I’ve been doing quite a bit of printing with a Z18 for the past couple of months - the machine is owned by my employer. Last month I invested in a Smart Extruder + and swapped it for the original Smart Extruder. Yesterday I began having issues with the extruder becoming detached repeatedly - I was running the filament from the drawer. I swapped the filament out for a new roll and ran it from the exterior instead and began a new, big print. I came in today to the same problem: the extruder was detached again and my print had failed. When I reattached the extruder and tried to pick up where I had left off, the carriage/extruder began acting REALLY strange.

First I noticed a grinding and clicking sound as the print re-started. When I took the lid off I saw that the carriage was grinding against the sides of the machine and hitting the back as well. It was spewing filament OFF of the back of the build plate. I cancelled the print and it “homed” just right of the wire brush. I calibrated the Z axis offset and tried again: same issue. I reset to factory defaults: same issue. The carriage even banged up against the sides of the machine. I then noticed that the front left pulley was making terrible noises as the belt fed. I also noticed that the pulley looked a little wobbly as it turned. I took the door and face off of the machine and tightened the pulley back down. I then started a new print…SAME PROBLEM. It started in the correct home position but still had issues.

I then decided to swap the Smart Extruder + out for the old extruder and ran a test print. It printed just fine. So I decided to retry my big print: it managed to print the raft and then stopped, saying that the extruder had DETACHED again. Can someone offer some advice? I’m at a total loss here and have this huge project deadline. Any help is much appreciated.

Hi Alison, The grinding and juddering is generally caused by faulty stepper motor wires, as the wires leading to the extruder carraige go through a lot of stress. Had the same problem on my makerbot w/ smart extruder. Joe

what is causing it to become detached? is the feed tube getting stuck anywhere?

Hi, I really have no clue how or why the extruder is becoming detached. Honestly, it doesn’t ever seem to be detached when I receive the error mid-print. I have to detach it manually and put it back on for the machine to reattach it. The feed tube is looped through the swinging metal arm on the interior as it should be so it shouldn’t be getting in the way

I’m thinking it might be a (or multiple) pulley levers. I took one out and it was almost ground to bits. If this isn’t the case, what was your remedy for fixing the stepper motor wires?

Hi Alison,

I think I know what the problem is, have seen it a few times with my new SE+
There’s no problem with your Z18 if you were already getting good prints out of it with SE.

There is a small misalignment in the extruder that can be fixed easily. You need to heat up the SE+ to 215C, remove the filament, then detach the SE+ and remove the nozzle, get your drill and use a drill bit exactly matching the size of the hole of the extruder (I forgot which size was it) and go all the way without drilling, just push it in and let it cool. Then open the extruder and remove the push sensor magnet and spring and take out the extruder head, hold the head with large pliers and slowly drill it. There will be a bit of plastic and a bit of metal powder mixed to it. Once it’s all done and free take out the drill bit but make sure while you are drilling it’s perfectly straight. Then clean up, close the extruder and heat it up, put the nozzle back in and you are good to go. Because of the misalignment the filament gums up after a while and chokes the extruder that causes the extruder to pop out of it’s place, the feeding motor rotating but the filament is jammed up. Hope this helps. Took me a while to figure it out but it worked. Even new extruders can be faulty.


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Also check the direction of the magnets when you open the extruder. It happened to me one time with a new SE+

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So the problems began with the SE+ and I switched out to the old SE which successfully printed a very small test print successfully. Since I had success with the old extruder, I decided to try one of my larger prints and the same thing happened. Maybe both extruders are gummed up? I’m going to replace one of the pulleys, lube everything up and see what happens. I really appreciate all of your input, though, it will give me other things to look for if the new pulleys don’t work. Thanks!

I would try straight replacing the idler pulley. I began hearing a scraping sound and finally isolated it to the pulley. Bought a new one, replaced it, and the machine started working fine. No detachment issues though, I am working on a fifth gen with great results.

From the limited info I have read, it almost seems like the pulley is causing misalignment issues, which are forcing the extruder off its magnet holder, but maybe just temporarily, as you mention it is attached when you see it. If you pull the extruder away mid print just for a sec, it will cause that error.

Ali Express has them cheap too.

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Something else you should do after replacing the idlers is to print this clip and put it on. I found that the aggressive movement of the extruder assembly was enough to jerk the extruder loose. I was constantly getting detachment problems. Once I put this clip in place I have never had the problem again.

btw I have had to replace all six of the idlers after about every 400-500 hours. I’m on my third set and have had the printer for two years.

not sure what joe_g is referring to with the stepper motors. Since the design of the z18 is different using an H configuration of the belt. there are no steppers on the extruder carriage like the other Makerbot models. The motors are stationary so there is no stress exerted on any of the stepper motor wires. What he is referring to doesn’t apply to this model.

Yes, that is what they’re sending me: an idler pulley. Do you think that issue would cause the carriage to hit the sides of the machine, as if the carriage is being overshot?

I have well over 500 hours on this thing. Maybe I should do all six. Oy!

I do, As the printer runs through its gcode, those tiny variations add up and could knock the nozzle of the printer on the model being printed, and if it comes off just a bit, it stops. Usually the magnets are more than strong enough to hold he extruder, but those stepper moors are rather unforgiving if they start doing what they are not supposed to do.