gr5

Which printer do you have? Please update your profile settings to indicate this. Also update your country/location as advice changes often depending on the country. What you describe can happen but usually if there is a layer like this it can also be caused by underextrusion due to temporary tangling filament, temporary cold layer (often due to fans coming on) and similar things like that.

There are two ways to produce gcode files: reprap or ultigcode. reprap mode is the older method and includes 6 or so settings that ultigcode does not. This is because those 6 or so settings are set on the printer. When you switch to reprap mode those settings are ignored on the printer and it uses the values in the gcode. The point is for portability among printers and filaments. Those settings are (I probably forgot some): nozzle temperature, fan, bed temp, retraction distance, retraction speed. These settings should all/mostly be settable in the filament settings on the UM2 or in Cura if you tell it your machine is a reprap style printer.

Ah!!! Yes! I see it now! Backlash. See how you have pairs of infill touching and then a gap? touching/gap/touching/gap - the pattern repeats. The is EXACTLY what I was looking for. I didn't notice this in the first picture. This means you have backlash/play. It could be due to friction (consider loosening the end caps slightly on the 4 long rods or belts too tight) but more likely it's the belts and most likely the short belts (those going to one or both stepper motors).

I'd like to see more pictures. Is this the bottom layer or top? I'd like to see outer edges also on top layers. Some of the issues causing square circles only affect the bottom layer (leveling off slightly). Some affect only upper levels. Loose belts and backlash affect how well the solid infill touches the edges. Typically with loose belts one is worse than the other and you get a pattern of alternating diagonal infill that is very distinct and clearly a belt issue - if both axes are EXACTLY equally loose then it's possible to get a nice pattern like in your picture but then the other problem is the infill doesn't touch the outer walls. Also with loose belts if you print certain rectangular/blocky objects and Cura switches directions (clockwise versus counter) you get very distinct patterns that instantly (to my eye) say "loose belt". Instead if this is a bottom layer picture it could be simply "move the nozzle closer to the bed by 1/4 turn on all 3 leveling screws".

To set temperature in Cura you can switch the machine settings to "rep/rap" mode but I strongly don't recommend this. You can also use a plugin that changes temp on different levels but that won't get you control over the starting temp.

The bad quality you see on overhangs is a problem with all FDM 3d printers. You can get better results with higher quality filaments. Overhang ability varies greatly by filament brand. corners are the worst (overhanging corners like the bow of a boat). You should be able to get absolutely perfect looking overhangs if they are at 45 degrees. As you get closer to horizontal it gradually gets worse - you get a raised lip starting near the corners of your overhang or the entire edge in your circular case. Each layer is worse than the last until some of the filament is pushed out over the edge. It's possible to remelt the lower layers if you slow the head to 5mm/sec but that's not a reasonable solution (although some have tried it on every other layer and it makes a better quality). Increaseing fan and lowering filament temp is a better solution. Try a small desk fan and blow it right on the print from outside the printer. Make sure it isn't so strong it cools the nozzle (not likely). Make sure your fans are at 100% within the overhang region (by default they aren't up to 100% until 5mm up). The basic problem has to do with the nature of PLA - it cools very fast but it doesn't solidify until well below 100C. So it because this stretchy liquid rubber band material (like snot) and pulls inward on outer corners. For vertical walls the layer below holds it in place but for overhangs it gets pulled inward and upward. Some brands of PLA are MUCH worse than others.

It is possible to set the temp in cura but it's MUCH easier to simply modify your PLA settings on your UM2. Go to the filament menu and choose CUSTOMIZE. Change the temp to 200C then scroll to the bottom and save it and then choose where to save it to: PLA. That last step is not obvious (choose where to save it to). Then always in the future it PLA will have a new printing temp. Note that if you print on tape (which you don't) 200C is much too cold for the bottom layer but with a heated bed even 180C is plenty warm enough.

At times it seems like a finicky machine and then you get in the groove and print 100 parts in a row with no fiddling necessary. I would burn it out with hot flame but don't melt the brass. There is a huge safety margin between carbonizing the pla and melting the brass but you can't just leave it in the flame thoughtlessly. Keep a low duty cycle (in the flame less than half the time) and when it seems hot enough that all the pla is burnt don't heat it any hotter than necessary. I've done this myself and was probably more careful than I needed to be. I would follow that by holding the block with pliers and doing many rapid "cold pulls" ouside of the printer with a short length of PLA or even better using nylon filament to get all the gunk out. Or you could try q-tips or toothpicks and water and soap. Having a steel hypodermic or guitar string or acupuncture needle helps greatly.

Soaking a nozzle that printed with ABS is a great idea. It shouldn't hurt PLA and might actually help but in either case you should soak for hours. Brass is unaffected by acetone. Acetone will actually dissolve PLA a little bit but it takes much larger amounts and much more time.

I just looked at the picture again! I see it now - we are looking *inside* a box. I thought I was looking at the outside. That horizontal line is probably nothing to do with XY errors but instead is a Z error. If the Z axis moves half as far as it is supposed to move then you get an over-extruded layer and it sticks out a bit like that on both inside and outside. Is that what happened? Sticking *out* on both inside and outside? Like it was too much extrusion? This can be caused also by varying thickness in the PLA filament. Or by temperature changes in the nozzle (hotter temperatures extrude more easily).

It's hard to tell from your photo but I think that might be normal. It's not a problem exactly with the printer but the PLA. It shrinks very quickly (milliseconds) as it comes out and while it is still liquid but shrinking it sticks to itself like a liquid rubber band. It's difficult to make vertical holes in this situation and they tend to be about .5mm smaller than where the head is positioned. However the holes although they tend to be smaller are usually mostly round but I don't always zoom in on them quite this much so I'm not sure if this is normal or not. Yes, too tight belts can cause a problem - it can greatly increase the friction causing play/backlash. It's weird but having the belts too loose or too tight will cause backlash but "too tight" is much more rare and is easily detected by pushing the head around with power to servos off.

There's a README file in the git repository of Marlin source code. That has some crucial hints.

The quality of the UMO is excellent and I think as good as the UM2. Because you put it together you will have less resitance to modifying it (e.g. changing to a smaller nozzle).

Go for it. The worst that happens you break a pololu and they are cheap to replace.

I only know the emails of maybe 10 forum members. Of those about 1/3 can't login. That seems very serious to me and should be higher priority than the spam I think.

I'm not sure what I'm seeing. Is the bottom of the print on the left side? If so the picture seems to be rotated clockwise and if so then there seems to be a horizontal seam there I think?. I'm really not sure what I'm seeing here.

I receive notifications at the top bar - next to the bell - there's a red circle with a number. But I don't get any emails. I thought it would be nice to be able to have some setting where I can get an email on every notification. Of course some people won't like that so it should be an option.

Bulldozer please flag gothampixels answer as "best answer", thanks.

re-level it? When you home the Z bed it should hit the switch on the bottom, breifly go up and then down a second time and either stop or then go up. If it slams into the bottom and makes a terrible racket then your Z switch isn't triggering. If it never goes all the way down then the Z switch is probably stuck closed. Issues about the home height probably mean you lost your "level" or you didn't calibrate it yet. It's pretty easy to find among the menus as it's one of the only 4 or so menus UM seems to want you to be able to find quickly (level bed, print, change filament).

ioan - what country do you live in (please update your profile) and which printer(s)?

And you can buy some at (currently) 10€ each at 3dsolex.com. That's swordriff's store and he stands by the product.

Is it possible to zoom in on posted photos - I squint like hell but still can't quite see what I need to see on some of the posted photos. Am I missing a feature? Or is this feature just not implemented?

Rather than filter other languages, in the old forum I could go to a category like "The Art of Printing" and follow that because that is something I'm particularly interested in. Then I would get an email for every new topic in that category. I've clicked "follow" in several categories but I'm not sure if that does anything yet. I get notifications of all topics I'm following but it seems like maybe I'm not getting the ones for new topics in a followed category. Also I *never* get emails unfortunately. Just listings under the notification menu at the top (the red circle).

Oh - to clarify - speed is more important than temperature (except on overhangs) and so lower speed is the most common way to get better quality. Lowering temperature without also lowering speed may cause underextrusion and cause quality to get worse.

Heated bed won't help with PLA quality. The difference in the above prints could be temperature - temperature alone can make quite a difference. More fan will absolutely help quality for printing PLA. Although many (most) fan shroud designs lower the air flow by 10X and cause more harm than good - they should have very little constriction if any. If you will be constricting flow you need a blower rather than a fan. The lines in the print on the left are because I think your shell width is only .4mm. Try .8mm next time. Right now the infill is showing through a little bit. Regarding temperature - higher temperatures can hide things like infill showing through but most of the time lower temperature means better quality.