Instructables
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 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.

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)  malokidaemon1 month 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)  malokidaemon1 month 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)  malokidaemon1 month 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! :)

PatrickW32 months ago

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

MikeTheMaker (author)  PatrickW32 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!
robboz43 months ago

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

MikeTheMaker (author)  robboz43 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.

seanobrien3 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.