Getting my CNC to work

That enclosure looks great! What kind of connector do you use? I have a 36pin ribbon cable now for everything. I use two wires for each motor wire, because ribbons are so small. Not sure if that’s enough. I still need to find an enclosure and add buttons and end stops… I have a big emergency button that cuts the 24V for the motors already :wink:

I used the gx type or “aviation” connectors. I wouldn’t opt for a ribbon cable, for the small cross-section as you mentioned, but also because of cross-talk between the signals. I’ve had some issues with the motor wires and spindle ac wires causes trouble on my end stops. That’s why I used shielded cable for everything, 1.5mm2 I believe. Cheers!

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Took me some time, but now I have it almost working! Today I bought some wood as a base plate(?) and moved everything into the garage, where I can make more dust :wink: it’s quite crowded there with all our bikes and stuff for the kids, but better than in the flat :slight_smile:
first project will be the panel for the control box!

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As I have written somewhere else, the cnc has problems with loosing steps at the moment :frowning: So, after some milling i notice that the axis is missing a few mm from where it should be. It’s only at the X-Axis and only happens occasionally. I already cleaned the axis and oiled it, but it did not help. I also reduced the maximum feed rate and acceleration, but no help either.
I am thinking now that it might be that I set the driver to a too high current limit for that axis, because that is the axis with a bigger motor. On the motor is written “2.4A” (see picture in first post), so I set the driver (a DRV 8825) to match. But now I read that the 8825 does only work for up to 2.2A per coil and only if it’s properly cooled. Could that be the issue? are the 2.4A on the motor also per coil or total?
I think it makes sense, because the missing steps usually occur after a few minutes, so when the thing got hot… I will try limiting the current and see if it helps tomorrow (tonight I need to stay in the house, since both of my children are not feeling well), but maybe someone already knows if that might be an issue :slight_smile: What can I expect when I lower the current limit? will the motor be weaker? that won’t be a problem as long as it can still move the machine, right?

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Drop the DRV8825 down to 2.0amps and see if the problem goes away? I doubt you need to squeeze every last milliAmp through your steppers, but I do understand the incentive to do so!

Also do you have heat sinks on the DRV8825? It absolutely needs them at higher current, otherwise thermal protection kicks in and … you loose steps.

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It did work!!

My first diy milled pcb! Yes, the cutouts are a bit deep in some areas and the traces very thing because of that, so little space for soldering, but still I am happy!! :slight_smile:
It’s my version of a madbean 4:1 (afterlife) compressor which I want to use with my bass!

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I think there is an equation you use the amps in to find the safe value for the stepper driver, thats just me saying from 3D printing anyway however those arent usually pushing against the material like a cnc would so i dont know if it all applies the same way

I believe its called the VREF
Off the top of my head for the DRV8825 i think it was VREF = max amps / 2
Then i think you run from there, if they skip and arent too hot then your safe to increase the amps a little.

I think for a standard nema 17 (not sure what you use) they have a max temp of 80c so you shouldnt worry burning those out.

But it looks like youve got it sorted anyway lol

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Hey, yeah thanks! I did that, but for me it was the other way round. The motor can take 2.4A, so I set the driver to 1.2V according to the formula. BUT I did not check that the DRV8825 can only put out 1.5A (2.2 if properly cooled), so that was too much for it. It worked for some time, but then it would get too hot and shut it self down to protect itself for a few (micro)seconds. I had these tiny heatsinks on it, but they were not enough, I guess.

I just realized that the solution was here already!! xD

I also found the reason why the autoleveling was a bit off: turned out that the spindle was a bit loose in its mount :see_no_evil:

oh interesting, im more of a tmc guy as silence is a must due tho the printers running in my room, i have the setting of those down by heart haha. Ive never really tried any other types.

Glad to hear the cnc is working for you though. Sadly something i cant run in my room lol

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