Skipping layers

#1
Hi All,

So I've been having issues with the printer skipping layers randomly. I've tried several slicing settings (through slic3r), both slic3r default, Gmax provided, and both of these with minor variations. In the two weeks I've had the printer I've managed to get one flawless print. The rest have flaws differing only in their frequency and time into the print.

Would LOVE to get the first extruder working, or slicer settings figured out, so I can move on to the second extruder.

Thanks in advance,

Larry
 

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#2
A couple of things might be causing your problem. First, you might have a partially clogged extruder. That would prevent the full amount of filament from getting out the nozzle. Your middle photo looks a bit like that. Your first photo of the heart gears looks like there was a clog of some kind that resolved itself. Is your filament dusty? The small particles can make there way into the extruder can cause problems.

Or, you could have your temperature set too low. With low temp, the extruder struggles to melt enough plastic and does not get enough out. This does not seem to be the problem with the last couple of photos because the prints are OK up to point.

Or, power to your extruder stepper motor might be set too. Can you hear it skipping (a light thunking as the extruder tries to push out filament). There a several posts in the forum on how to adjust the stepper motor power potentiometers.

Earlier this week I had a similar problem where prints would fail about 45 to 80 minutes into the print. My nozzle would totally clog. I believe that one of two things was happening. The humidity where I live (Las Vegas) spiked up on the days I was having issues. Humidity causes issues with PLA because it absorbs moisture. You can test to see if this is your problem by drying out the PLA in the oven prior to print. But the real culprit was likely heat transfer up into the nozzle. I was printing at a temp too high for the material. The heat would work its way up into the nozzle and melt the filament too high up, which would ultimately result in a clog. Your first and last photos seem to have the same thing happening where the print is fine then fails part way in.

I'm sure someone else is far better at diagnosing problems based upon photos. With hope, they will improve what I've relayed here.

Good luck.
 
#3
Yes, humidity is bad. Ideally, you'd want to use desiccant to remove the moisture by placing the reel in a closed container with some of these: http://www.amazon.com/Fairly-Odd-Tr...UTF8&qid=1405349781&sr=8-4&keywords=desiccant

I haven't tried them, but they are what people use, so if anyone gets these, please do let us know of your experiences.

I just place the reel in a toaster oven on minimum temp (150 F) and check on and flip the reel every 15 minutes. I got a $25 toaster oven specifically for this.
 
#4
Thanks for the guidance Chris,

I've tried a few ways to clear the extruder but have yet to pull everything apart, looks like that will be next on the list of things to try. Dusty filament is also a possibility, will look into making some sort of scrubber like what juliatruchsess built for her filament collection.

The typical print temp is 199 but for the print in the first picture I noticed that it jumped up to 208 for a period of time, that should really just be for the initial heating correct? As I've only noticed this happening once I would be more inclined to believe that the humidity is more of a culprit. Living in central Wisconsin summers are always a beast for humidity. Thanks for the tips on the silica packets and the oven temp raykholo. I'll have to give that a shot before the next print.

As for the motors, there isn't any clicking/skipping and per some of the other posts I adjusted the motor until it could turn uninhibited while being tightly pinched. I tried to read up on the forums before posting but as I am quite new to 3D printing I wasn't sure if the issues were hardware or slicing related.
 
#5
199 is your first layer temp and then it will jump to 208 for all the following layers. Reason being that if you exceed 199 your print will be permanently bonded to the acrylic bed. Printing the other layers at 208 helps ensure that the layers stick to each other. It's set up that way in the Slic3r profiles.