Z Axis Will Not Move

I am finishing my very first printer, a prusa i2. Everything works well, except for the z axis, which does not turn. I have adjusted the drivers and the steps/mm (I believe that's what it is called, its a speed setting in pronterface) and neither has worked. I know for a fact that the motors both work, and when I try to move the axis, they buzz - violently or softly, depends on the drivers' settings and speed setting. The motors are Nema 17 steppers, and yes, I have checked all code for bugs. At least the bugs I would, as a Noob, know of.

So my question is, how in the world do I get my z axis to move?? Are my threaded rods not straight enough perhaps? They are not warped or bowing any direction, although because of the nuts in the x carraige and idler, they are not perfectly perpendicular to the ground (I did not anticipate this being a problem). How do I fix this?? I can post pictures if needed, just not at this moment (apologies). \\

Thanks in advance, this is all I need to get my printer to work.

I had this problem with my i2 also.

We'd need to know what electronics board you're using and what firmware too, also the configuration.h from your firmware.

Make sure your vertical smooth rods are as close to perfectly parallel as you can get. I took a tape measure and measured the distance at the bottom, and then at the top.
If those aren't parallel it will bind. You would want to bring the top vertex frames closer or further together, or the lower part closer or further until those rods are parallel.

How thick are the Z threaded rods? The standard was 8mm. Those won't flex very much, a little bend in them is ok. Also what couplers are being used? Are they printed plastic, aluminum flexible (spiral cut) or aluminum static (no cut)? Anything but the static should allow for a slight bend, but a more extreme will cause them to bind.

I would also ensure both your Z motors are wired up correctly. Sometimes they're wired up wrong and they kind of cancel each other out.
I'd uncouple the motors from the threaded rod, and put a piece of tape on the shaft so you can see the direction it moves. Then plug only 1 of the Z motors into the spot where X or Y plugs in.
Then in pronterface, move whichever axis you chose for the test, the motor should move. If not, it's probably not wired correctly. Sometimes you can't trust the color of the wires.
You might have to use a multimeter on the motor connector to check continuity. There should be two wires that show continuity, those should be next to each other in the connector. The remaining two wires should also show continuity, and be next to each other in the connector.

Do the same for the other motor. Once you've confirmed they're both turning and the correct way. If one turns one way and the other turns the opposite, reverse the connector on one of them.

Also, in your firmware, you should have something like these.

#define DEFAULT_MAX_FEEDRATE {300, 300, 5, 25} // (X,Y,Z,E mm/sec)

I find the value of 5 to be way too fast for my machine, It's essentially 300mm per minute. Too fast.
Change it to .5
Which is 30mm per minute. Much more reasonable for the machine.

Edited 2 time(s). Last edit at 01/15/2016 04:01PM by FA-MAS.

I use RAMPS 1.4 and wired it according to this website: [www.nextdayreprap.co.uk] (which seems to work)

I am using MARLIN firmware and have configured it exactly (EXACTLY!) according to this website: [solidutopia.com] (I suppose I can post my config file if it helps.)

My smooth rods are parallel, I was able to be very precise with these, however my threaded rods are a tad off (they lean inward) and although this may be the problem I have no clue how to fix it... :\ The threaded rods are 8mm standard, and they are not bent, just angled because off my x carriage and idler. The couplers are aluminum, but I am guessing static (ugh) because there is only one seam in the middle of either.

I have tested the wiring on both motors, they both work and are wired correctly, but I have not tested for direction, which I will do asap. However, I unplugged one and tried to move the axis, only to achieve the same noisy failure.

Also, I will change the speed in my firmware, thanks for the very clear tip. I have not tried it that low yet

Thank you so much for the response, I am sure we can solve this problem!

Oh yeah, make sure the jumpers are in place under the stepper drivers on the ramps board. I'd say post your config and a picture of your printer frame.