need some help from someone with knowledge of electronics.
I have a prusa i3 (sunhokey i think?) with a “MKS GEN 2Z v1.1” board.
Im looking to replace the extruder motor “yh42bygh47-401a” 1.5A 0.55Nm
as it seems to be underperforming, the motor seems to “let go” intermittently, I think it can’t handle the pressure required to push the filament through the hot end.
It used to work fine, but perhaps a year or two of wear and tear, has caused it to get weak.
anyways, im looking at getting a stronger motor, perhaps a Nema23, which is 2.8A, and has 1.26Nm of torque.
What i would like to know is, can the board i have, support a larger motor such as this, in regards the Amps. Or am i stuck with buying the original motor it came with, which is 1.5A
hopefully i’ve made sense, im learning about these parts on the fly.
the printer is under extruding, no matter what settings i have tweaked with in simplify 3d, or cura, the problem persists. i’ve fiddled with print speed, extrusion multipliers, and nozzle temperature for example.
when it is printing, it tends to “let go” or give up, for a split second, which relaxes the pressure in the hotend. sometimes this, happens rapidly, causing a jitter sound. (usually if im printing too fast) but even at slow speeds… really slow speeds, it will still happen.
also happens when the nozzle is partially blocked, such as printing on the first layer.
i have found that if i tug on the filament being fed into the motor, i cause cause the motor to skip more. and when i help to push the filiment into the motor, i can cause the skipping to be less frequent.
this is why i came to the conclusion that the motor may not be strong enough anymore.
Sometimes when the motor starts to go bad it will emit a grinding noise. Are you hearing any such indications?
As Lukas brought up there are other things to check first if you have not already. The hobbed drive gear for the filament could be partially gummed up with chip or worn out.
You could also have a bad driver. The motor will run fine without load and under load intermittently skip or pause. Swap drivers for it if you can to test it.
As to your question of higher stepper amps through your board someone else will have to chime in. You seem to be well aware that sometimes increasing the amps (almost double) that are pulled can have a cascade effect on a lot of components that might not be worth the trouble or you wouldn’t have asked. 
i am not hearing a grinding noise, besides the noise from the skipping, it sounds alright.
i have checked on the drive gear, it is clean, and is firmly mounted on the shaft.
i don’t know anything about the drivers, is that the smaller board that sits on top of the main board? one of these for each motor?
i am unsure if these are replaceable on this board, and what the replacement part would be.
if they can be taken off, perhaps, i’ll just swap places with one of the others, and see what the results are.
i had no idea about what you were saying with the amps, and cascading.
i simply thought, that the output of those pins, might only put out 1.5 amps, and putting on a larger motor might not work. or perhaps they are able to put out more than 1.5amps, and id have no trouble… i don’t know
thats a good point, but im curious, I wonder what could have happened to the motor or board to cause it to not receive enough current, as i’ve never adjusted the drivers before. (assuming increasing the current fixes the problem)
as for the hot end, i’ve brought it up as high as 230 degrees, for PLA, and tried some slow prints. i’ve also tried replacing the PTFE tube, as well as the 0.4 nozzle as well.
Given your problem description I would suspect a hotend issue that has developed over time. If you have a PTFE tube in it and are printing at higher temps around 245 it could be worn out.
I would suggest changing out your nozzle as well.
If you are grinding the filament that is a good indicator that the motor is plenty strong and the obstruction is further down the chain.
If your driver chips are on the small boards that sit on top of the main board you should be able to swap places with two of them and test if that is the cause. If you have manual pots on them they can go bad over time. Very carefully adjusting them is what controls the current levels to the motors.
We seem to keep crossing posts.
i’ve also heard some horror stories about people increasing the current to the motors, and having the board, or the motor fry…
so im a little weary of trying that, considering i’ve never adjusted before, and it worked in the past just fine.
im not sure if there is some other way that the motor might not be getting the power it needs.
Short of swapping the drivers directly do you have other motors on the machine that you can swap places?
Adjusting the power to the steppers through the pots can be asking for trouble and is the last thing I recommend doing. But those pots and the drives can go bad so that is still a possibility.
I can see why you are thinking the motor is a problem. You have pretty much tried everything else but I still think there is a chance the motor is not the problem.
Something else to check is the spring that puts the tension grip on the filament against the drive gear. Maybe that is starting to wear out…
swap the motors in place for the extruder? yeah i could give that a try tomorrow. i guess that would help to diagnose whether its the motor, or the board that is cause the problems, good idea.
in response to your previous comment
i havn’t taken the hot end above 230 degrees. i’ve changed out the nozzle recently, and the bowden tube some time ago, (maybe ill try changing it again)
there isn’t any filament grinding going on, as i watch the motor, i can see that when if “gives up” for that split second, it is being back driven, from the pressure on the filament.
im not familiar with “driver chips” on the board. i’ve included a pic of the board im using. i assume the driver chips are the 5 green boards, next to where the motors plug in (bottom of picture)
i have also tried adjusting the tension spring, against the drive gear. i find if its too tight, it cause the motor to skip, and too loose, the filament just slides back, there’s a very small sweat spot where it doesn’t seem to slip, and only occasionally the motor skips.
as far as adjusting the pots, i don’t know nearly enough about it atm, to not fry anything lol id have to look into that more.
missing/deleted image from Google+
Yes, those 5 green boards are your driver chips. The little round silver button looking disk thing to the left of the chip is the pot.
You can just pop those boards out of the sockets and swap the extruder driver with another to test if the driver is the issue.
ok, awesome. i will give that a test tomorrow. wasn’t sure if they popped out or not, and diddn’t wanna pry out something that might have been soldered in.
i read online that sometimes they’re removable, and sometimes permanently soldered in.
Stepper motors are practically indestructible. They can run for 10,000s of hours at maximum load without wearing out. It’s very, very rare for any 3D printer problem to be caused by a failing stepper motor. When they do fail, they probably won’t get weaker, they will usually lose one coil entirely due to the internal wiring failing or shorting.
Much more likely is either an issue with your hot end, or an issue with your spring arm extruder drive.
When you say you have replaced the PTFE tube, do you mean the long flexible tube from the extruder to the hot end (the bowden tube), or the small tube inside the hot end and heatsink (the liner)? I don’t know specifically what hot end you have, but most i3s have a small liner tube inside the hot end that must be replaced periodically as a maintenance item. The PTFE degrades over time and loses its lubricity and causes molten filament to stick.
Another thing to look at is the alignment and design of the extruder spring arm. For example, if it’s warped and pushing filament at a funny angle, that will cause a lot of drag. You can do some experiments by removing the bowden tube from the hot end and loading filament through just the tube. See how much force is required to get the extruder stepper to stall.
Then you can push filament into the preheated hot end by hand, without the bowden tube. See how much resistance you feel.
@Ryan_Carlyle Funny thing about mentioning the indestructibility of stepper motors… just yesterday I was diagnosing problems with a failed Ultimaker and it turned out the Y motor was seized up. I could hardly get it to rotate and it made an awful grinding noise when you tried to power it up. Kept telling me the limit switches were bad but turned out only because the head never got there to trip them…
@Jeff_Parish It does happen on occasion You’re maybe the fourth or fifth person I’ve heard of in the last two years with a legit failed stepper.
@Ryan_Carlyle Yep. I’ve seen two in 18 months now. That’s out of hundreds of motors but still… I agree that it is rare.
thanks for all the replies everyone, heres an update.
so i tried switching the driver chips to see if one had gone bad, no effect. the extruder motor still was weak, and skipped.
I then tried switching the motors themselves. i swapped the extruder motor with 1 of 2, of the Z-axis motors (the ones that raise and lower the carriage)
the result of swapping the motors, was that now extrusion seemed to be stronger. and when i tried to raise the carriage, 1 motor performed normally, but the motor that was formally used as the extruder, could not rotate under its own power. it would just jitter.
it seems the problem is the motor i think.
at this point i switched two more of the driver chips (different ones this time) just to rule them out as a problem.
switching them had no effect on the motor.
what do you guys think? seems to me like a broken motor, is there something else i should try before buying a new one?
Spin the shaft by hand with the motor wiring disconnected and see if the bearings have issues. Then check the motor plug and wiring really carefully… Jittering instead of spinning usually means only one coil is getting power. That could mean a broken/intermittent wire internally, or a bad plug, or a bad board terminal, or some other kind of damage.