No idea what I'm doing

Do you have ferrite cores or shielding in place?

 

Ok, lets start simple then. Get some ferrite cores, and put them on your data cable(s). They are a cheap thing to start out with. Something like this: https://www.amazon.com/Jabinco-20pcs-Ferrite-Suppressor-Diameter/dp/B07ZQZQ5BQ/

 

Hi, I had exactly the same problem, it turned out that two machines I was running side by side while running my work bee were causing electromagnetic interference and the port was closing in exactly the same way yours did. Same as you, it would stop at random places - really annoyed me to as I couldn't figure out what was going on! So try not running anything but the machine itself. This solved my issues...

 

Yes, on the USB cable. If that doesn't work, you can try using shielded power cables as well. Do you have a VFD powering a spindle? That can also cause more interference. If your USB cable is running alongside your power cables, see if you can route it so it doesn't run parallel as much as possible.

These things may not resolve it entirely, but if you notice an improvement, that will let you know you are going in the right direction.

 

VFD = Variable Frequency Drive. If you didn't see that in your setup instructions, you don't have it. We can rule that out as a source of interference.

 

I suspect the problem may be code as well, especially if grbl's just complaining, not outright erroring.

What's the proper formatting of a feed line of G-code? There's a value missing there, for sure. You'll see it immediately once you look it up.

Not trying to be snide here or make you feel bad, but I think the problem is at least partially:

If you don't know how it works and you didn't spend a few weeks learning about CNC and how grbl works, why spend thousands of dollars? CNC is not a consumer-friendly, plug'n'play discipline. I know it's often advertised that way by unscrupulous vendors, but it really takes a lot of expertise to get good at it, and a fair amount of knowledge just to be confident around the basics. Think of it like cars in the 1910s, or firearms in the 1860s; commercial support available, but not for the feint of heart.

I think you need to stop trying to make the machine do anything until you know what you're doing and more importantly why you're doing it, and start reading.

The grbl wiki is probably the best place to start. Google terms and phrases you're unfamiliar with as you go. Yes, it may take weeks, or even months, to get through to the point you start really understanding it. They neglect to mention that little bit on the Facebook ads, I know. You'll need some basic electronics 101 as well- how a capacitor works, signal and noise, what Arduino is, that kind of thing. Lots of answers are available on the CNCZone and LinuxCNC forums- many of those answers won't help directly with grbl with its limited functionality, but they'll explain what you're reading and why on the grbl wiki, as well as expanding your horizons in general. So don't worry too much about Google results being irrelevant- almost nothing I've ever learned about CNC has been irrelevant, it's just taken different amounts of time to roll pieces of knowledge into my practice.

This is an activity with a very heavy emphasis on self-directed learning and a ton of patience. There are many local classifieds with barely-used machines that work perfectly well but their owners thought they were in for a very different experience- more like drones, or 3D printers, where most of the heavy lifting is already done. Unfortunately subtractive machining can never really work that way due to the sheer variability- you don't even get that experience if you spend high-six, even seven figures on a machine, never mind a couple thousand bucks.

 

Gotcha. Then the problem probably isn't code, and electromagnetic noise can be a nightmare to chase down. First thing I'd do would be to eliminate all possible sources of noise- keep the spindle off, of course, but also go into grbl settings and turn off limits. If the filters in the switches aren't working, that might be the problem. Same with lights, vacuum, all of it. Get rid of everything that isn't stepper motors, and then hand-write lines of code into the terminal- or even load short programs- to run. If that works, try running a program with the spindle on but without activating anything else.

Before you do this you have to understand how machine homing works in grbl both with and without limit switches, and how to G54 zero from there, or else you might crash the machine. If that works, then you can start figuring out the problems with whatever you have wired up that isn't working. It's a process, but you have to understand how things work in order to follow the process. Otherwise you're just doing stuff, and not understanding the results.

If you didn't understand all of that... Great! Now you have things to Google and increase your understanding.

If none of it wants to work, you could try a different CAM, different g-code sender, though you shouldn't need to, a different computer, etc. If reflashing grbl doesn't fix it, then the problem might be the BlackBox itself. It's not as bulletproof over the long term as a traditional Arduino Uno in my experience, though it is much faster and easier to get started with, and much better protected against accidental mixed-up wiring.

Yeah... I've seen that too, especially on socials.