Updated - Clogged up filament feeder tubes

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Depending on the environment and how you handle and store your cartridges/filament spools, sooner or later the filament (mainly PLA) will become brittle and brake.
(See Post: http://cubex3dprinting.blogspot.com/2013/11/taking-care-of-your-filament-cartridges.html

There is a good chance the filament will crack sooner or later somewhere in the feeding tube and it is quite a pain to get it back out. Besides that, your print probably failed also because there was no more filament coming.

Since two of my tubes are clogged up (filament feeding tubes, that is) with broken filament pieces and I don't want to spend more time clearing them out, I decided to make a more drastic change.

Note: Proceed at own risk. Ha-ha.
This is most likely not recommended by the manufacturer, but I just wanted to share what I do to keep me printing happily.
This direct filament feed method is only intended if you run your filament spools externally.
Due to too much frustration of binding etc.. I generally remove the filament spools from the cartridge anyway and run them from an external mount and stick the corresponding empty cartridge case into the holder so it can read the chip.

Read this post first before you open up a filament cartridge to avoid any damage to the chip:
http://cubex3dprinting.blogspot.com/2013/07/cartridges-and-filament-flow-errors.html


Here is what I changed to make filament changing and filament care a lot easier for me:

It is best if you can, to unload any filament you have loaded.
Otherwise turn off the power to the CubeX.
Then remove the feeding tube guide plate. Make sure to not drop the screws or nuts into the system.
If you have filament loaded, lift the guide plate carefully and clip the filament with side cutters right where it comes out of the feeder tube before it enters the feed motor.

After removal of Guide Plate.

Put some tape over the top edge because it is sharp and the filament can rub against it.

It is best to cover the not in use feed in holes with tape so no debris can fall in.

To load and unload filament it is best to use the "Replace" Menu button and go thru the process. Instead of feeding the new filament thru the tubing, feed it directly into the extruder motor from the top.

[Alternatively you can also exchange the filament as described below.

To load filament, go into the "240deg" menu

Then heat up the jet you want to load filament by tapping a couple times on the "TGT" (Target Temperature) temperature for the appropriate jet till it displays "230C" .
(In this example it is jet 2 (PJ2).

Then wait till the "T" temperature (Actual Temperature) to the left of the TGT temperature has reached the target temperature. (In this example the actual temperature is at 215C, so almost ready).

Tap twice on the "RPM" value so it displays "3.0" for the appropriate jet. This will turn the feed motor on, to advance the filament. I find it better to run the RPM at 3.0 and not higher. You want to feed the new filament right after the old filament.

When you insert the filament, you will feel it getting pulled in. Look at the print jet below and wait till a steady stream of filament comes out. You will see the color change from the old to the new filament.

Then hit the "+" button below the display to exit the Print Jet Control menu. This will turn the temperature and feed motor off. ]

Now while the print jet is still hot, it is a good time to give it some maintenance cleaning. It's quick and easy so I do it at least every time I change filament. (It keeps the print jet printing nice).

CAUTION: Don't touch with bare fingers. HOT HOT

I use a cloth to wipe any accumulated excess filament off the bottom jet. The crusted on filament should wipe off fairly easy while the jet it still hot.   - Caution - keep your fingers cover by the rag so you don't get burned.

Filament routing:

Routing the filament as pictured above gives it enough room to move around with the movement of the print carriage.

When I am done printing, use the "Replace" Menu button to remove the cartridge.

[Alternatively I just use wire cutters to clip the filament maybe 1" above the feeder motor. Make sure to do a straight clean cut and straighten the filament so the new filament can push straight against it when loading new filament the next time.]

Store the filament spool in a bag with additional desiccant to keep it fresh and prevent it from getting brittle and break.

Also, tape the end of the filament on the spool to the side of the spool, so it keeps the winding tight when the spool is bagged.

See "filament care" post:  http://cubex3dprinting.blogspot.com/2013/11/taking-care-of-your-filament-cartridges.html

In a nutshell:

Use the "Replace" Menu to get the old filament out and new filament in, except feed it directly into the extruder motor from the top (where the filament feed tube used to attach).

[Or if you just clipped the old filament above the extruder motor, make sure if there is previous filament in the print head, that the filament is straight with a straight cut, so the new filament can push straight against it when loading.

Just heat up the desired print jet, have the feed motor push thru the previous leftover filament that was clipped and insert the new filament right after it.  -   Ready to print.

After the print just clip the filament about 1" above the feeder motor and store the filament spool in a bag with additional desiccant to keep it fresh].

Make sure you have your spool and cartridge case marked, so you know what goes together.

Also, tape the end of the filament on the spool to the side of the spool, so it keeps the winding tight when the spool is bagged.

This method is for sure not as clean looking, but for me it is the least hassle and minimizes potential problems.

To me it has these advantages:

• Running the filament spool externally minimizes the binding issues or they can be detected early. I still have some cartridges where the filament was crossed over within the spool, so I had to rewind them (not fun) but the open spool is much less likely to bind because it is not restricted by the cartridge and how the filament comes out of the cartridge.
• It's easier to keep the whole filament bagged and sealed (except of course when you are printing) so it is less likely to get brittle and break.
• I can keep an eye on the filament spool and how much is left.
• Less filament waste when changing filament.
• The filament is a lot easier to insert. (Before you had to fiddle with it a lot to get it finally to feed thru).
• The filament change is a lot quicker.
• If you use filament that is already somewhat brittle it is less likely to break using the direct feed method because it does not get flexed or straightened out which happens if it would have to go thru the feeder tube.  
• It's not a permanent change and I can always convert back to the standard configuration.

Also, having hinges on the lid is sooooo nice.