Instructables
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Picture of Clogged MakerBot Nozzle
If your MakerBot Replicator doesn't produce a good plastic stream in the "load filament" mode, the nozzle may be clogged. A "drooling, thin stream that wraps on the nozzle" is a sign of a partial clog.

What causes a nozzle to clog?  In my case, anytime "something happens" and plastic doesn't get pushed through a heated nozzle for an hour or more, I have clog issues.  An unlevel platform, dirty drive gear, shrinkage and "upcurl" of a big part can cause the nozzle to quit extruding.  If I "walk away" from a 14 hour build, Murphy's Law increases the chances of "no extrusion but the heat's on."

First, open a ticket with MakerBot support.  They are excellent and will help you troubleshoot the problem.  If the result is "clean the abs plastic out of your nozzle," then you might want to follow these steps.

Materials needed:

Acetone (get this in the "fingernail polish removal" area of a drug store or grocery store)
7 mm wrench
3/16 inch diameter rod
pliers
hex wrench supplied with the Replicator
 
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Step 1:

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Safety first. Take your time.  There are multiple "heat up" and "cool down" steps involved. 

This is no more hazardous than pulling cookies out of an oven--but you wouldn't grab a cookie tray with your bare hands.  Don't touch hot parts until they have cooled to room temperature--be patient.

First, unload the filament from the extruders.

Step 2:

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Wait until the extruders have cooled to room temperature.  Power off.

Unscrew the extruder assembly (two screws) and set it on top of the Replicator.  Place the 3/16 inch diameter rod between the extruders.

Step 3:

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Turn the Replicator on and use the menu on the front panel to "preheat."

Step 4:

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Choose the nozzle (right in this case) and "Start Preheat."

Step 5:

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You should see the nozzle heating.  When it reaches about 220, you are ready to proceed.

Step 6:

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Using the 7mm wrench, remove the nozzle (turn counter clockwise).  The nozzle is hot; don't touch the nozzle or the "business end" of the wrench.  It should not take much force to free the nozzle.
MRDC18 days ago

You may try this also:

http://www.instructables.com/id/Easy-Cleaning-Clogged-3D-Printer-Nozzle/

Thanks for the detailed instructions!

VitaliyR1 month ago

Theres a guy on Ebay selling low friction plated MK8 nozzles. They were plated to prevent clogging.

Ebay # 321667110675

RobbieK12 months ago

Hello,

I tried this method on my Flashforge Creator Pro Dual Extruder on one of the extruders. The nozzle came off, but I haven't been able to put it back on. It doesn't seem to have screw threads like I was expecting, just one notch to catch when it turns, it sort of clicks back in, but when I load filament now, it pushes the whole entry tube and nozzle away from the square taped assembly. Doesn't look like there is broken metal either though. Can anyone offer advice on how these are put back together?

It sounds like maybe your plastic solidified on the threads and needs to be heated up again to screw in your nozzle. Make sure you heat enough to melt the plastic then carefully use needle nose pliers to screw it back in - the threads should be free if it is hot enough.

Thanks. After I took it apart and inspected, and looked at a picture of a replacement nozzle, The nozzle is snapped off and the screw thread is stuck inside the aluminum block. I wonder how I could get it out. I want to replace the nozzle and the heater block, but I'm not sure how to detach the metal filament entry tube from the block.
wkarraker2 months ago

Excellent instructable, useful for many 3D printers with similar technology. One thing I might suggest is 'rolling' the cooled extrusion between your fingers after you clean and assemble everything, if it is not perfectly round you may still have a blockage or partial clog. A stainless steel 28 gauge hypodermic needle (0.362 mm) can clear some clogs from .4mm nozzles without disassembly, the angled tip can be used to gently scrape out deposits while the hot end is up to temperature.

Why risk damaging the nozzle with a needle? I've never needed to use a needle to clean my nozzle to my printer ever. See my below comment- I hope to save you a nozzle part that can be a bit expensive.

rob.milliken3 months ago

This is a ton of trouble. Easier. Put your nozzle on a stainless steel platform with a small hole in it. Have the nozzle end where it screws in on top of this hole to let it drain the plastic. Now, put this steel platform and the nozzle into an oven. Turn the oven to clean. Let it go through its cycle for a few hours. Let cool (important!). Take out and clean out the ash with some rubbing alcohol. It will tarnish quicker but who cares? I am thinking running magnetic wire, needle etc, could cause the nozzle small end to become scratched easily. and possibly damage it I have done this oven cleaning technique and it works great and keeps your oven clean too! Credit goes to my wife who is a material scientist and runs material through ovens to see what they look like on a daily basis.

malokidaemon4 months ago

Quick question - hopefully not too ridiculous(!) - the purpose of the metal rod? I'm assuming that it is simply to provide counter pressure when loosening the nozzle, correct? Or am I missing something blatantly obvious.... :)

MikeTheMaker (author)  malokidaemon4 months ago

You are correct--without the rod, the "taped square assembly" turns . . . and who knows what problems that might lead to :)

Thanks, Mike...I hadn't considered rotation of the (very technically named) "taped square assembly". :) My initial consideration was rotation of the entire extruder assembly. I may not even use a metal rod given the purpose - it turns out that the handle of my 9mm (metal) wrench slides almost perfectly between the two square assemblies and puts pressure on both.

Out of curiosity, you wouldn't happen to have run across any good places to obtain replacement extruder nozzles, etc.? Since the device is two years old, it doesn't appear to have a direct entry on Maker's support site any longer, and the Maker store really doesn't seem to have anything.

MikeTheMaker (author)  malokidaemon4 months ago

Your wrench solution will work perfectly.

Actually, I just bought some nozzles from Amazon last week and am running one today for the first time. Seems to work fine (and for the price, is probably a lot easier than all the cleaning).

http://www.amazon.com/gp/product/B00IP6SSXM/ref=oh...

Cool...may give those a try. Have you seen the update to the Mk7/8 stepstruders? (Originally, I found it here: http://mike-ibioloid.blogspot.com/2013/02/important-upgrade-for-both-mk7-and-mk8.html) It's a replacement for the Delrin Plunger - been debating giving that a try as well. We tend to use the printer mainly for demos (I work for a science museum), so the plungers themselves aren't very worn, but I liked this new design...

MikeTheMaker (author)  malokidaemon4 months ago

Thank you for the information! I've been worried about what to do when the Delrin plunger wears out (it wore out quickly on my Replicator 2; then users/Makerbot came up with a replacement similar to what you show and it worked wonders for solving feed problems). I had not, however, found a similar solution for the mk7.

Yes...it appears that this is something that users came up with (kind of like adding plexiglass casework for the Replicator to keep consistent temperature with ABS, which then made it to the Replicator 2X) and Maker adopted.

Overall, I only have experience using the original Replicator (would like to try a newer model someday, or spend some time and build a RepRap type device just for fun), so I haven't seen a mk7. Rumor has it that we have a Thing-O-Matic around here somewhere, and that appears to use the mk7. I'd like to take a look at that stepstruder and see just how different they are. Looking at docs only tells you so much! :)

PatrickW36 months ago

Why is it important to remove the nozzle while it is hot?

MikeTheMaker (author)  PatrickW36 months ago
This is based on some instructions that I originally received from MakerBot for exchanging a nozzle--the threads may be damaged if one exerts too much force since the nozzle may be "tight" when cool (or stuck in place with hardened plastic).
You could try to remove it cool, just be gentle . . .
Thanks!
robboz46 months ago

Thanks for a great Instructable! I'm now able to print again!

MikeTheMaker (author)  robboz46 months ago

I'm glad it helped. Judging from the number of views on this instructable, we're not alone with clogged nozzle problems. Hey, I just had a book published, "A Beginner's Guide to 3D Printing: 14 Simple Toy Designs to Get You Started." If you know any kids (or adults) who need a very basic guide to "designing with 3d software," ask them to take a look.

seanobrien6 months ago

Thank you for putting this together. Replicator 2x was clogged with ABS - these instructions worked great!

luclalande1 year ago
Was it PLA or ABS filament that first caused the problem?
MikeTheMaker (author)  luclalande1 year ago
ABS--I haven't had this type of problem with PLA using the Replicator 2; also, acetone won't work with PLA, so a clogged PLA nozzle will be another animal to deal with
cpalmer71 year ago
Wow, this worked like a charm.