Hey Mo,
if you have issues when the two Y rails stepper motors are moving (or should move), I think you should first check two things:
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the manufacturer’s assembly instructions do not include a safe method to ensure the rectangularity of the machine. Many users have already noticed that after assembling, their machine was not “square”. Your machine could be a parallelogram instead of a rectangle. This can be checked with a method like this.
Even a slight deviation from the absolute right angle can affect the operation of the ball screws and cause them to block.
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If your stepper motors don’t move as they should, you should know that the Cable Connectors used on Onefinity are the weak spot on the Onefinity (not the controller), especially in combination with the lack of strain relief on this machine. As someone who has assembled and troubleshot many computers, I can’t have a good opinion of such tin-plated connector contacts. The Onefinity CNC manufacturer addresses possible connector problems in this FAQ document.
The flimsy and error-prone connectors were inherited from the Buildbotics controller, of which the Onefinity controller is a hardware and software fork. They may seem annoying, but one should always keep in mind that professional, industry-standard connectors would make the machine much more expensive, and since the Onefinity CNC machine addresses hobbyists, the low price of entry is an important argument.
You can make your own (maybe custom length) cables (howto crimping info is here), however you need to procure you a correct matching crimping pliers as they are specified here (scroll down a bit).
The Onefinity CNC manufacturer addresses various rails movement problems in this FAQ document: