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I definitely see quite a few lower layers compress as it prints upper layers. On the left side only. But I'm not convinced this is the *cause*. It might be the effect. I like Illuminarti's theory also. I'll call it the "surface tension mound" theory where surface tension on the plastic pulls it back inward and makes a pregnant ridge belly stick upwards.

I understand his point completely. If jerk is 20mm and your print speed is 30mm/sec there is almost no acceleration. It *starts* out at I believe half the jerk speed (not sure why not at the jerk speed) for the very first line segment and accelerates up to 30mm/sec. So a 20mm jerk is pretty high (lenient) compared to a 30mm/sec printing speed. Joe I think you'd like these photographs (with words) that tell a lot about certain aspects of 3d printing - easy reading since it's mostly all pictures: http://umforum.ultimaker.com/index.php?/topic/1872-some-calibration-photographs/ There's some printing in the purple cubes at 200mm/sec. But quality isn't going to be quite there if you want something that is a piece of art. But for functional stuff that can be ugly, 200mm/sec is reasonable as long as you keep the temperature high.

Illuminati - your z seam gets more pronounced as you move up to higher speeds. Any idea why? I guess with higher speeds you have higher nozzle pressures and you get more leaking during the Z movement? Well hell that is nice 100mm/sec at .25mm layers! I'm going to try that baby! Maybe at a few different temps.

Oh and to make the story more exciting - the build plate was at 70C during the print and it keeps shutting off the heater while I'm cleaning the nozzle and I'm scared that if the temp hits 40C or cooler my print will "pop" off the glass so I was kind of rushing (calmly) to get this working and I keep "fixing" it but not sure how I do it and I took the bottom cover off twice before I figured about the relay with the temp going back up to 60C then down to 40C then up to 60C then down to 35C... I learned a lot about the print head and how amazingly easy it is to service. It helped that I read everyone else's notes about it over the last few months.

The problem just started after having the printer for a few months. It was a little frustrating because I coincidentally had my first clog which I was able to clean out and fix and continue the print but in my video above there was a print sitting on the glass waiting to continue after 8 hours of successful printing with 20 hours to go... So I am diagnosing with the printer on the side and the print hanging sideways off the glass and I'm hoping the glass doesn't slip a millimiter in X or Y while it's on it's side and I"m careful not to bump the print. But it all worked out fine and I continued the print flawlessly I have 3 things I want to do with my UM2 as soon as I have some free time. One of them will be to remove the board from the bottom and look at the voltage on K1 coil at power up to see if the problem is K1 or the circuitry driving it. Actually I can probably probe from the bottom side. I also want to do some "overhang" tests and some "printing speed" tests. The printer has me trained - whenever I turn it on I just rap the board, lol. This is one of those cases where the printer is the boss and has me trained.

>returns after a very short time Is 5 minutes getting to the next layer the "short time" or is it the 4 second short time from when it does the inner pass to the outer pass? I think you keep thinking of your very tiny supports yet this happens on larger 30mm square supports as well. >picking up liquified parts by cohesion Hmm. So here's my latest theory which I will call "nozzle cohesion". I hypothesize that the PLA sticks a bit to the flat area of the nozzle tip. As the trailing edge of the nozzle goes by it lifts slightly on the PLA. When the other end (the bottom) of this PLA bead is touching solid PLA the cohesion to the surface print is strong enough to hold it down. When the bottom of the PLA is over thin air, the nozzle lifts this bead up at the trailing edge (slightly - maybe 1/3 of a layer height). Resulting in a lifted edge. I think your video would be more interesting if your cylindrical piece alternated between vertical and tilted segments so we could see the problem repair itself and then start anew on the next layer that is hanging partly over air. I love the quality of your video by the way- the only problem I have with it is that the problem is well under way. I want to see how it gets started. If my latest "nozzle cohesion" hypothesis is correct, the problem might be mitigated by thicker layers. Or less sticky PLA (different formulations) or different nozzle tip shapes. Or different XY speeds. Or different temperatures (high temp might make it flow more and gravity might help more here - low temps might make it stick faster to the existing solid pla).

Not sure this is relevant. In my first posting above, in the picture you can see that is only one leg of 4 plus other support structures so layer time is quite a bit over 5s, . But still you may have something as there are 2 or 3 passes of outer rim and the outermost pass is the last pass.

VERY cool concept - and that would speed up printing. But I don't think it's relevant here.

1) I'm pretty sure this has nothing to do with the "pause" effect of retraction because if you look at my first picture it happens on a part 30mm square. You could prove this by turning off retraction - you will still get this affect (and stringing also of course). 2) In the video, with the "lip" already there I can see that it prints in the "bowl" of the lip and then pushes the plastic around like a soup and some of it is pushed up the edge of the lip of the bowl to form more of a lip. BUT how does it get started on this lip in the first place? And why only on the overhang edge? 3) On both your part and my part there were at least 2 passes of the outer edge - I believe it does the inner pass and then the outer pass last, right? Could it be something to do with that inner pass? 4) On my part there were typically 2 MINUTES between when the print head comes back to make the next layer. So the part had long cooled to ambient air temp. This is probably not useful information versus all the above theories. 5) THANKS for looking into this and putting out your theories!

It's not "Merlin the Magician", it's "Marlin the swift fish". A Marlin can change it's direction seemingly effortlessly with a tiny flick of it's tail. The E (Extruder) position is the position along the filament of amount used so far. So if the final E value of the final move is 1.000 then your print used 1 meter of 2.85mm filament. After Cura calculates the X Y positions for the next line segment it (usually) calculates the amount of filament needed for that line segment by simply assuming a box shape line with height at layer height and width at nozzle width. However there are exceptions. For example you can print a .5mm wide line with a .4mm nozzle by "overextruding" by 25%. Cura takes advantage of this ability when fitting in a line where there is not exactly .4mm of space. I believe Cura will go up to 150% of nozzle width and down to 75% of nozzle width as needed - something like that - not sure exactly. For example if you print with a 1mm shell and .4mm nozzle width the outside path is .4mm and the second pass is .6mm worth of filament.

It's more like a 1956 chevy. Not as reliable as cars today. It may come missing the rearview mirror and a few screws. But it's damn easy to fix and the price is reasonable for what you get. I'm waiting for the day HP starts making millions of 3d printers. Every day. That's when the quality and price will totally blow away what you can get now. Also if you need a new part in that first week you get it, I'm pretty sure UM will ship you a replacement for free (I don't know - hasn't happened to me). Hopefully though you will be in the majority with no problems that can't be fixed after some questions and answers on the forum and a half hour of your time. I suspect you will have MUCH more time spent learning what 3d printers do well and don't do well. How to get your part to stick. How to deal with shrinkage and overhangs and how to get the best support material and the best quality and so on.

I understand your point, but I think some of the discrete stepping will get smoothed out in the rubber belts. I don't know if you are EE, or CS so I don't know the best metaphor but the belts act as a high frequency RC filter smoothing out those steps. Maybe. Or you can think of it as a mass on a spring with friction. But I don't know the mass or the spring constant or the friction values so I don't know where the damping frequency is but I suspect the steps you speak of are damped out.

Welcome by the way. I hope you stick with this printer and keep posting because if you do I can already tell you will be a great addition to the UM community.

So what about "jerk"? If you print for example a square pattern in X,Y. At each 90 degree corner you either have to come to a complete stop (very slow printing) or you get infinite acceleration (in theory only of course) at the corner. That's fine for a square but it gets worse for a circle with say 50 line segments. (a 50-gon). At each vertex you theoretically have infinite acceleration even though in reality you shouldn't have to slow down to speed zero at each vertex. That was when "sprinter" version of firmware came along and introduced a "jerk like" parameter which instead specified the max speed change at a vertex (the magnitude of change regardless of direction). This max speed change is typically 20mm/sec at each vertex. But it means now you have to plan the next 20 moves in advance if you want to be able to print fast but still slow down for sharp corners 20 line segments from now. As you can see it gets complicated. This algorithm hasn't changed much in a few years and Marlin uses the same algorithm as sprinter for planning moves. It makes sense to think of X,Y,Z,E moves as 4 dimensional moves by the way - where you want to travel in a straight line in all 4 dimensions so that the extrusion matches up nicely with the movement. Typical Max for UM1 and UM2 acceleration for X,Y is 5000mm/sec. That works well and is screaming fast (compared to some printers which are at 200mm/sec). There are very very smart people working on the firmware for Marlin right now - ErikZalm was taking care of supervizing it for a while and now it's been mostly Bernhard Kubicec (spelling?) who also designed the ulticontroller. Nether of them work for Ultimaker. There are probably a few dozen contributors in the last year (that's VERY rough guess based on a quick view a month ago) and there are a few commits every week. Mostly very minor, but also very useful features.

You *can* edit the Ulticontroller firmware (Marlin) pretty easily and especially changing the menu systems around is quite easy. Here's my standard blurb on building marlin: First get the source code files here: https://github.com/ErikZalm/Marlin Then edit Configuration.h – this is by far the hardest step and it's not bad. I recommend you go here: http://marlinbuilder.robotfuzz.com/ and use that website only to get the Configuration.h file. Then run winmerge or some other diff program to compare the latest ErikZalm version of Configuration.h to the one from robotfuzz which is usually a few months behind. Edit the ErikZalm version to match the robotfuzz generated version. Make any other edits as necessary. It sound complicated but it is extremely clear and well commented. Sometimes with paragraphs of explanation. configuration.h file detailed explanation: http://airtripper.com/1145/marlin-firmware-v1-basic-configuration-set-up-guide/ Then you need to build Marlin. There are instructions that come with the erik zalm download in the "README.md" text file. Basically you download and install arduino ide: http://arduino.cc/en/main/software Then copy the sanguino software as explained in README file. Open Marlin.ino file in Arduino IDE by double clicking it (not pde file as stated in README - I think that's old). Select board as "Mega 2560" as explained in README file. Go to "file" "preferences" and select "verbose output" so you can find your hex file. Then build it by clicking the check box in the upper left corner. At the bottom you will see it compiling Marlin. At the end of this it says where the hex file is. If you are currently connected to your UM through USB you can just click "file" "upload" and you are done! But you should locate that hex file and save it somewhere along with the Configuration.h file used to create it so you can recreate the same version with maybe one change. Also you can upload the hex file using Cura. Alternatively you can build Marlin with somewhat more detailed step by step instructions the command line way (which I don't prefer): http://www.extrudable.me/2013/05/03/building-marlin-from-scratch/

Could the retraction distance be too much or the speed too high?

I reduced flow to 90% and it didn't help - it made gaps between all the lines but still had a lifted edge. I did this for about 10 layers.

Okay, I ended up pausing that print for 16 hours for a few reasons but it continued nicely. Now about 12 hours into the print I have to disagree with foehnstrum's idea. The supporting structure in this photo is solid as all hell. Even that "lip" is sharp enough to cut a finger on (I didn't though). It is very strong for it's thin edge and the supporting leg in the lower part of that photo is incredibly strong. I don't think there is even .001mm deflection of the leg when the head hits that lip. I mean it's not bending down anymore than say a solid cube would bend down. I think I could pick the printer up by that leg and swing it around the room - it's on there very solidly.

So many questions! Maybe I answer just one? MAINTENANCE, ADVANCED menu, "lower buildplate". I know it goes all the way but should be fine for your needs. MAINTENANCE, ADVANCED "move material" to extrude. It shows you the temp and unfortunately when you leave this menu it sets temp back to 0C for the head. I don't like that myself. In my experience you don't have to do any of this. I can print 2 things in a row with a day or less in between and don't have to prime anymore. I *do* have to grab the priming filament and pull it to the side as it heads to start the print. It is important to use brim *or* Skirt in case the initial prime isn't enough. FEEL THE FORCE, LUKE! Go with it. I know going from UM1, to UM2 feels like you have no control. Just go with it and eventually I think you will like it.

Well - yeah. I prefer .1mm 50mm/sec. You are printing almost double the volume. When it is printing away nice and fast - look at the extruder motor for a full minute or touch it with your finger for a minute and feel if it is slipping back. I mean you *should* be able to do this if your nozzle is perfectly clean and you are at 230C. But if you are at say 210C then this could be the problem - you could be on the verge of printing too fast. Some people can print much faster. You will know if you are printing too fast on the UM2 because the extruder slips suddenly many steps and makes a sound. I plan to make a new test showing how fast you can print on the UM2 at various temps.

Ha! Even that is probably too long. The UM will print on it's side or upside-down. I recommend you at least use some kind of fan and put the UM on it's side for good access to the electronics with a fan.

Oh! This is good to know! I understand it completely now and will be able to help other people if this happens to them. Some of the moves are XY moves only, but some include some Z movement. So it moves the bed down and Z switch cancells so it doesn't move down. Then Z moves back up so nozzle can touch it and moves X,Y simultaneously but the Z switch cancelled the move and now it's in the wrong place.

First load the PLA setting. Then go CUSTOMIZE. Then change the values, then SAVE, then select PLA. This last step, if not done, means your save step didn't complete. You probably need the bleeding edge latest firmware for all this to work. For me it's flaky - if you create more than two custom profiles there is a bug also. I'm not sure how to delete them. But it usually works even without me doing anything with the LED settings.

This is partly solved. When I power on my UM2, lights and software comes on but the head won't home, no extruders move, and no heat comes on. The problem is with K1 - it's not closing. If I give the controller board a hard rap with my finger, the relay closes and the UM2 is fine until the next time I power it up. I will look at K1 more carefully in the future (check solder joints etc.) but right now I am printing something.

I still think you are printing too fast. But also the retraction speed is different in the UM1 I'm sure. What was the retraction speeds for the ulticode method versus the Cura-sets-retraction speed method. It's possible your retraction speed is too fast although I have been using the max - 35mm/sec on every print.