eldrick

"Bear in mind, however, that one of the purposes of the skirt is to provide a chance for the head to finish priming, so I don't see it as necessarily a problem if it's patchy at the start. Also, I would avoid priming the head manually - or at least increase the retraction distance to about 20mm, since that's what the printer is going to undo when it starts." It was a trail of disconnected dots throughout 14" of skirt and on into the first 12" of the print. Priming and retracting 8mm worked out just about perfect in this print. I'd rather have a glob under the Home position instead of no extrusion and an aborted print...

Re. Illuminarti firmware: I finished a print on a newly-cleaned-out nozzle. It sat for a few hours. When I started the next print, I did not prime the nozzle at all. When the print started, no visible priming took place, and it just left a sparse trail of tiny dots on the build plate. I Aborted it, and primed the nozzle until it extruded, then retracted 8mm. The result was a clean print with no glob when the head raised. Whatever priming took place after the 8mm or retraction only left a trace a half-inch long before the skirt started. No apparent grinding.

I, too, got a replacement thermistor and replaced the one with the broken wire. While in there, I cleaned out the nozzle with acetone and fab'ed a small deflector to improve the hot-end cool-side cooling by directing all of the fan output to the left extruder. And it's printing like a new machine again - 50% faster, 10 degrees cooler, with zero skips so far. Thanks for the help everyone.

Half of the 25mm fan output is useless on a single-extruder UM2, so while I had the hot-end apart to replace the temp. sensor, I made a small piece of sheet-metal to deflect the second-extruder airflow toward the left-side single extruder. The two left-most and right-most slots of the vertical piece are not in front of the fan, so blocking them is irrelevant. I used the second slot from the right. I just cut a small rectangular piece of sheet aluminum and sanded it down to slide-fit into the second slot at the right end of the vertical piece that holds the top and bottom plate together. It's about an inch by a half-inch. See images below. It is wedged in place by the screws that hold the top/vertical/bottom pieces together, which intrude into the second slot from the right. After inserting and tightening the top and bottom screws, I bent it toward the left, where it directs most of the output from the right half of the fan toward the bowden stop - it does a better job of cooling the teflon block and the cold filament inside.

Roberts extruder is a delight. Being able to disengage the filament allows for much easier filament changes, and there is no chance of clogging due to ground-up pieces of the extruder getting in the Bowden tube. I printed mine in while PLA to match the appearance of the printer and to be able to more easily see ground-up plastic when it happens. BTW, cleaning it is just a matter of blowing a bit or air or using a dustbuster if you want to contain the mess. I got also about 25% faster more-reliable extrusion vs. the stock extruder.

"what is the component value of ultimaker main board" Around $20 wholesale for quantity 100. 6^)

Has anyone drilled out the nozzle on a UM2 to .5mm, or is a larger optional nozzle available somehow? This would certainly reduce clogging, and offer faster printing as well.

I've been contemplating dual-extruders, but not for multi-color prints with poor quality, or for supports, but as an Alternate extruder: - I'd like to be able to switch nozzle sizes for speed vs. precision, perhaps .35mm on one, and a .5 or even .7mm nozzle on the other, - Reserve one nozzle for ABS and the other for PLA, to avoid the inevitable clogging that seems to go with switching materials on the UM2. If intermixed extrusion was not required, perhaps the cost could be lower if only a single extruder/motor were used, with a method to easily switch Bowden tubes to change from one material or nozzle to the other.

Still thinking about this... "So the cooling of the white teflon part is instead cooled by the 3rd fan on the UM2." So if it gets more cooling, no harm, right? I'm already using one of the alternate fan housings from Youmagine, which does a better job of avoiding cooling the tip, and actually seems to let me print with lower fan speed. With a deflector to put more of the fan output onto the teflon piece, I'd also block the second extruder hole, which could be contributing to cooling the nozzle if the stock metal shroud was used. Hmmm - perhaps I should use a thick piece of alu as a deflector, to let it help cool the alu bottom plate...

While you're in there, you might want to force tagging and suggest tags from a context-based list. The issue is that tagging is very inconsistent, and search does not seem to search the descriptions: as example, there are a lot of UM2 parts in there that cannot be found by searching for anything likely. Another approach would be to have someone curate and expand the tags and add search keywords.

Mine gave the Temperature Sensor error while printing, and now it won't print - heats up and shows the temp in pronterface, but stops with the error in seconds when I start printing. The issue is pretty obvious on inspection - the wire was hitting the motor behind it when in Home position, repeated flexing kinked and finally broke a wire at the brass block, and now it's intermittent. I've opened a trouble ticket, but I'm wondering how soon can I expect a response and a replacement (I've got product orders waiting on this machine)? Does UM have any US support or parts stock in the US yet?

After weeks of slowly-worsening under-extrusion with PLA, the machine threw a temp sensor error last night, and now won't print for more than a minute or two before halting. Oh well, it gave me a chance to open up the print head and clean out the nozzle. While I had it open, I shortened the Bowden tube by a couple of mm, and noticed that the teflon tube is not completely square to the metal heat sink. I don't know if a slight angle would make a difference in extrusion, but it seems like it could. So anyway, I heated up the nozzle while it was hanging there, and stuck a needle in from the intake side. Stirred it around for a bit, and pulled out a lot of black fragments that a half-dozen nuclear treatments had not extracted. I poked the needle all the way thru the nozzle until I could see the tip, then after reassembly, ran the nuclear treatment another 4-5 times, and still got black chunks out of it. This is pretty annoying, after I had been printing white PLA for a couple of weeks. Bottom line is that I think I addressed the under-extrusion (which pretty much had to be caused by chunks of the poorly-designed extruder getting in there) but now the machine won't print due to the temp. sensor. Sigh...

In the U.S., Makershed.com has the UM2 back in stock again for immediate shipment.

This brings up an interesting idea. Try removing ABS clogs by simply lowering the nozzle tip into some acetone for a while?

After seeing extruder skips of both kinds on my UM2, I set the extruder current higher with M907 E1500 and (I hate to jinx it by mentioning it) skips are greatly reduced. I'm now printing faster and several degrees cooler, with no skips in the last 20 minutes (wouldn't have happened before the change). Watching the edge of solid fill as it is printed, it seems to be better controlled, too - a straighter edge. We'll see if that shows up in print quality - I'm hopeful. Perhaps a batch of motors came through that were at the low end of the performance spec, and that is exacerbating the problems from the poor design of the extruder?

ABS does not cook in the nozzle - it's PLA that breaks down and turns to brownish stuff like crystalized sugar if you leave it in a hot nozzle. That said, when I change from ABS to PLA, in the future, I will definitely use the nuclear option to get as much ABS as possible out of the nozzle. BTW, is there any long-term risk in doing the nuclear cleaning? I've had to do this repeatedly to get clean extrusion without slowdowns.

While trying to locate the source of extruder skipping that happens often when printing light infill at speeds of 40mm/s or higher, I stuck an Allen wrench in the hole on top of the extruder to check the pressure. The screw was basically loose in the hole, so I tightened it a turn or two until it took up slack and another turn beyond that. The white indicator is now just past the first mark of four on the extruder, which seemed to reduce the number of extruder skips slightly. What should it be set at?

I see this on mine, too.

If it gives off nasty fumes, 260C is too hot.

I took the Ultimaker 2 Bowden Clip from Youmagine and scaled it taller in Z in Cura. I made several horseshoe clips ranging from 2.0 to 3.0 times taller and tried them out under the Bowden holder until I found one that just fit. It had the intended effect - the bowden tube now stands straight up at the head, so the filament has a lower-friction path at entry. With that and another one under the bowden clip on the extruder, blobbing is a thing of the past - it's back to new performance, aside from major underextrusion.

I notice that the bowden holder now sticks up at an angle to the head, and I'm thinking that a stretched-taller horseshoe clip could straighten out the filament entry into the head.

I did the procedure you describe and it cured the blobbing, but the white bowden holder now sticks up above the head by maybe 3mm. Next time it needs adjustment, should I cut off a few mm of the bowden tube to avoid this?

I've been seeing increasing blobbing on retractions with my UM2, and I'm wondering if it is caused by visible slack in the Bowden tube. There is now about 1mm or so of space visible between the Bowden tube end and the clip at each end of the tube. When a retraction happens, you can see the tube pull up that slack as it takes back 4.5mm of filament. If this is a probable cause, could a thicker clip take up the slack and reduce the blobbing and stringing that seems to be increasing? I'm thinking of remixing the bowden clip from Youmagine and scaling it to make it taller/thicker, in order to take up the slack. Thoughts?

PLA works nicely on a 65C bed, which keeps the plastic soft, but I usually drop the temp to 55 after the first layer or two to make it a bit firmer. For small pieces such as those, you can probably print them on a room-temp glass bed.