I run a high school 3D printer lab and we have several 5th generation MakerBot printers. On one of them I have considerable trouble with "thin" prints and filament slip warnings.

So far I've tried changing extruders and using different filament rolls with no luck. But, if I move the job and the extruder to a different printer it works.

I'd appreciate suggestions for how to sort this out. I would have expected the slipping problems to follow the extruder.

  • $\begingroup$ Do you have the Smart Extruder+ installed or still the original Smart Extruder? Also, what are your target parameters such as Layer Height, Infill %, Shell, etc.? $\endgroup$
    – tbm0115
    Dec 20, 2016 at 20:43
  • $\begingroup$ Not at school today, so some of this if from memory. All of the failures were with the original Smart Extruder. Parameters that I remember are: layer height = 0.2mm, infill = 10%, shells = 2, rafts = on. $\endgroup$
    – dlu
    Dec 20, 2016 at 20:47

7 Answers 7


Oh interesting. By slips, I take it you mean that the raw filament slips, not the print slips.

This will happen for a few reasons. First the tooth gear that grabs the plastic is either:

  • Worn out
  • Out of place
  • Not the correct distance from the guide wheel.

This is all part of the mechanism that the Smart Extruder attaches TO. Not the Smart Extruder itself. You might be able to fix this yourself, worst case you will need a replacement assembly from MakerBot. I would look into online auction sites for the part

Another option is to try thicker filament. Which you might be able to custom order. So instead of 1.5, maybe get 1.8. I am not sure where you can buy off sizes.

From there this machine might just be getting jammed. It happens to some machines. This again points to the base of the X axis assembly.

Last which I would say is not likely as you have tried multiple extruders, you might have the nozzle becoming clogged. I often pop open my extruders voids warranty and clean them out. Also micro hand drills are a good option here.

  • $\begingroup$ "This is all part of the mechanism that the Smart Extruder attaches TO" I don't think this is true. I have a Replicator+ extruder which based on YT videos looks very similar. The tooth gear is embedded inside the extruder and mechanically driven by the printer. $\endgroup$ Jul 28, 2022 at 14:08

I posted an edit to the top answer in hopes that it will get changed for anyone looking at this post in the future but in case it gets rejected here is the actual issue and fix.

If you just want the solution skip down to the bolded text.

I came across this post while browsing for resources to document my own experiences with "filament slip" in Makerbots and every suggested solution was wrong and potentially malicious to the machine. I'm an expert in the field and have taken apart and fixed dozens of machines.

First a bit about the anatomy of the extruder so you can understand better. The way that the toolhead detects slips is with an encoder wheel placed above the actual drive mechanism, not attached to it or the idler whatsoever. It's also not even tensioned against the filament at all. The filament is "held" in place with an injection molded piece of plastic that attaches to the rest of the extruder body just by the pin connectors on the internal PCB and a small positioning groove on both sides of the case.

The encoder wheel and its sensor are very unlikely to wear but what happens to every older head is that either the casing or the injection molded part that holds the filament wears and the encoder wheel no longer presses firmly against the filament which causes the filament to move without turning the encoder. The encoder then not moving while the drive gear is, reads a filament slip and sends an error message even though nothing is mechanically or functionally wrong. The wear is also not clearly visible even on close inspection. This problem seems to arise in every Smart Extruder+ once it reaches 150-200 printing hours.

Actual Fix As a temporary fix you can jam a piece of foam inside the right side of the extruder to push the poorly secured injection molded part against the encoder wheel. This will make the filament slip error much less frequent but won't completely solve the issue. I'm working on a 3D printed insert that should hold the part more securely, at least until the printed part wears after an additional 100 or so printing hours. I'm also working on a 3D printed replacement for the extruder body and some of the injection molded interior parts. It aims to be a drop in replacement which should greatly improve both reliability and functionality. If I can remember once I'm finished I'll come back and post a link here.

  • 2
    $\begingroup$ Hi Adam and welcome to SE.3D Printing! I would like to kindly ask you, please do not add additional information to someone else's answer. If you have something to add, please post your own answer (referring back to the answer that you wish to ameliorate, if need be, using the URL of the answer). Your suggested edit, while it may have been correct, was rather confusing, and caused some flags to be raised. Thank you for posting your own answer here... :-) If you wish to edit someone else's answer to correct typos, grammar, fix units, links, or incorrect formatting, please feel free to do so. $\endgroup$
    – Greenonline
    Jul 6, 2018 at 19:48
  • $\begingroup$ This was the cause in my case. I have my filament roll on the side and at just the right angle, the filament would bent slightly away from the wheel, losing contact. A bit of paper jammed behind the injection molded part solved the issue. $\endgroup$
    – Winfred
    Apr 16, 2021 at 23:23

Okay, the original Smart Extruder has many issues. I've clocked about 60 hours on a new Replicator+ w/ Smart Extruder+ and haven't encountered any of the issues I heard about with the original extruder. So, I might begin by re-recommending what MakerBot Industries has recommended to their customers which is upgrade your Smart Extruder to the new Smart Extruder+.

However, the extruder may not be completely at fault. A picture says a thousand words, so if you have one, please add one. Based on your description of the part's layers "thinning out", double check your extrusion settings in MakerBot Desktop.

Another potential issue is too much tension on the filament as it is being fed into the extruder. Here are some things that can lead to too much tension:

  • Filament wound around spool/spool holder
  • Filament kinked
  • Too much friction between the spool and spool holder
  • Too much friction between the filament and the filament guide (the plastic tube)

Finally, and my reason for bringing up the Smart Extruder, is that your extruder may be clogged or "gumming up". In the past, if there was too much tension on the filament and the drive gear was not adjusted correctly, the drive gear would grind the filament. This would lead to small deposits of filament gumming up the drive gear, eventually leading to the filament slipping. Once the filament began slipping, it would slowly no longer extrude and heat up further up the extruder assembly. This inevitably leads to the extruder becoming clogged. In short:

{Too much filament tension} + {Too tight drive gear} = Gumming

{Too much gumming} + Time = Slipping/"Thinning"

{Too much slipping} + time + heat = Clogging


You could also try printing at a higher temperature. Slips can happen when the filament is not melting and thus not pushing through the extruder consistently. E.g. I had a spool of PLA filament that would slip constantly at 190°C. I tried 220°C and then it printed smoothly after that.


I had the same issue, but my solution was a little different. Following along with what the others posted about the wheel, I had a jam inside the extruder around that wheel. I missed it the first time I tore it open so no matter how many times I tried the screwdriver trick it didn't work for me.

I figured I'd post so if anyone is coming along trying to find the solution, they can see that it might be a jam on the filament wheel and not just to check the nozzle area.


We had a similar issue with our Makerbot printer here in the CARIS lab. We would have slip, after slip and tried oiling, hand feeding, and roughing up the filament none of it worked. But we found an answer!!!

With the smart extruder, it's as simple as inserting a flathead screwdriver between the filament wheel and the housing, and prying the wheel towards the pin-side of the print head. Solved all our problems! Seriously, not a slip since and perfect prints.

I've a short solution video for YouTube, Fixing filament slip on your 3D printer.

Check out the makerbot trouble shooting page for reference: MakerBot Support > Troubleshooting > MakerBot Replicator > Error Codes ERROR 81


So I had this issue for months, was about to either give up and call my printer a paper weight, but I figured it out. And it doesn't cost anything.

I literally reprinted the same hose adapter 6 times (every time the filament slipped about 20 times and it was unusable). I changed 4 settings and since then I've printed the same print twice in a row without a single filament slip.

In "Device Settings" in Makerbot application: Extruder Temp: 220 °C Travel Speed (I think this is what is actually causing the slip): 115 mm/s

Then in the "Infill" section: Infill Density: 30 %

Lastly in "Model Properties": Shell Starting Point: 220 °C

Please let me know if this works for you as well.

(I should point out I just have the regular smart extruder, and I was planning on dumping the $350 for the top of the line model)

  • $\begingroup$ I use the "MakerBot Desktop" application, as opposed to the new application, because it won't work, so let me know if I need to modify based on application $\endgroup$
    – XMonsterX
    Apr 17, 2020 at 14:30

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