Z-Axis Noob Help

Spoiler alert: I don't know what I'm doing.

So I just assembled my P3Steel and have gotten to the motor calibration stage. I'm running Ramps 1.4 with DRV8825 drivers, Marlin and Pronterface.

Anyway, so I've adjusted the trimpots on all of the drivers to about .6V, which seems to be a good place for the x and y axis. My z-axis motors are run in parallel, so I initially set the voltage to 1.2v. All I got was a sort of high pitched hum and no movement. Here's what I've diagnosed so far:

- Moved z-axis motors to a x-axis driver and they work fine. So not the motors.
- Turned down the voltage to .6v and unplugged one of the parallel motors. Same result.
- Swapped out the DRV8825 for one of the working ones from another axis with same result.
- Detached threaded rods to see if the load was too great, but got nothing.

So it's either the firmware/software or I'm having issues with my ramps board. I read something on another forum about Pronterface needing to "calibrate" the z-axis home before it will move the z-axis, but I couldn't find any other documentation that backed up this statement. In addition, Pronterface is clearly sending a signal to the driver, since it's making noise. If that really was the issue, I'm sure Pronterface would just send nothing, or give an error, but perhaps I'm mistaken.

Any help would be greatly appreciated! Extra kudos all around.

I would start with checking the default steps per mm and motor speed settings for the z axis in configuration.h of Marlin, or whichever firmware you are running.

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Just an Artist, Musician, Designer, Programmer, Maker

Using: My H-Bot w/Mega RAMPS 1.4
M Prime 1 Custom Find me @ [www.thingiverse.com]
My SCARA Project Find me @ [www.thingiverse.com]
Zenbot 2424 CNC Router w/Mach 3

I've heard of that mentioned. Do you know what this should be set to? Is it a personal preference or is it listed somewhere in my motors documentation?

It is set in Marlin firmware under the configuration.h tab. The settings are somewhat unique to each machine, you will need the specs for your leadscrew (TPI, diameter) to set the z correctly. You can just search the net for your machine and find them pretty easy. My z steps for the 8mm acme I have are 2560, I have an ISO 3/8" acme that runs at 2020, those are pretty standard. The speed I use is 5mm/sec and 100mm/sec max.

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Just an Artist, Musician, Designer, Programmer, Maker

Using: My H-Bot w/Mega RAMPS 1.4
M Prime 1 Custom Find me @ [www.thingiverse.com]
My SCARA Project Find me @ [www.thingiverse.com]
Zenbot 2424 CNC Router w/Mach 3