dgsharp

I get these lumps and hairs all the time when I pull out my filament to change it, and I know I've seen other posts about this (people disassembling their hot-ends to remove them and such). I always just let them run through the extruder and it hasn't been an issue. I occasionally have to "move material" to retract and re-extrude a few times when it doesn't seem to prime properly, but then everything is good. I suspect my bowden may not be seated as well as it used to be before I disassembled it a few times (nasty clog issue a while back), as I seem to see the retraction more visibly than before. If the bowden weren't seated very well it might invite filament lumps to get caught there...

I printed up a part today using shiny black PLA, printed at 50 micron layer height, and 20 mm/s. It came out great, but it really highlights some interesting artifacts I was curious about. I've seen them before, but never quite so strongly, and I always assumed they were something else: there are concentric rings emanating from all 4 sides of a spherical section of the model. I measured the diameter of the sphere and the diameter of the first concentric ring on one of the sides, and worked out that the effective X/Y resolution is around 47.8 um -- suspiciously close to 50. I was just curious what this is caused by. Here are some hypotheses: - The stepper motor and driver's own inherent effective mechanical resolution. The website says the X/Y "precision" is 12.5um, but presumably that is microsteps, and maybe it just doesn't end up actually mechanically achieving the intermediate microsteps. This would imply a loss of a nice clean 4x the precision. - Stepper controller firmware. Maybe everything in the system can handle down to 12.5 microns except there's some little bug in the firmware that doesn't do the microstepping as expected? - Cura. I sliced it at 50 micron layer height. Maybe Cura imposed this limit? I looked at the G-code in this section and all the moves are on the order of 1mm, far larger than this limit I'm seeing. The smallest movement commanded on an individual axis appears to be around 30 microns in this slice [uPDATE: smallest X or Y move in this slice is exactly 10 microns, so Cura is not the culprit]. The part in question, exhibiting the concentric rings implying an X/Y resolution limit of 50 microns: The part as seen in Cura. Triangles in this section are all visually identical, no signs of concentric artifacts: The G-code from one of the slices near the center of the circle, plotted as X/Y positions (to verify that we're roughly looking at what we expect to be), and the distance between adjacent move locations (all in the ballpark of 1mm): Anyone know anything about this? Any other theories? I wouldn't call this a gripe, I'm just exploring and trying to understand what I see. Although if there is anything we can do to up our effective X/Y resolution even higher, I'm all ears! Thanks! [uPDATE: I think I missed the first concentric ring as it's not readily visible, making my estimates for X/Y resolution look worse, perhaps due to just a touch of backlash. I gathered more data and re-calculated in such a way that knowledge of the first concentric ring (whether or not it exists, let alone how small it may or may not be) is irrelevant, and the X/Y resolution is actually more like 26.5 um -- presumably 25 um. So it still appears that we are losing 2x the precision somewhere along the line.] -Dave

Has anyone bought from printbl.com in the last few months? I am wondering if they are still in business. They show items in stock, but I emailed them about a week ago and have heard nothing back, the most recent blog entry is from almost a year ago and the most recent Twitter and Facebook updates are from 2012. Everything I find online about them is people saying how much they love the Diamond Age filament, but it seems doubtful that they're still around. I'm giving ProtoParadigm a try but I am curious to hear if anyone knows anything. I'd order from Diamond Age directly but the shipping costs more than the filament! -Dave

Here's the response: The unlocking part is a relic from the past - in the beginning we only accepted orders in cities with at least 10 printers, now that we've grown and added different currencies and local support we do accept orders globally - we're updating the wording on the website next week. Sounds like we shouldn't worry about unlocking as it will be disappearing shortly. Cool.

That's what I thought too. Here's a quote from part of an email exchange with Brian, one of the co-founders of 3DHubs. I said: I'm a little confused, I understand that Orlando isn't "unlocked" but it appears I am able to at least get to the screen where I can send job requests to my hub. Does that mean that when I click "Send request to Hub" it just won't let me do it, or is it actually possible for people to send jobs to a hub in a city that is still locked? Brian replied: You can indeed order in any community today, we're just about to unlock those cities. So I'm still confused about what it means to be "unlocked". Orlando has only 2 hubs (including mine). <scratches head> I just emailed Brian back asking for some clarification. -Dave

I'm in the same boat with Orlando, Florida (USA). Oddly it seems that people can still send jobs to the different 3D hubs even if those hubs aren't in an "unlocked" city. I hadn't realized that until I tried it yesterday, and I'm not entirely sure what it must mean to be "unlocked" if you can still use those hubs. I don't have a lot of need for parties and such, so maybe it doesn't matter so much.

Hm, I think you're right. I measured in a few more spots and found one that's 3.01 (measured in 2 axes). <Grumble grumble> Maybe I need to find another US filament supplier..

Hm, maybe I spoke too soon.. I printed up a couple of UM robots and things seemed fine, and then I started getting lots of under-extrusion again, and hearing the filament transport stepper skip steps. On a whim I decided to try measuring this current filament diameter. It came from Makershed so presumably it's not junk, but the diameter came out at 2.97mm. I dialed that into my UM2 (the first time I've ever changed the diameter setting, as previous spools were very close to the default 2.85 mm) and am printing another robot now and have not yet heard another extruder stepper skip. Does that make sense to anyone? So previously it thought the filament cross sectional area was about 8% lower than it really was. I'd love for this to be the current culprit because it's an easy fix, but let me know if you think this seems reasonable or if you think I still have some kind of issue to track down.

Nice work! I opened it up and blew it out and a chunk of semi-burnt blue filament fell out. My best guess is it came off at some point between filament changes or something, and jammed things up a bit in there. I was able to print out another UM robot using the same exact settings and it looks great, and I didn't hear any filament slips. Thanks! Following is a picture of the inside of my extruder, although I think it should look fairly ordinary now that the little ball of evil fell out. Taking it apart and putting it back together wasn't as bad as I had feared.

I've been having more slipping of the extruder motor lately. I cleared a nasty clog yesterday that may have been building up and perhaps explains some of it, but I think I got it pretty cleaned out. Now I'm still getting some slipping while printing the stock UM robot (using the G-code that shipped with the machine). I've printed it fine in PLA, ABS, and nylon in the past, and now my PLA one using all stock settings is very under-extruded. I can't figure out if it's still some type of blockage, or some problem with my extruder, or both. I have noticed that it is easier than it used to be to manually push filament into the machine when the extruder stepper isn't energized. It used to be incredibly hard to push a fresh piece of filament into the extruder, and the last day or two I've been able to just push it in as far as I want by hand, backdriving the stepper with relative ease. Both of the little white indicators are in the uppermost position. Looking through some posts I saw the picture showing the vertical screw nestled inside the top of the extruder assembly. I tried tightening it and found that it had become completely loose, it was several turns before I felt any kind of load at all. How tight should this be? Does anyone have any ideas? My prints are all under-extruding now. I thought for sure the robot would print fine.

I'm in the middle of a long print so I can't verify this on the machine, but I rebooted and started fresh and it looks like the G-code does now have references to TweakAtZ in it. I didn't realize that the plugin doesn't actually change the feed rate parameter directly ("G1 F*"), rather it invokes another M-code (M220 IIRC, new one on me) to adjust it indirectly. So it's very likely that the combination of this misunderstanding, and my prior overlooking of the minimum layer time clamping the feed rate, is responsible, and everything is working as it was designed. I'll verify this when I get a chance, but I believe things are probably working fine. Thanks everyone for putting up with my noobishness again!

I tried changing speeds at 5mm, but I've also tried a number of them in a row (like 5mm, 10mm, 20mm) in the same print, and changing other settings like extruder temperature. I actually didn't notice that the speed was in percent, so I had put 13%. That ought to come out to 5.2mm/s though, which should still work fine, right? I tried other numbers as well, higher and lower, and the G1 feed rate doesn't change from the 2400 mm/m (40 mm/s). I've closed and re-opened and even rebooted the machine with no improvement. Hopefully I can figure out a workaround, this would be a handy feature.

Very odd. I downloaded the plugin from that link just now, installed it in the proper directory (moving the existing one elsewhere so it wouldn't be found), and tried it, and it still isn't working. I downloaded Cura 13.12 (I had been running 14.01), still nothing. I've made sure to select RepRap G-code generation in the Machine Settings. Not sure what I'm missing or if this is just a bug. I'm just asking it to lower the speed at 5mm from 40 mm/s to 13 mm/s (something I can easily search for manually), but it stays at 40mm/s the whole time. Kind of a bummer, TweakAtZ and PauseAtZ both seem really useful to me but it appears that neither works on my system for some reason. Edit: Mac OS X 10.9.1

Thanks! That's one thing I overlooked -- I disabled Brim and it works fine now. Bingo! I recall I ran into this before (it was a head-scratcher that time too) but somehow forgot about it. Hopefully two times is the charm. Here's a question: how come when I print a spiralized piece (the cylinders in question) with a single shell it has starts and stops running up the side? I expected to see a single continuous extrusion but it has clear starts and stops running up the side on all of my cylinders. Hopefully for non-spiralized parts we will one day get a feature like some other slicers have to at least scatter these starts/stops around so they don't draw as much attention and reduce strength in that region on thin parts. (I tried getting KISSlicer working and it promptly resulted in a head crash! Think I'll wait a while to try that again..) Thanks gr5!

When I was taking things apart I noticed that the machine uses the same sort of nut traps-in-sheet-material as on the OG Ultimaker, Cupcake, etc. This design coupled with the type of material seems like it is prone to compressing somewhat over time. I suspect that even if all the screws had originally been installed in the outer case with threadlocker and a torque driver, they would still loosen up somewhat due to the material compression. Granted, they wouldn't fall out, but they wouldn't be tight and the rigidity of the machine would be compromised regardless. Of course, this wouldn't explain what some have reported seeing on their pulleys.

I'm trying to understand how the speeds work on my UM2 with Cura. I often notice the head moving much slower than the speed that I specify. I created a cylinder (100mm circumference for easy eyeball timing) and set it to print with a single spiralized wall, at 100 mm/s speed. The generated g-code showed no G1 moves faster than 19 mm/s, and eyeball measurements confirm this is what the machine performs. I took the same cylinder and disabled "Spiralize", kept no infill, 0.4mm shell thickness, and it was the same, the highest feed rate it seemed to output was 19 mm/s. I then found that if I added any infill (like 5%), my outputted g-code would be full of F6000s (100 mm/s), exactly what I requested. So it appears that somehow the act of enabling infill makes it go the proper speed, but printing without infill forces it to go slower (in this case about 5x slower). Is that a bug? What am I missing? Why am I asking for 100 mm/s and getting 19 if there is no infill? I'd like to have some understanding so I can better judge what to expect. I was printing a bunch of parts at different speeds using Spiralize to save time and couldn't understand why the parts were printing so much slower than I was asking them to (and thus making my speed / surface finish observations meaningless for use on parts with infill). Can anyone shed some light on the matter? While we're talking about weird quirks, what is limiting the size of object I can print? In Machine Settings it says the max dimension is 230x225, but I have a large object that has a few mm surrounding it on all sides including near the clips' keep-out zones and it always shows up gray on the screen. I can't see any gray outlines from the part intersecting anything. -Dave

Does the TweakAtZ plugin work on UM2 for anyone? I've got the latest version (3.0.1) and switched to RepRap GCode generation, but when I scroll through the output GCode the feed never seems to change. Am I missing something?

I'm certainly not an expert but can you verify that on the Advanced tab under Quality / "Cut off object bottom" that the number in the box is 0? If it's a larger number than 0 then it will trim off that much from your model (useful when your model doesn't have a flat enough bottom surface to secure it to the build platform). Sorry if you looked at this already. The only other thing I can think of is if the model were slightly canted relative to the platform -- if it were tipped up at a fraction of a degree, Cura will place it so that the lowest area (which could be a single edge or point) is touching the build platform and the rest is floating. Try enabling brim and looking at the slices for the bottom, and if it doesn't draw a brim around the whole model then this could be it. I saw this yesterday with a model someone sent me that was tilted up ever so slightly on one side. I was able to use the "Lay flat" command, it took a few seconds to process but it did the trick. Good luck! -Dave

Ah, thanks for the heads-up illuminarti. I didn't see any difference on the website but I re-downloaded it and checked the executable and the new one has a creation date about 24 hours newer than what I'm running. I will give that a try as soon as my machine is done printing.

I recently upgraded to Cura 14.01 and installed the associated new firmware on my UM2. Since then I have had issues with the "Move material" command. I have used it many times in the past, but now it appears that when I try to use it (often after a filament change to help purge the last material, for instance) I have perhaps a 50% (maybe even less) chance that it simply doesn't do anything. I select "Move material", wait for the head to heat up to temperature, and spin the wheel, and there is no audible sound that usually tells me that the stepper is at least trying to extrude. Just nothing. I fix it by power cycling the machine and trying it again, which usually (though not always) seems to fix it. Has anyone else seen this? -Dave

Thanks for your comments. I was going to post something about aborting print resulting in too much retraction, but I see you beat me to that! Some updates: - After printing a bunch of things relatively successfully, all of a sudden anything I would print would lift up after a couple of millimeters. I tried cleaning the bed, adding glue stick, etc. I read over the manual again and it said to try re-leveling the bed, and that seems to have done the trick. Woo! How frequently would you say you have to re-level your bed? Maybe I was pushing too hard when removing some of my earlier prints. - I think I'll need a combination of more appropriate print settings (and the experience to come up with them), and also some built-in support structures on my models. For some of my parts (like a 3-bladed propeller) I think I'd do better if I just built some supports into the model, designed to be cut away with a hobby knife. I look forward to the day when I can take supports almost for granted like I used to on my Dimension machine. This is a great machine for the price though. - Lots of my parts seem to come out with the first couple of mm slightly shrunken compared to the higher layers (PLA, 0.1mm layer heights, 2mm shell thickness). My current theory is that this is a combination of large wall thickness, thin parts (perhaps 2-4 mm width), and the heated bed. I think I'll try printing on blue tape without the heated bed to see if that helps at all. Or maybe starting the fan earlier. Any other ideas? Printing objects using the "quick print" options doesn't result in this issue, but the walls are of course thinner. - The LED strips on the inside of the machine started to separate from the enclosure towards the top. No biggie, I just pressed them back down. - Now for a bigger issue: I went to print something this morning, and upon clicking the button to initiate a print, the machine started rumbling violently during the homing process. It appears that something has happened to the X axis limit switch (the axis with the linear rail in the back of the machine and the limit switch all the way at the back of the machine). It appears that said limit switch no longer works, presumably after some sort of crash or something resulting in a bent lever (image attached). I tried bending it back briefly and it didn't help. I think I can probably get it working right but there is also a decent chance that the metal snaps after a couple of re-bending attempts. For now I got it printing by carefully waiting with a paint scraper on the limit switch and hitting it when it tried to home (and waiting with my finger on the power switch for when it's done printing), but that's obviously not something I want to do much more of. (I just submitted a ticket about this one just now.)

I just got my UM2 (Yay Christmas!). I'm fairly new to the hobby/DIY 3D printing community, I've been around it at hackerspaces and even designed the "Hive76 Milled Bolt" for RepRap extruders, but haven't had a machine of my own until now. Until very recently I ran a Stratasys Dimension FDM machine at work for about the last 6-7 years, and I have parts made on pro SLS / PolyJet / FDM machines for work with some regularity. Hopefully my comments will be of some benefit to newbies, and maybe also help with the future documentation. My apologies for such a long message. Here goes: - There were 2 button head screws loose in the bottom of the box. It's not immediately obvious to me where they go. (They don't look like they go to the extruder.) So far the machine seems to be ok without them, so we'll see! - There didn't appear to be any documentation about cutting the zip ties that were holding the X/Y stages during shipping. Not a big deal, but in trying to follow all the directions to the T, I saw no mention of it. - The "getting started" documentation didn't seem to mention attaching the glass plate. Not super tricky, but a quick note in the unpacking docs would have been nice. - I've got 3 materials, the PLA that came with the machine, some ABS from Makershed, and some Taulman 3D nylon 645. I found that the UM robot model prints fine for me in PLA with no glue stick, but I needed the glue stick for ABS. For the nylon, I used 245C for the hot end with a cold build plate covered in 3M blue painter's tape ("Multi Surface! With EdgeLock!"). The ABS and nylon both have one or two small charred areas but are pretty decent, not much worse than I'd get with white ABS on the Dimension. A little stringy between the two knobs on the tops of the head and a little saggy in the rear-end (in all 3 materials), but overall pretty good. - I was surprised at how well the PLA seems to stick to the raw glass when the glass is at all warm. I had done several prints and it wasn't until I let it get way down to room temperature that the parts came off the bed with minimal force. I even broke one part removing it after the machine had reported the print was done and the bed was cooled. A razor blade or sharp paint scraper helps if you're impatient like me. - PLA smells worse than I expected. I've been around DIY machines printing PLA and never noticed any smell at all. I don't know if I was just distracted, or the ventilation in those spaces was better, or if this machine smells more than the others I've seen. I switched to ABS and while it is arguably more objectionable of a smell from close up, for me it's not that much worse, just different and more plastic-y. I needed to run a ceiling fan for an hour or two after a 2-hour print to get the room smelling normal again after PLA. I don't mind the smell but I don't want to bug my family so I'll have to be creative. The nylon seems to have no smell of its own, but the printer still smells like PLA (I assume it's PLA). In general changing material is fairly painless and quick. - I printed a test cube and it came out about 0.015" too tall (0.381 mm -- I believe in metric but most of my experience is with imperial, sorry!), and about 0.010" (0.254 mm) too small in the X/Y dimensions with PLA. - I measured the diameter of my UM-supplied PLA with a micrometer and found the average to be about 2.852mm or so. There was a lot of variability but mostly just out-of-round, so that's presumably fine. Pretty close to the specs. - Bed leveling: it would be nice if these machines could include a limit switch and automatically do the bed leveling the way the Stratasys Dimension machines do. You just plop a build plate in it, and it checks the build plate in 4 places before every print so you never have to think about it. Might require some redesign and a larger machine, I suppose. Anyway, something to think about for the future. - Customizing material presets on the machine: this seems incomplete or at least undocumented. If you just want to jump between the stock settings for PLA or ABS it works great, but I don't understand the customization interface. Through trial and error I have set up a new preset called "CUSTOM1", which I can't see any way to rename. The UM2 manual has no mention of these presets at all as far as I can tell. Several times while trying to change the values of my new custom preset I have inadvertently changed the values of the stock ABS and PLA settings, and I don't understand why. Is there some way to interface to this stuff from within Cura and send it to the machine over USB or something? I couldn't figure it out. - I created a 1cm cube, and to test out Cura's support structures I put it at a 45 degree angle. No support structure was created despite having it enabled in software, I guess because of the angle, so it air-printed spaghetti. I tilted it further and it generated support material under one side that did a reasonable job of supporting it and it turned out reasonably. - While switching material the extruder's stepper motor apparently loses steps when the material goes into the hot end, resulting in a periodic "click....click...click" sound. Seems ok during printing, I'm hoping this isn't anything to worry about. I have seen some posts mentioning that the extruder/hot end doesn't quite have the oomph of the previous one. How do I think the UM2 compares to my old Dimension machine? The Dimension could only do ABS. It had no smell whatsoever (even if you aborted a print and stuck your head right inside the machine -- nothing), but could only do ABS. I actually find that I like PLA, it's much more rigid than ABS, which can be useful. Nylon is extremely flimsy for thin-walled items but its toughness is awesome and the bonds between layers are impressive. The UM2 can do much finer layer thicknesses (the Dimension's thinnest was 0.010" / 254 microns), which I'm hoping will help me print more void-free thin parts like the trailing edges of prototype prop blades. The Dimension machine will almost never give you a bad print, it just works every time (due to the breakaway support material), but having this machine in my own home is tough to beat. The Dimension machine also cost about 8x as much at the time. All in all I'm very impressed with this machine. I have some experimentation to do but overall it seems very capable. Thanks for putting all your hard work into it, and keep up the great work!