Weak Z Axis Steppers

Starting a new topic regarding weak Z axis steppers. What I originally thought was a faulty MiniRAMBo has been ruled out. The issue: My Z steppers do not have enough torque to raise the carriage (even without the router on it).

Everything has been bought from this website (except the power supply) and is built per spec. Everything has been re-wired 4 different times. Wiring is not the issue. The power supply is providing 21 volts and should be able to supply up to 15 amps. Voltage has been confirmed with a multimeter and I will follow up in the morning with the amperage I’m getting when only the Z steppers are moving.

Note: I put a torque wrench on them earlier this afternoon and couldn’t get a reading. The tool was rated to read in inch-pounds but I think this might be a little much. I am looking online to find a tool that will give me an accurate torque reading.

Any ideas what my issue might be??? I’m really tired of not understanding why my machine won’t work :frowning: It is time to be cutting parts.

Even when they are not moving there is current flowing through the drivers. So you can turn it on, send a Z move and only the Z driver should be enabled. Or you can unplug the X and Y motors (with the machine off). There will be some current used by the minirambo but if you measure before and after energizing the Z, then you should get a ballpark number.

Have you ruled out mechanical reasons? Does the Z drop on it’s owm when you have it up and you turn off the motors? Does the Z fit all the way down? Do you have any trouble lifting one side of the gantry by twisting the leadscrew with your finger (with the motors off)?

Yeah, I’m sure you’re ready. It’s probably one mistake and it’s not usually anything dramatic. There are a lot of these LRs out there working. We will figure it out as long as you stay with us. You’re observations are going to be key.

Did you post information about this somewhere else? So you have a video of it trying to lift and some pictures of the gantry?


Mechanical reasons have been ruled out. Currently, I have the motors dismounted from the machine and sitting on my work bench with nothing but the couplers and lead screws connected to them. (This is more or less a continuation of my “faulty minirambo??” thread but I have created a new one at Ryan’s request).

This evening I toyed around with three different power supplies. As I noted, this was the only part of the system not bought from this website. First, the one I have been using and have not gotten anywhere. Second, is the power supply that came with the second recommended spindle for the MPCNC. Third, was the 12v 6a power supply that IS specified for this project and WAS bought from this website. All yield the same results…

I’m guessing here, but when I have only one motor hooked up to the Z axis port on the MiniRAMBo, it seams to have ample torque. As soon as I wire the other one up with it, it drops substantially. Ryan mentioned in the other thread the z steppers should be wired in series not parallel. This has to be my issue. Does anyone have a wiring diagram showing how to wire the steppers in series? I have all the same color wires on my Z steppers connected and then ran into the Z port. Basically just like this link only they spin the same way bc they face the same direction. Link: https://www.youtube.com/watch?v=cLhvnmZK_mQ&t=58s

Jeff I appreciate all the questions and I believe you are right - my observations will be key. That said, I work for a General Contractor on very large projects as my day job. My responsibilities include ensuring everything is built per plans and specifications. So, without trying to sound like an arrogant ass hole, please have confidence when I say it is built correctly. The issue lies somewhere within the electronics, wiring, or power supply.

This won’t do anyone any good but I have attached a picture of the machine prior to tearing it all apart… It used to look decent… I would just love to get it working.


Series is crucial for this.


Oh man. That’s great. Definitely the problem. And what a great looking machine.

That video shows how to wire them in parallel. Parallel halves the current to each motor. Since the drivers are current based, and they don’t know what’s connected to them, you’ll get half the torque wired in parallel. Definitely wire them in series.

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Got it!!! WOOOOO HOOOOOO!!! Thank you both so much. I’ll post pics and vids of my project once I work through feeds and speeds :slight_smile: Can’t wait!

still a little confused as to how the machine was able to work normally in the very beginning… but hey, all good now.