What is the most common failue mode while printing

From what I have read, the most common failure mode is the extruder jamming or the tip coming loose. Less often the X and/or Y axes loose lock. What other problems are people having that us newcomers should watch for, and designers should be thinking about fixing. In particular, how important is the glass nozzle in reducing extruder jamming, tip popping out, coming loose, or getting off center? Is this a common problem, or not worth changing out a working extruder for?

Mike

Extruder jamming is by far my biggest failure mode. The other problems I commonly have are Darwin issues and have already been fixed. I don't depend on PTFE for anything structural so I've never had the tip fall out.

I can run reliably without the extruder jamming, but I'd like to be able to run faster or with a smaller nozzle. Whenever I try to push my machine in one of these ways the extruder jams.

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Darwin clone, Gen 2 electronics, Arduino Duemilanove w/ AtMega328, 5D Firmware, Pinchwheel extruder
[www.codeerrors.com]

mccoyn,
what size nozzle opening would you like? I think I can get some down to 0.2mm that will not jam, possibly smaller.


Mike

At .2 you start running into issues with the quality of the plastic, and getting the parts to adhere to the build plate. .2 nozzles require a VERY VERY level build plate.

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repraplogphase.blogspot.com

Or a raft laid down by a bigger nozzle.

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[www.hydraraptor.blogspot.com]

I just finished making 26 glass nozzles with the blunt nose, 11 with flanges and keying strip for clamp mounting, and 15 plain for compression fitting mounting. I have received the first set of drill bit blanks sized #76 through #80. It allows me to use them as a pin gauge for 0.33mm up to 0.49mm Most pass the 0.49mm rod, and so are 0.5mm or larger. But I kept a few 'specials' that are big enough to see, but to small for even the smallest pin gauge to go through. So they should be around 0.2mm. I have ordered better metrology, but it has not arrived yet. I will put these on ebay shortly as bulk buy items, so they don't have to be listed individually. I think they will flow better with little or no jamming compared to the standard brass nozzles, but until someone runs them on a working machine and compares, it is hard to say for sure.

Mike

I can run reliably with a .5 mm nozzle, but I have a .25 mm nozzle that gives me lots of trouble. I still have a shaft driven pinchwheel extruder. I suspect that the Wade extruder will be able to work with the smaller nozzle.

A glass nozzle will reduce my failure rate if the friction in the small hole is less than the stainless steel nozzle I have now.

I have also been observing a strange issue. If I don't shut down my heater right away when the extruder jams, then the next time I run it, it will be more likely to jam again. It took me quite a while to recognize the pattern because I can restart the extruder (with a little push at first) and it runs, but only jams again after 1 or 2 hours of operation. It will continue to be unreliable until I back-out the PLA and clean the barrel. I know someone else with an extruder that is very similar to mine and he describes similar behavior.

My working theory is that the PLA that is in contact with the heated nozzle for a long period of time changes in some way that makes a residue that adhere strongly to the nozzle. Since it also sticks well to PLA, this means it greatly increases the friction in the nozzle. When I clean the nozzle, I have to run the temperature up and back out the filament. During this time, the residue will be heated and exposed to air, which causes it to burn up and go away or turn into something that isn't as much of a problem. A glass nozzle could help in two ways. First, I could observe the residue forming, breaking down and then being cleared away. Second, it is another material and maybe the residue doesn't adhere to it as well.

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Darwin clone, Gen 2 electronics, Arduino Duemilanove w/ AtMega328, 5D Firmware, Pinchwheel extruder
[www.codeerrors.com]