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Prusa iteration-2 x-axis distance doesn't make sense

Posted by derekmjenkins 
Prusa iteration-2 x-axis distance doesn't make sense
June 08, 2013 07:17PM
I am building a Prusa iteration 2 and am having lots of issues due to the lack of correct documentation. Anyway I won't go on a rant, but man!

I have the current x--axis motor, idler, and carriage from GitHub that uses press fit for the 420mm smooth rods (i.e. no nut traps). When I press the smooth rods in as far as they can go in both the motor and idler pieces I end up with a center-center distance for the z-axis threaded rods of about 363mm.

However, after I built the frame the center-center distance for the z-axis motors is about 327mm. My z-motor mounts are right against the nuts that are going through the top vertex. So I need to either shorten the distance between the x-axis motor and idler or I need to increase the distance between the z-motor mounts.

Which should I do?
Was I supposed to drill out the two smooth-rod holes in the x-axis idler all the way through so that the distance between the motor and idler can be adjusted?
Are my z-motor mounts in the right spot?

Unfortunately the documentation is either for iteration 1 and doesn't cover these pieces, or the videos from engineglue where he decided not to use GitHub parts which use a different x-axis motor and idler pieces.



Edited 1 time(s). Last edit at 06/08/2013 07:18PM by derekmjenkins.
Re: Prusa iteration-2 x-axis distance doesn't make sense
June 09, 2013 12:37AM
I attached a picture of what I did to solve that problem. It works, but it isn't pretty. If you look at the bottom where the bar clamp attaches to the bottom threaded rod, you'll see that the outside nut is just barely on the rod. It's only threaded about half-way though and it's like that on both sides. It's worked well for the last several months like that so I guess it's okay. I was originally going to print out replacement X ends that had deeper shafts to swallow up more of the rod length but decided against it since the fan on my new X carriage would prevent me from getting full X travel. I've just begun the process of building an I3 and I'm using this machine to print the parts after which I will probably dismantle this one to reuse the other (non-printed) parts. One thing I've found when building this machine is that Google isn't always your friend. You'll find contradictory information all over the place.
open | download - Reprap-ZMM-Spacer.jpg (561.2 KB)
Re: Prusa iteration-2 x-axis distance doesn't make sense
June 09, 2013 01:28PM
If I understand your issue correctly, you can easily widen the entire machine by moving the two triangle portions of the frame further apart. You could also cut your smooth rods shorter, but I would stay away from that because it will cut down on your x movement.
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