I forgot to mention that the Vref is 0.0 when it’s not moving, and the software thinks it’s moving.
I should check the fault pin, and the sleep, enable, and reset pins… Out of time, I’ll try that tonight. Any other suggestions?
Jeff,
I read above you have removable connectors. I had a similar problem and found a connector loose. Once it’s loose, the stepper will stop working even if I swap with another stepper, it will knock that one out and there will be two dead steppers. I found a power down and restart fixed the steppers. I see you checked your cables, but maybe the problem is in the connector?
Hope this helps, good luck,
Dave
Could it be that the driver is overheating? Too large a vref and/or no fan can cause what you’re seeing.
Drew
It might be. I’m especially inclined to think it’s heat because I can’t quickly unplug/replug it to get it to work, I have to wait several minutes. The driver’s heat sink and the motor don’t feel warm at all, but it’s happening fast, so maybe the heat doesn’t have time to dissipate into the heat sink fast enough.
I also don’t think it should be overheating, because the current limit is pretty low (0.85A), but I’m just learning about that kind of stuff now.
I decided to re-terminate all the wiring. I do think it’s possible that something is occasionally shorting, and the driver is protecting itself, so all I do to debug it points to the driver, but the short is causing the fault.
I can’t get it to work at all now, so something is more broken than before. I can switch the cables, drivers, and motors around and the only thing that consistently doesn’t work is that port on the RAMPS board. I am going to reconfigure the software to use the extruder 1 port for the Z axis and see what that does.
I’ve also got well crimped dupont connectors on the Z axis, and most of the X,Y now. I’m going to tie the connectors together with wax string to make sure there’s no chance it will be my wiring if it takes out another port.
Also, I made a video the other day, and I finally uploaded it. Maybe this will be useful to someone:
Not sure when the color pink became an issue with guys. Pink used to be a very popular color with men and women. Poor pink…now so discriminated against. 
When the saw dust flies…you won’t even notice what color a CNC is anymore. Get it dirty!
You swapped X and Z? Isn’t the voltage setting for X almost twice that of Z because of the parallel setup of X and Y. That is probably why X wouldn’t move and Z did after the swap. Do you have an IR heat gauge that you can point at the Z when it stops working to make sure it didn’t overheat? Also a fan on the ramps is always a good idea if you don’t already have one to keep the stepper drivers cool. Another thing to swap is maybe one of the other stepper motors and see if maybe the one you have on Z is failing.
Very possible that the Z port is dead or almost dead from what all you have posted. Luckily a new ramps is pretty cheap. Being able to swap that out would be a good test. If not, then a spare is good to have anyway. Good luck. Electronics can be frustrating at times.
The X, Y are set at 0.7V, (1.4A) and the Z is at 0.43V (0.86A). I have gotten the Y axis to move around a bit with the 0.43V setting. It will skip steps though. So I think that’s still a decent test.
If your point is that my quick testing is maybe causing more problems that are muddling this issue, I think you are right. I’ve got a different arduino, different software, and a different configuration of the drivers. Any one of those things might be causing a problem right now. My wife is going to be watching the kid tonight, and I’m going to spend as much time as I can trying to get this thing to work again.
After tonight, I’ll admit defeat, and start shopping for another board. I don’t think I want to continue with the RAMPS/mega combo, though. I might try something like this instead: http://amzn.com/B01BAJK29I or one without the builtin 8825s. Then there’s always the RAMPS FD. Or maybe the CNC shield or the CNC shield for the raspberry pi.
OK, I think I have this thing kicked, but I’m short of parts now. I’m currently sitting in my garage listening for any motor skips. This is what I think happened:
- I had too tight a setup. The two big problems I had were:
- The anti-backlash nut was way too tight.
- Not enough/not grease. I’m not sure if it came with grease from the kit, or not, but after adding some, it’s a lot smoother.
- The driver went from working fine to overheating, without skipping any steps. I’m not sure why that is, maybe it’s normal, maybe there isn’t good conduction between the chip and the heatsink. No way to tell now, it’s dead.
Then, through my sarcasm expert /sarcasm debugging skills, I went ahead and toasted one arduino, and the questionable driver. I also think the second arduino I used had some other problem with it. I found it in my parts bin, and I think 1/3 of the pins don’t work, somehow.
I am playing a gcode file through it, but I have the Y driver in the Z spot, I have the Vref set at 4.7V, and I have the max Z speed set to 3mm/s and max Z accel set to 55 mm/s/s. So far, I haven’t heard any skips, and it’s 45 minutes in. So… I’m hopeful I can get to cutting as soon as I get a replacement driver. I went and bought one at Microcenter, but they are $13! and they are the A4988. I just can’t bring myself to open it when I can get them 3-5x cheaper. Plus, it doesn’t have a heatsink.
I also have all new terminations (duport crimps, with waxed string holding them together) which should last a long time. In the time I’ve been sitting and watching it move up and down I have mostly installed the cable chain, and I’m working on wire management (It’s hard when it’s currently connected).
I also have a case for the screen, which is a remix of some on TV. I have to fix the STLs before I post them.
I need to find a place to mount it, and the ramps board (which survived all the shorts, magic smoke, etc of this process).
I am reprinting the motor mounts without the solderless thing, and in PETG. This new material can be pretty fickle, but I think I have it dialed in.
I know it sucks but you do learn a lot from your mistakes. I have designed the new center assembly without the anti backlash because it has bee causing so many people problems and the tension we use it at I don’t think it does anything. Sorry I do kinda feel like that part of your issues was my fault, me trying to fix a problem that isn’t even a problem. Leave it to an engineer to over complicate things.
Hopefully you will be getting it dirty soon.
Is it your fault when I read, “Put slight tension on the spring, you should feel very little extra friction” as, “tighten that f’er as much as you can, backlash is the devil!”?
If the instructions were in a wiki, I would definitely be editing that though. Just a thought…
Hahahahahahahahaha!!
If there were signatures on this forum, this would be my new one!
“tighten that f’er as much as you can, backlash is the devil!”
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I made it through the pattern on the foam.
I printed a case with a fan adapter for the ramps board, so I might increase the current on the drivers. There is a lot of airflow. I’d also like to add a filter of some sort on the fan to keep the dust out of the ramps box. I also need to find a good way to mount it on the stand somewhere.
I’m out of time again, but I cut that with 4mm depth and 5mm safe distance in the z. It took 1h4min, and tomorrow I’ll change that to 1.5mm or so, with a 2mm safe height, and it should go a lot faster. I have to cut wood before I think of this as done, but seeing how clean the final output is gives me great confidence in this machine.
So far so good! I’m rebuilding the original cnc I built. Even though I have another one running I can’t wait to get it running again and I feel the same way, not done until I get some wood chips dirtying it up. This thing had so many prototype parts and sparse infill testers on it, the rebuilt one is going to be so much smoother…and hopefully all new designs (fingers crossed).
Done!
Video:
So I can see now why plywood isn’t the material of choice for CNCs. I should try the exact same thing with a downflute bit and see how well that works. This ply split a lot on me when cutting too, so I think this is really worst case. I have a ton of 3/4" ply leftover from another project, but it’s nicer. I hope I can get that stuff to cut better.
After looking past the chipout on the veneer, there were a couple spots where the lower layers broke on sharp corners. Generally though, the cutout was really good. I’m impressed by this thing.
Thanks Ryan for creating this beast, and thanks everyone here for your help. Of course it’s never done, and the fun is just starting.
Sweet!
The downflute works wonders. I think I put up a video using it on some thin ply. Left me a near perfect surface, but blew out the back a tad.
Keep getting it dirty.
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