the needed10/15 mm. Visually it looks like it will now fit so long as the Z motor mounts are out at the limit of the 440mm rods - I should know this weekend for sure.

Those push-fit X ends can be deceptive. I thought my rods were fully seated before.

Eric

I have managed to get the Z motors in line, but the Z smooth rods area out to far for the bottom threaded rod (the rod that holds the Z clamps). So I guess I'm going to find a M8 threaded rod (> 480mm) to replace the 440 I have - unless anyone has an easier idea.

Eric

What I have ended up doing (for the time being, at least) is drill through the idler rod holes and slide the rod completely through them to get the separation I want. Then I have tapped some 3/8" nuts (inner thread is large enough to slide onto 8mm rod) on one side to use M3 set screws to hold the idler in place, though I don't think it's going anywhere.

I also considered taking an M8x1.25 die and threading the end of the rods that came past the idler, then using some M8 nuts to hold the idler in place. But I found it more than a bit harder to cut outer threads.