I've fed in new filament after an old one has ran out on the fly several times. All I did was firmly press the new filament against the old one as it entered into the feeder. It's a bit boring since you have to sit there and baby it for a few minutes but it's doable (small price to pay on a 30 hour print). So in your case I'd just cut the filament, remove the blob and then do what I described above.
edit: I should mention this was on the UM1, I haven't tried it yet on the UM2.
How to continue a failed print even if you already hit power switch:
http://umforum.ultimaker.com/index.php?/topic/4213-ideas-for-recovering-failed-prints/
The instructions above could use some work... let me know whats confusing about it.
@gr5 @IRobertI - Thank you so much for the quick reply. You guys are great!
I don't know if using a razor blade will work as the filament seems to be internally broken. I think that I'll cut off the filament before the kink and "spoon feed" clean filament using IRobertI's technique.
Thanks also for the instructions re a failed print. Hopefully, I won't need them but it's good to have a plan B if all else fails.
I've fed in new filament after an old one has ran out on the fly several times. All I did was firmly press the new filament against the old one as it entered into the feeder. It's a bit boring since you have to sit there and baby it for a few minutes but it's doable (small price to pay on a 30 hour print). So in your case I'd just cut the filament, remove the blob and then do what I described above.
edit: I should mention this was on the UM1, I haven't tried it yet on the UM2.
True.. but if you do this retraction doesn't work anymore because what happens at the feeder mechanism doesn't affect the seperated piece of filament.
What I have already done a couple of times is:
Prepare a new reel of filament. (straighten the tip)
Very quickly open the feeder upgrade, pull out the filament
Grab the new reel of filament, feed it up in the tube
Close the feeder upgrade
Swap the reels on the reel holder.
While I was typing the above, I realized you had an Ultimaker 2.
Because you can not manually open the feeder, I would recommend to use a little knife or whatever to shave it down a bit. It would even be better to make it too thin. You would hardly notice if it is only that spot.
Thanks Sander. I'll try that first.
I gather that it's not possible to pause a print on the UM2?
Cheers
Phil
True.. but if you do this retraction doesn't work anymore because what happens at the feeder mechanism doesn't affect the seperated piece of filament.
Very good point, I guess it didn't affect the prints I did this on so it never crossed my mind. Oops!
PAUSE. would be nice 
I believe I'm using the latest stable UM2 firmware and pause (in the Tune menu) works just fine for me. I used it a few times today while printing some ABS -- there were some steep overhangs that left some very ugly areas curling up sharply, and I just paused after that layer, carefully trimmed the curled areas down with a scalpel, and resumed the print.
I recall that Pause At Z wasn't working on the UM2 before (something about the relevant G-code not being properly implemented on the UM2). Anybody know if that works now? Manual pause is very handy though, still.
I think dgsharp is correct. Pause as a gcode doesn't work on UM2 for sure, but I guess the pause function while printing may work just fine.
Thank you all for your help. By way of an update, I followed gr5 and Sander's suggestion to trim the kink with a razor blade and it has worked so far. The printing is still ongoing and I'm hoping that it will be finished by the time I come home from work tonight...
Are these kind of kinks to be expected, or is this a defect that I should mention to UM?
Are these kind of kinks to be expected, or is this a defect that I should mention to UM?
I've never seen one of these before. Ever. It doesn't look like a kink, it looks like the filament is wider at that spot.
..Is it ours?
What color is it? You should fix your WB 
But no, that is not very common no.
@Sander - It's one of yours, I'm afraid (9029 PLA Pearl-White).
Came home yesterday to find that the print had failed after about 24 hours. Another kink was hidden in the roll and got stuck in the feeder system :(
I'll try gr5's method of recovering from a failed print over the week-end. Unfortunately, the print is for some architects and it needs to be pretty much perfect... Let's see what happens.
It doesn't look like a kink, it looks like the filament is wider at that spot.
I think that you are probably correct. The defect basically consists of a wider segment (c. 1mm in length) followed by a narrower section (also c. 1mm).
If your bed was heated during the print - try to keep the bed heated until you continue the print. If it's off right now, turn it back on - you don't want the part to pop off the bed. It's okay to leave the bed warm for many days until you figure this out.
Once the part pops off the bed you probably need to start at the begining.
If you want parts to look perfect, you can fill holes with bondo (auto body filler) and you can sand and then paint with automobile primer paint. After priming you can use any kind of paint you want. This will give you absolutely amazing quality and can hide holes, bumps, and other imperfections (but it can be a ton of work).
The reason parts pop off the bed is because the expansion coefficient for glass is different for plastic so they shrink by different amounts. Don't even touch your part gently until the bed is back up to temp.
@gr5 - Thanks again for your comments and all your help. It's really nice to have somebody that's so knowledgeable to help! Unfortunately, it was too late when I saw your message and I had already switched off the printer (and therefore the heated bed). When I came home, the print had popped off on its own. :roll:
I'll relaunch a new print tonight, cross my fingers and see what happens. At least, I'm learning...
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gr5 2,265
I would shave that down with a razor blade.
UM1 can pause print. I'm not sure if UM2 can but I've been able to continue a long print after it failed. It's tricky - let me know if you want all the details - I have an explanation written up somewhere...
So in summary - if you have a UM2, try to stop it in a recognizable spot - memorize where the print head is, and then just cut power and quickly push print head off to the side before it leaves a big blob on your print. Then you can take your time (maybe hours?) and continue the print at your leisure. However you should keep the bed hot the whole time. If the bed cools to much your print might just pop off.
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