gr5

If the PLA is wider than the inside of the tube, no amount of oil will help. You could try reducing the pressure on the feeder so that PLA stays more round I suppose. Personally I would just throw it away. Or purchase a larger Bowden. A few people have purchased larger Bowden tubes. I don't remember the details.

I think everyone who has a UM2 will have to spend some time unclogging a nozzle some day. Fortunately I haven't had to yet. This means everyone who has a UM2 will hate it - on that day that they get a clogged nozzle. But hopefully that will pass. It's very unfortunate that this happened to you peter on your first day. I watched a UM employee unclog a UM2 head under pressure in about 3 minutes. He kept the nozzle hot and unscrewed the 4 screws and it happened so fast I don't know what happened after that although it involved some metal tools (small screwdriver maybe?) digging out the clog. Personally on my UM Original I removed the nozzle completely and brought it over to a gas stove and burned everything out and used wires to unclog. Daid says every UM2 should possibly ship with an acupuncture needle to clean it out (push the clog back the other way). Some people own a .4mm drill bit that they use to clean it out (while the nozzle is hot). In my experience I would get the nozzle to work for only 10mm of filament and would repeated reclog until finally I got the object out the back - whatever it was just wouldn't fit through the .4mm hole. I used a copper wire strand removed from a power cord - fished it through and pulled out out the other side bringing pla and such out.

You could set it to zero maybe? .5mm of filament at 2.85mm diameter is the equivalent of a 250mm string of filament .1mm high (125mm if .2mm layers). Are you sure you printed more than 250mm since the previous retraction?

Great idea! Please add this as a feature request for Cura gadgetfreak. You can do this here: https://github.com/ErikZalm/Marlin/issues

Drilling PLA is more like melting PLA. The friction causes it to heat so fast you never really get to the cutting state so much as pushing around soft pla with the drill bit. Unless you dip the drill bit in ice water every 3 seconds. If you want to use metal M3 (3mm) threads (the small bolts that come with the UM and UM2) you can set the hole diameter to 3mm and it will print a bit small and the 3mm screw will self tap screw threads nicely. Not as strong as using a metal bolt but pretty decent.

What the hell? Mine is set to 2.5mm I thought that was too little! Really? 4.5? I think I might change mine to that as 2.5mm just doesn't look like enough - the filament is still pushing up on the top of the bowden tube arc.

They are *almost* cut but not quite. I don't think that's the problem. No - look at that big black cable bundle at the top right corner - inside there are 2 gray ribbon cables plus other stuff. Those 2 gray ribbon cables are the problem. I think.

These look like different layer numbers. Can you show the same layer in each photo instead?

That is *much* tighter than my belts. Probably twice the force. Maybe 3X the force (my belts really aren't that tight and I get great results). Although that is about the same as the tension on my UM2. As far as acceleration is concerned I use 5000mm/sec on my UM original. I don't think I set that myself but that's what it's been for many months. At this point I think your hardware is fine. The next thing I would try is raising your print bed so that the first layer lines are squished more. I would go up about .05 to .1mm. Try turning each of the 4 screws counter clockwise by about 1/8 of a turn. Looking at your photo the plastic should be squished more so that it stays where it's supposed to go and doesn't pull inwards to the center of the circles. If the PLA is squished a little flatter into the blue tape and the contact outside is still bad then I would just blame Cura for not compensating well enough on bottom layers and just increase the infill overlap from 25% to 75%. But I have to tell you - the UM can do this. I printed a cell phone case with a UM Original back in August and it came out great. However because of the complicated nature of what I was doing (changing filaments) I was printing .4mm off the bed but Cura thought it was .2mm off the bed and I had flow at 200%: https://www.youmagine.com/designs/galaxy-s4-ballistic-case#!design-comments?data-id=208 Actually in the above photo it was at 150%. I did it again with 200% and it came out better.

Be aware that if you change XY acceleration using ulticontroller (or pronterface) the change is not saved such that when you power cycle the UM it will go back to defaults. There *is* however a save command to save it permanently (M500 maybe?). Also acceleration of 800mm/sec/sec is very rapid (I think 5000 or 8000is the default?) and not much different from the default. Whereas an acceleration of say 30mm/sec/sec is quite noticeable and might be more reasonable for bridging tests. Think about it: at 800mm/sec/sec, within one second the head could be moving 800mm/sec! To get up to 100mm/sec it takes only 1/8 of a second.

printing over USB is fine for quick prints but it is unreliable so don't try anything that will take over an hour because the chances that it will fail are much more likely and the amount of time lost is higher. In other words - expect print jobs over USB to stop part way through once every few hours for no apparent reason. Other than that printing over USB is fine.

Does the fan spin the correct direction? It should be blowing air into the head not sucking air away from it.

As illuminarti mentioned, you have to print about 3X slower than normal (and first layer 6x slower). Do your normally print 150mm/sec with .06 layers? If so then you should be fine. Note that this print will still come out fast as it is basically printing 200% flow (personally I would try something more manageable like .6mm wall).

The Arduino can measure only 10 bits from 0 to 5V so voltages that will stay between 0v and 5v can be measured directly to within 5v/1024 or about 5mv accuracy.

If that was a typo then I have totally different advice...

WTF? That's a typo, right? Seriously? If it really printed 7mm short then something is very very wrong. With heat off place a ruler on your bed. Move the test head to a postiion over the ruler and then move the test head 50mm. It should move 50mm. Not 48. Pronterface is a very useful tool for messing around - moving an axis 10mm at a time or whatever and for examining and changing the steps/mm values.

I'm not a bridging expert. You might know more about this than me. But I thought you might find this interesting: http://umforum.ultimaker.com/index.php?/topic/1872-some-calibration-photographs/?p=25304 Post #17.

I don't know if this helps.

rhyme - I don't think you followed nacho's links. There are different types of laywood and his is designed for smaller nozzles (finer wood particles). Are you sure you got the correct spare UM2 nozzle? Or did you get the UM1 nozzle?

If you are printing this cold (which is fine!) keep the speed around 20mm/sec.

When you put the UM on it's side it's pretty obvious. I think it might have been only one screw - maybe two. Anyway it's the screw that is CLEARLY holding the cover on the the metal box. We are talking the bottom covers, right? It's very simple. Compared to changing the battery in my watch which required me to watch two videos? This is amazingly simple.

This is begging for a plugin. The plugin could for example have one temp at the bottom and another temperature at the top and you could have the plugin linearly interpolate in between. I nominate Jonny!

I know someone who got an email the moment his UM2 was shipped. My email came 2 days after it was shipped. But I just decided to do a test - I went to DHL and put the "R" number in DHL and it showed my package! So try it.

You make convincing points. It *could* be backlash/play. Or it might be something else. play: So are all the belts tight enough to get at least a very low audible pitch? Like the bass string on a string Bass (or higher - higher pitch is fine also) and also it might be play in the head or nozzle. With the nozzle cold (or your fingers protected) push the nozzle around and see if there is any play before the rods start moving. The head could be loose or the bearings that attach the head to the rods could be loose. Assuming not play: Inner diameter circles are *OFTEN* smaller than desired. I think as you lay down the layer, the PLA pulls a bit like a rubber band and the circles are "pulled" in towards the center. Also if your model only has say 10 line segments on a circle - well that decagon is effectively now a smaller circle as each line segment cuts into the circle. Plus PLA shrinks. Combine those 3 properties and you get smaller circles. You can fix by increasing your temperature - a lot - try 240C but only for the first layer. Once the first layer is almost done put it back to what you had before. Also you can try raising your bed height by a tiny bit (loosen the 3 thumb screws by a half turn maybe). This will squish the bottom layer a bit more making it closer to the .4mm wide "strings" that Cura intended. Although I might not do this last thing as the infill bottom layer looks quite good. Third point: 25% overlap is for wimps. Go for 50%, 100%, 200%, 300%, lol. Personally I use 15% and it usually works fine for me. At least on blue tape it works fine - haven't printed a bottom layer hole on glass yet.

If you loosen both pulleys on either end of the rod, then the rod can slide around and the pulleys can slide inwards. If you push both pulleys out as far as they can go and make the rod flush with the edges and then tighten the pulleys then the rod will behave but you might get a little clicking. If you move one or both pulleys in away from the edge just a few mm then maybe can you compromise where the rod is free to slide a little bit but not enough to fall out one side and the pulley's stop clicking. These pulley's positions have 2 purposes: lining up with the belts and also holding the rod from falling out. On the UM1, the rods were held with end caps so on the UM1 you could position the pulleys where they belonged. On the UM2 you have a little less freedom but if it is designed right it shouldn't matter much.