leon-grossman

I'd like to see: Dramatically improved feed system. Nozzle that doesn't jam constantly Nozzle that is changeable for different sizes Easier access for maintenance on the hot end Dual extrusion (That's why I bought the UM2 to begin with) 1.75mm filament Larger build volume 300x300x300 (if the patents allow it) a proper enclosed chamber Faster bed heating times I don't need or want printing from PC but, for the love of god, let me perform maintenance actions like jogging, heating, filament change, etc from the PC.

This is not quite correct. I've been running a stainless steel Pico hot end with PLA consistently for months and it jams essentially never. That is more than I can say for the UM2 hot end which decides that PLA is something it does not wish to print that month. The trick is to season the hot end. Personally, I didn't even have to go that far as I just rubbed some oil on a couple of meters of filament and let it go. I've just periodically added a very small bit of oil to the surface of my filament every few weeks and things work amazingly. I've since started doing this with my UM2 and have had fewer problems with PLA jamming recently.

Are you printing PLA? I just replaced my nozzle, teflon spacer and cold end on my UM2 which temporarily solved the underextrusion issue. After a few prints, however, the problem came back. It seems that switching between ABS and PLA is a problem for these printers. I'm still not sure it is a 100% solution but I put some vegetable oil on my PLA filament and have run a couple of very good prints in PLA after doing that. It seems that vegetable oil is a known cure for PLA's stickiness to just about everything.

I wanted to come by and make a quick update. The cold end and white spacer have been replaced with the newer models and the nozzle was replaced with a fresh one. I've been printing frequently for two weeks with only one annoyance (which I'll get to) and I've been able to switch back and forth between PLA and ABS with no issues. So, finally, this printer is living up to its promise. The annoyance is pretty minor and that is that switching from ABS black to PLA doesn't seem to flush out of the nozzle easily. An hour into a three hour print, about 20 minutes of printing was mixed orange PLA with black ABS. I'm not sure how the black is getting trapped in the system for that long. That' said it's a minor annoyance that's probably solved by using a cold pull before printing.

@gr5 and @illuminarti thanks for the help!

OK, I've had my UM2 at my office since just after Christmas last year. When it works, this printer is fabulous. However, I've had under extrusion problems from the beginning. When my printer arrived, the drive wheel pulley set screw was loose. It's just gone downhill from there. PLA printing is a sometimes thing when I clean everything out just right and the extruder housing doesn't shed too much ABS plastic then I can get amazing PLA prints. Most of the time, however, the extruder just jams. I'll be trying vegetable oil next to see if that helps. ABS printing usually works OK but that jams as well. I can currently print at a max of 50mm/sec at 0.1mm without problems with ABS. Anything higher and I get under extrusion. So, yes, I guess I need to disassemble and clean the nozzle again. that would be great if the nozzle were removable. Instead, it's semi removable but you'll never get the heater cartridge out so what you can do is sort of let it dangle and hope that's enough to get in and clean everything out. So, to sum up. The nozzle clogs, doesn't play nice with PLA, isn't replaceable, isn't easily cleanable, and the drive mechanism likes to grind up material to send up the bowden tube for later. Of course, you can't get to that to clean it out between filament changes. I've posted about these problems here before and had lots of suggestions, which I've implemented with no improvement machine operation. In the end, I have a fantastically assembled XYZ axis* with a barely functional extruder and I'm getting royally annoyed. Leon (who had intended to buy two more for my company's other offices but not any more) *Fantastically assembled in that the gantry was mis-assembled from the factory and I had to adjust one of the pulleys so the rod was in the hole and then realign the gantry to be square. It is now fantastic...

I've been playing with 3D printing for about 1.5 years now. Four different printers. I've only ever had to go for a full disassembly cleaning once. I don't count the trials I had figuring out the UM2 issues as it was never actually a clogged nozzle. My current belief is that my problems have been 99% because of ABS clinging to the walls of the nozzle a little longer than expected. When running PLA, the temps are not high enough to get this residue off the nozzle walls but it does seem to handle the flakes of ABS coming up the bowden tube. FWIW, it should be an *exceedingly* rare case where you should need to go full disassembly and then it was probably because of cheap filament with metal shavings or running PLA way too hot and causing it to crystallize.

I'm back for a status update. I didn't expect this problem since I swap between ABS and PLA on my home printer all the time. As a result, it never occurred to me that it could be material remaining in the nozzle that was my primary problem. My clue came when I noticed that t-glas print on my home printer had a dark shading on the bottom half due to residual black ABS in the nozzle. Since that discovery, I just let the PLA feed through the nozzle for about a minute after ABS to PLA material change on my UM2 and I haven't had clogging issues since.

Looking at the print I'm doing today, I swapped white ABS for silver PLA. There are white ABS flakes in the bowden tube, presumably from being ground off by the drive wheel and no black flakes. This indicates that my problem is not the plastic cold end housing but, instead, the drive wheel.

OK, I'm bringing this topic back from the dead. Shortly after @gr5 posted about Geeks' design, the heat bed suffered a failure on the thermister and had to be replaced. FWIW, the connector would go to open connection with moderate pressure. When the new bed came in, I finished printing Geek's design and installed it but PLA still frequently clogs. As a result, I inspected the original cold end and the amount of material wearing off of the inside is not enough to produce the material I was seeing. My current working theory is that the ABS doesn't flush completely from the nozzle when switching to PLA. I have a lot more investigation to do and I'll keep everyone updated when I figure it out.

@gr5, I wasn't aware of that. I've been following the old internet tradition of whining on the board to get people to help me with my problem. Fortunately, you are all way too nice and have been helping me out.

I confirmed it. There's little black specks of plastic traveling up the bowden tube. I've relocated the roll to the floor but I'm still seeing a small amount of the debris. I don't yet know whether it's leftover or new so It looks like I'll be disassembling the feed mechanism this afternoon.

I hadn't considered that. I'll take a look!

When I mentioned earlier about black stuff coming out of the nozzle, this is a good example. I was printing this guy at fast/low/ABS default settings and he printed for a large portion of the print before starting to spit garbage out of the nozzle and then it was clean again for awhile beofre doing it again near the end of the print.

I'm printing in an office environment so there is minimal dust. The UM ABS I'm using can be manually pushed through pretty easily at 240. I will, however, make an SOP to flush the ABS at 260 and see if that helps.