Symptoms of bad stepper motors?

[dajay23D]

Hello,

Now that I finally got my calibration the way I want it, not 100%, but 95%, something else comes up. I was experimenting maxing out my print area one or multiple stepper motors started to grind or had a grinding sound while trying to reach X Z direction. In KISS, I was safely within the print area, although not much. When trying to reach the edge of the bed, it seemed like it didn't have enough power or started grinding. After the noise, the nozzle would just lift and print in midair. I recalibrated after that and it wasn't the same. Mid print, the arms would just go out of wack. It seemed like it just lost it's power or skipping teeth, not sure. It would plunge into the print, shoving it off the bed and then it would just print mid air. I continued to recalibrate and now, it won't even print 1st layer. Z side is too close to the bed while the X, Y side is higher. This is w/ a good level calibration where the bed center and x, y, z, all match same distance. Just after it runs, it goes berzerk. I checked all my belts multiple times, checked to see if the pulleys are loose or the grub screw got loose. All still good. I don't hear any weird noises coming out of the motors, either. If anything, my extruder motor sounds worse when running w/ the grind/squeaking sound.
Are these symptoms of a bad stepper motor? Just thought I'd ask before I take apart my printer.
Also, I've been noticing that when it retracts, it sounds like the hot end nozzle is slamming in to the print, but it's not. Sounds like it's bouncing off a hard surface before it gets to where it needs to be. Either way, this hasn't affected the quality of my prints.

Thanks,
J

[dajay23D]

Still haven't figured out what's going on. I took the belt off and checked the carriages. Everything checks out. The gears, grub screws attached to the stepper motor are NOT loose in any way. I can turn the motor cw and ccw no problem. I also bought one of those Wixey digital angle gauges/leveler and it turns out I installed my towers within .1 degree, just using my old steel square. All 3 towers are either 90 or 89.9 degree. Build surface/boro glass is level as well. I did notice a small gap on one side where I can slide my .003 feeler gauge between the glass and the heat bed, so I just clamped those areas down w/ more clips.
I'll put everything back and see what happens..?

One thing I know is that the Z height constantly changes in the EEPROM. I have to adjust Z height in beginning of everyday if I shut off the printer. Not sure if this is normal. If I leave the printer on 24/7, it might be ok?

[Xenocrates]

Have you considered moving all your steppers to plugs one third rotation around? As in make it so Y is now X, X is now Z, Z is now Y? or something like that. If the problem follows the changed plugs, then it's a driver/rambo issue, and you can send the RAMBO to Ultimachine for repair. If it stays in the same place, then it's mechanical. It may also be that you need to re-adjust your end stops and their offset, as well as the horizontal radius. I'd also check your U-joints/ball joints on the arms themselves, as they may now be binding in some way.

Do you have the injection molded carriages or not? It could just be an issue with maladjusted cheapskates.

If all else fails, and you're fairly certain it's not a mechanical issue, then blow away all the calibration and firmware on your rambo, reload it from scratch, and begin calibration from the default values.

[dajay23D]

Thanks for the reply Xeno! I'm using trick laser's cf arms and the joints are good and are not binding. I've had the printer for about 6 months, it came w/ the melanin carriages. In my previous post, i removed the belts and checked the carriages and all good as well. Cheapskates are still good. Good idea on clearing the EEPROM and starting fresh, I'll try that to see if it works. I have not swapped steppers around, that will be my last resort since it requires more dis-assembly. That's also the reason why I posted to see if anyone had experience w/ symptoms of a bad stepper or it's dying. I'm not sure how sensitive these steppers are, but I've grinded them a few times, so not sure if that's all it took to ruin them or at least partially damage them to the point where they run, but not accurately. I can turn them by hand they're operating just fine, but, it's the symptoms I described in my earlier post that's worrisome.

[dajay23D]

so the problem persists after I put everything together, erased EEPROM and recalibrated..etc. Again, the Z side is lower than my x, y side. You can say the upper half will print lower than my lower half or towards the front, LCD of the machine. I clocked the print, and it seemed to print better, but still has the issue. On top of that, it looks like the lines are merging. See pix below. I flipped the disc over, so the bottom is the top or towards the Z tower. It seems to get better towards the bottom, but the merge is still there.

[img]https://farm1.staticflickr.com/712/2235 ... e5b5_z.jpg[/img]

[teoman]

Try powering the printer off, hold the nozzle and move the end effector around to see if there is anything awkward or some resistance.

Then home towers an try to move the nozzle by hand to see if anything is loose.

Check that the limit swithches have not come loose.

What was suggested was not changing the motors but just the plugs on the rambo. ( you also need tho change the connection to the limit switch, they go together with the motor)

[dajay23D]

ok so nothings loose. There's only so much i can check mechanically and i did all that, moved the effector around and as mentioned, I checked the carriages, bearings..etc and they all move fine. I did do what you guys suggested; changing stepper and end stop plugs. I wish one of you guys would've tipped me to change my firmware too...doh!! rammed right into my tower when i tried to home. lol. I should've known that! I knew i was still missing one more step!

So anyways;

the steppers are now;

x -> Z
y -> X
z -> Y

I'm not sure if my logic is right, but from the above picture, i mentioned it was merging. So from the picture, it looks like it's the X axis(left to right). Switching the axis allowed me to see a bit better since the lines are now moving up and down in front of me. I noticed when it's printing the beads/lines, it would cross back in towards the middle of the disc, making a small S before it finishes at the end and coming back the same track, therefore, printing on top or thru the existing bead. The nozzle is able to shift from one line to the next, the Y. I'm totally confused, so do I have 2 bad steppers? The issue appears to be clocked as well. But, if I was already having this issue on the X, that means X is bad. After I clocked it, Y became X, so does that mean Y is bad as well? If Y is bad, how come the issue wasn't noticeable on the Y before I clocked it? I'm only printing 1 layer disc, so maybe the issue wasn't apparent until I moved or force the steppers to do certain things? I guess I could try clocking it one more time to see if it happens when the Z becomes X....

[Xenocrates]

How did you change your firmware? In theory, all the motors are identical ( unless you got mixed ones in the kit, where one or two needed inversion, but not all of them) It may also be that a bad driver (Control board issue), managed to damage a stepper (Mechanical issue), and thus when you spun it about it showed issues on two towers, although I'm rather at a loss as to how a driver could actually damage a stepper electrically. I would at this juncture consider sending the Rambo to Ultimachine, and if the problem doesn't disappear, buying a set of steppers (I'd buy 4 at once, to have a set and a spare as similar as possible, personally), or even just one or two. If the problem doesn't disappear after that, well, then you get to imitate a field circus tech, and just replace components until they work.

Also, if Ultimachine tells you what the problem is, if it's just one driver, you should be fine, especially if it matches up to your origin point for failure. If it's two drivers, it may be that a stepper is badly enough out of spec to be damaging the drivers. Be very careful if that is the case, or get the new steppers before testing the repaired board.

[dajay23D]

I just erased the EEPROM, reuploaded and recalibrated. I used the method in the manual. I'm just going to buy new steppers and see what happens. I think that's an easier option for me at this point. I don't want to take out all the wire and the board..etc. I'm leaning towards a bad stepper, although I took all 3 apart and didn't see anything that's eye popping, but then again, I haven't really figured out what exactly I'm looking for, either. I think something grinding and shifted slightly in one of the motors, but i'm just guessing. In my first post, I mentioned all this happened after I tried to max out my print area where it just grinded one of the motors and the Y motor seemed to loose power and kinda just dropped or went haywire. I'm not saying you're wrong, but a bad driver out of nowhere is kinda awkward, but not like it can't happen. It was running fine until I pushed it, could that cause a bad driver? I'll send my board out if it's not the motors.


Thanks,

j

[geneb]

You disassembled THE STEPPER MOTORS?!

FYI, if you un-plugged or plugged in a stepper while there was power to the RAMBo, you quite likely did damage to the driver for that channel.

g.

[dajay23D]

hehe...yes i did! I was going to replace them anyways, so since I like taking things apart, why not? I did all of this stuff at the END. I didn't start out by just ripping things apart...lol. I've tried troubling shooting it for more than a week, even though I posted about a week ago.
Thanks for the tip on unplugging the stepper motors from the board w/ power. Again, I didn't unplug it until yesterday. But when I did, luckily, nothing really happened, besides the problem I'm trying to solve. But, in the future, I'll unplug from outlet before I unplug it again.
So if it's a bad driver, are these the symptoms? What are the symptoms? Everything works fine, besides that shift/overlapping.

[Eaglezsoar]

hehe...yes i did! I was going to replace them anyways, so since I like taking things apart, why not? I did all of this stuff at the END. I didn't start out by just ripping things apart...lol. I've tried troubling shooting it for more than a week, even though I posted about a week ago.
Thanks for the tip on unplugging the stepper motors from the board w/ power. Again, I didn't unplug it until yesterday. But when I did, luckily, nothing really happened, besides the problem I'm trying to solve. But, in the future, I'll unplug from outlet before I unplug it again.
So if it's a bad driver, are these the symptoms? What are the symptoms? Everything works fine, besides that shift/overlapping.

The symptoms of a bad motor driver is that the stepper that is connected to that driver will quit operating.

[dajay23D]

hehe...yes i did! I was going to replace them anyways, so since I like taking things apart, why not? I did all of this stuff at the END. I didn't start out by just ripping things apart...lol. I've tried troubling shooting it for more than a week, even though I posted about a week ago.
Thanks for the tip on unplugging the stepper motors from the board w/ power. Again, I didn't unplug it until yesterday. But when I did, luckily, nothing really happened, besides the problem I'm trying to solve. But, in the future, I'll unplug from outlet before I unplug it again.
So if it's a bad driver, are these the symptoms? What are the symptoms? Everything works fine, besides that shift/overlapping.

The symptoms of a bad motor driver is that the stepper that is connected to that driver will quit operating.

In this case, it's running fine. So it all goes back to my first post and my subject, which no one really answered, yet; what are the symptoms of a bad stepper or one that's going bad? I'm not talking about one that has obvious symptoms like seizing or just all out nothing's working. Thanks for all the help so far, helps me rule certain things out.

[KAS]

I'd say that's a tricky one to answer. No real mechanical operation going on besides the bearing/bushings. Possibly a weak magnetic field causing missed steps. Even the cheap steppers are pretty well designed and seem to run without issue. Obviously that's not to say you wont find one without manufacture flaws.

It's often some external force like the belts are over tight or off alignment that can cause other issues.

I suppose the easy test would be to swap your Rambo XYZ connections to YZX ( make the end stop switches match) and see if the issues follow the rotation or stay the same.

[Xenocrates]

KAS, he's already done that once, and it turns out that now he has 2 tower's going wahooni shaped. So unless he missed the issue earlier, it is something electronics related, and may be mechanical as well. Could be the belt/cheapskate/u-joint on original tower is problematic, could be corrosion on the pins causing intermittent signalling. It's a bit hard to diagnose at this range and point in time, as none of us with any experience great experience with the printer have any access, and some amount of missed communication is happening.

Geneb, good to know the stepper drivers will simply fail to move/power up when they go sideways, rather than potentially screwing up in less obvious ways.

Symptoms might be things like missed steps, or failure to micro step in accurate increments. Those, considering how small the steps can be, would be hard to notice. Increased stiction in the assembly would also be a sign (the minimum move it's capable of will decrease, but once it gets rolling it works like normal), these are more of mechanical failures than electrical, and would result from things like bearing wear (which I doubt it the issue), although having the steppers run at the wrong temp for whatever lube they use might do it (unless you're printing someplace quite frigid, I doubt this as well, in which case, tell me your bed heating secrets).

Take a look at the contacts for the steppers on the rambo, and see if any are corroded. If they are, either attempt to clean it gently, send it to Ultimachine, or if you're some sort of electrical whiz, remove and replace the connector. I recommend sending it in, as attempting to clean pins often results in bent or damaged pins (At least on motherboards, for me.) If you know how to clean the pins, that's good. If you don't, don't try experimenting on the rambo. Also examine the connectors on the steppers. It may be that corrosion is causing an intermittent connection (if these were say, USB connectors, or something that got plugged often, i might mention deformation of the contacts, but here it should be irrelevant.) There's good reason in coating connectors in gold, and it isn't just for the bling factor.