dergoldstein

I default to 0.1mm layers at 50mm per second, which I think is the cura defaults. While I understand that there's a correlation between the 3 factors (well, at least now I do...), surely there's a specific melting point to specific polymers? What I mean by 205 is actually not while printing, it's when you use the "insert material" function to run filament through the nozzle. I do that and mess with the temperature until the feeder is no longer clicking (I dial down the temperature very gradually to find the lowest point where it's running smoothly). I then stop the process, disconnect the 2 ends of the bowden tube, and make sure there isn't any unusual friction when moving the filament through the tube manually (possibly by bumps forming when the feeder clicks and grinds a bit of material). That's how I figure out the temperature for a particular filament. For PLA it's often around the default -- 210. About the sensor, I've disassembled the hot end a couple of times and there isn't a clear stopping point to inserting the thermocouple, it lets you keep pushing it until it's really stuck and hard to get out again, so I don't push it in as far as it can go. This could mean that I'm getting a lower reading than what the actual temperature is. Maybe with the olsson block it's different but I don't have one yet.

General-purpose: Flush cutters (often to remove the slight brim on the first layer), xacto knife, small (jeweler's) files, small pliers (to remove supports), sand paper. I also print a lot of mechanical parts that need to be press-fit, screwed in, connect snugly to other parts, etc, so I use some tools that others might not: Drills, reamers, and countersinks -- you can print pretty accurate holes when they're on the z-axis, but otherwise you need to drill them "the rest of the way" to smooth them out (just make sure the wall thickness is enough so that you don't poke through to the infill). Taps -- both PLA and ABS can be easily and effectively tapped, I use this a lot. Most often M3, but also M2, M4, and M5. Don't rotate the tap too quickly though, especially with PLA, or it will melt the plastic. Loctite "Super Glue Gel" -- Loctite probably makes hundreds of different glues and I can't give you a specific product number, the label just says "SUPER GLUE GEL". I use it to connect PLA prints, it's quite strong. It being a "gel" lets you accurately position the glue without dripping or spreading. The only downside that I know of is that it discolors the plastic around it a bit (usually turning it a bit white).

I've been using it for work pretty much around the clock since I got it. I'll sometimes go through a 750 grams spool in a week. Also earlier on I read somewhere that to really purge the nozzle you should bump up the temperature to the maximum and let it run for 30 seconds, which was obviously a mistake (and I've must have done it like 10 times in the first month). The lowest I can go with the PLAs I use (mostly colorfabb) is 205, any lower and the feeder starts grinding the filament. But at 205 the squish isn't enough and material can build up around the nozzle.

I think I managed to solve it, though the solution seemingly has nothing to do with the problem... I went over a long list of possible issues and found one thing I hadn't done -- check the isolator. I'd already removed and cleaned the nozzle a couple of days ago, but I didn't remove the isolator to check if it deformed. It actually didn't, but the part that touched the nozzle was almost black, so I did what I saw on a bunch of different posts and used an exacto knife to shave off the ~0.5mm from the end (so that it's completely white). I also added an extremely slight bevel using a drill bit (manually), so that there's a slight funnel on both ends (almost unnoticeable, I knew not to go overboard with this). Here's the latest print, a few layers in: (There's an extra outline on top because I didn't pause right after a layer had finished) Lines now print smoothly and tightly together. I've been through enough problems with the printer to be too optimistic right away, but for now it appears that it's printing almost as smoothly as when I first got it. I forgot it was able to print such clean surfaces and walls, I just got used to rough surfaces. My takeaway from this is to avoid temperatures over 230. I'm going to put ABS aside for now and try to remain within 220 for most prints (my standard is 215, depending on the filament). Thanks for the ideas.

That's actually something I played with a lot, and it's not it. I get the right amount of "squish" when looking at single lines of the first layer (look at the perimeter line on the first layer). If I raise the nozzle any higher I get lines that don't connect to each other no matter where they are. If it were too close all the time then there wouldn't be patches where there's a smooth surface, it would just drag everywhere evenly. This is why I'm thinking that there's a cyclical problem -- there's a batch of lines that print well, followed by a batch that prints poorly.

I've had my UM2 for about 4 months now, and in the past couple of weeks the print layers have become very irregular. With the same materials and settings I used to get perfectly smooth surfaces, so I'm trying to figure out what changed. Here are 2 photos of a first layer: Ignore the discoloration of some areas, I had just replaced a black PLA spool so those are just leftovers. The gaps between certain lines indicates that there's a belt backlash problem, even though this print was made after I tightened the short belts and equalized the tension on the long belts (if there are other operations I should try with the belts please let me know). What I don't understand is the gradual alternation between relatively smooth lines (about 20 of them) followed by a bunch of very rough, noisy lines. There seems to be a cyclical problem. If all of the lines were noisy I'd think there's a problem with the nozzle, but it comes and goes. Now here are 2 photos of the same part, several layers into the print: Same exact problem, except the cyclical nature is even easier to see. A bunch of smooth lines with good spacing between them, followed by a bunch of rough lines that seem to come in "pairs" (two close lines followed by a gap). In some of the rough areas the lines become so thin that even a pair of close lines aren't enough to close the gap. If anyone has any idea what's going on please let me know.

I found the following post which not only had the same problem, but also (almost) the same cause: https://ultimaker.com/en/community/15979-printer-head-cant-find-home Except for me the wires of the Y axis were pinched by the feeder's motor. I've disassembled the feeder so often that it didn't occur to me that this would be the cause. Some type of filament or another either gets jammed, or the feeder starts grinding it. So the last time I re-attached it the Y limit switch's wires were clamped and shorted. This caused the UM2 to keep getting a positive read on the Y limit and think that the head was all the way to the back, all the time. I cut out the crushed part of the wires and re-soldered them, that solved the problem.

After stopping a print mid-way, the positioning of the X/Y belts seems to have messed up. Usually the printer will move the print head to the back-left until both limit switches are tripped, to zero out the position, but now this doesn't seem to be working anymore and the UM2 will often try to move the print head beyond the "front" of the machine. This happens whenever I do anything that requires the print head to move to the front. When the print head reaches the front the motor will keep turning and the timing belt will skip over the pulley, quite loudly. I shut down the machine and moved the print head around manually, there doesn't seem to be any location where it jams or there's unusual friction. I tried resetting to the factory default, but that didn't solve the problem. The one difference in "behavior" that I've noticed is that the UM2 no longer does the zeroing out procedure after printing or replacing the filament, the print head just remains at the front of the machine. I can't imagine what setting would cause this to happen which would remain that way after resetting the printer to factory settings. I don't know how much damage the timing belts skipping over the pulleys causes, so for now I'm not trying anything else to avoid harm to the machine. If anyone has any ideas, please let me know.