Ultimate Jams!

uh oh!

Summary: Keep an eye on your prints in case something goes wrong. Things can get really messy, really fast. A little glue is cheap insurance for long or multiple prints.

No, I'm not talking about music here. This is what happens when your prints don't stick to the build platform. I was printing a bunch of spirograph gears. I had printed many sets before. So, confident that it would print without problem, I walked away from the printer and let it do its thing. I came back a while later to this...

bottom view of print head

One or more of the gears had slipped off of the build platform and stuck to the print head. The printer kept going, knocking off other gears. Eventually the nozzle got blocked by the parts, but the extruder kept going. The melted plastic oozed up around the nozzle and hot end engulfing both. It looked like a total nightmare to clean.

this is what was stuck to the print head.

I peeled the mass of plastic off of the print head before it cooled down. But there was still a big mess of melted plastic surrounding the hot end up inside the fan shroud. I though I would have to disassemble the entire print head to clean it. After closer inspection I could see that the fan shroud is attached by four allen screws on the outside of the print head.

one of the screws holding the fan shroud on

mess of PLA around the hot end

Once I removed the fan shroud I could see it wasn't as bad as I thought. I turned on the machine and used the advanced settings to heat up the nozzle to about 190°C; hot enough to melt the plastic, not so hot that it burns or makes a bigger mess. I gently pulled on the mass of PLA with pliers until it came off easily. With the nozzle still not, I wiped off the hot end and used a dental pick to remove the last little bits of PLA from around the nozzle threads.

all clean and extruding properly

With the hot end all clean, I advanced the extruder to make sure the nozzle wasn't clogged. The PLA flowed nicely so I screwed the fan shroud back on. I printed the gears again, this time using glue on the build platform. They printed perfectly. Even if you may not need it, use glue to make absolutely sure your prints don't come loose.

Maintenance Time!

these lines should be touching

Summary: Tighten your belts and lube the rods every 120 hours or whenever your print lines drift apart.

I just hit 120 hours of printing on my UM2. My last print was going to be a long 19+ hours. So you can imagine my despair when I noticed the first few layers weren't looking too good. There were noticeable spaces between the lines. I was printing with the normal quality defaults where the initial layers print nice and slow. It wasn't an issue of my print settings being too aggressive. The filament wasn't skipping and the lines were uniform, just not touching. So it didn't seem to be a case of under extrusion. I wasn't going to chance ruining a long print, so I aborted after just a few layers to troubleshoot.

Once again, I went to my favorite troubleshooting guide. I found the solution here. It looks like after so many hours of printing, either the belts have stretched a little, or the stepper motors have drifted in their slotted mounting holes. Luckily it is an easy fix. Simply loosen the screws for the stepper motors, apply downward pressure, and tighten the screws. Oddly enough, none of the included Allen keys fit the bolts properly (they're 2 mm). It took me longer to find the correct driver than it did to tighten the belts. While I was at it, I added a drop of silicone oil to the X and Y guide rods on the print head. Then I manually moved the print head to all extremes to distribute the oil.

initial layer after adjustments

That did the trick. Right after the maintenance, I started the print again. This time the lines were touching as expected. I was a little surprised at the improvement since the belts felt nice and tight before I adjusted them. I think Ultimaker should consider some sort of tensioner on each stepper to keep things tight. With all of the work those steppers are doing, it seems inevitable that the motors will drift some in the mounts. So just a little preventive maintenance can save you from lousy prints.