Purchased the J1 before it launched, new to the forum. I used the printer a good amount when I got it then let it sit dormant for over a year. I have enjoyed refamiliarizing myself with the machine. Today when I was unloading filament from the left extruder I noticed what looks like rust particles accumulating in the extruder assembly. I checked the right extruder and it is there also I am wondering whether this is from the stepper motor or something else? Has anyone delt with this issue? Any ideas on how to go about troubleshooting this? Not afraid to get my hands dirty and disassemble whatâs needed. I have printed no filaments with metal particles embedded
Wow, I just checked my J1 and same thing. Wonder if maybe itâs from a bushing.
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Weird, it really looks like rust. I just checked my J1 and I see no such thing. The only thing left from the rusty place is the stepper motor of the extruder, there is no separate bushing.
Is the needle roller bearing inside the gear located on the door okay? I wonder if that one might be stuck on your printer. If I remember correctly, Snapmaker did not really lubricate that one, and if that gets stuck, the result is that the the axle which holds it in place rotates against the U-bent metal piece holding it as soon as the filament gear is turned - which it should not and which might create rust from fretting corrosion (and will destroy the axle and/or the metal part on the door sooner or later)
I had the same problem in left extruder of my J1. Cleaned several times and wondered a bit as this was not rust, just similar in color. At the end extruder got stuck and I recognized something is wrong with stepper motor - front bearing was broken. Luckily printer was on warranty still so Snapmaker was very helpful and sent me replacement - new stepmotor.
After I recovered the very extruder replacing step motor and was able to resume printing with both extruders, I opened up the broken one motor. In fact it was plastic separator of frontal bearing ground into dust. So I did replace bearing later myself (cost was negligible indeed, few EUR) and have now good stepper for spare.
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I donât know how you knew that but I am tentatively in agreement with your diagnosis of the needle roller bearing inside the gear located on the door. I have no photo to show it but slight signs of corrosion in the axle on the side of the gear that the retaining ring is. I have relubricated this bearing for both left and right with KROWN Rust Protection & Lubricant. I am curious as to why the rust particles only came out of one side of that bearing?
I removed and inspected left and right extruder stepper motors and I saw no evident problem with them.
I plan on running a couple prints on my machine and will reinspect.
Thank you for your assistance.
Quite simple: rust coming from seemingly nowhere is something where every engineer working with steel checks if there might be any fits being subjected to motion nearby 
If I understood you correctly, you did push out the small circlip right next to the gear in the assembly of the door and took out the axle and then the gear itself. That gear is loaded off-centre since the filament groove is on one side which means the force on the bearing is higher on one side as well, which may explain why corrosion forms just on one side - keep in mind that type of corrosion depends only on relative motion of steel parts being pressed together while lacking lubrication and has nothing to do with moisture. Fretting corrosion is a whole science in itself though.
I fear I do not know the lubricant you used, but as long as it is suitable for small roller bearings you should be fine.
Apiologies but my communication on technical subjects is lacking. No I did not disassemble the axle. The gear has slight side to side movement on the axle and just from visual inspection, the corrosion I saw was a very minute amount within the gap between the gear and the aluminum frame piece. I just sprayed the whole gear, bearing, axle and aluminum frame piece that holds it with Krown. My hope is that this will be sufficient short term however I understand I will need to revisit this in future and I may disassemble and properly lubricate this bearing then. I have confidence in my ability to disassemble the axle, less confidence in my ability to reassemble (will the needle rollers fall out of the housing cage?) I donât like disassembling key components without having spare part on hand.
Krown is an automotive rust proofing spray. It has good rust protection, penetrating and lubrication properties. Are there better lubricants to use; possibly. Is my solution a half a** one; probably.
That you knew the needle bearing was poorly lubricated from factory; where does one even acquire information like? Impressive.
Ah, okay. Donât fear, the rollers are in a separate cage, you wonât create a 3D puzzle by dismantling that. I would expect your roller bearing to be quite worn considering the amount of rust on your picture. In general, the rust penetration oils I know are known to not lubricate too well, some even tend to resinify easily which will then clog up the bearing completely.
In case you find serious damage: both drive gears and the roller bearing are Bondtech clones, you can easily replace them using the original Bondtech drivegear kit - should be the 1.75/5.0mm one if I remember correctly, I can dig through my data from two years ago if needed. (The same applies to the spiral spring in the lid btw, which is Bondtech compatible as well).
The only fincky thing is getting the retaining ring out and back in, I almost shot mine out of the window when reinserting it. If you fear loosing it: those things are standard DIN 6799 retaining rings, you can buy them anywhere. The only thing that can only be obtained from Snapmaker is the axle and the metal bracket.
I learned about all that when we searched for the hotend clogging issue back in 2023. The first attempt we tried was âis it the extruder gears?â (answer: no)
Just search the old posts here in the forum
Hello,
I just found the video explaining problem with my ârust from nowhereâ is SJ1. So called rust (in my case) was brown plastic powder from frontal bearing of stepper motor. When dust was gone (bearing was completely broken), rotor of stepper started to grind by stator as bearing was not centering it any more and I had occasional underextrusion. I thought beast of heat creep is back but it was already new hotend from Snapmaker so this luckily was not a case - it was motor becoming stuck for a moment.
Your stepper had a plastic bearing?? Unless I overlooked something, the ones in my J1 are metal, thankfully. But if I have to take the hotend apart for some reason, I will definitely doublecheck. Thanks for the information!
Bearing was quite a common one - steel rims and balls spaced into phenolic resin or call it bakelite type of caging. This plastic caging was ground into dust and when it was gone, balls gained possibility to travel unequally spaced.
Replacement bearings I have used were SKF but I donât remember what material the ball cage was made of.
Ah, now I understand, thanks a lot for clarifying! For some reason I hand understood your stepper had a plastic bearing - not a plastic ball cage inside a metal bearing.
Okay, that tells me the manufacturer of the original bearings has some serious quality issues! At least they are simple to replace. Do you have the bearing type no. at hand? Depending on how much you rely on the printer, it might not hurt to buy one or two as a replacement before such things happen - the repair itself is done in 20 minutes.
Unfortunately I did not made a note on bearing type. I had a lot to print at that time and was in hurry to get things running again as fast as possible.
I just remember it was stock item by local SKF representative and was not expensive at all.
The very replacement was easy like you say.
In fact currently I am running SJ1 with original motor I got as warranty replacement and there are no " rust" issues yet. But to tell the truth - load on printer is much less now, I use it only for ASA, ABS and carbon filled materials.